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Oil & Gas

We are the world leader in rapid gas decompression (RGD) resistant elastomers and seals, with a range of verified materials including: AF69/90, Elast-O-Lion® 985, Elast-O-Lion® 101, FR25/90, FR58/90, and the new generation FR68/90 based on innovative polymer architecture. The four latter grades are qualified to Norsok M-710 for RGD resistance and sour-gas ageing.

Our world-leading position dates back to the early 1980s, when we initiated a comprehensive research programme into the phenomenon of RGD (or ED, explosive decompression, as it was then known) following reports of seal failures in North Sea fields during exploration and production operations.

In collaboration with oilfield equipment manufacturers and the research arms of two leading offshore operators, we investigated the causes of RGD — with gas permeation and diffusion into elastomeric components at very high pressure.

Under these conditions, there is no real deterioration in performance of the component as long as the internal gas pressure of the elastomer remains equal to the external pressure. However, when the external pressure is removed suddenly, or fluctuates, large pressure gradients are created between the interior and surface of the component, and the gas expands far faster than it can naturally diffuse/permeate through the elastomer. If the material cannot physically resist crack or blister growth under these conditions, then the component suffers structural failure.

RGD damage manifests itself in various ways: from internal splits that are not visible on the surface of the seal, to surface blisters, fractures and complete fragmentation.

FR58 — the first proven RGD-resistant elastomer
Our initial development work in the 1980s resulted in the RGD-resistant fluoroelastomer designated FR58, followed by the introduction to the Oil & Gas sector of two proven grades, FR58/90 and FR58/98 (90 and 98 IRHD respectively) a few years later.

Over the past 20+ years, we have built on this success in terms of both elastomer technology, and RGD research and testing capability. Our James Walker Technology Centre now has the most advanced RGD test facilities belonging to any fluid seal manufacturer, and equal — or superior — to those of most specialised independent test houses.

We advocate that, when validating sealing systems for our customers, RGD tests should be performed on seals in realistic, service-simulation housings. Standard ‘bomb’ testing of unconstrained samples is often unrepresentative of normal operating conditions, as the results relate only to applications that require unconstrained seals — such as shear blade BOPs.

In-house testing
With four seals housed independently in a test rig, the procedures we follow are:

Pressure/temperature ranges: 15MPa (2175psi) @ 200°C (392°F) up to 35MPa (5076psi) @ 65°C (149°F).
Media: 90% CH₄ + 10% CO₂.
Seal size: SAE AS 568-329 (and larger sections up to 10mm).
Soak 'O' ring samples at pressure and temperature for 72 hours, then decompress at 3.5MPa (508psi) per minute. Rest at ambient for one hour, then repeat for a total of 10 cycles with 24-hour soak at temperature and pressure.

Pressure/leakage is monitored constantly throughout testing, using pressure gauges and OVA/sonic leak detection. Each of the seals is then visually examined externally, and cut into four sections where the following criteria are applied:

0 rating: No internal cracks, holes or blisters of any size.
1 rating: Less than four internal cracks; each shorter than 50% of cross section, with total crack length less than the cross section.
Ratings 2, 3, 4 and 5: Lead up to complete separation of the seal into segments.

The highest Norsok rating of 0000 (zero faults in all four cut sections) has been achieved by our four leading RGD-resistant elastomer grades: Elast-O-Lion® 101 (6.99mm section ‘O’ rings); FR25/90 (6.99mm & 5.33mm sections); FR58/90 (5.33mm section), and FR68/90 (6.99mm. 8.40mm & 10.0mm sections).

We also in-house test to RGD specifications required by Shell and Total. Our own highly developed test procedure — JW ARD/20/RGD — uses 80% CH₄ + 20% CO₂, at 100°C (212°F) and 13.8MPa (2000psi) with 20 decompression cycles to ambient.

Click here for a pdf copy of our guide to Elastomeric seals & components for the Oil & Gas Industry.