High Temperature Gaskets

Most gasket applications are satisfied by various forms of synthetic rubber. Neoprene, NBR and SBR for example all work well when temperatures are below 200 °F. Above this, things get more complicated. If you have an application for hi-temp gasket material, here’s what you should know.

How Hot is Too Hot?

Gasket material specifications sometimes give a range for the upper temperature limit. This is because there’s no single temperature at which a material stops working. Instead, it breaks down gradually.

Heat hardens rubber and rubber-like materials, but time at temperature is as important as the peak value the material sees. Pressure is another factor: in a high-pressure application it might be prudent to use a material with a higher upper temperature limit.

Most commonly-used gasket materials top out at around 200 – 225 °F. If you have an application where temperatures are consistently above 225 °F consider exploring options for high temperature gasket material.

Hi-Temp Gakset Material:  Elastomeric Materials

With a sustained temperature limit of 225 °F, EPDM is an elastomer that goes hotter than NBR, SBR and Neoprene. Most grades of silicone, fluorosilicone and fluorocarbon (Viton) gasket material will endure 500 °F, and 600 °F for short periods.

Hi-Temp Gasket Material:  Compressed Non-Asbestos and PTFE

Compressed non-asbestos materials are composed of fibers, (mostly aramid,) in an elastomer binder such as NBR or SBR. The fibers provide strength and pressure resistance and the binder holds them in place.

Compressed non-asbestos materials are made in many grades and formulations but most will withstand up to 750 °F. In contrast, the limit for PTFE is 600 °F.

Very High Temperature Gasket Materials

Choices are limited for temperatures above 750 °F but one of the most widely used materials is vermiculite (a clay-like mineral.) This is either applied to a solid gasket or incorporated into a spiral wound gasket for pipe joints. Its upper temperature limit is around 1,800 °F.

Advice on Gasket Materials for High Temperatures

High temperatures are bad for many gasket materials. As gasket material suppliers of a large inventory of materials, ask us for a material quote if you need to seal hot fluids or in a hot environment.

For gaskets, “If you can’t stand the heat, stay out of the kitchen,” becomes, “If it can’t stand the heat, stay out of the joint.” Using the wrong gasket material in a high-temperature application is the fastest route to failure. It could also be expensive and even dangerous. Here’s some advice for choosing heat resistant gaskets and gasket material.

Heat Resistant Gaskets:  Know the Application Conditions

When choosing gasket material always consider temperature, environment, media and pressure (remember them with the mnemonic TEMP), and temperature comes first. It relates mainly to the media that’s being sealed-in, which could be hot liquid, steam or high temperature gas, (exhaust gases for example,) but it can also refer to the temperature where the gasket is installed and used.

Heat and Gasket Materials

Elevated temperatures affect gasket materials in different ways, and the threshold at which the changes kick in varies widely too.

• Rubbers (NBR, SBR,) harden and become brittle at temperatures over 300°F (149°C). They can also oxidize, which has the same effect.
• EPDM and silicone will go to higher temperatures before losing the ability to seal. An upper limit for EPDM is around 400°F (204°C) while heat-resistant grades of silicone will go to 500°F (260°C).
• For temperatures up to 600⁰F (316⁰C) PTFE is a good choice. It also has good chemical resistance, which makes it suitable for many process plant applications.
• Compressed non-asbestos gaskets are an exception to the point about With an SBR or NBR binder that fixes a matrix of aramid fibers, these are suitable for 750⁰F (399⁰C) and some grades will go higher. (These have good resistance to steam, oil and fuels, but always check your application with us before buying!)
• For resistance to really high temperatures, graphite is the answer. Available laminated, as a foil and also in spiral-wound gaskets, this will seal at 1,000⁰F (538⁰C) and higher. Other options are ceramic fiber (which tends to be brittle,) and fiberglass.

High temperatures will lead to sealing failure faster than almost any other factor. Always consider temperature when selecting gasket material, and ask for heat-resistant gaskets whenever temperature is a concern.

Contact Hennig Gasket & Seals for a free quote.