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Understanding Pipe Fittings |
Posted by: uuxko845s - 09-24-2021, 02:19 AM - Forum: Welcomes and Introductions
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Pipe fittings are components used to join pipe sections together with other fluid control products like valves and pumps to create pipelines. The common connotation for the term fittings is associated with the ones used for metal and plastic pipes which carry fluids. There are also other forms of malleable iron pipe fitting that can be used to connect pipes for handrails and other architectural elements, where providing a leak-proof connection is not a requirement. Pipe fittings may be welded or threaded, mechanically joined, or chemically adhered, to name the most common mechanisms, depending on the material of the pipe.
There is some inconsistency in terminology surrounding the terms pipe, tube, and tubing. Therefore, the term Carbon Steel Pipe Fitting will sometimes be mentioned in the context of tubing as well as pipe. While similar in shape to tube fittings, pipe fittings are seldom joined by methods such as soldering. Some methods overlap, such as the use of compression fittings, but where these are commonplace for connecting tubes or tubing, their use in pipe connections is rarer. It suffices to say that while there are general distinctions, the common usage of terms can differ from supplier-to-supplier, although they represent the same items.
In this article, the concentration will be on discussing typical fittings and connection methods associated with rigid pipe and piping, with a limited presentation of the fittings that are associated with flexible tubes, tubing, or hose.
To learn more about the varieties of pipe, consult our related guide to pipe and piping.
Pipe Fittings Explained: Fitting Materials and Manufacturing Processes
Cast and malleable iron
Fittings for cast iron pipe fall under hubless and bell-and-spigot styles. Hubless designs rely on elastomeric couplers that are secured to the outer diameters of the pipe or fitting by clamps, usually a stainless steel band clamp that compresses the elastomeric material and forms a seal. These hubless or no hub designs are sometimes referred to as rubber pipe couplings or rubber plumbing couplings and are especially popular for transitioning from one material to another—from copper to cast iron, for instance. Bell-and-spigot, or sometimes, hub-and-spigot, fittings are joined today primarily with elastomeric gaskets that fit inside the bell and accommodate the insertion of the plain pipe end or fitting. Older systems before the 1950s were caulked using a combination of molten lead and a fibrous material such as oakum. Cast iron pipe is sometimes joined with bolted flanges, or in some cases, mechanical compression connections. Flanged joints employed in underground applications can subject the pipe to settlement stresses unless the pipe is adequately supported.
While there are both malleable iron pipe fittings and ductile iron pipe fittings available, the improved mechanical properties and lower cost of ductile iron is causing a shift towards greater use of that material.
Fittings for steel (aka, “black pipe”) and galvanized pipe as found in residential and commercial plumbing work are generally cast and referred to as “malleable iron fittings." They can be galvanized. Although standards list threaded fittings up to fairly large diameters, these generally are not used today as the threading of large-diameter pipe is considered needlessly difficult.
Steel and steel alloys
Galvanized malleable iron pipe fittings are often extruded or drawn over a mandrel from welded or seamless pipe. In smaller sizes they are often threaded to match threads on the ends of pipe. As sizes and pressures increase, they are often welded in place by either butt-weld or socket-weld methods. Socket-weld fittings, usually forged, are restricted to smaller pipe diameters (up to NPS 4, but usually NPS 2 or smaller) and are available in 3000, 6000, and 9000 class pressure ratings, corresponding to Schedule 40, 80, and 160 pipe. Socket fittings are welded into place with fillet welds, which makes them weaker than butt- welded fittings, but still preferable to threaded fittings for high-end work. The need for an expansion gap in the fitting precludes their use in high-pressure food applications.
Flanges are also used, with the resulting flanged sections of pipe connected via bolts. The use of flanges makes breaking the pipeline feasible so as to enable replacement of valves, etc. Most pipeline equipment such as pumps and compressors are also connected via flanges for this same reason.
Flange fittings are available in a handful of styles, rated by pressure and temperature. These styles include lapped, weld neck, socket weld, ring-type joint, screwed, and slip-on. The threaded flange is suitable only for low- to medium-pressure applications. The other various welded-on flanges permit higher pressures to be used. Lapped flanges are often used where disconnections will be frequent as the flange can spin freely, simplifying bolt-hole alignment. A special case is the so-called blind flange, which is used to seal the end of a pipeline but allow connection to another pipe or piece of equipment later.
Flanges can incorporate several different methods to seal adjoining faces, including O-rings, seal rings, and gaskets. Seal rings provide an especially tight joint and for the same bolt stress applied to a flat-face gasket, can resist a higher pressure.
Primarily, three standards govern pipe flanges. ASME 16.5 defines the ANSI flange, the most commonly-used flange. ASME B16.47 covers two series, A and B, which represent large diameter applications. Series A flanges are heavier and thicker than Series B for the same pressure and size. Series B flanges are normally selected for refurbishment work. ASME B16.1 defines the AWWS flange, but it is only for flanges used in potable-water service at atmospheric temperatures. Then, there is the so-called Industry Standard flange which is not defined by a governing body but instead reflects historical practice. The dimensions for these flanges are covered by ASME B16.1, the standard for 25, 125, and 250 class cast-iron-pipe flange and flange fittings.
Stainless steel pipe fittings can be used for sanitary applications such as food and dairy processing, and are commonly fitted with quick-connect clamps to enable dismantling of the line for internal cleaning. The flanges for these clamping systems are available as weld-on entities or in many instances available as wyes, tees, etc. with the flange integral to the fitting.
Metal pipes sections may also be joined and built up as pipelines using pipe couplings and other standard black malleable iron pipe fitting such as metal pipe end caps or 180-degree pipe elbows.
Nonferrous
Aluminum fittings are typically cast. They are available in all the same forms or shapes as steel fittings. Aluminum threaded fittings such as caps or nipples are available, as are fittings that feature a combination of threaded and butt weld connection styles. Socket weld options also exist. Welding of aluminum fittings usually requires a MIG or TIG process.
Aluminum pipe is also a popular choice for use in creating handrails, and a host of fittings for structural applications are available, both weldable and slip on/clamp-on varieties.
Red brass fittings such as brass pipe nipples are available corresponding to pipe diameters, and these are often assembled by soldering or brazing.
Concrete
Concrete pipe fittings are available in a variety of styles suitable to their application in large civil projects such as storm-water control. Aside from the typical wye connections, specialized fittings include utility hole portals and various styles of vaults. Typical connections use shouldered ends on the fittings which mate with counterparts on the receiving pipes. A rubber gasket provides for a leakproof joint.
Plastics
Plastic pipe fittings are available in both socket weld (sometimes called solvent weld) and threaded styles, with the former the most common. Socket weld fittings are designed to be welded in place chemically, thereby making installation quick and straightforward to complete. Plastic pipes are usually dry fitted, then marked, as the solvent used to connect them is especially fast-acting. Couplings are typically used to connect and join straight lengths of pipe together.
Fittings are available in standard shapes and styles and with the dimensional size ranges of material common to plastic pipe, including PVC, CPVC, PE, PEX, PP, and ABS.
Common PVC pipe fittings include reducers, elbows, caps, tees, wyes, couplings, unions, and crosses, to name a few. The standard cross-sectional profile for most PVC pipe or tubing fittings is circular, but there are other profile shapes available, such as square PVC fittings. However, these alternative fitting profiles are usually associated with PVC pipe that is designated for structural use, such as fences, railings, or furniture grade use, and are not associated with PVC pipe that is fluid handling applications. Besides PVC, other materials may be used for structural fittings, one example being galvanized pipe railing fittings.
Other PVC fittings include barbed insert designs, which are intended to be used with tubing and are pressed into the tubing and secured with band clamps.
CPCV pipe fittings, as well as ABS pipe fittings (Acrylonitrile Butadiene Styrene), also are usually joined with fittings that are solvent welded. Suitable conversion adapters for changing material types, such as from CPVC to brass, are also commonly available.
In some applications using plastic pipe, such as in plumbing for sink drains, certain pipe fixtures such as p-traps may be joined with a threaded connection using nylon washers and a retaining or locking nut. This feature facilitates easy disassembly to clear clogs.
Polyethylene pipe fittings and polypropylene Galavanized carbon steel pipe fitting are usually available with both threaded style or barbed style connections, and socket weld or fused options being also available. Similarly, PDVF pipe fittings also are produced with socket or threaded connections.
Where an air or watertight seal is needed, nylon pipe fittings may be employed and can be used with nylon tube or pipe as well as with other types of plastic or metal pipe.
Glass
In some specialized industrial fluid process settings, glass pipe and fittings are employed. Borosilicate glass offers several key advantages over alternative forms of piping systems. The material has high purity, so it will not contaminate process fluids. The natural transparency of glass permits the inspection of the process as needed, while the smooth surface prevents the development of scale or other residues on the interior surface of the pipe.
Laboratory applications may also frequently employ glass tubing and glass profile fittings.
Glass pipe should not be confused with pipes that employ a glass lining, which would be more correctly identified as glass-lined pipe.
Vitrified clay
Fittings for vitrified clay pipe are available in the typical configurations required for sewer installations. Like cast iron, bell-and-spigot is the usual coupling method for these fittings, with an O-ring or gasket used to seal the joint.
Types of Pipe Fittings: Applications and Industries
Callouts
Threaded fittings follow a standardized format on drawings. The nominal dimension comes before the description. When two or more ends of the fitting are not of the same dimension, the dimension of the run precedes those of the branches, or for reducing fittings, the largest dimension precedes the smallest dimension. Thus, a 1 x 1 x 3/4 Street Tee; a 1 x 1x 3/4 45° Y Bend; a 1 x 3/4 x 1/2 x 1/4 Cross; and so forth. The thread size on threaded fittings will correspond to the nominal pipe size thread as specified by ANSI.
Thread Types
Most pipe applications use threaded fittings whose connections can be typically characterized by one of the following systems:
American National Standard Pipe Threads (NPT)
British Standard Pipe Threads (BSPT)
The principal difference between these two is the taper angle. The NPT system uses a thread taper angle of 60 degrees, whereas the British Standard Pipe Thread (BPST) fittings use a slightly lower taper angle of 55 degrees. In addition to threaded pipe fittings which are tapered, these systems also specify straight pipe thread fittings, which do not rely on a taper to seal against pressure loss or leaks. Generally, a suitable sealant is needed to assure that the seal integrity of the joint or connection is achieved. Most threaded pipe fittings are designed to be right-hand threads, but there are some left-handed (LH) thread options available.
Metric pipe fittings are also available, identified by the nominal outside diameter and the thread pitch. So an M12 x 1.5 metric pipe nipple would have an outside diameter of 12 millimeters and a thread pitch of 1.5 threads per millimeter.
Screw fittings are usually threaded internally. The exception is the street fitting, which, in the case of a simple elbow, has one external thread and one internal thread. Pipes are readily threaded in the field. Joining threaded pipes and fittings can be aided by Teflon tape or pipe compound. When applying the compound, it is recommended that it be placed on the external thread only, to avoid introducing any impurities into the pipeline during joint assembly.
Piping layouts are generally one-line or two-line drawings, depending on the complexity of the installation. Where clearances are tight,and for many shop-fabricated pipelines, the two-line drawing is used, which shows the pipe dimensionally to scale. For simpler installations, the one-line drawing suffices, with fittings, valves, etc. designated symbolically. Pipeline drawings are sometimes shown as “developed,” which assumes the vertical pipes are revolved into the horizontal plane, or vice versa, to allow the entire piping system to be shown in the same plane.
Weldolets
These small, weldable branch fittings reinforce the pipe where a hole is made, eliminating the need to add reinforcing. Different forms of these fittings are available under various trademarks, covering butt- and socket-welded styles, thread-on varieties, as well as some special designs which enable connections at elbows, etc.
Welding process
Pipe ends and flanges are prepared for butt welding according to pipe-wall thickness. For walls 3/4 inch thick or less, the walls are beveled to an included angle of 70° and a 3/16 inch gap is left between them. The welder makes a root pass, a fill pass (or passes), and a capping pass, often varying the filler material between passes. For larger thickness, the pipe is tapered to a similar angle but only partway up the wall. In addition, a small relief angle is ground on the inside wall, serving as the location for a backing ring. Socket welds are generally used for thinner-walled pipes. Welding procedures are spelled out by an engineer in Weld Procedure Specifications and the welder making the weld will be certified for the specific process. Pipes sometimes must be preheated prior to welding and heat-treated after to relieve heat stress.
