Effect of Temperature, CO2 Content and Design
Rapid Gas Decompression (RGD) or Explosive Decompression (ED) is a failure mode which can occur in elastomer materials following exposure to high pressure gaseous molecules followed by a rapid depressurisation event.
In this work seals manufactured from a low temperature FFKM, designed primarily for use by the oil and gas industry, were exposed to a pressure and temperature profile based on the ISO23936-2 standard. The pressure was held at a constant 15 MPa. The temperatures used were 100, 121, and 155°C. Gaseous mixtures of 10, 15 and 20% CO2 were used with the balance made of CH4. It was found that as temperature increased the performance of the seal decreased, and it was similar for CO2 content.
The standard calls for the seals to be compressed by 20%. This is would usually be considered to be on the high side for a normal application. To investigate the effect of the squeeze testing was carried out at 155°C an 20% CO2 unconstrained (0% squeeze) and 10% squeeze. It was found that lowering the squeeze prevented RGD failure that was observed in testing at 20% squeeze.