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Elasto Proxy's Sealing Solutions Blog

Elasto Proxy's Sealing Solutions Blog is the place for conversation and discussion about the design and custom fabrication of rubber and plastic components. For nearly 25 years, our family-owned company has provided high-quality, low-volume seals to a variety of industries. Doug Sharpe, Elasto Proxy's co-founder, is a former president of the International Sealing Distribution Association (ISD), a not-for-profit trade association that enhances member success through information, education, and interaction. By blogging for CR4 in this same supportive and collaborative spirit, Doug and other members of the Elasto Proxy team will share our experiences with you.

NSF Gasket Materials for Food Equipment and Drinking Water Systems

Posted September 11, 2017 9:37 AM by Doug Sharpe

NSF gasket materials are used in commercial food service equipment, water treatment or distribution systems, and other applications that can affect human health and safety. Rubber compounds that are registered with NSF International (formerly the National Sanitary Foundation) must pass rigorous tests to ensure that potentially harmful substances won’t migrate from the gasket material when in contact with food or drinking water.

NSF standards aren’t regulatory requirements, but failing to use NSF gasket materials can put larger product designs at risk. Conversely, using NSF certified compounds can increase the likelihood of regulatory acceptance. In some jurisdictions, public authorities such as health departments require food service equipment and drinking water systems to meet a specific NSF standard. Buyers also expect to see an NSF mark on products such as commercial ovens or water filtration systems.

NSF Certified vs. NSF Compliant

NSF marks or labels aren’t component-label designations, but product designers still need to understand the differences between NSF certified and NSF compliant materials.

  • NSF certified gasket materials are registered with NSF International and have been tested and evaluated by NSF International to a specific standard.
  • NSF compliant gasket materials meet relevant NSF requirements, but are not registered with NSF International. Typically, these materials are tested by the supplier or an independent laboratory.

Both types of materials cost more than commodity rubber, so it’s important to select the right compound for your application. You don’t want to over-engineer the gasket, but you don’t want to use a material that can’t meet your requirements either.

If your application requires NSF gaskets, then there are two major standards you need to know about. Both were developed in junction with the American National Standards Institute (ANSI), a U.S. standards organization.

  • NSF/ANSI 51 applies to commercial food service equipment.
  • NSF/ANSI 61 covers water treatment or distribution products.

These aren’t the only NSF/ANSI standards that can apply to gaskets, but they’re commonly used.

NSF/ANSI 51 Gasket Materials

NSF 51 applies to materials and coatings that come into contact with foodstuffs. In addition to rubber gaskets, this standard covers components such as tubes and valves. Applications for NSF 51 gasket materials include broilers, beverage dispensers, cutting boards, and stock pots. This NSF standard is for commercial food equipment, but some household appliances (such as coffee makers) may also contain components made of NSF 51 materials.

Rubber compounds that meet NSF/ANSI 51 requirements can be approved for contact with all food types, or for contact with specific types of food substances. Test reports for NSF gasket materials also indicate the material color and the maximum use temperature. The latter specification can be especially important for gasket designers who need to meet high-temperature requirements for bakeries or dairies.

Silicone gaskets are often used in food contact applications because these synthetic elastomers are chemically inert, won’t outgas, and won’t leach into food. Additional NSF 51 gasket materials include food-safe EPDM. If an NSF 51 registered material isn’t certified for all food types, then the test report may call-out approved substances such as:

  • Aqueous acidic
  • Aqueous non-acidic
  • Bakery products with free fats and oils on the surface
  • Bakery products without free fats and oils on the surface
  • Dairy, oil in water emulsions
  • Dairy, water in water emulsions

NSF/ANSI 61 Gasket Materials

NSF 61 applies to a wide range of water system components. In addition to rubber gaskets, this standard covers adhesives, lubricants, pipes, filters, and fittings. Applications for NSF 61 gasket materials include faucets, drinking fountains, and water treatment systems. In both the U.S. and Canada, products that are certificated to NSF/ANSI Standard 61 meet regulatory requirements for public health and safety. In California, Title 22 drinking water standards also apply at the component (gasket) level.

NSF/ANSI 61 compounds are subjected to a battery of tests. The simplest is a cold water test at pH levels 5, 8, and 10, which are the most common pH levels for waters in North America. Chemical testing is more challenging, but for good reason. Often, sodium hypochlorite (bleach) is used to disinfect drinking water systems. Rubber gaskets that are made of standard Viton® can withstand bleach, but they’re cured with lead that can migrate into drinking water. To achieve NSF 61 certification then, lead-free Viton® GF is used. NSF 61 EPDM rubber gaskets are also used in drinking water systems.