The necessity of proper pipe-end preparation and the need for careful fit-up prior to joining butt-welded fittings makes the use of socket-weld fittings appealing. No bevel is required for socket-weld fittings and the socket itself serves to align the pipe. About the only special requirement is that the pipe must be backed out of the fitting slightly to allow for expansion during the weld.
Prefabrication of pipeline sections, called “spools,” is often done indoors where automation can be applied to the fabrication process. Pipes joints can be rolled on slow turning machines to bring the work to the welder. Robot welders can be used. Techniques such as submerged-arc welding can be applied for productivity gains.
There are non-welded pipe fittings or no weld pipe connectors available as alternatives to the traditionally welded piping systems. Using a combination of swaged mechanical fittings along with the cold bending of pipe or tubing, this solution eliminates the stresses to the pipeline from the welding operation, reduces costs, and can provide for a modular system that is easier to disassemble or modify as needed.
Plastic pipe, and HDPE pipe, in particular, can be joined by heat welding, sometimes referred to as electrofusion welding. Pipes can be butt-welded or socket-welded. This is a fairly common practice for large-diameter HDPE pipeline installations. A range of specialized equipment is available for producing these welds.
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Are Blankets the New Going-Out Accessory? |
Posted by: uuxko845s - 09-24-2021, 02:18 AM - Forum: Welcomes and Introductions
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From Sarah Jessica Parker’s monogrammed Burberry poncho to Norma Kamali’s Sleeping Bag Coat, fashion has long embraced blanket-inspired styles. During a time when most socializing takes place outdoors, would you wear one outside the house?
A weighted blanket is exactly what it sounds like - it’s a blanket with extra weight in it. Weighted blankets are unique as instead of being filled with cotton or down, it contains materials like glass beads to make them heavier. This weight is evenly distributed across the body for a feeling of being gently hugged. The deep touch pressure offered by the weighted blanket is supposed to make you feel safe, relaxed, and comfortable.
Blankets, a symbol of coziness and warmth usually relegated to the indoors, can also be a great piece to layer for fall and winter outfits. Though temperatures are just starting to drop in New York City, WSJ. staffers have spotted a few in the wild—mostly while outdoor dining, which New York City recently extended permanently. (It was originally set to expire ahead of the winter months, on October 31.) For the first time in recent history, the preferred environment for socializing has become “anywhere outside.” And during a pandemic and period of worldwide unrest, most people are seeking comfort more than ever. As a replacement for the timeworn going-out top—obviously better suited to the indoors—the going-out blanket suddenly makes sense.
Over the years, blankets have inspired fashion, from the upscale double layers blanket poncho that Sarah Jessica Parker wore in 2014, personalized with her initials, to Norma Kamali’s famous blanket-adjacent Sleeping Bag Coat, which she first designed in 1973. In 2012, Lenny Kravitz went viral after being photographed by paparazzi while ensconced in an enormous scarf on his way to buy groceries. Six years later, he defended the accessory on an episode of The Tonight Show Starring Jimmy Fallon. “But Lenny,” Fallon said, “this is not a scarf. This is a blanket.”
After my sister gave me a weighted blanket for Christmas, it became the gift that I didn't know I needed. It's one of the best things ever to happen to me.
As someone with anxiety, I've struggled with restful sleep: Falling asleep can take up to two hours, or I wake up at least twice during the night.
The first night I started sleeping underneath a 15-pound flannel blanket, I slept straight through the night for the first time in months and felt more rested during the day. After a few days of good sleep, I learned that my sister had done her gift research — she had read that people with anxiety tended to feel more grounded when using the blankets.
Fascinated, I asked experts on mental health and sleep to explain why these heavy blankets — which are filled with plastic, glass or metal particles and layered with extra fabric — have eased the, ahem, weight of some people's anxiety-related sleep struggles.
Weighted blankets, which range from 5 to 30 pounds (2.27 to 13.6 kilograms), have been used by special needs educators and occupational therapists since the late 1990s, but have become mainstream in the last few years. Regular blankets can weigh around 3 to 5 pounds.
The dominant theory is that weighted blankets provide deep pressure stimulation, a feeling that resembles a "firm, but gentle, squeeze or holding sensation and ... triggers these feelings of relaxation and of being calm," said pulmonary and sleep specialist Dr. Raj Dasgupta, an assistant professor of clinical medicine at Keck School of Medicine at the University of Southern California. Feeling relaxed is what decreases cortisol, a stress hormone that typically runs high in people with chronic anxiety, stress and other disorders, he added.
There is evidence suggesting that deep pressure stimulation reduces sympathetic nervous system arousal — that's our fight-or-flight response — and increases parasympathetic activity, which may cause the calming effect, said Dr. Fariha Abbasi-Feinberg, the director of sleep medicine at Millennium Physician Group in Florida.
Pressure to stimulate the sensation of touch to muscles and joints is the same proposed mechanism behind massage and acupressure, added Abbasi-Feinberg, who is also a neurologist on the American Academy of Sleep Medicine's board of directors. "This calming (effect) can promote better quality sleep."
If you're interested in using a weighted blanket to aid sleep problems related to mental or sensory disorders, here's what you should know about their effectiveness, any caveats and how to choose one.
Weighted blankets have been growing in popularity, but there isn't actually much research on their effectiveness. That may be due to the newness of weighted blankets, their relative harmlessness and that other health issues are more urgent for researchers to study, Dasgupta said.
Some people with anxiety, depression, bipolar disorder or insomnia have reported improved quality of sleep and feeling more restful during the day, a few recent, small studies have found. Many study participants experienced a decrease of 50% or more in their Insomnia Severity Index scores after using a weighted blanket for four weeks, in comparison to 5.4% of the control group, according to a small study published in the Journal of Clinical Sleep Medicine last September.
In the follow-up phase of the study, which lasted one year, people who used fleece blanket continued to benefit. People who switched from lightweight control blankets to weighted blankets experienced similar effects. And those who used weighted blankets also reported better sleep maintenance, a higher daytime activity level, remission from insomnia symptoms and alleviated symptoms of anxiety, depression and fatigue.
Researchers who studied the effects of weighted blankets on children with attention-deficit/hyperactivity disorder or autism have found either some positive associations or no associations with better sleep or reduced symptoms.
"A 'grounded feeling' due to the use of weighted blankets may be attributed to the psychoanalytic 'holding environment' theory, which states that touch is a basic need that provides calming and comfort," Abbasi-Feinberg said via email. "Weighted blankets are designed to work similar to the way tight swaddling helps newborns feel snug and secure."
Many, if not all, of the available studies on weighted blankets used participants who had a psychiatric, developmental or sleep disorder such as anxiety, depression, autism, ADHD or insomnia. That's likely because of "the fact that these segments of the population are the ones who could benefit most from touch- or sensory-related therapies," Abbasi-Feinberg said.
However, given how weighted blankets might work to reduce cortisol levels, they could help to reduce general stress, too, Dasgupta said.
People have shared their fondness for weighted blankets in studies and online, but people with the same psychiatric disorders may not have the same relaxing experiences with weighted blankets. One person in the follow-up phase of the 2020 study discontinued their participation due to feelings of anxiety when using the blanket. People who are claustrophobic may also not fare well. More studies on factors that make individuals more or less helped by weighted blankets are needed, Dasgupta added.
A weighted blanket's calming abilities may help to regulate breathing, but some health professionals are hesitant to recommend weighted blankets to people with obstructive sleep apnea, asthma or other respiratory conditions. "You'd have to be pretty brittle and pretty sick if a blanket's going to stop your breathing," Dasgupta said. But if you're not sure, he added, be careful and talk to your pulmonologist first.
Children should be assessed by occupational therapists or pediatricians before they try sherpa blanket, as many weighted blankets haven't been tested for the effectiveness and safety for children.
"Weighted blankets shouldn't be used for toddlers under 2 years old, as it may increase the risk of suffocation," Abbasi-Feinberg said. "It's important for parents to always consult their pediatrician before trying a weighted blanket."
Dogs sometimes benefit from pressure-applying garments during storms or other anxiety-inducing events, but weighted blankets can be dangerous for pets, said Dr. Douglas Kratt, president of the American Veterinary Medical Association.
If you're looking for a weighted blanket, there are multiple options in terms of weight, materials and size. A blanket that weighs 7% to 12% of your body weight is typically the range to choose from, but that may depend on personal preference. "Some individuals might want a heavier weight to feel a sense of 'hugging' and calmness, while others might want something lighter," Abbasi-Feinberg said.
And there are weighted blankets for year-round use, she added — some are made with a higher proportion of fabric layers made from cotton, which is lighter than other materials and allows air to pass through its fibers, therefore better managing your body temperature.
Dasgupta thinks of sleep as a puzzle, and sometimes people with insomnia or mental disorders are missing some of the pieces needed for great sleep, but "no one really knows what puzzle pieces are missing."
Weighted blankets could help, but they're not a cure-all — a healthy sleep routine is still necessary for getting enough of both sleep time and the deeper stages that leave you refreshed. If you think that a weighted blanket could be your missing puzzle piece, "it's worth a try," Dasgupta said. The downside is that these blankets can be pricey.
During the pandemic, "sleep really took a hit" when it comes to insomnia, altered circadian rhythm and nightmares, Dasgupta said. "A weighted blanket is something that might have a role during this pandemic. ... That sense of the basic need to be touched and hugged could actually provide some comfort and security. Maybe that's why some people benefit from a weighted blanket."
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Environmental impacts of wooden, plastic, and wood-polymer composite pallet: a life c |
Posted by: uuxko845s - 09-24-2021, 02:16 AM - Forum: Welcomes and Introductions
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Environmental impacts of wooden, plastic, and wood-polymer composite pallet: a life cycle assessment approach
Waste recycling is one of the essential tools for the European Union’s transition towards a circular economy. One of the possibilities for recycling wood and plastic waste is to utilise it to produce composite product. This study analyses the environmental impacts of producing composite pallets made of wood and plastic waste from construction and demolition activities in Finland. It also compares these impacts with conventional wooden and plastic pallets made of virgin materials.
Methods
Two different life cycle assessment methods were used: attributional life cycle assessment and consequential life cycle assessment. In both of the life cycle assessment studies, 1000 trips were considered as the functional unit. Furthermore, end-of-life allocation formula such as 0:100 with a credit system had been used in this study. This study also used sensitivity analysis and normalisation calculation to determine the best performing pallet.
Result and discussion
In the attributional cradle-to-grave life cycle assessment, wood-polymer composite pallets had the lowest environmental impact in abiotic depletion potential (fossil), acidification potential, eutrophication potential, global warming potential (including biogenic carbon), global warming potential (including biogenic carbon) with indirect land-use change, and ozone depletion potential. In contrast, wooden pallets showed the lowest impact on global warming potential (excluding biogenic carbon). In the consequential life cycle assessment, wood-polymer composite pallets showed the best environmental impact in all impact categories. In both attributional and consequential life cycle assessments, plastic pallet had the maximum impact. The sensitivity analysis and normalisation calculation showed that wood-polymer composite pallets can be a better choice over plastic and wooden pallet.
Conclusions
The overall results of the pallets depends on the methodological approach of the LCA. However, it can be concluded that the wood-polymer composite pallet can be a better choice over the plastic pallet and, in most cases, over the wooden pallet. This study will be of use to the pallet industry and relevant stakeholders.
Pallets are used for storing, protecting, and transporting freight. They are the most common base for handling and moving the unit load, carried by materials handling units, such as forklifts. The pallet market is growing due to the rising standard of goods transportation, the adoption of modern material handling units in different industries, and market demand for palletised goods (McCrea 2016). It was estimated that the global pallet market reached 6.87 billion units in 2018 (Nichols 2020). More than 600 million European Pallets Association (EPAL) approved pallets are available to the global logistics industry. In 2019, 123 million wooden EPAL pallets and other carriers were produced, which is 1.2 million more compared to 2018 (EPAL 2020).
