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How Rapid Gas Decompression Damages PEEK Parts

September 26, 2026

Sources: manufacturer datasheets and published standards. See editorial standards.

Explosive decompression is one of the more misunderstood failure modes in downhole and process equipment, partly because the name overstates what happens and partly because it gets treated as an elastomer problem that plastics are simply exempt from. Neither is quite right, and the gap between those two mistaken ideas is where PEEK parts fail unexpectedly.

What is actually happening

Any polymer sitting in a pressurised gas environment absorbs some of that gas into its structure over time. How much depends on the gas, the pressure, the temperature and the polymer itself. As long as pressure stays high, the dissolved gas stays dissolved and causes no problem.

The failure happens on the way down. Drop the surrounding pressure quickly and the gas that dissolved into the polymer tries to come back out fast, because it is now vastly oversaturated relative to the new, lower pressure. If it cannot diffuse out through the surface quickly enough, it comes out inside the material instead, forming bubbles, blisters and internal cracks. In a severe case that looks close to what the name suggests, visible swelling and splitting right after a pressure drop. In a milder case it is internal damage that only shows up on sectioning or on the next pressure cycle.

This is a physical process, not a chemical one. The polymer is not being attacked by the gas. It is being damaged by gas that was already inside it trying to leave too fast.

Why PEEK does better than elastomers, and where that stops

Elastomers absorb gas readily and swell significantly under pressure, which is exactly why rapid gas decompression testing became a standard requirement for O-rings and other rubber seals in gas service. PEEK’s semi crystalline structure absorbs far less gas at the same pressure and temperature, which is the main reason it resists this failure mode noticeably better than the elastomers it often sits next to in a seal stack.

That resistance is relative, not absolute. Where PEEK still gets caught out:

• Thick or solid sections, because more volume means more absorbed gas and a longer path for it to escape during decompression.
• Very fast decompression rates, the kind seen in a fast blowdown rather than a controlled pressure bleed.
• CO2 rich or high partial pressure gas service, where more gas dissolves into the polymer in the first place.
• Sharp internal corners and stress concentrations, which is exactly where a decompression failure starts even in a part that would otherwise have survived.

None of this means PEEK is a poor choice for gas service. It is one of the better plastic choices available. It means the material choice alone does not answer the question, and the part still has to be evaluated for its own geometry and service conditions.

The standards, used correctly

NORSOK M-710 is the qualification standard most commonly cited for rapid gas decompression testing in the oil and gas industry, and it includes an RGD test method. It was written primarily for elastomeric sealing materials, so citing it for a PEEK part without checking what was actually tested, and against which material, is a common and easy mistake.

ISO 23936-1 covers non-metallic materials, thermoplastics included, for use in the oil and gas industry, and addresses stability in simulated production media. The 2022 edition states that blistering by rapid gas decompression is outside its scope, so decompression resistance needs a separate test basis named by the operator or equipment maker. It is still the more directly applicable media reference when the part is thermoplastic rather than elastomeric.

The useful question to ask a supplier is not “is this material RGD rated,” which is close to meaningless without a standard and test conditions attached. Ask which standard, which test method, at what pressure and temperature and at what decompression rate. A grade that passed at one set of conditions is not automatically qualified at a harsher one.

What this means for a buyer’s RFQ

For a critical part, in gas service, at meaningful pressure, request decompression test data as part of qualification rather than assuming a grade is fine because “PEEK is used in oil and gas.” That phrase describes a category, not a qualification. Ask for the test method, the conditions and whether the data covers the actual part geometry or only a standard test coupon, since a coupon and a thick machined ring do not necessarily behave the same way. Background on how PEEK parts get specified and qualified for downhole service more broadly is in PEEK parts for oil and gas, and the paperwork trail that should back up any material claim is covered in verifying PEEK material.

If the part also functions as a seal backup ring, the same geometry rules that reduce decompression risk overlap heavily with good extrusion resistant design, covered in PEEK backup rings and seal design.

Send the drawing with the gas composition, pressure profile and expected decompression rate, and we match you with shops that ask for that information before they quote, not after the part fails.

Frequently asked questions

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