Which hydraulic seal is best for high temperature?

Hydraulic systems are often operating under harsh conditions: high pressure, high loads, and, often, extreme temperatures. The most important components of such systems are the seals for hydraulics. If temperatures increase, normal seals could quickly fail, resulting in leaks in efficiency, decreased efficiency, and the cost of downtime.

Which hydraulic seal is the best for applications with high temperatures?

The answer is contingent on a variety of aspects, such as the operating temperature, the type of fluid pressure, and the type of seal you are using. dynamic or static. However, certain seals consistently excel in their reliability in extreme temperatures.

This blog will look at the most effective hydraulic seals for high temperatures, analyze their characteristics, and assist you in selecting the best seal for your particular needs.

Understanding high temperature in hydraulic systems

Before choosing a seal, it's crucial to understand the meaning of "high temperature" means in hydraulic systems.

In many industrial settings, temperatures over 150 degrees Celsius are deemed to be high. In more extreme environments--such as chemical processing, power generation, or heavy machinery temperatures can exceed 250 °C or even 300 °C.

When temperatures reach these levels, common sealing materials such as nitrile (NBR) start to break down quickly and lose the ability to stretch and strengthen. This is why choosing the right material is crucial.

Why is high temperature a challenge for seals?

The high temperatures can affect seals for hydraulics in a variety of ways:

• The degradation of the thermal materials degrades or gets harder
• Inelasticity decreases. Seals can no longer hold an appropriate contact
• Wear and tear are increased. The softened material deforms under pressure
• Chemistry reactions: Heat speeds up the incompatibility between fluids and materials

If the wrong seal material is employed, the failure will be almost certain.

Key properties required for high-temperature seals

For them to perform effectively in environments with high temperatures, the hydraulic seals need to include:

• Excellent thermal stability
• Resistance to ageing and oxidation
• High compression set
• Hydraulic fluids are chemically compatible with HTML0.
• Mechanical force under pressure

The best material will not be perfect for every situation. However, some materials come close.

Best hydraulic seal materials for high temperature

Let's take a look at the most widely used high-temperature seals and their capabilities.

1. PTFE (polytetrafluoroethylene) - best overall for extreme heat

PTFE, commonly referred to as Teflon, is widely thought to be the top material for high-temperature hydraulic sealing.

Key features:

• Resistance to temperature for continuous time up to 250 °C
• Excellent resistance to chemicals (almost inert)
• Low friction coefficient
• Ideal for environments with a lot of force

Advantages:

• It can handle extreme temperatures better than many Elastomers
• It is ideal for use in chemical or corrosive use
• Long-lasting service life under harsh conditions

Limitations:

• Not elastic (requires back-up rings or spring to energizers)
• Can experience creep under load

Best applications:

• Hydraulic cylinders with high-temperature
• Chemical processing equipment
• Valves and pumps

Review:
If your system is operating at or above 200 degrees Celsius, PTFE is usually the top choice.

2. FKM (Viton) - best for high temperature + oil resistance

FKM (commonly called Viton) is among the most sought-after materials for hydraulic seals that are exposed to both oil-based and heat-based fluids.

Key features:

• Continuous temperature range of 200-240 degC
• Superior resistance to fuels, oils, and hydraulic fluids
• Good mechanical strength

Advantages:

• Keeps its elasticity intact even at extreme temperatures
• Excellent compression set resistance
• Ideal for sealing that is dynamic

Limitations:

• Not recommended for extremely low temperatures.
• Some resistance is limited to certain liquids with polarity

Best applications:

• Motors and pumps that are hydraulic
• Aerospace and automotive systems
• Hydraulic systems based on oil

The verdict:
For most hydraulic systems operating at or below 200 degrees Celsius, FKM is the most effective combination of efficiency and price.

3. Silicone (VMQ) - best for temperature flexibility

Seals made of silicone are famous for their broad temperature range and their flexibility.

Key features:

• Operating range: -60degC to ~200degC
• Great flexibility even in extreme temperatures

Advantages:

• It is able to perform well in high and low temperatures.
• Keeps its elasticity longer than other materials.

Limitations:

• Lack of resistance to oils and fuels
• Lower wear resistance

Best applications:

• Air systems
• Non-oil-based settings
• Static sealing

Review:
Good for extreme temperatures; however, not suitable for hydraulic oil systems.

4. FFKM (Perfluoroelastomer) - best for extreme conditions

FFKM is a top-quality material that is designed to be used in the most demanding of environments.

Key features:

• Extremely resistant to high temperatures (often at or above 250 °C)
• Excellent chemical compatibility

Advantages:

• Combines PTFE-like resistance and elastic elastomer
• Performs in harsh thermal and chemical environments.

Limitations:

• Very expensive
• Only used in the most critical of applications

Best applications:

• Chemical plants
• Aerospace
• Semiconductor manufacturing

Review:
The highest-performance seal, however, is only if cost isn't an issue.

5. Graphite and metal seals - best for ultra-high temperatures

In temperatures that exceed 300 °C, traditional polymer seals might not be adequate.

Key features:

• To withstand extreme temperatures
• It is suitable for static sealing

Advantages:

• Excellent thermal stability
• Long lifespan in extreme heat

Limitations:

• Flexible but not as much
• Not suitable for applications that require dynamic input.\

Best applications:

• Boilers and turbines
• High-temperature static joints

The verdict:
Used in extreme industrial conditions, not common hydraulic systems.

Comparison of high-temperature seal materials

Factors to consider when choosing a high-temperature seal

Selecting the ideal hydraulic seal is not only about temperature. Also, take into consideration:

1. Type of hydraulic fluid

Certain substances (like silica) are not compatible with oils, whereas FKM is extremely effective when working with hydrocarbons.

2. Pressure conditions

Pressure that is high combined with high temperature can increase the risk of deformation and extrusion.

3. Dynamic vs static application

• Dynamic seals need elasticity (FKM, FKM)
• Static seals may be made of the use of rigid materials (PTFE or graphite)

4. Cost vs performance

Materials with high-performance properties like FFKM provide higher performance but come at a higher cost.

Common mistakes to avoid

• Utilizing NBR at high temperature - It is degraded at temperatures above 120 °C.
• Not considering compatibility with chemicals leads to a rapid failure of seals
• Overlooking the effects of pressure, the high temperature causes materials to soften
• Do not use backup rings that contain PTFE - Leads to leakage from creep

Practical recommendations

Here's a quick guide that is based on the temperature range:

• up to 120°C: NBR (standard applications)
• 120degC - 200degC: FKM (best choice)
• 200degC - 260degC: PTFE (preferred)
• Above 260°C: FFKM or graphite

Which seal for hydraulics is ideal for high temperatures?

It's not a one-size-fits-all answer. But in the majority of cases:

• PTF is the ideal choice to resist extreme temperatures and chemicals
• FKM (Viton) is the most comprehensive choice for hydraulic systems.
• The FFKM is the most suitable choice for the most challenging conditions

The best seal for hydraulics is dependent on the particular application you are using it for, which includes the temperature, pressure, type, and price restrictions.

Selecting the best seal for your needs does more than improve performance, but also extends the lifespan of the equipment reduces maintenance costs, and helps prevent unexpected failures.