The global pallet market can be classified based on materials, sizes, and management strategies (Deviatkin et al. 2019). Among various segments of pallets, wooden pallets dominate the market share, followed by plastic pallets (Leblanc 2020). Wooden pallets are inexpensive and can easily be manufactured and repaired compared to rackable plastic pallets. One of the most significant downsides of wooden pallets is the cost to forests (Retallack 2019). Furthermore, wooden pallets are heavier than plastic pallets, imposing an environmental burden on freight shipment. Even though plastic pallets are lighter than wooden pallets, plastic pallets’ production is an energy-intensive process. In addition, repairing plastic pallets is impossible because the materials have to be melted down and remoulded in the plastic pallet repairing process.
Waste recycling is one of the pathways taken by the European Union to move towards a circular economy, as highlighted in the circular economy action plan (European Commission 2020). The central idea of a circular economy is to minimise the consumption of virgin materials, which means that an item that can be recycled should not be landfilled or incinerated. The EU is planning to recycle 50% plastic and 25% wood waste by 2025, which will increase to 55% for plastic and 30% for wood by 2030 (European Commission, 2018). By following the EU’s target, Finland’s objective is to fortify its role as a pioneer in the circular economy by implementing the strategic programme for circular economy (Ministry of Employment and the Economy 2021). The transition to a circular economy is essential for Finland to strengthen its export-driven economy with minimum environmental impact.
The environmental benefits of recycled-based plastic products are well known and quantifiable (WRAP 2019). Also, materials made from wood waste can deliver low carbon-based products with less pressure on forests (WWF 2016). One of the possibilities for reducing the environmental burden of plastic and wood waste is to utilise these wastes for wood-polymer composite (WPC) products, such as WPC pallets. However, analysing the environmental performance of WPC pallets requires a complete life cycle analysis. Furthermore, it is important to consider that different materials have different life expectancies, reuse capabilities, and recyclability.
According to International Organization for Standardization (ISO), life cycle assessment (LCA) is one of the environmental management techniques that “addresses the environmental aspects and potential environmental impacts throughout a product’s life cycle from raw material acquisition through production, use, end-of-life treatment, recycling, and final disposal” (EN ISO 14040:2006; EN ISO 14044:2006). Several LCA studies have been conducted on pallets focusing on pallet manufacturing, management strategies and supply chains, repair intensity, and pallets manufactured from various materials, such as wood, virgin plastic, cardboard, and waste plastic. Gasol et al. (2008) conducted an LCA study to compare the environmental performance of wooden pallets with high reuse intensity and low reuse intensity in the European context, and with the findings showing that due to transportation, high reuse intensity pallets have more adverse impacts on climate change than low reuse intensity pallets. Bengtsson and Logie (2015) performed an LCA comparing one-way wooden pallets, disposable compressed cardboard pallets, pooled softwood pallets, and plastic stackable pallets in Australia and China. The study results pointed out that pooled softwood pallets have the minimum environmental impact among all types of studied pallets. Tornese et al. (2018) examined pallets’ economic and climate change impacts, demonstrating that manufacturing a pallet causes more damage to the environment than repairing a pallet. The study also identified that the cross-docking system has equivalent emissions as the take-back system due to higher transportation distance. Almeida and Bengtsson (2017) compared the LCA of waste plastic-based pallets with wooden pallets and virgin plastic-based pallets and demonstrated that plastic waste-derived pallets outperform all other alternatives. Franklin Associates (2007) compared the environmental impacts of pooled pallets versus non-pooled pallets. The study indicated that pooled pallets have less of an environmental burden than non-pooled pallets. Kočí (2019) studied the environmental impact of wooden pallets, primary plastic pallets, and secondary plastic pallets. The study found that wooden pallets have a better environmental impact than primary and secondary plastic pallets if energy recovery occurs. Furthermore, the study also showed that the weight of the pallet plays a significant role on its total environmental impact.
The authors of previously conducted LCA studies analysed various pallets, making their cross-comparison a difficult task. Previous literature, including the above mentioned studies, have conducted LCA from an attributional point of view and excluded consequential LCA, which is thought to be an important method for identifying the changes in the system as a consequence of using a particular pallet. It is important to investigate the differences in the results, conclusions, and suitability of attributional and consequential LCA for cases where waste recycling is included. Furthermore, all the former studies assumed that various pallets perform equally well during their life cycle. None of the studies considered that pallets made with different materials have different life expectancies, repairing times, and recycling rates. In addition, end-of-life (EoL) is an integral part of the cradle to grave LCA. The methodological difference of the EoL allocation might have a significant impact on the overall result of LCA. It is found that the allocation of the environmental burdens of the EoL of the pallets was absent in the studies as mentioned earlier.
The goal of this LCA study was to calculate and assess the environmental impacts of manufacturing, utilising, and disposal of pallets made of different materials. Both attributional LCA (ALCA) and consequential LCA (CLCA) methods were used in the study. An ALCA investigates the environmental impact of the physical flows to and from a product’s life cycle and its subsystems (Ekvall et al. 2016). In contrast, consequential LCA investigates the environmental impacts of the product system and the systems linked to it that are expected to change for production, consumption, and disposal of the product (Ekvall et al. 2016). Despite the ISO 14040/44 standards not explicitly distinguishing between the two types of LCAs, there is a clear difference in the definition of the scope for those assessments, as described below. The study results are intended to guide the selection of materials for the production of pallets.
Scope of the ALCA study
The attributional LCA follows the cradle-to-grave approach, meaning that the product system includes the processes starting with the provision of raw materials from the environment in the form of elementary flows, i.e. the flows created by nature, through the use of the pallets and ending with their disposal and with the release of emissions into air and water, and to the generation of waste.
The system boundary of the ALCA comparing the impacts of the pallet’s production, use, and EoL is shown in Fig. 1. The modelling started with producing the raw materials and the energy generation for the pallets, such as wood harvest, timber production, and plastic production. It should be noted that the system boundary for WPC starteds from the collection of waste. Once the materials are produced and delivered to the production facilities, the pallets are manufactured. Nails are used to secure the parts of the wooden pallets, whereas plastic and WPC pallets are compressed into the required shape and do not require any fixing elements. The pallets are then delivered to a pallet pooling company, which operates by delivering the produced pallets to customers who can use them for their own purposes. After which, the pooling company collects the pallets and repairs them in the case of wooden pallets, if needed. After being used, the pallets are crushed for incineration. In the case of wooden pallets, ferrous metals are separated before incineration. By incinerating wooden, plastic and WPC pallets’ waste, energy is substituted. Nevertheless, materials are also substituted by separated ferrous metals from wooden pallets.
EoL allocation
There are no strict or specific requirements for modelling the EoL in LCA, and several allocation methods exist, such as 0:100 approach, 100:0 approach, 100:100 approach, 50:50 approach, etc. (Allacker et al. 2017). 0:100 EoL method can be conducted in two different ways, such as 0:100 with no credit for avoiding virgin materials and 0:100 with credit for avoiding virgin materials (Allacker et al. 2017). The system boundary of the study ends at the recovery of energy and material from the EoL phase. Therefore, in this study, the 0:100 EoL method with credit system had been used.
In the CLCA, the correct way of modelling environmental impact is to use marginal production technology data for the substituted product. Marginal production technologies are those technologies that are changed by the small changes in demand (Weidema et al. 1999). It was found from this study that a significant amount of heat and electricity substitution was impacted when wood and plastic waste were not incinerated but used for WPC pallet production. In this case, marginal heat and electricity were used in the modelling of CLCA. Biomass will be the prime heat production source in Finland by 2030 (Ministry of Employment and the Economy 2017), and wind and solar power will provide the maximum share of electricity by 2030 (SKM Market Predictor 2019). Therefore, the biomass-based heat source was selected as the marginal heat source and wind, and solar-power-sourced electricity was selected as the marginal electricity source in CLCA modelling. The more detailed information on the selection of marginal heat and electricity is presented in the supplementary materials.
Selection of the pallets
A great variety of pallets exists, as dictated by the specific requirements of customers. However, this study exclusively focused on pooled pallets, with the dimension of 1200 mm × 800 mm, made of either wood, plastic, or WPC. The pallets with the above-specified dimension are widely known as EUR pallets and are the most widely used type of pallets in Europe (EPAL 2019).
Table 1 specifies the key parameters of the studied pallets in their baseline scenario. Wooden pallets are made of virgin wood, which is a mixture of softwood and hardwood as specific to Finnish conditions. The studied wooden pallets were block-type pallets, which are commonly used in Europe. Based on the review of LCA studies of wooden and lightweight plastic pallet by Deviatkin et al. (2019), the expected lifetime of the wooden pallets is 20 cycles, yet the number ranged between 5 and 30 cycles in most of the publications reviewed. The repair need of 7 cycles was estimated based on the mass of produced EUR pallets in Finland (3.2 × 103 kg), alongside with repaired (25 × 103 kg) and reused (167 × 103 kg). The expert views from a Finnish pallet pooling company suggested that the expected lifetime of the wooden pallets is somewhat higher, whereas the repair need for the pallets occurs on average after every 12 cycles. The variations in the expected lifetime of the pallets were examined in the scenario analysis of this study. It was assumed that, at the EoL, 90% of wooden pallets are incinerated, whereas 10% are used as a bulking agent in composting facilities.
The plastic and WPC pallets are identical in structure and production method. Plastic pallets are manufactured using injection moulding, whereas WPC pallets are produced by extrusion followed by a compression moulding process. Both pallets are made to allow their nesting, thus saving the space occupied by the pallets. The exact height occupied by wooden stackable pallets can fit 1.7 times more plastic or WPC pallets. According to the literature on plastic pallets, plastic pallets are more durable than wooden pallets (Deviatkin et al. 2019). The expected lifetime of Double Sided Plastic Pallets could be 66 cycles, whereas the lifetime ranges from 50–100 in most of the studies reviewed (Deviatkin et al. 2019). In this study, the lifetime of plastic pallets was considered to be 66 cycles by following the review study conducted by Deviatkin et al. (2019). The WPC pallets were assumed to be of comparable properties as plastic pallets in these terms. Plastic and WPC pallets are suitable for demanding applications, such as those with expected exposure to water, or specific industrial demands, like those of the pharmaceutical industry. Such features of plastic and WPC pallets are, however, not considered in this study. Once damaged, neither plastic nor WPC pallets can be repaired.
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den 内容: The Science of LED Grow Lights for Your Indoor Garden |
Posted by: uuxko845s - 09-24-2021, 02:14 AM - Forum: Welcomes and Introductions
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Indoor Gardening isn’t exactly a new thing, but LED’s are changing the way we light our indoor gardens. LED lights are more efficient than traditional fluorescent and incandescent lights. That’s because LED lights convert nearly all of their energy (95%) into light, while other lights turn a significant amount of energy into heat. But, there’s another very important reason that LED’s are more efficient when it comes to growing plants. With LED lights, we have the rather unique ability to customize the type of light that is emitted, and that means we’re not wasting energy to create light that doesn’t help our plants grow. At the end of this article, you’ll understand the science behind why spyder grow light series come in many different colors, as well as why some LED grow lights cost so much more than others.
Plants Only Use the Visible Light Spectrum for Photosynthesis
It’s important to know that plants only use visible light (the colors of light that we see every day) for photosynthesis. However, as the chart below demonstrates, the complete spectrum of light is far greater than just the visible light spectrum. On the outer edge of the visible light spectrum is Ultraviolet (UV) light and Infrared Radiation (IR). UV light is the invisible light emitted by the sun and other sources that will cause sunburns when we don’t wear sunblock. IR light can only be seen with special equipment, like night-vision goggles. Even further out from the visible light spectrum are light waves that we don’t traditionally think of as light. These include X rays, Microwaves and even Radio Waves.
One of the most important things to understand is that scientists have demonstrated over and over again that plants only absorb visible light for photosynthesis. Plants do react to other forms of light like UV, but that reaction is typically negative. I’m told that marijuana growers actually use UV light to induce the production of psychoactive chemicals like THC, which seem to be produced in part as a defense mechanism against the damaging effects of UV light to the plant.
What is PAR?
PAR stands for “photosynthetically available radiation.” PAR is made up only of visible light, because this is the only light that plants use for photosynthesis.
For decades, many indoor growers have used Lumens to measure a grow light’s efficacy, but the industry is getting smarter and turning to PAR. Lumens are used to measure the brightness of a lamp to the human eye. But plants and people see light differently. Humans see yellow and green more brightly than other colors. Therefore, yellow and green lamps may have higher Lumen values than red and blue lights that put out just as much actual light, and which plants are likely to respond better to.
