by Bill Vardeman Bill Vardeman No Comments

Types of Seals for Oil and Gas Industry

seals for oil and gas

Seals used in the oil and gas industry must withstand high temperatures, high pressure, and a chemically hostile environment. The conditions limit the material used to make the seals for this industry. The most common types of materials include

  • PTFE
  • PEEK
  • UHMW
  • PCTFE
  • Hytrel

Let’s look further into these materials, their benefits, and their limitations. 

What is PTFE?

Polytetrafluroro Ethylene (PTFE) is a synthetic fluoropolymer with high-temperature resistance, commonly known as Teflon. It is a hydrophobic, high-molecular-weight polymer consisting of carbon and fluorine.

Benefits of Using PTFE

PTFE is ideal for use in the oil and gas industry as it is resistant to extreme high and low temperatures. In addition, PTFE has a low coefficient and a low dielectric constant. Finally, the hydro resistance nature of the material makes it a top choice for working with steam or heated seawater. 

One of the most significant benefits of using PTFE is the resistance to harsh chemicals. It has the broadest chemical resistance of commercial polymers. For example, seals made of this material are resistant to hydrogen sulfide, ferric chloride, ferrous sulfate, hydrochloric acid, and hydrofluoric acid. 

Limitations of PTFE

PTFE’s limitations make it unsuitable for some uses. For example, it is sensitive to creep and abrasion, requiring regular maintenance. PTFE also has low radiation resistance and can corrode and produce toxic fumes as it breaks down.

Properties of PTFE

PTFE has a density of 2200 kg/m3 with a melting point of 327°C (620°F). PTFE maintains self-lubrication, strength, and toughness at temperatures down to -268 °C (-450.67°F). Additional properties include:

ptfe seal used by oil and gas

What Are Some Common Oil and Gas Applications of PTFE?

PTFE is one of the more common materials used in oil and gas seals. For example, O-rings, slipper seals, backup rings, piston rings, and spring-energized seals use PTFE material. In addition, natural gas, cold media seals, bearings, and wear components also use PTFE for manufacturing.

 

What Is PEEK?

Polyetheretherketone, or PEEK, is a colorless organic thermoplastic semi-crystalline polymer with excellent mechanical and chemical resistance properties. It’s high-resistance to terminal degradation makes it useful in oil and gas environments.

Benefits of using PEEK

As with PTFE, PEEK has several benefits for oil and gas companies. It has good dimensional stability and chemical resistance. In addition, PEEK is resistant to gamma radiation and X-rays.

PEEK has high mechanical strength and is ideal for high vacuum applications. Its robust nature makes it suitable for demanding applications such as the oil and gas industry. It works well in compressors, pumps, and pistons.

Limitations of PEEK

Despite PEEK’s many benefits, there are some drawbacks to using this material. It has low UV light resistance. It is also unsuitable for nitric acid, sulphuric acid, sodium, and halogens. In addition, it is expensive to make and requires high temperatures to process. 

Properties of PEEK

PEEK has a high tensile strength of 25000 to 30000 psi. It has a V0 flammability rating of 1.45mm and can withstand high loads for extended periods without residual damage. Additional properties include:

What Are Some Common Oil and Gas Applications of PEEK?

Labyrinth, spring-energized piston seals, backup rings, and seal packing in the oil and gas industry are manufactured using PEEK materials. In addition, it is the material most often chosen for the face seals at the wellhead to contain the high-pressure production of gas and fluid.

What is UHMW Polyethylene?

Ultra-High Molecular-Weight, UHMW, Polyethylene seals are thermoplastic, semi-crystalline materials. It is lightweight with a high-pressure tolerance that makes it ideal for spring energized seals used by the oil and gas industry.

Benefits of Using UHMW Polyethylene

Seals made from UHMW have the benefit of being both abrasion and impact resistant. This self-lubricating material has a low friction coefficient. It withstands extreme colds and high temperatures.

 It has a high molecular weight, meaning UHMW is not likely to melt and flow as a liquid. This material cannot be molded by traditional methods, thanks to the high molecular weight. Instead, it is compression molded to make it stronger.