Do you have questions about NSF gasket materials? Elasto Proxy works with a trusted network of material suppliers and can convert sheets and extrusions to create custom gaskets. With our water jet cutting equipment, we can eliminate tooling charges and make fine, fast cuts that maximize material usage. We can also store your finished goods and ship them according to your sales forecasts or on-demand.

For more information, contact us.

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UL Gasket Materials for Flame Resistance and Ingress Protection

Posted September 05, 2017 10:00 AM by Doug Sharpe

UL gasket materials can provide flame resistance, ingress protection, or other specialized properties. For engineers, it’s important to understand what the different standards from Underwriters Laboratories (UL) mean. It’s also worth knowing if UL gasket materials are truly required in your component-level designs. Otherwise, you may “over-engineer” your gaskets and pay too much for materials.

Compared to commodity elastomers, the prices for UL compounds are higher. The minimum order quantities (MOQs) are greater, too. In the case of rubber extrusions, the compounder has to use special tooling to account for different flow rates. The number of suppliers who offer UL materials is also limited. Unless you really need them, UL gasket materials can add unnecessary expenses to your application.

Of course, some sealing and insulation projects require UL gasket materials to meet specific requirements. In this blog entry, the first in our September series about compound selection, Elasto Proxy explains what engineers need to know about UL gaskets for flame resistance and ingress protection. These aren’t the only UL standards for gaskets, but they’re the most common – and they can be confusing.

UL 94 Gasket Materials

UL 94 is a family of flammability standards that defines 12 different flame ratings for rubber and plastic materials. The most common classifications are UL 94 V-0, UL 94 HB, and UL 94 HBF. The V and HB designations indicate whether a material specimen was subjected to either a vertical (V) or horizontal (HB) burn test. As a rule, UL 94 V ratings are more demanding than UL 94 HB ratings.

As you can see then, getting the right flame-resistant compound isn’t as simple as asking for a “UL 94 gasket material.” When considering which UL standards may apply to your gasket design, you’ll also need to consider the following:

  • UL 94 V-0 applies to both rubber and plastic, and to both solid and foam materials.
  • UL 94 HB applies to rubber and is generally considered the easiest flame rating to achieve.
  • UL 94 HBF applies to foams and contains multiple flammability ratings.

Material thickness and certifications also drive compound selection. Thinner UL materials may not provide the same amount of flame resistance as thicker materials with the same UL 94 flame rating. Products that are described as “capable of passing UL 94” or “compliant with UL 94” probably don’t have a UL yellow card – proof that Underwriters Laboratories (UL) has tested and recognized the material.

Does your rubber gasket require a UL recognized material, or can you use a compound that’s UL 94 compliant instead? If the elastomer was tested to UL 94 standards, was the testing done by Underwriters Laboratory or at the compounder’s in-house testing facility? To ensure both the safety and the cost-effectiveness of your products, these are important questions to ask.

UL 50E Gasket Materials

UL 50E is an ingress protection (IP) standard against dust and water. It applies to enclosures for electrical equipment that will be installed and used in non-hazardous locations. Specifically, UL 50E covers 16 different types of enclosures that are defined by North American electrical codes used in Canada, the United States, and Mexico.

  • Enclosure types 1, 2, 5, 12, 12K, and 13 are for indoor locations
  • Enclosure types 3, 3X, 3R, 3RX, 3S, 4, 4X, 6, and 6P are for indoor and outdoor locations

In addition to electrical safety requirements, UL 50E covers enclosure construction and performance. Yet UL 50E does not include requirements for protection against the following:

  • condensation
  • icing
  • corrosion
  • contamination that occurs with the enclosure

Engineers who specify UL 50E gasket materials need to account for the scope of this standard. It’s also important to consider the effects of aging and cleaning on UL 50E gaskets. For example, short-term testing of UL 50E gasket materials may not reveal long-term compression set. If an enclosure will be cleaned with high-pressure streams of water, the entire enclosure design needs to support this.

UL Gasket Materials and Custom UL Gaskets

Elasto Proxy can source the UL materials that you need and then fabricate gaskets that meet all of your sealing and insulation requirements. Our technical team also provides design assistance and help with compound selection. So whether you need UL gaskets or are wondering if your application really requires UL gasket materials, we invite you to contact us.

