Low-Temperature, High-Pressure Seals – A Complete Guide

Within the energy sector, extreme combinations of temperature and pressure are commonplace and require robust systems to withstand these. For example, these conditions are often seen in applications such as hydrogen transport infrastructure, subsea oil and gas equipment, and carbon capture and storage (CCS).

For elastomeric seals, this combination presents a significant engineering challenge. Materials must maintain elasticity at sub-zero temperatures while also resisting extrusion, rapid gas decompression (RGD), and chemical attack under pressures that can exceed 1000 bar.

In this blog, TRP Polymer Solutions explores the best elastomer materials for low-temperature O-rings and how our extensive expertise in custom rubber mouldings can assist.

Why low temperature and high pressure are challenging for seals

Elastomers are viscoelastic materials whose behaviour changes significantly with temperature and pressure. At low temperatures, rubber materials begin to lose flexibility, reducing their ability to maintain sealing contact. At high pressures, the same materials can be forced into clearance gaps, leading to seal extrusion and failure.

When these two effects occur together, the sealing system must be carefully engineered to ensure:

• Sufficient elastic recovery at low temperatures
• Resistance to extrusion under high differential pressure
• Compatibility with aggressive media such as hydrogen or CO₂
• Resistance to rapid gas decompression events

These challenges are particularly relevant in modern energy infrastructure, as explained below.

The key applications for low-temperature, high-pressure seals

Hydrogen transport and storage

Hydrogen systems present a particularly demanding sealing environment. As hydrogen molecules are extremely small, they can permeate through many elastomers more readily than other gases. When combined with high pressure and low temperatures in hydrogen transport pipelines or storage systems, seals need to provide low gas permeability, resistance to rapid gas decompression, and stable sealing behaviour at temperatures below −40°C.

Therefore, specialised elastomer formulations are often needed to ensure that all of these factors are accounted for.

Subsea oil and gas equipment

Subsea environments commonly experience high pressure with low ambient temperatures, especially so in deep-water installations. Sealing systems used in subsea valves, connectors, and instrumentation must therefore resist external hydrostatic pressure, low-temperature environments, and gas exposure leading to explosive decompression.

To assure their suitability and dependability, materials used in these applications often require certification to standards such as NORSOK M-710.

Carbon capture and storage (CCS)

Carbon capture and storage infrastructure frequently involves the transport and injection of compressed CO₂. Depending on the operating conditions, CO₂ can cause elastomer swelling, rapid decompression damage, and changes in mechanical behaviour.

As a result, seals used in CCS systems must combine chemical resistance, low-temperature flexibility, and pressure stability.

The effects of low-temperatures on elastomers

Understanding how elastomers behave at low temperatures and the problems they can face is critical when designing seals for extreme environments.

TR10 and elastic recovery

One useful indicator of low-temperature performance is TR10, which indicates the temperature at which a material recovers 10% of its deformation after stretching. Lower TR10 values generally indicate better low-temperature flexibility.

For example:

• Our F318 low-temperature, high-hardness FKM has a TR10 value of −40°C
• Our TRPlast® LT45-AED, low-temperature, high-hardness FFKM has a TR10 value of −30°C.

These materials are designed to maintain static sealing performance at temperatures down to approximately −55°C and −45°C, respectively, depending on application conditions.

Compression set

Compression set is another key performance parameter for sealing materials, with high resistance to it being a leading factor for choosing it for low-temperature, high-pressure seals.

At low temperatures, some elastomers may struggle to recover their shape after being compressed, potentially reducing sealing force over time. TRP run comprehensive compression set characterisations as standard and can run customer compression set tests for specific applications if necessary.

Below is an example of a compression set curve for our low-temperature, high-hardness TRPlast® LT45-AED FFKM, where TRP has the capability to run tests up to 400 °C

Figure 1. Compression set of TRPLT45-AED low-temperature FFKM at 200 °C

The effects of pressure on elastomer seals

While low temperature affects material elasticity, high pressure also introduces additional mechanical challenges.

