Beyond Omniseal® Blog

Explore 4 Critical Considerations for Choosing Polymer Spring-Energized Seals in Oil & Gas Applications

Aug 22, 2018 / by Geert Vanthienen

Oil and gas production is on the rise. U.S. oil output is expected to reach an all-time high this year and Europe’s offshore drilling continues to grow, with strong contribution from UK and Norwegian Continental Shelf production. Simultaneously, Russia, Brazil and countries in the Middle East continue to produce.  Growing demand is pushing oil and gas companies to locate and produce new and more complex downhole reserves with conditions often requiring the ability to withstand high pressure, high temperature (HPHT), cryogenic temperature, sour gas, heavy oil, and other demands. Safety and environmental protection are major concerns. Proven designs and high-performance solutions are increasingly critical as new designs are developed to push the technology limits, one of which is polymer spring-energized sealing solutions. 

Importance of Seals in Oil and Gas Industry

Applications in oil and gas often require numerous locations where media needs to be controlled or sealed:

  • Subsea – in couplings, ball, gate and choke valves and API 17D wellhead and X-mas tree equipment that need to cope with extreme pressure and temperature conditions pushed by exploration and production from more complex reservoirs.
  • Floating Production - in Floating Production, Storage and Offloading (FPSO) vessels with large, complex high pressure and high temperature turret swivel stack systems, that are growing in use often required to remain on location in harsh environments.
  • Surface – in numerous API 6A and API 6D valves from low pressure up to 20kpsi operating pressure compliant with PR2 test procedure.
  • Fugitive Emission Valves – in high-performance stem sealing systems that comply with international standards such as ISO 15848 and SHELL MESC SPE77-312.
  • Cryogenic – in ball and butterfly valves and loading arms with low leakage challenge requirements driven by strict industry standards.   

Saint-Gobain OmniSeal® spring-energized seals are used in all of the above applications and solve reliability and durability problems caused by limitations of elastomeric seals. They consist of a PTFE, PEEK, or other polymer jacket encapsulating a metallic spring energizer and mostly combined with an anti-extrusion back-up ring. Originally used for one of the most challenging sealing environments, cryogenic liquid propellants in rocket engines in the 1950s, OmniSeal® seals were a precise fit for the oil and gas industry, maintaining resilience and sealing force in aggressive media, sour gas environments, and extreme operating conditions as well as being resistant to rapid gas decompression. 

Important Considerations for Polymer Seal Selection in Oil & Gas Applications

The process of determining which seal might be right for a specific application often is influenced by several factors, including: 

1. The Application – in valves, loading arms, turret swivels for FPSO, or downhole tools, look for important aspects such as:

  • Size/Diameter – Since parts are less standardized in oil and gas, a partner like Saint-Gobain Seals can meet vast measurement requirements, e.g., large diameter and custom sizes.
  • Position – The seal can be used in various areas within the application, i.e., the stem, seat, or static parts.
  • Durability – Reducing servicing and maintenance and ensuring long-lasting reliability are the main benefits of the right sealing solution.

2. The Working Conditions – addressing corrosive media and other stringent conditions such as:

  • High pressure: To improve processing control and durability, OmniSeal® spring energized seals offer vacuum pressure of up to 2,068 bar or 30,000 psi and beyond.
  • Extreme temperatures: There is always a potential of exposure to cryogenic or high temperatures. Our seals, for instance, can withstand temperatures from -253°C to +365°C (-424°F to +690°F).
  • Harsh chemicals and sour gas: As the oil and gas industry produces from more complex reservoirs, the percentage of sour gas (H2S, CO2) can increase, requiring materials to withstand higher concentrations up to 25% and above.

3. Compliance & Fugitive Emissions: With the increasing need for zero leakage and enforcement of even stricter regulations, the seal must be compliant and environmentally-sound. At Saint-Gobain Seals, we have designed and tested our seals to be compliant with the most stringent fugitive emission standards for on-off valves in accordance to ISO 15848-1 and SHELL MESC SPE 77-312. In addition, all our polymer materials have been certified to API 6A annex F and NORSOK M710. 

4. The Need for Proven Design: Reliability of seals is paramount in oil and gas; as such, designs need to be validated to work in real-world conditions. Our seals are pre-validated and field proven on test rigs built specifically for finite element analysis (FEA), 3D modeling, and more to ensure the highest levels of quality and reliability.

Specific Examples of Polymer Seals in Oil & Gas Applications

OmniSeal® spring-energized seals have been used in the oil and gas industry to solve reliability and durability requirements since the 1970s.  As one of the earlier applications, the seal has survived the rigors of the extreme Alaskan temperatures on the Trans-Alaska pipeline.  A few other examples include: 

  • Cryogenic Trunnion Mounted Ball Valves (TMBV) – Saint-Gobain Seals recently presented at Valve World Americas in Texas regarding development of new generation seat seals for cryogenic trunnion mounted ball valves in full compliance with SHELL MESC SPE 77-300 up to class 2500.
  • Cryogenic Marine Loading Arms - OmniSeal® PTFE lip seals are used in cryogenic rotary swivels for emergency release systems in loading arms required to transport large volumes of cooled gas with extreme cryogenic temperatures of -196°C.
  • In Axial Control Valves in Gas Compression Systems – Forecasted to grow in use, subsea compression technology improves gas recovery and offers reduced investments and operating costs, a smaller environmental footprint, and safer operations over new platform installs. Our seals have been used in water depth of 3,000m (9,842 ft.) on the world's first subsea gas compression station in the Norwegian Sea since 2015. The seals were custom-designed and manufactured with a unique blend of Fluoroloy® material. They successfully completed 500,000 strokes endurance without leakage according to API6A PR2 testing.

Although spring-energized seals are widely used in oil and gas, other high-performance polymer materials can also offer benefits.  Meldin® tolerance control products are excellent for high pressures and temperatures and Rulon® LR and Rulon® AR are chemically resistant, non-rusting, low stick slip materials.  

The above four considerations are key to ensuring a precise fit and lifetime confidence for oil and gas customers.  Working closely with oil and gas majors and EPCs to anticipate future sealing challenges is also critical. This collaboration helps us to develop the best polymer formulations and designs. In addition to leveraging our unique FEA simulation capabilities, we have built a comprehensive range of test rigs that allow us to pre-validate our sealing solutions in full compliance with industry standards for cryogenic temperature, up to 30,000 psi and fugitive emissions. 

We are continually seeking to push the limits of our materials and were the first to be certified to NORSOK M710, today holding 2% H2S, 15% H2S, and 25% H2S certifications along with API 6A annex F1.13.5.2 Immersion Testing in fluid HH. Our proven success and expertise resulted in a major U.S. oil and gas customer to recently request us to develop a technical engineering manual with selection guidelines for polymer lip seals in API 6D isolation valves. Widely distributed among operations, this technical document is leveraged to improve awareness of the importance of seals making the difference in severe service operations.  Our design engineering and R&D teams continually strive to show how the right sealing solution can make THE difference in oil and gas core systems. 

Do you have a need for a particular seal in oil and gas applications? Contact us today to see how we can help.

Topics: Industry

Geert Vanthienen

Written by Geert Vanthienen