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How to Install Bulb Trim Seals

Posted August 28, 2017 11:20 AM by Doug Sharpe

Bulb trim seals keep out air, water, dust, and noise. They are used in doors with radiused corners and consist of a compressible bulb and a solid retainer section. When the door is closed, the bulb is compressed to create a seal between the door and the jam. The trim or solid retainer section installs over the edge of the door and combines a finished appearance with edge protection. Applications for bulb trim seals include mobile equipment and enclosures for electronics and machinery.

In this “How to” article from Elasto Proxy, you’ll learn how to install bulb trim seals so that they won’t over-compress or kink. First, you’ll learn about materials and measurements for the bulb section. You’ll then learn how to specify the trim section of your seal. Along the way, we’ll cover some calculations and best practices for ordering and installing the industrial rubber products that you need. Bulb trim seals are sold in coils, but they also come cut-to-length to help you speed installation.

The Bulb

The bulb portion of a bulb trim seal is made of a sponge rubber that provides environmental sealing and resists compression set – the permanent, unrecoverable deformation of a seal after it’s been compressed, such as when a door is closed. Different materials are available, but EPDM and TPEs are often used.

  • EPDM sponge rubber remains flexible at low temperatures and provides excellent resistance to weather, ozone, aging, water, and steam.
  • Thermoplastic elastomers (TPEs) are also weather-resistant, but provide greater impact strength. TPEs are more expensive, but they’re also recyclable.

Both bulb materials have a hardness or durometer (Shore A) that’s medium-density. Generally, the shape of the bulb is round. If an extended lip is required, choose a seal with a teardrop-shaped bulb instead. You can also specify bulbs that resemble a half-moon with a flat bottom. Bulb location varies. Depending on how the door swings open, the bulb is usually atop or side-by-side the trim.

Bulb size is especially important. To determine this measurement, find the average jam dimension. An easy way to do this is to place some modeling clay in each corner and then close the door to compress the clay. Next, insert calipers into the clay and record the measurement for each corner. Now divide this number by four to get the average jam dimension.

To account for bulb compression, add 25% to 50%. Most bulb trim seals are designed to compress by this amount. The percentage that you use doesn’t have to be exact, but it needs to be close enough. Remember that over-compressing the bulb will not create a better seal. In fact, over-compression can reduce seal life and cause compression set.

The Trim

The trim portion of a bulb trim seal is made of a solid rubber like EPDM or TPE, or a plastic like PVC – a strong, lightweight material that’s easy-to-handle. Depending on your requirements, the durometer for the trim section can be harder (or softer) than for the bulb section. Rubber trim is usually black, but comes in different colors to support various product designs. Trim can have a smooth or textured finish, too.

For additional gripping, choose a solid retainer section with interior tongues. To help absorb impact, choose trim with steel wire or segmented steel cores. Cutting this type of trim in-house may seem cost-effective, but using a hand tool can result in poor-quality cuts and material waste. By ordering cut-to-length products from Elasto Proxy, you can save both time and money.

Regardless of the cutting method you choose, you’ll need to specify two trim dimensions – edge thickness and leg length – in order to get the bulb trim seals that you need. The edge thickness of the trim needs to match the thickness of the door’s edge. Do not add a percentage like you did with the bulb. Leg length indicates how much the trim will cover the flange. As a rule, shallower flanges require shorter legs.

Choose trim with a minimum edge radius that meets your application requirements. Unlike some other industrial rubber products, the trim in a bulb trim seal isn’t designed for 90-degree corners. If you use bulb trim seals in this way, the corners will kink and the kinks will form valleys that leak. When you press the trim portion into place then, avoid any type of buckling in the corners.

Bulb Trim Seals and Value-Added Manufacturing

Elasto Proxy can review your designs for dimensions like edge radius, and can suggest improvements for superior sealing and insulation. We help you with material selection, too. Importantly, the value-added manufacturing that we offer can help you to avoid problems (such as over-compression and kinking) that can occur during product installation. To learn more about bulb trim seals from Elasto Proxy, contact us.

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How to Install Locking Gaskets

Posted August 21, 2017 2:21 PM by Doug Sharpe

Locking gaskets are lengths of rubber that lock into place to provide a secure seal between stationary glass and a body panel. These rubber gaskets are used with the windows and windshields on mobile equipment such as trains, trucks, and buses. They’re also used with the viewing windows on enclosures for machines, instruments, and equipment. Additional applications include boat windows, clean rooms, and the windows used in high-traffic doors found in warehouses.

