gasket material

Low Temperature Gasket Material

Jul 22, 2019

Many elastomeric gasket materials have a problem with low temperatures. Here we’ll look at some applications that pose challenges and suggest low-temperature gasket materials worth considering.

Low-Temperature Gasket Material Applications

Seals and gaskets are used in many low-temperature environments. One of the most common is food storage. Freezers and cold rooms are typically kept between -80 and 20°F, depending on the application. Pharmaceuticals and medical products are other industries with low-temperature storage requirements.

Industries that do product testing often employ climatic chambers. These need effective seals to minimize the expense of maintaining low temperatures, and it’s also important to consider the equipment inside. And as Chicagoland residents understand, midwest winters can challenge sealing materials used outdoors, especially if exposed to wind.

Glass transition and TR10

Polymers get their flexibility from chains of molecules moving against one another. As temperatures fall the chains are less able to move and eventually become fixed. Materials scientists call this point the glass transition temperature.

For people who need to choose and use gasket material a more useful indicator of low-temperature flexibility is the TR10 value. This was explained in, “What is TR-10 (temperature of retraction) for Gasket Material?”

Good Low-Temperature Gasket Material Choices

Oil-resistant FKM only goes down to around 5°F. NBR is useable as low as -20°F and some specialized grades will go lower. However, these aren’t low enough for many freezer-type applications. Silicon is good for temperatures as low as -65°F and fluorosilicon will go to -80°F but both are expensive. That leaves cost-effective EPDM as an excellent low-temperature gasket material.

The TR10 value for EPDM is between -49 and 9°F, depending on grade. That makes EPDM seals a good choice for many commercial and industrial low-temperature storage facilities. Furthermore, EPDM is available in FDA-approved grades for food industry use.

The chief limitation of EPDM seals is poor resistance to mineral oils and hydrocarbon products. They are good with steam and hot water though, as well as caustic cleaners.

Consider price as well as performance

In low temperatures, many gasket materials become too stiff to seal effectively. Silicon offers good performance but less expensive EPDM comes close for many applications.

Applications, EPDM Gaskets, Silicone Gaskets

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CIP Process and Affect on Seals and Gaskets

Jul 08, 2019

PTFE seals are widely used in the food and beverage industries. One reason is that they won’t contaminate foodstuffs. A second is that PTFE resists attack by acidic products like fruit juices. And third, they stand up well to the intensive cleaning and sterilization processes used in those industries.

Here’s a closer look at how those processes influence gasket selection.

Gasket Cleaning Protocols: CIP

Food and beverage (F&B) manufacturers are acutely aware of the risks of product contamination. That’s why regular cleaning and sterilization is a way of life. Facilities producing liquid products often employ Clean-in-Place (CIP) protocols.

CIP is where cleaning fluids are pumped through the pipes, tanks, mixers, kettles and filling equipment. A combination of aggressive chemicals, turbulence, and rinsing remove contamination from surfaces that contact the food and could otherwise harbor pathogens.

The alternative, Clean-out-of Place (COP) entails stripping down plumbing systems to remove components like valves for cleaning. For many F&B companies, it’s slower and less effective than CIP.

Gasket Cleaning: The CIP environment

CIP usually starts with a hot water pre-rinse. This is followed by running caustic soda through the system at 80°C (176°F). Caustic soda, chemical formula NaOH, (sodium hydroxide,) is highly corrosive. It kills and removes practically everything it comes into contact with. The caustic is then followed by thorough rinsing to get the surfaces food-ready.

Some plants and processes use acid in place of caustic soda. Nitric or peracetic acids are common choices. Steam and ozone are other alternatives sometimes used.

Gasket Cleaning Impact on Gasket Material Selection

Materials like NBR, EPDM, and neoprene have no problem handling CIP temperatures. Where they struggle is with resistance to acids, alkalies and often also water, steam, and ozone.

PTFE seals and gaskets function at temperatures up to 260°C (500°F). More importantly, they won’t react with any chemicals, whether acidic or alkaline. In addition, most grades of PTFE don’t impart any taint to product and are FDA-approved.

If you’d like to learn more about the advantages of PTFE seals in processes that need cleaning and sterilization, contact a material specialist at Hennig Gasket.

FAQs

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PTFE Seals – When Elastomers Aren’t Up to the Task

Jun 24, 2019

Elastomers are often the first choice for sealing and gasketing, but they’re not always the best. Silicone, neoprene, EPDM and Buna-N all have limitations that disqualify them from some applications. When that’s the case it may be time to consider PTFE seals.

Limitations of Elastomers

Elastomers are challenged by temperature extremes, aggressive chemicals and UV light. Some swell when in contact with oils, others outgas or give up molecules to the fluid being sealed against.