Limitations of UHMW Polyethylene

While UHMW Polyethylene has many benefits for the oil and gas industry, there are some limitations, such as having a lower maximum continuous surface temperature than other materials. 

UHMW Polyethylene has a compressive strength of 3000 psi. In addition, it has a maximum safe workload of 1000 psi in some industries. Overload can cause UHMW polyethylene to crack or break.

Properties of UHMW Polyethylene

UHMW polyethylene seals are self-lubricating and have low surface energy, which makes them ideal for the oil and gas industry. Other UHMW polyethylene properties include

uhmw seals used by oil and gas

What Are Some Oil and Gas Applications for UHMW Polyethylene?

UHMW polyethylene material is used for seals in the oil and gas industry. It is used to make spring energized seals. It is also used for cargo dock impact bumpers and liners.

What is PCTFE?

Polychorotrifluoroethylene (PCTFE) is a chemical compound with a high tensile stretch and good thermal properties. Its chemical-resistant properties make it ideal for use in the oil and gas industry for seals and other components.

Benefits of Using PCTFE

Seals made with PCTFE are nonflammable and heat resistant up to 175°C (347°F). They are also resistant to acetone, hydrochloric acid, sodium peroxide, citric acid, and sulfuric acid. It is water-resistant as well.

PCTFE has a board temperature range with a useful temperature range of -204.4°C (-400°F) to  193.3°C (380°F). When comparing PCTFE vs PTFE, PCTFE is a stronger polymer with better mechanical properties.

Limitations of PCTFE

PCTFE has many beneficial properties for the oil and gas industry. However, some limitations, such as a lower melting point when compared to PEEK or PTFE, might make it less desirable. Seals used in extreme temperatures may need to be a different material.

Additionally, PCTFE is a stiffer material. While this does allow it to maintain its dimensions better, it does break easier than PTFE. Along with being stiffer, it is not as non-stick when compared to PTFE.

Properties of PCTFE

PCTFE has V-0 flammability and a hardness of 67 at 100°C and 80 at 25°C. Other properties include

 

 

What Are Some Oil and Gas Applications for PCTFE?

Like PEEK or PTFE, PCTFE is a great material for seals in the oil and gas industry. It’s chemical resistance, which means it can be used in the most volatile industries. Fillers within the seals can enhance some of the properties. PCTFE is also used in component designs and valve seats.

What is Hytrel?

Hytrel is a thermoplastic polyester elastomer that is plasticizer-free. It is a stable material with needed flexibility while handling high temperatures. It is a worthwhile option to consider for the oil and gas industry.

Benefits of Using Hytrel

As a seal material for the oil and gas industry, Hytrel has good chemical resistance. It can withstand exposure to fuel, hydrocarbon solvents, and oil. Additionally, as the material is exposed to higher temperatures, it becomes more rigid. At lower temperatures, it is more flexible.

Hytrel is abrasion resistance. It offers impact and creep resistance to the seals. It also is resilient and excels at providing flex fatigue and tear resistance. Hytrel has a natural spring-like property and has low hysteresis.

Limitations of Hytrel

As there are several models of Hytrel, only a few are best for use in seals. Hytrel 4556, 4056,4068,4069, and 6356 are the ones that work best. However, these don’t always work well in the oil field, so you should know which ones to look for.

Properties of Hytrel

Hytrel has V-0 flammability and a hardness of 67 at 100°C and 80 at 25°C. Other properties include

 

seals for oil and gas

 

What Are Some Oil and Gas Applications for Hytrel?

Hytrel is useful as a seal material in the oil and gas industry. As it is resistant to many chemicals, including hydrocarbon solvents, it is ideal for hazardous conditions.

Which Seal Type is Best for the Oil and Gas Industry?

Each seal type has its uses and benefits for the oil and gas industry. However, the best options are PEEK, UHMW, PCTFE, and Hytrel. It is because they have the best physical properties to withstand the harsh conditions in the oil and gas field. 