In this “How to” article from Elasto Proxy, you’ll learn how to install locking gaskets properly – and without risking breakage to windows or windshields. We’ll start with measurements and material selection, and consider the advantages of buying rubber gaskets that are already cut-to-size. Most importantly, you’ll learn some installation tips and best practices that can save you time while helping to avoid damage to body panels.

Locking Gasket Measurements and Material Selection

Choosing the right locking gasket begins by taking some basic measurements. First, measure the thickness of the glass that the rubber seal needs to fit. Elasto Proxy supplies locking gaskets for standard thicknesses, but we can also supply custom profiles for specialty sizes. Next, measure the height and width of the glass. Add these numbers together and then multiply the sum by two. This gives you the overall length for the locking gasket that you’ll need.

Some engineers are more familiar with metal parts than with rubber profiles. That’s why it’s important to know that rubber can shrink and stretch significantly. Tight tolerances are possible with metal channels, but not with the rubber extrusions used in locking gaskets. When you define your seal design, the part tolerance needs to correspond to a class from the Rubber Manufacturers Association (RMA). Elasto Proxy can review your part drawings and help you to define seal tolerances in terms of RMA classes.

You’ll also need to specify the locking gasket material. With mobile equipment, EPDM is often used because this rubber remains flexible at low temperatures and resists both moisture and sunlight. For food processing and medical equipment applications, locking gaskets made of FDA-approved silicone rubber may be required. Elasto Proxy can help you with compound selection.

Advantages of Custom-Fabricated Locking Gaskets

When you source locking gaskets from Elasto Proxy, you can buy lengths of rubber that you cut yourself, or you can order custom-fabricated gaskets that are ready-to-install right out of the box. Cutting your own locking gaskets might seem cost-effective, but using a hand tool like a wire cutter can result in poor-quality cuts and material waste. If you decide to make your own cuts, marking the length on your workbench or other cutting surface can help speed the process, especially with higher volumes.

For fast, cost-effective, and high-quality cuts, choose custom-fabricated gaskets instead. The cut-to-length gaskets that Elasto Proxy provides harness the power of our water jet cutting machine, which makes fine, fast cuts without tooling or waiting for tooling. Elasto Proxy can ship your custom-fabricated products on-demand, or in accordance with your sales forecasts. No matter who does the cutting, however, you’ll need to follow some installation tips and best practices.

Locking Gasket Installation Advice

As you learned earlier in this article, the rubber that’s used in locking gaskets will experience shrinkage. To prevent the edges of the gasket from separating, you need extrusions with a bit of extra length. When you press the locking gasket onto the body panel, push the gasket ends together so that there’s more material in the loop that forms. Pressing this loop downward forces material into the application and prevents stretching.

Before installing the glass, lubricate the locking gasket with a mixture of soap and water or a silicone-based spray. Apply the lubricant generously, but avoid fluids that could damage the gasket or the panel. To prevent the lubricant from wetting other surfaces, hold the spray bottle or can in one hand and a piece of cardboard in other. Position the cardboard on the other side of the window or windshield area that you plan to spray.

To install the glass, start with the body side first. In other words, don’t start inside of the cabin or enclosure. Rest the bottom of the glass in the locking gasket so that you don’t have to struggle with the weight of the window or windshield. Using a knife-like tool with a plastic blade can help to prevent glass breakage as you work the gasket’s lip over and around the glass. When lip is fully over the glass, the window or windshield will pop into place.

Next, lock the gasket into itself. Some installers use a screwdriver, but the blade can slip and scratch the paint on the body panel. Tools with a screwdriver-like handle and hooked end are a better choice. These gasket locking tools can feature a pointed tip or metal ball at the end. Some installers prefer the latter type because the ball tends to stay in place and won’t rip the gasket. Plus, if the tool comes loose, the metal ball is less likely to scratch the paint on the body panel.

Finally, slide the tool around the gasket’s edges to lock the seal into place. If there’s residual lubricant on the window or windshield, wipe the surface clean with a rag. No matter which type of locking gasket you choose, it’s important to follow the proper installation steps. Elasto Proxy keeps over 700 standard profiles in stock, and can supply lengths in bulk or custom-fabricated products. To learn more, contact us.