Food processing is a difficult environment. While it’s important to avoid product taint the materials must also endure aggressive cleaning regimens. Medical and pharmaceutical equipment presents similar challenges.

Many elastomeric materials harden in UV light, making them unsuitable for outdoor environments. Others will outgas, making them a bad choice for vacuum applications.

How PTFE Seals Score

PTFE is composed of carbon atoms bonded to fluorine. That makes it almost totally inert and a good choice for food, pharma and medical applications.

Less flexible than an elastomer, PTFE can nevertheless seal down to around -460°F. It’s also functional at temperatures as high as 570°F.

PTFE is unaffected by UV light, making it useful for outdoor applications or those involving UV sterilization. It has excellent electrical insulating properties and won’t swell when exposed to steam or oils. Another benefit from using PTFE seals in dynamic applications is a very low coefficient of friction.

PTFE Seals Limitations

Under load, especially at elevated temperatures, PTFE will creep. Joints should be designed to minimize the clamping forces applied directly to the material.

A second limitation is low strength. Some elastomers offer higher tensile strength combined with less elongation at breakage.

To address these issues PTFE formulators incorporate a range of fillers. Ranging from glass and carbon fiber to bronze and molybdenum disulfide, these can increase strength and hardness and reduce friction.

Seek specialist advice

When your sealing application challenges elastomeric materials it may be time to consider PTFE. However, with a large number of PTFE formulations available it’s difficult to know which is ideal. In such cases consult a materials specialist like those at Hennig Gasket.

PTFE Gaskets

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Garlock Gasket Material – A Trusted Name

Jun 10, 2019

Trust takes time to earn but can be lost in seconds. That’s why people stick with brands that have served them well. Why risk something new when you already know what works? For this reason, many gasket buyers specify Garlock gasket material. Either they’ve had good experience with it or they know someone who has.

About Garlock

Garlock has been around for over a century, so they’re doing something right. While their business is sealing, Garlock focuses on the benefits gaskets deliver: keeping people safe and helping businesses be more profitable.

One hundred years ago we used natural materials like rubber and leather but industrial processes have changed since then. Today, increased temperatures and pressures demand gasket material that’s stronger and more resilient.

Garlock invests heavily in R&D to develop innovative materials that meet these challenges. Their research and testing facilities are state-of-the-art and they have a strong environmental commitment. Together, this ensures Garlock gasket material stays at the forefront of sealing technology.

An overview of Garlock gasket material

Whether you’re dealing with extreme temperatures, high pressures, vacuum or aggressive chemicals, there’s a Garlock material to suit. Scan their product catalog, (or speak with a Hennig specialist,) and you’ll discover PTFE in many grades, graphite, compressed fiber, and natural and synthetic rubber gaskets and gasket material.

Brand names you may be familiar with include GYLON® restructured PTFE, GRAPH-LOCK® flexible graphite sheet, BLUE-GARD® compressed rubber and THERMa-PUR Extreme Temperature material.

Known for excellent chemical resistance, GYLON® is used in many industries including pharmaceuticals and food processing. GRAPH-LOCK® is a high-temperature material with good creep-resistance. BLUE-GARD® also offers a wide temperature range and is available with a range of rubbers. THERMa-PUR, however, beats them all as it will operate at temperatures as high as 1,832°F (1,000°C).

A reputation you can trust

When a business endures you know it’s doing something right. Garlock isn’t the only company to make gasket material, but they’ve been at it a long time and make a quality product. If you’d like to use Garlock gasket material in your next project, speak to us.

Gasket Material

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Gasket Material Selection

Mar 19, 2018

It’s said that what comes out of the joint is what goes back into the joint, but sometimes we’re asked if there’s a better material to use. That’s because the expense of replacing a gasket often far outweighs the cost of the part. When that’s the case a little extra spent on better gasket material might save a lot.

Unfortunately, there’s no easy answer to the material question. All we can say is, “It depends.” Here’s why, along with some guidance on selecting the best gasket material.

Four Key Criteria

It’s impossible to determine an appropriate material without knowing the temperature, environment, media and pressure the gasket will experience. It’s also important to determine the actual range of every parameter and every operating condition. Cleaning with caustic agents, for example, creates very different gasket challenges than handling a benign fluid like milk.

Temperature

This refers to the temperature of the media. Many elastomers harden when cold, making them less able to resist pressure and reducing their ability to flex as the joint changes size. Neoprene, for example, has a lower limit of -40°F while high-performance fluoroelastomer (FKM) only goes to -10°F.