PAR measures all light from the visible light spectrum equally, and does not measure light outside of the visible light spectrum, which does not help the plant photosynthesis. So, for plants, the PAR value of a light is currently the best basic measurement of a grow light’s brightness. Accurate PAR meters are quite expensive and generally cost $500 or more. Inaccurate PAR meters can be purchased for much less, but there’s really no point to owning an inaccurate PAR meter.
The best way to get PAR values for your 400W LED grow light, assuming you don’t want to purchase your own PAR meter, is to check with your reputable grow light manufacturer or provider for the PAR rating of their lights.
How Much PAR do My Plants Need to Grow?
The amount of PAR your plants require depends on what you are growing, as well as how far away from your plants the light is. Generally speaking, leafy greens like lettuce only need a PAR value of ~200, whereas tomatoes and other plants that flower and produce fruit require 400-500 or more PAR. Unless you place your 600W LED grow light right on top of your produce, you will need an even higher PAR rating from your grow light, to take into account the distance between your plant and the light source.
In the example below, you can see a very powerful grow light that puts out nearly 1,900 PAR (measured in umol) 8 inches from the source. Very few lights put out this much PAR, and they are typically quite expensive. This light will emit 1,900 umol every second. But at 23 inches from the source, the strength of the light is reduced to 890 umol. The PAR value is reduced further and further as you get further from the light source. When we get to 6 feet away from the light source, our PAR value is down to ~100umol, which means we would have trouble growing even lettuce well. So, always make sure you understand not just the PAR emitted from the light, but that every 8 inches or so away from your light, the PAR value will be reduced by ½ or more.
There are many inexpensive grow lights on the market that make big claims, but they will ultimately leave their owners disappointed. This issue is especially rampant on the internet. Remember to check the PAR value of any light you purchase. Also, remember to take into account how far your light will be from your plant to ensure there is enough photosynthetically available radiation (PAR) for your plant to flourish.
Leafy Greens require 200 PAR for proper growth
Tomatoes, cucumbers and other flowering/fruiting vegetables require 400-500 PAR
Fruiting Trees should be given 600 PAR or more
What is the Temperature of Light I Should Use?
Interestingly, ‘Kelvin temperature’ is the metric used to describe the visual color that a light emits. As you can see in the chart below, ‘warmer’ light temperatures that have a red color have a lower Kelvin rating. On the other end of the spectrum are ‘cooler’ temperature lights which have a blue color and higher Kelvin rating.
Different temperatures of light have different impacts on plants. Generally, higher temperatures (blue) light encourages photosynthesis which leads to bushy plants that don’t feel inclined to elongate and reach for more light. This is great if you want to grow in a compact space. Lower temperature (red) light reduces photosynthesis and signals to plants that that it’s time to flower and produce fruit. Plants put under a red light will also be more inclined to stretch and grow taller, as opposed to growing bushier and more compact.
IGWorks focusses on providing full spectrum lights with a natural color temperature of between 4500K-6500K as these are most pleasing to the eye. They also allow plants to grow bushy and compact, without hindering the ability of plants to flower and fruit.
What Color of Light Should I Use?
LED lights can come in almost any color. Plants respond most to red and blue light. Interestingly, plants generally respond less well to green light. In fact, the reason that plants appear to be green is that they tend to reflect green light, while they absorb other parts of the light spectrum more readily. This is why a large scale or industrial grower of plants will often use a combination of red and blue lights to photosynthesize their plants. They don’t want to waste electricity producing green and even yellow light, which plants use less effectively.
However, for those of us growing produce in our living spaces, it’s probably worth the extra pennies it costs to produce a nice full-spectrum color that will be more natural and pleasing to the eyes. Full-spectrum grow lights will often come with a chart, which shows the distribution of blue, green, yellow and red light that is emitted. See the example below
Choosing the right grow light spectrum for your commercial operation can be a challenge. Many 800W LED grow light suppliers have conflicting information on the topic due to bad marketing or simply a lack of knowledge in plant and light research.
In this article, our light spectrum experts break down what light spectrum is, how plants respond to light, and how light spectrum influences plant growth.
What is Grow Light Spectrum?
Light spectrum is the range of wavelengths produced by a light source. When discussing light spectrum, the term ‘light’ refers to the visible wavelengths of the electromagnetic spectrum that humans can see from 380–740 nanometers (nm). Ultraviolet (100–400 nm), far-red (700–850 nm), and infra-red (700–106 nm) wavelengths are referred to as radiation.
As growers, we’re most interested in the wavelengths that are relevant to plants. Plants detect wavelengths that include ultraviolet radiation (260–380 nm) and the visible portion of the spectrum (380–740 nm) which includes PAR (400–700 nm), and far-red radiation (700–850 nm).
When considering light spectrum for horticultural applications, greenhouse and indoor environments will differ. With indoor environments your grow light’s spectrum will account for the total light spectrum that your crop receives. Whereas in a greenhouse you must consider that your plants are receiving a combination of folding grow light series and solar spectrum.
Either way, the amount of each waveband that your crop receives will have significant effects on growth. Let’s learn more about how this works.
Plants use light for photosynthesis and photomorphogenesis. Photosynthesis is the process by which plants and other organisms convert light energy into chemical energy. Photomorphogenesis refers to how plants modify their growth in response to light spectrum.
One example of photomorphogenesis is a plant bending toward a light source. Light also affects plants’ developmental stages, such as germination and flowering.
The light that plants predominately use for photosynthesis ranges from 400–700 nm. This range is referred to as Photosynthetically Active Radiation (PAR) and includes red, blue and green wavebands.
Photomorphogenesis occurs in a wider range from approximately 260–780 nm and includes UV and far-red radiation.
Although results are dependent on other factors, there are general rules of thumb that you can follow when using light spectrum to elicit different plant responses.
Outlined below is an overview of how each waveband is used for horticultural purposes so that you can trial light spectrum strategies in your own growth environment and with your chosen crop varieties.
Blue light has distinct effects on plant growth and flowering. In general, blue light can increase overall plant quality in many leafy green and ornamental crops.
A minimal amount of blue light is required to sustain normal plant development. In terms of adjustable spectrum lighting strategies, if we were to equate red light to the engine of your car, then blue light would be the steering wheel.
When combined with other light spectrum wavebands, blue light promotes plant compactness, root development, and the production of secondary metabolites. Blue light can be utilized as a growth regulator, which can reduce your need for chemical plant growth regulators (PGRs). Blue light can also increase chlorophyll accumulation and stomatal opening (facilitating gas exchange), which can improve overall plant health.
One example of blue light influencing secondary plant metabolite production is how blue wavebands promote anthocyanin development in leaves and flowers. Increased anthocyanin levels result in more pronounced color.
Blue light also promotes other secondary metabolic compounds associated with improved flavor, aroma and taste. For example, blue light treatments have been shown to improve terpene retention in some varieties of cannabis.
Higher intensities of blue light (>30 μmol·m-2·s-1) can inhibit or promote flowering in daylength-sensitive crops. Blue light does not regulate flowering at low light intensities (<30 μmol·m-2·s-1), so is safe to be applied at night to influence the other plant characteristics listed above
Since chlorophyll does not absorb green light as readily as other wavelengths, many have written off the green waveband as being less important to plant growth. This lower chlorophyll absorption rate, compared to blue and red light, is what makes most plants appear green. Depending on the plant, leaves generally reflect 10-50% of green waveband photons.
In contrast to assumptions, studies of green light in crop production have concluded that green light is important to photosynthesis, and especially in a plant’s lower leaves. Around 80% of green light transmits through chloroplasts, whereas leaves absorb approximately 90% and transmit less than 1% of red and blue light.
So what does this all mean? When light is plentiful, chlorophyll reaches a saturation point and can no longer absorb red and blue light. Yet, green light can still excite electrons within chlorophyll molecules located deep within a leaf, or within chloroplasts lower in the plant’s canopy. And so, green light enhances photosynthetic efficiency—potentially increasing crop yields, during bright light conditions.
Additionally, the ratio of green to blue and red wavelengths signals to the plant a leaf’s canopy position. This can induce morphological changes to maximize light absorption. Green light also plays a role in regulating stomatal aperture (opening and closing of plant pores that make gas exchange possible).
Greenhouse applications require less supplemental green light since plants receive adequate green light from solar radiation. Indoor environments may benefit more from supplemental green light since no sunlight is present.
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The air conditioning trap: how cold air is heating the world |
Posted by: Y456X - 09-24-2021, 02:14 AM - Forum: Welcomes and Introductions
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The air conditioning trap: how cold air is heating the world
The air conditioning trap: how cold air is heating the world
On a sweltering Thursday evening in Manhattan last month, people across New York City were preparing for what meteorologists predicted would be the hottest weekend of the year. Over the past two decades, every record for peak electricity use in the city has occurred during a heatwave, as millions of people turn on their air conditioning units at the same time. And so, at the midtown headquarters of Con Edison, the company that supplies more than 10 million people in the New York area with electricity, employees were busy turning a conference room on the 19th floor into an emergency command centre.
Inside the conference room, close to 80 engineers and company executives, joined by representatives of the city’s emergency management department, monitored the status of the city power grid, directed ground crews and watched a set of dials displaying each borough’s electricity use tick upward. “It’s like the bridge in Star Trek in there,” Anthony Suozzo, a former senior system operator with the company, told me. “You’ve got all hands on deck, they’re telling Scotty to fix things, the system is running at max capacity.”
Power grids are measured by the amount of electricity that can pass through them at any one time. Con Edison’s grid, with 62 power substations and more than 130,000 miles of power lines and cables across New York City and Westchester County, can deliver 13,400MW every second. This is roughly equivalent to 18m horsepower.
On a regular day, New York City demands around 10,000MW every second; during a heatwave, that figure can exceed 13,000MW. “Do the math, whatever that gap is, is the AC,” Michael Clendenin, a company spokesman, told me. The combination of high demand and extreme temperature can cause parts of the system to overheat and fail, leading to blackouts. In 2006, equipment failure left 175,000 people in Queens without power for a week, during a heatwave that killed 40 people.
This year, by the evening of Sunday 21 July, with temperatures above 36C (97F) and demand at more than 12,000MW every second, Con Edison cut power to 50,000 customers in Brooklyn and Queens for 24 hours, afraid that parts of the nearby grid were close to collapse, which could have left hundreds of thousands of people without power for days. The state had to send in police to help residents, and Con Edison crews dispensed dry ice for people to cool their homes.
As the world gets hotter, scenes like these will become increasingly common. Buying a VRF air conditioner is perhaps the most popular individual response to climate change, and air conditioners are almost uniquely power-hungry appliances: a small unit cooling a single room, on average, consumes more power than running four fridges, while a central unit cooling an average house uses more power than 15. “Last year in Beijing, during a heatwave, 50% of the power capacity was going to air conditioning,” says John Dulac, an analyst at the International Energy Agency (IEA). “These are ‘oh shit’ moments.”
There are just over 1bn single-room air conditioning units in the world right now – about one for every seven people on earth. Numerous reports have projected that by 2050 there are likely to be more than 4.5bn, making them as ubiquitous as the mobile phone is today. The US already uses as much electricity for air conditioning each year as the UK uses in total. The IEA projects that as the rest of the world reaches similar levels, air conditioning will use about 13% of all electricity worldwide, and produce 2bn tonnes of CO2 a year – about the same amount as India, the world’s third-largest emitter, produces today.
All of these reports note the awful irony of this feedback loop: warmer temperatures lead to more air conditioning; more air conditioning leads to warmer temperatures. The problem posed by air conditioning resembles, in miniature, the problem we face in tackling the climate crisis. The solutions that we reach for most easily only bind us closer to the original problem.
The global dominance of air conditioning was not inevitable. As recently as 1990, there were only about 400m air conditioning units in the world, mostly in the US. Originally built for industrial use, air conditioning eventually came to be seen as essential, a symbol of modernity and comfort. Then air conditioning went global. Today, as with other drivers of the climate crisis, we race to find solutions – and puzzle over how we ended up so closely tied to a technology that turns out to be drowning us.
