Low temperature elastomer sealing

Low service temperatures can result from environmental elements such as ambient winter temperatures. In parts of Canada, Alaska, Russia and northern Europe, it is common for oil and gas equipment to operate year round in very harsh conditions where ambient temperatures can drop to -40°C (-40°F) or even lower.

Low temperatures can also result from significant gas pressure changes. Where a gas is allowed to expand quickly for example during a ‘blow down’, this expansion can induce rapid and significant temperature drops. This can cause localised cooling to take place reducing the surrounding temperature drastically.

Both scenarios can cause challenges for seals. When cooled, elastomeric seals begin to stiffen, they steadily become more rigid until they reach their glass transition temperature, after which they become brittle. Depending on the material, this transition to a stiff brittle material can happen anywhere from approximately 0°C (32°F) down to around -60°C (-51°F). This potential operating range highlights how critical it is to understand both the capabilities of the elastomer and the expectations of the seal in its operating environment to ensure that an appropriate material is selected.

A rigid and brittle elastomer that has been cooled beyond its glass transition temperature will recover, with no lasting effects or damage if left undisturbed and allowed to return to typical operating temperatures. However, while at these ultra-low temperatures, the elastomer will be unresponsive to changes, for example the application of pressure or the actuation of a valve. If these occur, then the risk of bypass leakage is increased. In extreme cases if the seal is exposed to shock loading, there is a risk that the brittle elastomer will fracture.