Explosive Decompression (RGD) — Protecting Filter Seals in High-Pressure Gas Service
When high-pressure gas is depressurised rapidly, dissolved gas trapped inside elastomer seals expands violently — tearing the material apart from the inside. The result: catastrophic seal failure and uncontrolled gas release.
Recognise the Symptoms
- Seal blisters, cracks, or complete fragmentation after pressure cycling
- Gas leaks at housing joints or element connections after depressurisation events
- Visible rubber fragments in the housing bowl or downstream pipework
- Loss of housing pressure integrity during or immediately after blowdown
- Recurring seal failure despite using nominally correct seal materials
- O-ring extrusion into backup ring gaps after rapid pressure drops
Root Causes
Gas permeation under pressure
CO₂, CH₄, H₂S, and other gases dissolve into elastomer seal materials at high pressure over time
Rapid depressurisation
when system pressure drops quickly (e.g., ESD, blowdown, process trip), dissolved gas expands faster than it can diffuse out of the elastomer
Internal void formation
expanding gas creates micro-cavities inside the seal material, which grow and merge to form blisters and cracks
Incorrect seal material
standard NBR and many FKM compounds have poor resistance to RGD, particularly in CO₂ and H₂S-rich gases
Temperature effects
higher operating temperatures increase gas solubility in elastomers, making RGD damage more severe on depressurisation
Diagnostic Checklist
- 1What is the operating pressure? RGD becomes significant above approximately 30 bar
- 2How fast is the depressurisation? Rate of pressure drop is the critical factor — not absolute pressure
- 3What gas composition is involved? CO₂ and H₂S are the most aggressive gases for RGD
- 4What seal material is currently installed? Standard NBR is unsuitable above 30 bar in CO₂ service
- 5What is the operating temperature? Higher temperatures increase dissolved gas content
- 6How frequently do depressurisation events occur? Repeated cycling is worse than a single event
- 7Is the housing rated to NACE MR0175 / ISO 15156 standards for sour gas service?
Related Applications
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