Like the aqueduct or the automobile, air conditioning is a technology that transformed the world. Lee Kuan Yew, the first prime minister of independent Singapore, called it “one of the signal inventions of history” that allowed the rapid modernisation of his tropical country. In 1998, the American academic Richard Nathan told the New York Times that, along with the “civil rights revolution”, air conditioning had been the biggest factor in changing American demography and politics over the previous three decades, enabling extensive residential development in the very hot, and very conservative, American south.
A century ago, few would have predicted this. For the first 50 years of its existence, air conditioning was mainly restricted to factories and a handful of public spaces. The initial invention is credited to Willis Carrier, an American engineer at a heating and ventilation company, who was tasked in 1902 with reducing humidity in a Brooklyn printing factory. Today we assume that the purpose of air conditioning is to reduce heat, but engineers at the time weren’t solely concerned with temperature. They wanted to create the most stable possible conditions for industrial production – and in a print factory, humidity curled sheets of paper and smudged ink.
Carrier realised that removing heat from the factory air would reduce humidity, and so he borrowed technology from the nascent refrigeration industry to create what was, and still is, essentially a jacked-up fridge. Then as now, air conditioning units work by breathing in warm air, passing it across a cold surface, and exhaling cool, dry air. The invention was an immediate success with industry – textile, ammunition, and pharmaceutical factories were among the first adopters – and then began to catch on elsewhere. The House of Representatives installed air conditioning in 1928, followed by the White House and the Senate in 1929. But during this period, most Americans encountered air conditioning only in places such as theatres or department stores, where it was seen as a delightful novelty.
It wasn’t until the late 1940s, when it began to enter people’s homes, that the TICA air conditioner really conquered the US. Before then, according to the historian Gail Cooper, the industry had struggled to convince the public that air conditioning was a necessity, rather than a luxury. In her definitive account of the early days of the industry, Air-Conditioning America, Cooper notes that magazines described air conditioning as a flop with consumers. Fortune called it “a prime public disappointment of the 1930s”. By 1938 only one out of every 400 American homes had an air conditioner; today it is closer to nine out of 10.
What fuelled the rise of the air conditioning was not a sudden explosion in consumer demand, but the influence of the industries behind the great postwar housing boom. Between 1946 and 1965, 31m new homes were constructed in the US, and for the people building those houses, air conditioning was a godsend. Architects and construction companies no longer had to worry much about differences in climate – they could sell the same style of home just as easily in New Mexico as in Delaware. The prevailing mentality was that just about any problems caused by hot climates, cheap building materials, shoddy design or poor city planning could be overcome, as the American Institute of Architects wrote in 1973, “by the brute application of more air conditioning”. As Cooper writes, “Architects, builders and bankers accepted air conditioning first, and consumers were faced with a fait accompli that they merely had to ratify.”
Equally essential to the rise of the dunham bush air conditioner were electric utilities – the companies that operate power plants and sell electricity to consumers. Electric utilities benefit from every new house hooked up to their grid, but throughout the early 20th century they were also looking for ways to get these new customers to use even more electricity in their homes. This process was known as “load building”, after the industry term (load) for the amount of electricity used at any one time. “The cost of electricity was low, which was fine by the utilities. They simply increased demand, and encouraged customers to use more electricity so they could keep expanding and building new power plants,” says Richard Hirsh, a historian of technology at Virginia Tech.
The utilities quickly recognised that air conditioning was a serious load builder. As early as 1935, Commonwealth Edison, the precursor to the modern Con Edison, noted in its end-of-year report that the power demand from terminal air conditioner was growing at 50% a year, and “offered substantial potential for the future”. That same year, Electric Light & Power, an industry trade magazine, reported that utilities in big cities “are now pushing air conditioning. For their own good, all power companies should be very active in this field.”
By the 1950s, that future had arrived. Electric utilities ran print, radio and film adverts promoting air conditioning, as well as offering financing and discount rates to construction companies that installed it. In 1957, Commonwealth Edison reported that for the first time, peak electricity usage had occurred not in the winter, when households were turning up their heating, but during summer, when people were turning on their air-conditioning units. By 1970, 35% of American houses had air conditioning, more than 200 times the number just three decades earlier.
At the same time, air-conditioning-hungry commercial buildings were springing up across the US. The all-glass skyscraper, a building style that, because of its poor reflective properties and lack of ventilation, often requires more than half its electricity output be reserved for air conditioning, became an American mainstay. Between 1950 and 1970 the average electricity used per square foot in commercial buildings more than doubled. New York’s World Trade Center, completed in 1974, had what was then the world’s largest AC unit, with nine enormous engines and more than 270km of piping for cooling and heating. Commentators at the time noted that it used the same amount of electricity each day as the nearby city of Schenectady, population 80,000.
The air-conditioning industry, construction companies and electric utilities were all riding the great wave of postwar American capitalism. In their pursuit of profit, they ensured that the light commercial air conditioner became an essential element of American life. “Our children are raised in an air-conditioned culture,” an AC company executive told Time magazine in 1968. “You can’t really expect them to live in a home that isn’t air conditioned.” Over time, the public found they liked air conditioning, and its use continued to climb, reaching 87% of US households by 2009.
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Why is fiberglass mesh needed? |
Posted by: Y456X - 09-24-2021, 02:12 AM - Forum: Welcomes and Introductions
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Why is fiberglass mesh needed?
Why is fiberglass mesh needed?
Composite sheets of fiberglass mesh for marble reinforced polycarbonate were prepared by hot compress molding. The effects of lay-up structure, lay-up angle, area density of fiberglass mesh and the thickness of PC film on tensile property were studied. The results reveal that the alternative lay-up structure of reinforcement mesh and matrix film is optimal and tensile property declines as lay-up angle increases. Fiberglass mesh with lower area density is appropriate for thinner composites. Composite sheets fabricated with thinner PC film show better tensile property. SEM analysis shows that alternative lay-up structure is favorable to the immersion of the fiber bundle of marble mesh cloth with low area density in the melting matrix, and thus the improvement of tensile property.
This paper investigates the effect of surface treatment for glass fiber, stainless steel wire mesh on tensile, flexural, inter-laminar shear and impact properties of glass fiber/stainless steel wire mesh reinforced epoxy hybrid composites. The glass fiber fabric is surface treated either by 1 N solution of sulfuric acid or 1 N solution of sodium hydroxide. The stainless steel wire mesh is also surface treated by either electro dissolution or sand blasting. The hybrid composites are fabricated using epoxy resin reinforced with glass fiber and fine stainless steel wire mesh by hand lay-up technique at room temperature. The hybrid composite consisting of acid treated glass fiber and sand blasted stainless steel wire mesh exhibits a good combination of tensile, flexural, inter-laminar shear and impact behavior in comparison with the composites made without any surface treatment. The fine morphological modifications made on the surface of the glass fiber and stainless steel wire mesh enhances the bonding between the resin and reinforcement which inturn improved the tensile, flexural, inter- laminar shear and impact properties.
The fiberglass mesh filter is an inorganic non-metallic material with excellent performance. It has a wide variety of advantages. The advantages are good insulation, strong heat resistance, good corrosion resistance, and high mechanical strength, but its disadvantages are brittleness and poor wear resistance. It is made of glass balls or waste glass as raw materials through high-temperature melting, drawing, winding, weaving, and other processes. In this article, we will take a closer look at the characteristics and types of fiberglass mesh filters.
Characteristics of Fiberglass Mesh Filters
The filter has high tensile strength and low elongation (3%).
The filter has a high elastic coefficient and good rigidity.
The filter has large elongation within the elastic limit and high tensile strength, so it can absorb impact energy.
The filter is made of inorganic fiber, which is non-flammable and has good chemical resistance.
Its water absorption is small.
High-temperature resistance.
High filtration efficiency.
Types of Fiberglass Mesh Filters
ULPA(Ultra Low Penetration Air) Filter
ULPA (Ultra Low Penetration Air) filter has a filtration efficiency of more than 99.999% for 0.1~0.2μm particles, smoke and microbes, and other dust particles.
ULPA filter characteristics: Its filter element is made of ultra-fine glass fiber filter material by gluing and folding. The outer frame can be made of laminated wood, galvanized copper, stainless steel, and aluminum alloy, and it is tightly bonded by polyurethane glue. It has the characteristics of lightweight, large air permeability, dust collection rate as high as 99.95-99.999%, and alkali resistance, and high-temperature resistance.
ULPA filter applications: It is suitable for class 10000-100 clean systems, air conditioning systems, so the product has been widely used in electronics, microelectronics, semiconductors, optical devices, biological and medical circuits, cameras, and optical instruments, precision machinery, and other fields.
High-Temperature Air Filter
The high-temperature air filter still has a partition structure. It is assembled with high-temperature resistant glass fiber or ultra-fine glass fiber filter paper, aluminum foil partition, stainless steel frame, and special high-temperature resistant sealant.
High-temperature air filters are mainly used in ultra-clean ovens that require drying in the production process of food, pharmaceuticals, etc., or high-temperature air purification equipment and systems. The maximum working temperature is 350 degrees.
High Humidity Resistant Air Filter
The high-humidity air filter has a partition structure, using special moisture-proof ultra-fine glass fiber filter paper, special rubber sheet or aluminum foil partition, galvanized sheet, or aluminum alloy profile frame. It is suitable for high humidity under normal temperature and pressure, especially in high humidity environments such as infusion production in the pharmaceutical industry. The maximum working humidity is 100%.
The Disadvantage of Fiberglass Mesh Filters
Due to the poor ductility of glass fiber, the glass fiber filter is easily damaged, so be careful when installing it.
Conclusion
Thank you for reading our article and we hope it can help you to have a better understanding of the characteristics and types of marble fiberglass cloth. If you want to learn more about fiberglass mesh filters, we would like to advise you to visit Stanford Advanced Materials (SAM) for more information.
As a leading supplier of fiberglass mesh filters across the world, SAM enjoys over two decades of experience in the manufacture and sale of fiberglass mesh filters, offering customers high-quality fiberglass mesh filters to meet their R&D and production needs. As such, we are confident that SAM will be your favorite fiberglass mesh filter supplier and business partner.
Fiberglass mesh is a neatly woven, crisscross pattern of fiberglass thread that is used to create new products such as tape and filters. When it is used as a filter, it is not uncommon for the manufacturer to spray a PVC coating to make it stronger and last longer. The most common place to find fiberglass mesh is in tape products.
Sheetrock finishers use the mesh frequently. In fact, it is common to replace the paper tape used to float the joint between two pieces of sheetrock. The mesh that sheetrock finishers use comes on a roll just like paper sheetrock tape. The added benefit for the sheetrock finisher is to roll out the mesh over a great distance before having to apply the first coat of joint compound. Not only does it help them in this manner, but it also causes a stronger bond between the joint compound, the tape and the wall.
Sheetrock finisher's also use this tape to patch holes. The most common hole in the sheetrock generally occurs where a doorknob has hit a wall too many times. If it is only slightly damaged, a couple of short pieces of the tape will be formed into a square and placed over the hole. A joint compound will then be applied directly to it. If the hole is too large to patch with fibreglass mesh for wall alone, a piece of metal flashing can be added behind the tape before applying joint compound. Construction work is not the only use for fiberglass mesh.
As a filtering system, fiberglass mesh works really well. As the water flows through it, the mesh catches even the smallest impurities. In addition to this use, it can also be used as a mosquito net.
Finally, fiberglass mesh is sometimes woven into protective clothing used by those who work with dangerous chemicals or firefighters. Tightly woven mesh is put together and shaped into jackets that firemen wear when they are battling a blaze. It protects them from any fire that might ignite their clothing while fighting a fire. Fiberglass mesh can also be used in mold making and as protection against corrosives.
In your letter dated January 31, 2008, on behalf of your client, SpiderLath, Inc., you requested a tariff classification ruling on a woven fiberglass article. A sample of a piece of the material comprising this product was submitted with your ruling request.
The subject article, identified as “SpiderLath”, is a woven fiberglass mesh/fiberglass lath system with ethylene vinylacetate (EVA) backing strips that will be imported in rolls 4 feet wide by 75 feet long. You indicated in a telephone conversation that the fiberglass mesh is coated with a stiffener.
According to the information that was submitted with your ruling, the fiberglass mesh/fiberglass lath system is used as a cladding masonry support. The product can be used to install stucco and stone veneer. It can also be used over existing surfaces to apply masonry finishes.
