Oil and Gas Seal Materials: Subsea, Sour Gas & Refinery

Oil and gas seal materials often work where failure is hardest to fix. Subsea equipment, sour wells, and refinery units combine high pressure, extreme temperatures, and aggressive fluids. In addition, replacing a seal can mean pulling equipment or shutting down a unit. This article explains which compounds resist explosive decompression, H2S, and high-temperature refinery service. It also covers how material choice and hardware design work together to prevent extrusion. For a complete overview of seal materials, visit our Complete Guide to Elastomer Seal Materials.

Oil and Gas Seal Materials

Oil and gas seals combine high pressure, wide temperature swings, and aggressive fluids. In addition, access for replacement is often difficult or impossible. Marco’s oil and gas sealing page and High Pressure O-Ring Material Selection Guide cover the full range.

Best O-Ring and Seal Materials for Subsea Oil and Gas Equipment

Subsea oil and gas equipment sits in cold seawater under high pressure for years. Therefore, subsea seals need three things: low-temperature flexibility, rapid gas decompression (RGD) resistance, and long-term compression set resistance.

The best subsea options include:

Low-temperature FKM: Marco V1160 is an XLT ultra-low-temperature FKM rated down to -50°F (-46°C). It is NORSOK and NACE tested for explosive decompression. Similarly, V1090 is a GLT-type FKM rated to -40°F (-40°C).
HNBR: Marco R1008 is a 90-durometer HNBR tested to NORSOK M-710 for explosive decompression.
FDA silicone: handles baking and freezing temperatures and is odorless. However, it wears quickly in dynamic seals.
Low-temperature FFKM: Markez® Z1322 pairs AED resistance with a -50°F (-46°C) low-temperature rating. As a result, it offers the best overall mix of temperature range and chemical resistance.

Rubber Materials with the Best Extrusion Resistance for Explosive Decompression and High Pressure

Most O-rings are designed for up to 1500 psi, or a maximum clearance gap of .040 inches. Above those conditions, or with a combination of high pressure and a large gap, the seal compound must be a more extrusion resistant grade.

Additionally, rapid pressure drops let dissolved gas expand inside the seal and cause blisters or splits. Under these conditions, choose hard, AED-rated compounds. Marco V1090, for instance, is a 90-durometer FKM built for greater extrusion resistance. When chemical and heat extremes are also a concern, Markez Z1412 is a 90-durometer FFKM with NORSOK M-710 AED resistance.
Material alone is rarely enough, though. Pair these compounds with tight clearances and O-ring backup rings. For the most extreme pressures, consider metal spring-energized PTFE seals.

Sealing Materials That Withstand H2S and Sour Gas

Hydrogen sulfide attacks many elastomers. Furthermore, sour wells often contain amine corrosion inhibitors and steam, which degrade standard FKM and NBR.

For sour service, three choices stand out. First, FFKM offers the broadest resistance. Markez Z1412 provides excellent resistance to sour gas, associated chemicals, and steam up to 590°F (310°C). Second, Aflas® (FEPM) resists amines, bases, and steam at lower cost. Marco L1009 is an AED-tested Aflas rated to 482°F (250°C). V1090 has excellent explosive decompression resistance and performance in low-temperature high-pressure environments. Third, base-resistant FKM (Marco L1010) tolerates up to 40% H2S, compared with only 2% for standard Type A FKM. By comparison, Aflas is rated to 20% H2S.

Best Sealing Materials to Prevent Failure in High-Temperature Refinery Applications

Refinery seals see hot hydrocarbons, steam, and process chemicals, often with thermal cycling. Consequently, compression set and heat aging are the main failure modes.

FFKM perfluoroelastomer is the top choice above 450°F. For example, Markez Z1028 handles up to 610°F (321°C) with wide chemical compatibility. It is used in petrochemical service as an alternative to Kalrez® 6375, 4079, and 7075. For even hotter points, Z2000 extends to 630°F (330°C). Below 450°F, Aflas and high-performance FKM offer a lower-cost option. Explore Marco’s high temperature O-rings for more choices.

Elastomer Materials by Industry and Application

Visit our Complete Guide to Elastomer Seal Materials to consult our quick reference tables for typical temperature ranges and elastomer seal materials by application. Read on to find application-specific recommendations for other industries.

—

Elastomer Seal Materials for Oil & Gas: Subsea, Sour Gas, and Refinery Service