Environment

Temperature is one factor, sunlight another. A gasket used outdoors in a midwestern winter could see low temperatures while one exposed to the desert sun will get extremely hot. In addition, UV light damages some common gasket materials. NBR, for example, has poor UV resistance while EPDM holds up much better.

Media

Some gasket materials suffer swelling when exposed to oils and other will oxidize rapidly. Brake fluid is incompatible with nitrile rubber and FKM while silicone and EPDM are a poor match for gasoline.

Pressure

The pressure inside a pipe or enclosure can force gasket material to extrude out sideways. Harder materials generally hold up better but require higher clamping forces. In extreme cases, it may be necessary to consider PTFE, spiral-wound or metal gaskets.

Seek Advice

Every gasket application is different and it’s never easy to say which is the best material to use. Start by determining the four criteria listed above, then consult a material specialist.

Gasket Material

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Oxygen Compatible Materials

Mar 05, 2018

Many industries use oxygen. It’s one of the most reactive elements, which makes it useful in processes from steelmaking to paper production as well as healthcare and waste treatment. This reactivity, (a willingness to form chemical bonds with other elements,) also creates sealing problems. Here’s an overview of the challenges posed by oxygen and a discussion of the best gasket materials to use.

The Air We Breathe

Oxygen is one of the most plentiful elements and makes up some 20% of the air we breathe. It’s also locked into the oceans as water. At temperatures above -297°F (183°C) it’s a gas. Oxygen has a strong affinity for electrons, which is what lets it bond readily with many other chemicals. Rust and oxidation are the common results, although fire and explosions are always possible.

Oxygen Production

Oxygen is produced by cryogenic distillation or pressure swing adsorption (PSA). As the name implies, the cryogenic process entails cooling air until it becomes liquid, allowing the oxygen to boil off. This produces a very high purity gas.

PSA involves pushing air through aluminosilicate minerals. These take up the nitrogen, leaving just oxygen, but at a lower purity than the cryogenic process.

Keeping Oxygen Systems Clean

Given that oxygen is highly reactive, it’s essential that any surface it touches is clean. Some industries have special requirements for oxygen-clean surfaces. The standards applicable to your industry will specify the type and degree of cleaning needed.

Materials for Gaskets in Contact with Oxygen

Liquid oxygen can only be sealed by materials capable of withstanding very low temperatures. PTFE gaskets are a good choice as is FFKM (perfluoroelastomers) gasket material.

Good gasket materials for gaseous oxygen include neoprene, EPDM, silicone, butyl and Viton® (a DuPont brand name for FKM.) Rubber materials such as SBR and natural rubber should be avoided because of their tendency to react with oxygen.

Ask an Expert

Always consider temperature, pressure and the environment along with the media being sealed. For this reason, it’s prudent to consult with a materials specialist before ordering gaskets or gasket material.

Gasket Material

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When to Use Felt Gasket Material

Jan 08, 2018

Most gasket materials are elastomeric or rubber-like in nature, but there’s another material that’s surprisingly effective in some sealing applications: wool. When compressed to a uniform density wool becomes felt. Felt has been used for sealing and gasketing for a long time and still has its uses. Felt seals suppliers offer a variety of options.

A “Non-Woven” Material

Most felt is produced by compressing wool into rolls of material. Wool fibers have a kind of “fish scale” surface that lets them hook together randomly. This creates a material that’s soft and compliant with a high level of resiliency. It can absorb and hold liquids even better than an open cell foam while resisting attack by oils and temperatures up to 200°F. An added benefit is that felt won’t unravel or fray like woven fabrics.

Industrial wool felt is specified by an SAE standard. This assigns grades from F-1 to F-55. Higher numbers indicate lower density, and these grades have less ability to absorb vibration and resist abrasion.

Felt is produced from other materials, most notably polyester fiber. Polyester felt will withstand temperatures up to 300°F but its properties and behavior are not addressed by the SAE standard.

Uses of Felt Gasket Material

Noise-deadening

Thanks to strong resilience, felt gasket material can absorb movement between surfaces that would otherwise cause rattles and squeaks. By preventing the transmission of vibration it’s also a good sound-deadening material.

Filtration

The random orientation of fibers in felt make it a very effective filtration medium. Filtration is further enhanced by soaking in oil. Wool fibers hold oil on their surface, which traps very small particles being drawn through.

This ability to retain oil also makes felt a good seal against moving surfaces such as shafts. The wool adapts to changes in gap while oil provides lubrication and simultaneously prevents fluid transmission.

Compliant but Durable

As a soft gasket material, felt is similar to an open cell neoprene, EPDM or silicone foam. Its upper-temperature limit is lower, but depending on grade, abrasion resistance can be higher. If you’re looking for a material that can lubricate as well as seal, ask about felt.

felt

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