In your presentation, you suggest classification under subheading 7019.31.0000, Harmonized Tariff Schedule of the United States (HTSUS), which provides for glass fibers (including glass wool) and articles thereof...thin sheets (voiles), webs, mats, mattresses, boards and similar nonwoven articles: mats. This subheading does not apply since the product is a woven article.
The applicable subheading for the woven fiberglass mesh for construction/fiberglass lath system with EVA backing strips will be 7019.90.1000, HTSUS, which provides for glass fibers (including glass wool) and articles thereof (for example, yarn, woven fabrics (con.): other: woven. The rate of duty will be 4.8 percent ad valorem.
Duty rates are provided for your convenience and are subject to change. The text of the most recent HTSUS and the accompanying duty rates are provided on World Wide Web at http://www.usitc.gov/tata/hts/.
This ruling is being issued under the provisions of Part 177 of the Customs Regulations (19 C.F.R. 177).
A copy of the ruling or the control number indicated above should be provided with the entry documents filed at the time this merchandise is imported. If you have any questions regarding the ruling, contact National Import Specialist Jacob Bunin at 646-733-3027.
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What is a rod seal? |
Posted by: Y456X - 09-24-2021, 02:11 AM - Forum: Welcomes and Introductions
- No Replies
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What is a rod seal?
What is a rod seal?
There are so many different types of seals out there that it might be hard to understand all the different terminologies and functions. In this article, we give you our guide to what rod seals are, how they are manufactured and why you should choose rod seals from Martin’s Rubber.
Rod seals are often the decisive factor in ensuring that a hydraulic cylinder operates at peak performance. Leakage through the rod seal can lead to environmental damage and accidents, which is why it’s crucially important to select the correct seal for your application. While leakage past a piston seal will affect its efficiency, the system fluid or gas remains contained in the system. With a rod seal, failure will allow external leakage, and it should be paired with an appropriate wiper and gland housing design to ensure correct operation.
How do rod seals work?
Rod seals perform the difficult balancing act of creating a seal at both high and low pressure. This is often in combination with alternating high and low temperatures. As such, they need to leave an oil film, thin enough to return into the cylinder, after having passed an effective wiper seal. When selecting a piston rod seals, it is important to define your area of application and provide carefully defined specifications. Martin’s Rubber can then give you our recommendations for an appropriate rod seal to match your specific operating conditions.
How are rod seals manufactured?
Our rod seals can be CNC machined to bespoke sizes, including making adjustments away from original seal sizes to compensate for worn rod or gland conditions. Plus, we can help to restore the original performance of used equipment, as well as provide components for new build designs. Our standard rod seals can be rapidly manufactured in a variety of different materials, depending on your application. We also stock standard products for immediate shipment if your requirements are particularly time critical.
Why choose our rod seals?
“What sets us apart, I think, is that we’re flexible,” says Adam Hooper, Operations Director at Martin’s Rubber. “We deliver the quality that people need in the most responsive way possible, and we add value in terms of engineering and creative input,” he adds. Contact one of our expert advisers today on 023 8022 6330 or email sales@martins-rubber.co.uk to discuss your rod seal requirements.
Designers often specify buffer seals be placed in front of primary rod seals in heavy-duty hydraulic applications to extend the life of the seals. As the name indicates, buffer seals “absorb” pressure spikes typical on heavy-duty cylinders to protect the primary rod seals.
But how do these two types of seals interactions interact, which parameters affect those interactions, and how can they be used to extend the life of cylinder rod-sealing systems?
What was learned during these investigations will give engineers insights into seal types and interactions between seals so they can specify the most appropriate seals for their applications.
The key element of the buffer seal is the lubrication film thickness which passes the sealing edge. It is responsible for the performance of the entire rod sealing system. Different pressure and speed conditions during the in- and outstroke of the piston rod are typical for heavy-duty hydraulic cylinders and result in different oil film thickness. Therefore, the buffer seal needs to be designed to ensure a hydraulic cylinder rod step seals and absorb pressure peaks during operation.
Generally, buffer seals use one of two basic design principles:
High sealability buffer seals have good sealing abilities and can handle all of the system pressure and possible pressure peaks. Therefore, the primary rod seal will not be pressurized and can’t be damaged by pressurization. The seal’s high sealability means only a thin film of lubrication film can pass it, which could cause starve the primary rod seal of lubrication. This can lead to stick-slip, higher friction and sealing-edge temperatures, and possibly damage to the sealing material, all of which shorten the rod seal’s life.
Friction optimized buffer seals let thicker oil film pass the sealing edge to properly lubricate the primary rod seal. Depending on operating conditions, they can also let pressure build-up between the primary rod and buffer seals (intermediate pressure).
These buffer seals should keep out system pressure, because if the intermediate pressure is equal to system pressure, it cannot buffer. It is also important to use a primary rod seal and a wiper for good sealing and back-pumping ability to guarantee a leak-tight system.
An additional advantage of this type of seal is that the primary cylinder rod seals SPNO gets better lubrication, leading to smooth running equipment. If the buffer and primary rod seal work together correctly (as described above), friction in the entire rod sealing system can be similar to that of a single rod seal component. Reducing friction extends the life of the rod seal and the entire hydraulic cylinder.
Both working concepts have their place. Friction optimized buffer seals might be best in OEM components to extend a hydraulic cylinder’s service life. But high-sealability buffer seals might be more suitable in the aftermarket, where repair work and maintenance on hydraulic cylinders is more common and a leak-tight rod seal is more important.
Buffer Seal Designs
There are many different buffer seal designs and various material combinations available on the market. Here are the three most common designs.
Lip seals with back-up rings. These seals are good in heavy duty applications, where pressure spikes climb past 600 bar. The best lip seals are made of polyurethane with a thermoplastic back-up ring. This design enjoys a longer service life because the back-up ring resists extrusion. On the other hand, the back-up ring can influence the motion of the film of fluid on the piston rod, and seal installation requires more attention.
O-ring energized glide ring seals. These seals are widely used in light- to medium-duty application. Generally, the O-ring acts as an energizer to push the glide ring towards the piston rod. A big advantage of this is that various materials can be used. For example, a low temperature rubber grade can be used for cold climate conditions. The various material combinations give designers a wide choice. These seals have less resistance to extrusion compared to those with back-up rings.
The buffer seal’s main task is keeping the lubrication film thickness that passes through the seal’s edge at the right thickness. According to the Reynolds equation, the flow of a thin film oil/lubricant between two surfaces is influenced by its velocity, the gradient of the contact pressure distribution and the oil’s viscosity.
An important aspect of the investigations was to understand lubrication behavior under different test parameters. The lubrication level of lubrication determines friction and is essential for seal life. On the other hand, the lubrication level also determines the number and size of leaks, which should be minimized for the sake of performance and environmental concerns.
The influence of different in- and outstroke velocities has already been analyzed for a common U Cup rod seals ISI (see above graph). The results show that if outstroke velocity is much higher than instroke velocity, the likelihood of leaks increases. On the other hand, if instroke velocity is much higher than outstroke velocity, it is more likely the low-level of lubrication will increase friction on the instroke.
The second driver for the lubrication film thickness is contact pressure between the seal and piston rod. The higher the pressure gradient, the thinner the film. The gradient is influenced by seal design, the pressurization level, and the resulting deformation and dynamics between piston rod and seal.
The third driver for the lubrication film thickness is the lubricant’s viscosity. The lower the viscosity, the thinner the lubrication film.
In the second installment of this series, tests will be set up and run and the results analyzed, revealing what factors of buffer seals matter most to rod seal performance and longevity.
Thomas Schwarz is manager of testing, materials technologies & research; Wolfgang Swete is manager of product technology and development; Silvio Schreymayer is manager of testing; Martin Wallner is the manager of product development; Emmanuel Pichlmaier is a product development engineer; and Michael Liebminger is a testing engineer for SKF Seals.
The rod seal of a hydraulic cylinder is a crucial component as it controls leakage directly into the environment. Several testing methods can be used to detect a decreasing sealing ability, even before measured leakage occurs. This feature article describes the results of leakage measurements, pumping rate measurements and film thickness measurements on the rod surface. The differences between the individual methods are described and discussed, and also compared with predictions from finite element calculations.
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Contact lenses: a look at the risks and recommendations |
Posted by: Y456X - 09-24-2021, 02:10 AM - Forum: Welcomes and Introductions
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Contact lenses: a look at the risks and recommendations
Contact lenses: a look at the risks and recommendations
Thanks to the existence of contact lenses, it can sometimes be impossible to tell if someone has a visual impairment or not. These lenses can make huge differences to the lives of their wearers, providing a certain level of freedom that traditional glasses are unable to.
According to the Centers for Disease Control and Prevention (CDC), around 41 million people in the US wear contact PC lenses.
While they might feel like a relatively modern invention, rigid contact lenses made from plastic were first manufactured in the US between 1938 and 1940. The soft contact lenses currently worn by an estimated 93% of contact lens wearers were first introduced in 1971.
On a personal level, I first started wearing them as a temporary measure when my declining eyesight made playing sports difficult. However, no longer having my vision affected by raindrops and fogging up (along with the boost in self-esteem that came from not wearing glasses) meant that contact lenses quickly became my main method of improving my vision.
But despite their prevalence and the benefits they can provide, many people (myself included) wear contact lenses in a way that can compromise eye health, increasing the risk of damaged corneas and infection from microbes.
This week has marked the second annual Contact Lens Health Week – a week organized by the CDC to increase public awareness and promote healthy wearing and caring of contact lenses. In this Spotlight, we take a brief look at a few of the “do’s and don’t’s” of contact wear. In addition, we will have a look at some of the interesting “can’s and can’t yet’s” of new contact lens innovations.
Healthy habits mean healthy eyes
Although they are similarly effective at improving vision as glasses, contact Pc anti fog lens wearers can be more at risk of eye complications than those who use glasses. If wearers do not follow contact lens care instructions properly, they can put themselves at risk of serious eye infections that can lead to blindness.
The CDC have previously reported that between 40-90% of contact lens wearers do not properly follow their contact lens care instructions, which may explain why serious eye infections affect around 1 in 500 contact lens wearers each year.
Many people compromise their visual health due to bad habits when it comes to wearing contact lenses. While it is easy to manhandle glasses, contact lenses need to be afforded a greater level of care.
This means washing hands with soap and water and drying them comprehensively before ever touching contact lenses. Doing so prevents the transfer of germs from the hands to the lenses and consequently the eyes.
Exposing the lenses to water should be avoided as water can carry bacteria and other microbes that cause infection. With soft contact lenses, water can also alter the shape of the lens and potentially damage the cornea. As a result, contact lens wearers should remove their lenses before showering, swimming or using hot tubs, as tempting as it may be to keep them in.
One particular germ, an ameba called Acanthamoeba, is typically found in tap water as well as other water sources. If it causes infection (Acanthamoeba keratitis), patients can require a year or more of treatment, and possibly a corneal transplant.
Another bad habit that should be avoided where possible – unless prescribed by a doctor – is sleeping in contact PC super blue cut lens. In addition to making the eyes feel uncomfortable, sleeping in any type of lens increases the wearer’s risk of a corneal infection known as microbial keratitis by between four and five times.
Fast facts about keratitis
Keratitis is inflammation of the cornea, the clear tissue that covers the pupil and iris
Keratitis can be caused by infectious microbes or by minor injuries to the cornea
In severe cases, keratitis can permanently damage an individual’s vision.
This risk extends to the wearers of contact lenses that are designed to be slept in. Recently, the story of a man who went blind in one eye after sleeping in contact lenses for almost a week has come to the media’s attention.
“The kind of contacts I have are called ‘Night and Day’ contacts,” Chad Groeschen explained to USA Today, “and it was my impression you could leave them in for 30 days straight. I figured the less I was messing with my eyes, the better.”
While people can opt to use disposable lenses that are designed to be worn daily, many choose to wear lenses that last for longer periods and need to be stored properly when not in use. Unsurprisingly, many eye problems arise from bad habits pertaining to the storing of contact lens and associated products.
Contact lenses need to be kept clean if they are going to be used for multiple days. Lenses should be cleaned using a specific contact lens disinfecting solution and never water or saliva, as should the case that the lenses are stored in when not in use.