At Advanced EMC Technologies, we offer custom-engineered sealing systems that provide reliable sealing solutions. Our seals perform under high temperatures, high pressure, and chemically hostile environments. Contact us for more information.

 

Seals for Oil and Gas Industry FAQ

IS PEEK environmentally friendly?

There is no evidence that PEEK has a significant environmental impact in its service life, disposal, or manufacturing. Toxicity is low and does not contain anything known to be toxic. There is low smoke, poisonous gas emissions, and fire when involved in a fire.

What are spring-energized seals?

Spring-energized seals can store mechanical energy by compressing the spring. As a result, they withstand more pressure and heat than their conventional counterparts. In the end, the mechanical energy stored in the seal keeps it from leaking.

Rotary Shaft Seals for Oil and Gas Industry | Advanced EMC Technologies
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Rotary Shaft Seals in the Oil and Gas Industry

Seals in the oil and gas industry face some of the most intense challenges, HPHT (High Pressure, High Temperature) and corrosive media. Trying to find the right rotary shaft seal for such an application can be challenging but is far from impossible.

Introduction to Oil and Gas Seals

Seals are needed in many different areas of the petrochemical industry. They can be found in compressors, motors, gearboxes, pumps, top drives, and steam turbines. Seals are required for mixers, extruders, fans, cooling towers, and blowers. Swivel stacks, wellhead connectors, subsea connectors, and rotary drill bits are also in need of reliable seals to do their job safely and effectively.

And whether these seals are for upstream, midstream, or downstream petrochemical processing, they often serve in a critical application: when a seal in the oil and gas industry fails, it is more than an inconvenience. Seals failures can quickly prove devastating to personnel, the equipment, and the environment. And the costs of seal failure can easily extend beyond equipment downtime and repair costs, as there may be fines related to environmental damage as well as costly lawsuits and out-of-court settlements involved.

With all that said, it can be agreed that seals for rotary shaft applications must be especially reliable, extremely rugged, and able to provide excellent performance in some of the most hostile operating environments in existence.

Spring-Energized Seals

Spring-energized seals include a spring energizer that keeps the seal lip in contact with the sealing surface when other seals would fail. They can maintain a seal even in the presence of wear, out of roundness, eccentricity, and runout. In addition, spring-energized seals outperform traditional lip seals in extreme pressures (including vacuum pressures) and extreme temperatures (including cryogenic temperatures). 

Most oil and gas applications using spring-energized seals take advantage of canted coil springs and their ability to provide a consistent load on the seal lip over a wide deflection range. In addition, canted coil springs are also highly resistant to damage unless they are stretched upon installation.

Labyrinth Seals

Labyrinth seals do an excellent job of sealing and are very effective at contaminant exclusion. They accomplish this through a barrier with a complicated set of maze-like paths (hence the term “labyrinth”) that (1) restricting the clearance through which leaks can occur and (2) creates areas of turbulent flow and high flow friction to further prevent leaks and contamination.  They are considered a dynamic mechanical clearance seal.

One of the benefits of labyrinth seals is their ability to provide sealing without making contact with the sealing surface. This means they experience far less wear than traditional lip seals and generate less frictional losses, as well. They are highly efficient, extremely reliable, and are even easy to install.

Seal Materials

Rotary shaft seals can be exposed to highly corrosive chemicals including methanol, H2S, aromatic hydrocarbons, oil, and supercritical CO2. Many of the chemicals that seals must interact with are also highly flammable gases and liquids. Operating temperatures can range from cryogenic below zero temperatures all the way up to 800°F, depending on the application and media involved. To complicate matters further, some liquid products are handled near their vapor temperature where they can unexpectedly flash into vapor. In addition, the materials used need to be resistant to chemical permeation while also being extremely wear-resistant and flameproof.

Two options typically lie at the top of the list for seal jacket materials: PEEK and PTFE. Both of these high-performance polymer materials are extremely compatible with a wide range of chemicals. They offer excellent performance in the HPHT environment found in most oil and gas applications: PEEK has a maximum operating temperature of  500°F and PTFE can handle temperatures up to 575°F. They also perform well in below-zero cryogenic temperatures, such as those used with LNG.