Seal extrusion

At high pressures, elastomer seals can be forced into clearance gaps between mating components. This phenomenon is known as seal extrusion. The factors that can influence extrusion resistance include material hardness, clearance gap size, seal geometry, and system pressure.

Harder materials and properly designed grooves can significantly improve resistance to extrusion in high-pressure environments.

Below is a graph showing the max pressure an O-ring may be exposed to before extrusion for a given clearance.

Rapid Gas Decompression (RGD)

In gas systems, high-pressure gases can permeate into elastomers over time. If pressure is released quickly, the gas may expand inside the material and cause internal damage. This effect is known as rapid gas decompression, or explosive decompression.

Materials used in high-pressure gas applications are often tested to international standards, such as NORSOK M-710, to ensure they can withstand these events.

The best elastomers for low-temperature, high-pressure sealing

Several elastomer families can be used in extreme environments, but FKM and FFKM are often the preferred rubber materials due to their chemical resistance and mechanical stability.

Low-temperature FKM compounds

Low-temperature FKM formulations such as GLT, GFLT, and ultra-low-temperature FKM offer improved flexibility compared with standard fluorocarbon elastomers. For example, our compound F318, a 90 IRHD ultra-low-temperature FKM, is designed for demanding environments. Being ideal for hydrogen transport and subsea oil and gas systems, its key characteristics include:

• Operating capability down to approximately −55°C
• High chemical resistance
• Low gas permeability
• Pressure capability exceeding 1000 bar when used with appropriate groove geometry
• NORSOK approved for explosive decompression

FFKM for Universal Chemical Resistance

For applications where a single material needs to withstand multiple aggressive substances, FFKM provides the ideal solution due to its chemical compatibility across many fluids. These materials are commonly used where customers require maximum chemical compatibility across multiple fluids

For instance, TRP’s TRPlast® LT45-AED compound offers:

• Operating temperatures down to −45°C
• Hardness of 90 IRHD/Shore A
• Universal chemical resistance
• Suitability for high-pressure environments exceeding 1000 bar

Design considerations for high-pressure sealing

Material selection is only one part of successful seal design, as the following design aspects of low-temperature, high-pressure seals are also important.

Seal geometry

Correct groove design is critical to ensuring reliable sealing performance under extreme pressure conditions. In fact, poor groove design can lead to premature seal failure, even when high-performance materials are used. The key parameters for a seal’s design include:

• Compression levels
• Clearance gaps
• Surface finish
• Tolerance stack-ups

Back-up rings

Back-up rings, also known as anti-extrusion rings, are frequently used alongside O-rings in high-pressure applications and are particularly useful in pressures above several hundred bar. These are placed behind an O-ring within a gland to prevent seal extrusion, support the elastomer under load, and extend seal lifetime

Engineering support and simulation

Advanced sealing development, through the use of finite element analysis (FEA) and experimental testing, for example, can help to evaluate:

• Seal deformation under pressure
• Contact stresses
• Extrusion risk
• Load deflection behaviour

Combining modelling with physical testing provides greater confidence in seal performance before deployment.

The need for custom material development for extreme environments

In many cases, standard materials may not fully meet application requirements for low-temperature, high-pressure environments. TRP Polymer Solutions develops and formulates materials in-house, and we will design an elastomer material for specific applications. For example, we can

• Reduce gas permeability for subsea systems
• Improve low-temperature flexibility
• Enhance resistance to explosive decompression
• Optimise hardness for high-pressure sealing

In one project, we successfully reduced seawater permeation by 50% while maintaining mechanical performance, with our tailored materials being highly capable of solving complex sealing challenges.

Resilient low-temperature, high-pressure seals at TRP Polymer Solutions

With our expertise in designing robust seals, with both the most appropriate custom material and physical design carefully considered for your unique application, TRP Polymer Solutions are the foremost choice for low-temperature, high-pressure seals. We offer custom rubber seals and many more custom rubber moulding solutions to dependably meet the needs of the hydrogen energy, carbon capture, and subsea engineering industries.

To find out more about our expert services for custom rubber moulded components and how we can design the perfect component as per your application’s requirements, contact us today. A member of our team will be more than happy to discuss your ideal solution.