The CDC report that fewer than half of contact lens wearers report always cleaning their contact PC blue cut lens cases, and the number of moderate to severe lens-related infection could be halved if case cleaning practices were improved. Contact lens cases should also be replaced at least once every 3 months.
Contact lenses are stored in a purpose-built solution that is recommended by an eye care specialist. Contact lens wearers should stick to the recommended solution as the recommendation will be based upon the wearer’s eyes and medical history. Water should never be used, again due to the fact that it can increase the risk of infection.
Old solution in a lens case should never be “topped off” with new solution – instead, only fresh solution should be used. Solution can become contaminated with microbes that cause infections, and simply adding fresh solution to old solution reduces how effective it is at eradicating germs.
According to the results of a recent CDC study, these bad behaviors are incredibly prevalent. The Contact Lens Risk Survey was completed by approximately 1,000 contact lens wearers, and around 99% of respondents reported at least one behavior associated with an increased risk of eye infections.
“Good vision contributes to overall wellbeing and independence for people of all ages, so it’s important not to cut corners on healthy contact lens wear and care,” reports CDC Medical Epidemiologist Dr. Jennifer Cope. “We are finding that many wearers are unclear about how to properly wear and care for contact lenses.”
The following figures illustrate how prevalent some risky behaviors were among survey respondents:
Napping while wearing contact lenses – 87.1%
Showering while wearing contact lenses – 84.9%
Not replacing contact lens cases as frequently as recommended – 82.3%
Swimming while wearing contact lenses – 61.0%
“Topping off” contact lens solution – 55.1%
Sleeping in contact lenses overnight – 50.2%.
“Nearly one third of all wearers reported ever having experienced a contact lens-related red or painful eye that required a doctor’s visit,” the researchers write.
Considering how common contact lenses have become, the figures produced by the CDC’s study are significant, illustrating just how important it is that people become more aware of how contact lenses should be used and the impact bad practice can have on health.
The health problems that can be caused by risky contact lens behaviors may be enough to put some people off wearing them. However, there are a number of other benefits that specific types of contact lenses can provide that no other devices are able to.
Contact lens designs have become more sophisticated over time. While original products may have only been able to correct nearsightedness (myopia) and longsightedness, newer models of lens can be used to treat and monitor additional conditions that affect the eyes.
Orthokeratology, also known as Ortho-K, is a PC clear lens fitting procedure that offers a temporary degree of vision correction by changing the curvature of the cornea to improve its ability to focus on objects.
Altering the cornea’s curvature is achieved through the use of specially designed rigid contact lenses that are typically worn overnight. Ortho-K lenses are most commonly used to correct myopia.
Some people wear multifocal glasses because they have a condition known as presbyopia, whereby the eye’s ability to focus on nearby objects is lost. However, the condition can also be treated with multifocal contact lenses.
There are two main designs for these types of lenses. Alternating vision lenses have two distinct areas for short- and long-distance prescriptions. The pupil alternates between the two different prescriptions as the wearer’s gaze shifts up or down.
Simultaneous vision lenses involve the pupil looking through short- and long-distance prescriptions simultaneously. The two prescriptions can either be laid out in alternating concentric rings or blended together across the lens.
Presbyopia is one condition that a “smart lens” being developed by Google and Novartis should hopefully address. Last year, Novartis suggested that the use of technology such as noninvasive sensors and microchips contained within the lens could “provide accommodative vision correction” to restore the eye’s ability to focus.
Their smart lens might also provide benefit outside of visual health. Novartis stated that such a lens could provide a continuous measurement of glucose levels in diabetic patients and deliver this information to a mobile device using a wireless connection.
“We are looking forward to working with Google to bring together their advanced technology and our extensive knowledge of biology to meet unmet medical needs,” announced Novartis CEO Joseph Jimenez. “This is a key step for us to go beyond the confines of traditional disease management, starting with the eye.”
One of the most frequently repeated recommendations concerning contact lenses is that wearers should always follow the advice of their eye care providers. Unlike glasses, contact lenses are in direct contact with an opening into the human body, and as such there are far more things that could go wrong from a health perspective.
When used correctly, contact lenses can have a transformative effect on the wearer’s quality of life. The same can be said for when they are used incorrectly, only for wholly different and more unpleasant reasons.
It does not take much time to wash hands before handling lenses, to remove them before showering or to clean out a storage case properly, and yet by skipping these simple steps, thousands of contact lens wearers are putting their vision at risk. Follow the advice of eye care providers and vision can be protected for years to come.
Previously, Medical News Today reported on a study that suggested wearing contact lenses may alter the microbiome of the eye.
Once an optometrist has confirmed a diagnosis of myopia, several treatments are available. Speaking to an optometrist can help a person decide on the best option for them.
The sections below will discuss some of these treatment options in more detail.
Glasses and contact lenses
Glasses and contact lenses are the most common treatment options for myopia. An optometrist will order custom lenses that have the right prescription for that person. These will fit into the frame of the glasses and correct any nearsightedness.
Contact lenses are clear discs that sit on the surface of the eye. Like glasses, contact lenses are also customizable for different prescriptions.
Many people who do not like the look or feel of glasses will choose to have contact lenses, as they are a lot smaller and harder to notice. However, it is necessary to change and clean them regularly.
Orthokeratology
People with mild forms of myopia may benefit from a nonsurgical process called orthokeratology, or corneal refractive therapy. This treatment involves wearing a series of rigid contact lenses to reshape the cornea.
These lenses put pressure on the cornea to flatten it. This, in turn, changes how light focuses as it enters the eye. People tend to wear these contact lenses while sleeping.
This process can help people experience clear vision temporarily. However, it also carries a risk of eye infections.
Surgery
There are a couple of different types of surgery available to people who would rather not wear glasses, who want a more permanent solution, or who have severe forms of myopia.
One form of surgery is laser surgery, wherein an eye doctor will use a powerful beam of light to change the shape of the cornea.
Laser surgery adjusts how the eye focuses light, meaning that images that were once blurry should now be clear.
The surgery takes around 10 minutes per eye. This option can be expensive, but it is usually painless. Vision should return to normal within a day or so of the surgery.
However, it is normal to have occasional blurred vision or dry eyes for weeks or months afterward. Attending follow-up appointments after this procedure is important to make sure that the eyes are healing properly.
Other forms of surgery can involve placing a PC photochromic blue cut lens inside the eye, either in front of the person’s lens or in place of it. Eye doctors tend to recommend this form of surgery for more severe forms of myopia.
Prevention
Given that myopia has genetic links, it can be hard to prevent in people who have a history of nearsightedness in their family.
Spending time outside, in the daylight, could help lower the progression of myopia. Making sure not to spend too much time doing up-close work, such as reading or working on a computer, can also help.
Outlook
In most cases, myopia does not cause any further health problems. There are a range of treatments available that allow people to experience no symptoms of the condition in their daily lives.
For those who have more severe forms of myopia, it is important that they tell their optometrist about any changes in their vision. Without treatment, they could be at risk of developing additional eye problems, or even vision loss.
There is evidence that both genes and environmental factors, such as spending less time outdoors and more time indoors reading and using computers, can increase the risk of myopia. Before this study, however, it was not clear what the underlying molecular mechanisms were.
One way to observe the biological development of myopia or hyperopia is by altering the focal length of the eye in laboratory animals. Specialists can do this by placing a lens in front of the eye for several weeks.
Depending on the type of lens, the exposure causes the eye to develop to a length that is either too long or too short.
The scientists used this method in marmosets to study the development of myopia and hyperopia. They placed a PC photochromic lens in front of only one eye for up to 5 weeks and let the other eye develop normally for comparison.
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What Is A Seed Tray? |
Posted by: Y456X - 09-24-2021, 02:08 AM - Forum: Welcomes and Introductions
- No Replies
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What Is A Seed Tray?
What Is A Seed Tray?
Starting your own plants from seed will often give you healthier plants at a lower cost. If you want to start seeds in bulk, you may want to consider a seed tray to help with germination.
So, what is a seed tray? A seed tray is a container used to sow multiple seeds at once. After seed germination, seedlings grow in the seedling tray until they are large enough for transplant. A single seed tray can hold anywhere from 6 seeds to over 1000 seeds!
Of course, when choosing a seed tray, there are lots of options for the material, the type of tray, and the number of cells.
In this article, we’ll talk about seed trays and the options that are available. We’ll also get into how to use seed trays and how to water the seeds and seedlings.
Let’s get going.
What Is A Seed Tray?
A seed tray is a container that is used to plant multiple seeds at once. A seed tray is sometimes called a seed starting tray.
A seed tray allows you to plant many seeds together in one container. This makes it much easier to water them and transport them.
After the seeds germinate, the seed tray holds seedlings as they grow, until they are ready for transplant outdoors or into larger containers.
There are a few different types of seed trays, including:
Mesh seed tray – a mesh seed tray allows water to drain out easily. A mesh seed tray is best for holding multiple individual containers (pots). A drawback is that the holes in a mesh seed tray are too large to hold soil without it falling through or washing away when watered. You can find mesh seed trays from Johnny’s Selected Seeds.
Solid seed tray with drainage holes – a solid seed tray with drainage holes allows for adequate drainage, but allows soil to stay moist enough for seed germination. A solid seed tray with drainage holes is best for planting multiple seeds together in one place. A drawback is that the seedlings do not have individual cells, so their roots can get tangled together as they grow. You can find solid seed trays with drainage holes from Johnny’s Selected Seeds.
Solid seed tray without drainage holes (leak proof seed tray) – a solid seed tray without drainage holes does not allow for any drainage. A solid seed tray without drainage holes is best for holding a cell flat (also called a plug flat). Since it holds water, it can be used to catch excess water from watering seeds, or it can be used to water from below (more detail on this later). You can find cell seed trays without drainage holes from Johnny’s Selected Seeds.
Another interesting option is this seed flat with 20 rows from Johnny’s Selected Seeds. Instead of separate cells, there are separate rows to keep different plant varieties from getting mixed up.
If you decide to use a cell flat for seed germination, each cell should have its own drainage hole. The tray below the cell flat should be solid without holes if you want to water the seeds from below.
The main problem of adapting the SRI techniques is high labor requirements for manual and lacking of mechanized system for planting single seedling in the field. The existing seedling preparation methods remain challenging among SRI practitioners due to traumatic condition. This study was intended to create modern techniques for increasing the quality and transplanting potentials to improve seedling preparation and reduce transplanting shock. It involved development of rectangular tray having 924 square growing cavities with sliding base to facilitate seedling transfer. Seed selection was conducted and 100% germination was obtained from the sunken MR219 seeds collected in 80 g/L of NaCl solution. SRI-tray seeding was 100% placed into cavities with SRI-seed picker at 150 g/L of tapioca solution. Two different media (Soil + Burnt husk (1:1) as M1 and Soil + Compost (1:1) as M2) were used to evaluate the growth performances for 10 days. The measured parameters (Seedling Height (SH), Leaf Length (LL), Leaf Number (LN), Root Length (RL) and Loosening Index (LI)) were compared between SRI-tray and conventional ones. The SAS revealed that M2 on SRI-tray had the highest significant values for SH, LL, RL and LI with the mean values of 155.6, 109.3, 89.3 and 75 sec when compared with conventional tray which had 125, 91 and 52 mm with no LI, respectively. The seed rate, nursery area and seedling age to support one hectare of planting area were found as 5.34 kg, 36 m2 and 8-10 days on SRI-tray against 15-50 kg, 250-500 m2 and 12-30 days on conventional practices.
The more pellets that are placed in the mould, the denser and stronger the seedling tray with lids.
In cheaper trays, there tend to be slightly bigger gaps between the expanded pellets, and fine plant roots can enter these, making it difficult to pull out the plants.
Damping off organisms can also lurk in these small spaces, and the growing plants can become infected and die. One of the Pythium species (fungus-type pathogens) is usually the main culprit, but it’s not the only one.
I have used horse manure compost as a medium for 23 years and have never had damping off problems. This may be because the medium is a rich source of beneficial organisms, which suppress development of pathogens. I also never get powdery mildew on Brassica seedlings.
Once the pathogen has appeared, the trays must be sterilised, or the problem will keep cropping up and possibly cause major losses.
The most effective way of sterilising trays is in a heat chamber. To save cost and effort, some growers wait until damping off starts before using heat sterilising.
Another solution is to use a commercial dip containing copper; this will also reduce the penetration of roots into the fine gaps in the polystyrene.