These engineering polymers are also wear-resistant and flame resistant with low coefficients of friction and thermal expansion. In addition, they are dry-running so no additional lubricants are required.  And PEEK in particular offers excellent performance even in sour gas environments, which often destroys other seal materials.

For spring-energized seals, both PEEK and PTFE are excellent choices. For labyrinth seals, however, PEEK or Flourosint (enhanced PTFE) usually performs more effectively. And keep in mind that these materials can be enhanced with fillers to increase their mechanical properties, including stiffness, strength, and wear resistance.

Conclusion

When traditional rotary shaft lip seals fail in oil and gas operations, consideration should be given to spring-energized seals and labyrinth seals combined with PTFE, PEEK, or enhanced PTFE. This combination of sealing technology and engineering polymers can provide the reliable performance needed in critical applications where seal failure is simply not an acceptable option. Both types of seals and the materials described here have proven performance records for their ability to handle the rugged, corrosive, HPHT environments of the petrochemical industry.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Spring Energized Seals in the Oil and Gas Industry

The oil and gas industry is home to some of the most intense operating conditions for seals: HPHT (High Pressure, High Temperature), corrosive chemicals, and very dangerous repercussions if seals fail. When all other sealing solutions fail, spring-energized seals are often the answer.

How are spring energized seals used in the oil and gas industry? Spring energized seals are used for a variety of applications including valves, well head connectors, couplings, loading swivels, and more.

Spring Energized Seals in Oil and Gas Applications

Seals are used throughout the oil and gas industry, including applications as diverse as …

  • Anti-Blow Out Seals
  • Couplings
  • Downhole Tools
  • Emergency Release Systems
  • Loading Swivels
  • Logging Tools
  • Quick Connect/Disconnect Couplings
  • Rotary Drill Bits
  • Surface and Subsea Well Heads
  • Swivel Stack Seals
  • Top Drive Units
  • Valves
  • Well Head Connectors

A seal failure in any of these areas could quickly lead to injured personnel, environmental damage, and ruined equipment. Seals for such applications must be rugged, reliable, and chemically resistant. They must be compatible with corrosive chemicals such as H2S, aromatic hydrocarbons, supercritical CO2, oil, and methanol,–and they need to be resistant to chemical permeation, as well. They generally need to be flameproof, tough, and wear-resistant as well.

Spring-Energized Seals

A spring-energized seal has a spring (the energizer) that applies additional force to the seal lip to maintain contact between the lip and the sealing surface. This energizing effect can account for issues related to dimensional changes, extreme pressure variations, wear on the edge of the seal lip, and other phenomena that can lead to a leaking seal. 

With the right choice of spring geometry, a constant force can be applied to the sealing lip to ensure its full engagement with the sealing surface, even through extreme pressure variation, temperature changes, wear on the shaft, and alignment issues. Spring energized seals can also be used with backup rings, or BURs, to prevent extrusion problems with the seal lip.

Lip Materials for Spring-Energized Seals

The seal lip material is also key, with the most commonly used polymers for oil and gas sealing challenges being PEEK and PTFE. They are both chemically inert, tough, wear-resistant, flame resistant, and offer outstanding performance even in the presence of extreme temperatures. Both of these materials work extremely well with spring energizer to result in excellent spring-energized seals for the oil and gas industry. They also have very low coefficients of friction and low CTEs (coefficient of thermal expansion).

PEEK performs well at pressures up to 20 kpsi, has a maximum temperature operating temperature of 500°F, and is also available will fillers to provide additional strength and hardness. Many grades PTFE has a maximum operating temperature close to 575°F and can handle high pressures. They are both dry running, as well, which makes them ideal for situations where traditional lubrication is not feasible.

Conclusion

If you are in the market for a reliable sealing solution for an oil and gas application, be sure to consider spring energized seals. They perform where many other types of seals fail, can be used with backup rings, are commonly used in petrochemical applications, and can be designed with a PEEK or PTFE seal lip for maximum performance.