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How to Install Edge Trim

Posted August 14, 2017 5:40 PM by Doug Sharpe

Edge trim protects exposed edges and the people who come into contact with them. In addition to sealing and insulation, edge trim provides a finished appearance to surfaces such as the metal doors on vehicles, machinery, and equipment. Choosing the right type of edge trim for your application is important, but you’ll also need to install these seals with care. Otherwise, edge trim can buckle or separate.

In this “How to” article from Elasto Proxy, you’ll learn how to select edge trim based on dimensions and material requirements. You’ll also learn some best practices for cutting trim seals, as edge trim is also known. You can buy lengths in bulk and cut them yourself, or you can buy edge trim that’s been cut-to-size for your application. Either way, you’ll need to install edge trim by pressing the seal onto the edge.

Edge Trim Dimensions

Choosing the right edge trim starts with measuring the thickness of the edge to cover. Make sure that the seal you select has the same thickness as the edge. In other words, don’t select a trim seal that’s too thick or too thin for the flange. For example, if you need to cover an edge that’s 0.125” thick, specify a trim seal with an edge thickness of 0.125” – not 0.120” or 0.130”.

Leg length is another important measurement. As a rule, shallower flanges require shorter leg lengths. If the edge that you need to cover is curved, measure and record the bend radius. Then compare this measurement to the minimum bend radius for the edge trim you’re considering. If the edge trim buckles because it can’t accommodate the radius, the trim seal may not perform properly.

Edge Trim Materials

Materials of construction are also important to consider. Select a rubber or plastic that can withstand the application environment and that resists compression set. Rubber edge trim can be made of solid, sponge, or dual durometer rubber. Bulb trim, a type of edge trim, can have a softer (lower durometer) bulb and a harder (higher durometer) retainer that’s pressed into place over the flange.

Elasto Proxy provides standard edge trim in these and other materials.

  • EPDM edge trim remains flexible at low temperatures and resists moisture and ultraviolet (UV) light. Fire-rated EPDM that meets flame, smoke, and toxicity (FST) requirements is available.
  • Neoprene edge trim provides more limited flexibility at low temperatures, but offers flame and water resistance.
  • PVC edge trim is strong, lightweight, and abrasion-resistant. It’s easy-to-install, but may crack in the cold and fade in the sunlight.
  • TPE edge trim is less likely to crack in the cold than PVC; however, TPE trim seals are more expensive.
  • Silicone edge trim provides low toxicity, low chemical reactivity, and thermal stability over a wide temperature range. Dust and other particles may adhere to silicone rubber, however.

Most edge trim is black, but you can choose trim seals in colors such as silver or white to match your larger product designs. Edge trim can have a smooth or textured (pebbled) finish, too. For additional gripping, edge trim can have interior tongues.

To help absorb impact, edge trim may contain steel wire or segmented steel cores. Steel wires are spaced apart and run parallel to the length of the legs. Segmented steel cores consist of sections that cover more surface area beneath the rubber or plastic. Because of steel’s ability to withstand impact under colder temperatures, a steel core may be required for outdoor applications such the doors on mobile equipment.

Edge Trim Cutting

As explained in the introduction to this article, edge trim comes in lengths that you can cut yourself. You can also buy edge trim that’s been cut-to-size based on your specifications. Cutting lengths of rubber in-house may seem cost-effective, but using a hand tool like a wire cutter can crimp the ends and result in material waste from poor-quality cuts.

Custom-fabricated edge trim from Elasto Proxy features precise cuts and clean, smooth edges. The abrasive saw blade that we use won’t put pressure on the profile either. If you still decide to make the cuts yourself, make sure to use the right tool. Also, feel for the gap between the clips if the trim seal has a segmented core. If you don’t find the right spot before cutting, the edge trim may crush and deform.

Creating mitered corners can be especially challenging. Typically, these angled cuts are made at 45° angles into the face of the edge trim. When two complementary cuts are joined together, the mating lines need to be uniform. If you’re making the cuts yourself, use a 90° miter tool rather than tin snips. Cut a notch from each leg, but cut only one leg at a time.

Edge Trim Installation Tips

Edge trim is pressed into place over the flange. For high volume installations, you may want to use a pneumatic air hammer instead of your hands. For best results, always install lengths of edge trim so that the ends won’t separate. Push the ends together and leave some material in the loop that’s created. Then push down on the edge trim to ensure a proper fit avoid stretching.

We hope you’ve enjoyed this article from Elasto Proxy and encourage you to read last week’s blog entry, How to Install Rubber Gaskets, if you missed it. Next week, we’ll explain how to install locking gaskets. Until then, please contact us with your questions.

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