If you are a small grower, you can use a simple, home-made steriliser such as bleach mixed with water at a 10% solution, or hydrogen peroxide at 3% concentration. Leave the trays suspended in the solution for 20 minutes, then rinse and dry them.
The ideal sealant
One of the most effective ways of treating seedling trays is to dip them in a water-based roof paint when they are still new.
Obtain a flat receptacle slightly larger than the tray and dilute the paint with 10% water. Push the tray face down into the paint until the paint reaches the drainage holes. Lift and allow the excess paint to drip back into the tray, then place it face-up to dry. (It’s unnecessary to paint the base.) You should be able to coat about 10 trays per litre.
Some farmers are put off by the price of paint, but this treatment is well worth the cost: not only does it extend the life of the rice seedling tray by many years, but it seals the fine gaps in the polystyrene.
This reduces the risk of pathogens lurking in these crevices and also makes it much easier to pull out the seedlings.
Roof paints come in many colours, so you can use different colours for different years to keep track of the lifespan of each batch of styrofoam seed trays. There are often specials on roof paints and you can take advantage of these to cut the costs of the treatment.
Biodegradable plastics have been widely introduced into agricultural production, but their impacts on the soil ecosystem remain unclear. The present study investigated the impacts of a biodegradable seedling tray (BST) on the microbial communities in paddy soils. A 110-day rice culture experiment was conducted with three different paddy soils developed from black soil (BS, black chernozem soil), chao soil (CS, Fluvo-aquic) and red soil (RS, Alfisols) and three application rates of BST (0, 0.02 and 0.2?g?kg?1). Soil phthalic acid ester (PAE) concentrations, physicochemical properties and enzyme activities were determined to evaluate the influence of BSTs on soil quality. 16S high-throughput sequencing was used to study bacterial community composition and the Biolog EcoPlate? test was used to profile microbial activity and community function. Results show that the application of BSTs did not markedly affect soil quality, and the potential release of PAEs from BSTs was negligible. Interestingly, the microbial community was affected by BSTs in a soil-dependent and time-dependent pattern. The microbial community in RS was not significantly influenced by BSTs. Relative abundances of some predominant genera in BS (e.g. norank_f__BSV40) and CS (e.g. Norank_f__Nitrosomonadaceae) were significantly influenced by BSTs, and db-RDA results show that community composition in BS and CS was shaped mainly by BSTs. Community level profiling shows that BSTs significantly increased microbial activity and decreased functional diversity in BS after 55?days, but the impacts disappeared after 110?days. The results contribute to the knowledge of how biodegradable plastics influence microbial communities in paddy fields and provide information relevant to the practical use of BSTs under field condition.
This experiment investigated the effect of different plug-tray cell designs on root development of red maple (Acer rubrum), red oak (Quercus rubra), and quaking aspen (Populus tremuloides) seedlings. In April of 2015, seeds of each species were sown into three plug trays with different substrate volumes and grown for 17 weeks. Two trays had permeable walls for air-pruning, one with vertical ribs and one without. The third tray had impermeable plastic cell walls. Harvested seedlings were analyzed for root dry weight, length, volume, surface area and number of deflected roots. Root length per volume was highest in the impermeable-walled tray for red maple and quaking aspen. The total numbers of deflected root systems were higher for all species in the impermeable-walled tray. Seedlings grown in the air-pruning trays had smaller proportions of deflected root masses. Greater substrate volume did not influence root deflection development. The air-pruning tray without vertical ribs had the lowest total number of root masses with misdirected roots and lower proportions of root masses with misdirected roots for all species. These results indicate that improved root architecture in root-air pruning tray designs is achievable in tree propagation; however, vertical plastic structures in air-pruning trays can still cause root deflections.
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What is a Ramadan crescent moon tree? |
Posted by: Y456X - 09-24-2021, 02:07 AM - Forum: Welcomes and Introductions
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What is a Ramadan crescent moon tree?
What is a Ramadan crescent moon tree?
One particular decor element that has taken root – and is quickly gaining ground in the region this year – is the crescent tree.
Chances are you’ve come across it yourself: the artificial tree comes in a number of sizes and colours, with its defining feature being its distinct crescent moon shape.
With its Instagram-friendly appearance, it has blown up online under different names – moon tree, green ramadan eid crecsent moon tree, Ramadan tree and even Eid tree – as more families take to them. A search for #RamadanTree on Instagram turns up more than 1,000 posts, while one for #EidTree yields over 1,500; impressive since three years ago, they didn’t really exist.
So how did it all begin? It all seems to have started in Michigan, in the US, where resident Samar Baydoun Bazzi decided to mark the holy month with some festive cheer. As a mother, she wanted to create a special experience for her daughter, so she began incorporating Islamic-themed art into the home. When that wasn’t enough, she tried a Christmas tree, but that only confused her child further, she told local media.
That is how Bazzi ended up taking things into her own hands – by creating Ramadan trees in the shape of a crescent moon as a tribute to Islam. As the pictures of the trees circulated online, she started getting orders and the trend just picked up from there.
How did trend reach the UAE?
The crescent-shaped tree is making its way across to the UAE, too. Zahirah Marty, founder of brand development agency Think Liquorice, purchased one in 2020 through Amazon, but she found it quite difficult to source one at the time, and options were limited.
Today, however, it's easier, as a number of brands have starting selling them.
Crate & Barrel, which introduced the tree in 2020, saw sales of the crescent tree soar this year. The hugely popular item can be bought item both online and in-store, for Dh400.
Why get a crescent tree?
UAE resident and mum-of-four Taghred Chandab, who bought one before Ramadan from Kibsons, says it worked as a great way to start a conversation with little ones about Islam and Ramadan.
“We like to decorate for Ramadan and Eid, to give the children a sense of excitement around both the holy month and Eid. My youngest is 5 and she has asked over the years if we could have a Christmas tree at Christmas, but as Muslims we didn't feel this was appropriate as it didn't reflect our beliefs.
"She was really excited when the white ramadan eid crecsent moon tree arrived and we explained to her why the moon was important in Islam, particularly around Ramadan and Eid. She feels the spirit now. Sometimes kids need visual aids to understand."
When Marty posted a picture of her tree on social media last year, she received many queries from other parents, also looking for a way to “bring the month to life for their children and make it something tangible and memorable”.
"Growing up, we didn't have anything like this," she tells The National. "There weren't decorations and lights. At best we shared plates of food or dates with neighbours and family and waited for Eid; for a day of family and food. We did a little less that month, and besides the wave of energy at iftar, it was a pretty non-eventful month from a child's perspective.
“I want Ramadan to be a month-long celebration of who we are, and time at home together, and most importantly I want to create new traditions for my family based on our diversity and mixed cultural background, because that’s a part of our identity.
"It is a month to reflect, and reconnect with ourselves, our home, our family, our creator and I want that to be done in a lively and festive space. Having that centrepiece is a symbolic display of that for me."
Marty says she makes setting up the tree an educational and fun experience for her son Noah, who loves it, too. “While we decorate it, we chat about why it’s a moon and not a tree, why we have it out, what fasting means and how he has so much to look forward to with Eid.
“I want Noah to fall in love with his faith, and all that it comes with. We live in a very challenging world, and children today won’t accept things ‘because we say so’. I want my son to view religion as the beautiful part of his world it is from a young age, and creating reasons to celebrate, decorate and bring joy is how I choose to do it. Everything else will follow."
A response to criticism
Despite its popularity, the trend is not without its criticism. A cursory search online will find comments about it copying western traditions, while others believe it can be ostentatious.
“In any area of life there will always be critics, and I respect that as humans we will differ in our opinions," says Marty. "I prefer to focus on my intention to create happy, celebratory moments for my family as a medium of education, and a way of carving out our space with our circumstances.
“If a decorated moon sparks joy in my toddler to look forward to the month of Ramadan, ask me questions, and open his mind and heart to the lessons, stories and memories, then I’ve achieved my goal.”
How to decorate a Ramadan tree:
Some trees come pre-decorated, but if you prefer to decorate the gold ramadan eid crecsent moon tree together with your family, there are options in the UAE.
Marty recommends Daiso as a place where one can get a range of lights in the shapes of mosques, stars and moons. She drapes her family Ramadan tree with lights, camels and even baubles.
“I grew up with a childhood tradition of new Eid pyjamas and either money or gifts. I keep that tradition in our home. The silver ramadan eid crecsent moon tree is a place we have all this sitting until the night before Eid, which adds to the excitement of Eid day,” she says.
Other places where one can get Eid and Ramadan decorations, as well as trees, include Amazon, Kibsons and noon.com.
DEARBORN — Celebrating Ramadan in the U.S. doesn’t come as naturally as it does in Muslim-majority countries. From fasting during long summer days to lackluster holiday cheer and enduring anti-Muslim sentiments, Muslim Americans have to try just a little harder throughout Islam’s holiest month.
Samar Baydoun Bazzi, a 29-year-old Dearborn resident and nursing student, knows that all too well and is trying to change that— one crecsent tree decorations at a time.
Bazzi told The AANews she remembers feeling like the “odd one out” growing up as a Muslim in Michigan, especially after she began wearing the hijab. During Muslim holidays, she rarely would feel any enthusiasm as gatherings were mostly isolated to family and close friends. Her home would only light up with decorations during Christmas.
Although simple Ramadan-related decorations adorn some properties in Dearborn, Bazzi said she wants to bring a little extra Ramadan spirit to a city that’s home to one of the most concentrated Arab and Muslim American communities and one of the largest mosques in the nation.
“People can get more creative,” she said.
The project, now in its fourth year and selling nationwide, began when Bazzi’s daughter, 4-years-old at the time, thought it was Christmas when she put up a tree along with other banners and crafts, in preperation for Ramadan.
That same day, Bazzi said she took the tree apart and rearranged it in the shape of a crescent moon, a widely-recognized symbol in Islam.
“I wanted her to be excited about her own religion and holiday,” she said about her daughter.
Bazzi, who crafts the trees by hand in her basement, said she quickly learned that many Muslim households face the same obstacles and people wished they’d had such trees in their childhoods.
“The parents want their kids to feel like their own holiday is the most amazing time of the year,” Bazzi said. “It’s a time when they’re supposed to be closer to God, to pray and fast; we want them to fall in the love with the whole process.”
Bazzi said her intention was not to blend Anglo-Christian and Pagan traditions with Islamic ones by using a Christmas tree and that she initially only used a tree because that’s what she had available.
“It really makes no difference to me,” she said. “It doesn’t look like a Christmas tree anymore.”
At a time when political tensions are high and bigoted rhetoric is rampant, Bazzi said her goal is to ensure Muslim Americans, especially the youth, can be unabashedly proud and more openly celebrate their faith.
It takes her about five hours to make each tree. The six-foot-and-eight-inch-tall trees are available in white and green and include lights and a hanging star. They’re being sold nationwide, with requests for them coming from around the world.
Bazzi said the Ramadan Trees have garnered enough interest for a wait list to fill up, forcing her to stop accepting orders this year.
She said she hopes to partner with a manufacturer and expand the project into a large-scale business.
For Samar Baydoun Bazzi, the Ramadan Tree grew out of a desire to mark the Islamic holy month with festive cheer.
Growing up as a Muslim in the U.S., Baydoun Bazzi, 29, of Dearborn said she noticed a lack of decorations during the month-long holiday, which Muslims observe by fasting from sunrise to sundown to commemorate the revelation of the Quran to the prophet Muhammad.
“Obviously, Ramadan’s important,” Baydoun Bazzi said. “You gotta pray and fast, and you want to become closer to your creator. But I never as a kid felt like there was any decorations or like a celebration. I wanted something exciting.”
When she became a mother, she decided to take matters into her own hands and create the kind of Ramadan experience she wished for as a child.
She began by decorating her west Dearborn home with Islamic-themed art, like acrylic paintings of Arabic calligraphy and a cardboard model of a mosque.
It wasn’t enough.
So in 2014, she said, she decided to put up a Christmas tree.
It didn't last long.
“Oh, Christmas!” Baydoun Bazzi remembers her daughter Zahraa, then 4 years old, shouting.
“I knew that it was a mistake,” Baydoun Bazzi said of her decision. “So I looked at my tree and decided to take it apart.”
That’s when the Ramadan Tree first took root.
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