Elastomers: Evaluating Compatibility in Severe Operating Environments
We measure elastomer compatibility in different service environments. This can include exposing coupons to combinations of:
- Hydrocarbon liquids and gases;
- High temperature; and
- High pressure.
Tests may also include full-scale equipment with elastomer components. This can include sealing elements such as o-rings. Structural components, such as stators in progressing cavity pumps and drilling power sections, can also be made from elastomers.
Elastomer behaviour can be very complex. Operating environments can include changing pressure, temperature and chemical exposure. For instance, an elastomer component operating in an oil well may:
- Thermally expand and soften due to elevated temperature;
- Swell due to hydrocarbon and gas penetration; or
- Shrink and harden due to leaching of some components of the elastomer.
The rate of change of the operating conditions can also affect the elastomer response. Explosive decompression can occur by removing pressure or load rapidly after the elastomer has been exposed to gases.
In elastomer material tests, coupons are exposed to the service environment for a period of time. The specimen is then removed from the environment to measure how the exposure has affected the material properties and dimensions. These tests can show if the elastomer is permanently changed by the operating environment. However, the tests do not indicate the actual condition of the elastomer while operating. In addition, the material properties are tested after the specimen has gone through a decompression cycle that could also alter its properties.
We have developed specialized testing methods to measure the dimensions of elastomer specimens continuously through a service cycle. These tests can show the initial compression of the elastomer as pressure is applied. Thermal expansion is measured as the specimen is heated. The rate of swell can be measured as the elastomer interacts with the chemical environment.
Specimens may also shrink as the test fluid leaches material from the elastomer. These tests can indicate whether the elastomer will stabilize in the environment or will continue to change in volume until it can no longer serve its purpose.
Finally, the elastomer dimensions can be monitored continuously during the decompression cycle. This information can be used to determine what decompression rate can be tolerated without damaging the elastomer.