Everything You Need To Know To Find The Best high temperature oil seal

The group of oil seals used in dynamic applications include radial shaft seals that seal a rotating shaft around its circumference. They are also known as lip seals, but in this blog we will use the term oil seals.

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Usually, these oil seals are used to seal lubricating oil or grease and contain it within the application, so that moving parts such as bearings are continually supplied with enough lubrication. However, such seals are also used for sealing other liquids, gases, and solids, such as powders or granules.

All are fitted with a spring to preload the sealing lip. All these types are for non-pressurised or low-pressure applications up to 0.5 bar for diameters of a limited size. For diameter of 500 mm or more, the maximum pressure is 0.1 bar. For higher pressures, special types or PTFE lip seals can be used.

ERIKS type M (type B according to the DIN standard) has a single metal casing and rubber sealing lip. Since the casing is made of metal, it must be fitted in a well-finished, undamaged groove. Large volumes of oil seals with metal casings are often cheaper, which is why they are often used as original equipment in machines. However, if an oil seal has to be replaced, types with a rubber exterior (type R or RST) are easier to fit. Type MST is similar to M and commonly used. The difference is the dust lip in the MST oil seal that prevents dust and dirt reaching the sealing lip, and extends its service life in dusty environments.

ERIKS type GV (type C according to DIN) is equivalent to type M, but is a heavy-duty version with a double metal casing. This can be a useful solution with larger diameters in more demanding applications. There is also a version of this type with a dust lip; the GVST (type CS according to DIN).

ERIKS type R (type A according to the DIN standard) is identical in shape to type M, but has a rubber outer case with metal reinforcement on the inside. The rubber creates a good seal in the housing, even if the housing has suffered minor damage or is not in its best condition for other reasons. The RST version has a dust lip. These types are often chosen to replace a type with a metal outer case because they are easier to install and can cope with minor damage to the groove, such as scratches.

ERIKS also supplies the types GR and GRST. These are virtually identical to the types R and RST, except in this case the metal inner ring is also completely encased in rubber. ERIKS uses FKM rubber here as standard, so these seals are ideal for use in acidic environments.

An overview of the different standard types of oil seals and their main characteristics is shown below.

Outer case

• Metal

The metal used in the outer case of oil seals is usually made of carbon steel. Upon request, and depending on quantities, a different type of steel (such as stainless steel) can be used.

• Rubber or rubber fabric

The quality of the rubber or rubber fabric used to make an outer case is the same as the quality of the rubber sealing lip. Fabric reinforced rubber is, as the name suggests, rubber reinforced with a fabric.

Spring

Standard springs are made of carbon steel. We use stainless-steel springs for our GR and GRST oil seals made from FKM rubber. In some rare cases, an O-ring is even used as a spring element. Standard PTFE lip seals are not fitted with springs.

Sealing lip

The sealing lip is always made of a rubber or synthetic material. For oil seals with a rubber outer case (R, RST, GR, GRST), the rubber quality of the sealing lip and the outer case are the same.

The material of the sealing lip is chosen according to the liquid to be sealed and the rotational speed. For larger shafts, an NBR sealing lip can cope with surface speeds of up to 10-12 m/s, while an FKM lip is suitable for speeds of up to 35-38 m/s. 

Nitrile Butadiene Rubber (NBR, nitrile)

NBR, also known as nitrile rubber or nitrile, is the most popular material for an oil seal because of its good resistance to many oils and greases, such as mineral grease and hydraulic oil. Depending on their composition, synthetic oils and greases, such as those based on glycol, can damage NBR rubber materials. Depending on the amount of glycol, a PTFE lip seal may be the best choice. NBR is also unable to cope with contact with acids and solvents. The rubber is suitable for oil and grease at temperatures from -35 °C to 100 °C.

Most ERIKS oil seals, such as the types M, MST, R and RST, are made of NBR as standard.

Fluorine rubber (FKM, Viton')

FKM or FPM, which is in well-known brand Viton', can withstand higher liquid temperatures of up to 180 ˚C. FKM is highly resistant to strong acids and bases, as well as to synthetic oils and greases. Glycol-based oil and grease, however, can also damage FKM.

Because of the higher temperature resistance of FKM, this material is also chosen for applications where higher speeds play a role, which raise the temperature at the sealing lip considerably. Usually, using FKM will result in a longer life than using NBR. This compensates the higher price of FKM compared to NBR, as an FKM does not have to be replaced as frequently. The low temperature resistance of standard FKM is limited to -15 ˚C.

Polytetrafluoroethylene (PTFE, Teflon®)

PTFE, which is used in the well-known brand Teflon®, is less commonly used, but it is the preferred material for specific rotating seals in the chemical, food and pharmaceutical industries. This material is notable for having a very low frictional resistance and the best chemical resistance. It can also withstand a very wide range of temperatures in these types of seals; -80 ˚C to 200 ˚C. The shafts on which oil seals with PTFE lips are used require a harder and finer finish. Something like an axle sleeve can also be used to meet this requirement.

EPDM

EPDM oil seals are less common. They are used in solvent, hot water and steam applications, EPDM resists low temperatures down to -50 °C and UV radiation well. Some types of EPDM are also suitable for higher temperatures up to +150 °C. EPDM oil seals are usually available upon request.

VMQ (silicone)

VMQ, also known as silicone, is also used for oil seals, but this is less common because the mechanical strength of VMQ is low and this material has poor wear-resistance This makes it less suitable for dynamic applications, but it can withstand fairly low and high temperatures from -60 °C to 200 °C. Many types of VMQ are also suitable for contact with pharmaceutical and food products, so VMQ is an option worth considering. VMQ oil seals are usually available on request.

To install an oil seal properly, the shaft must be undamaged. This is so the oil seal can do its job properly on the one hand, and to prevent it from being damaged during fitting on the other. In addition, it is very important to lubricate the shaft, the sealing lip and the bore with plenty of grease. This will allow the oil seal to slide more easily over the shaft and prevent dry running after the first rotation. The oil seal may also come into contact with the keyway, thread or other grooves when sliding over the shaft. By taping or covering the shaft at the location of these irregularities with oil-soaked paper, the oil seal can be mounted without damage to the sealing lip.

Other important factors are ensuring the hardness and roughness of the shaft are correct. A shaft hardness of HRC 45 is recommended for a rubber sealing lip, with a roughness of Ra 0.4-0.8. A higher shaft hardness of HRC 60 and shaft roughness of Ra 0.1-0.4 is recommended for a PTFE lip.

Seals are an integral part of many industrial types of machinery. It is the common opinion that high-temperature seals are tougher to manufacture when compared to low-temperature seals. This is because high-temperature resistant seals have to be manufactured from the most suitable material to withstand very high heat and pressure in given conditions.

Not sure where to start when it comes to heat-resistant seals? Then this article is the right place for you! Read ahead to know more about seals that are used to seal high-temperature situations.

What Are High-Temperature Seals?

High-temperature seals are devices that are used for many purposes including preventing leakage, containing pressure, and avoiding contamination. The specialty of high-temperature resistant seals is that they are designed to prevent leakage across parts even when the machine is present in high-temperature situations. Usually, these devices can seal high temperatures up to '.

Due to their application in places like turbines, exhaust systems, and fuel cells, these seals need to be made of the most suitable material to minimize leakage and offer high resistance. As the seals endure extreme situations, they will eventually wear off if it is not made from the right material. 

Applications of High-Temperature Seals (about 470 words)

High-temperature seals find a wide range of applications in various fields because of their capability to withstand temperatures up to '. Manufacturers like Dechengwang employ expert designers who consider all the necessary factors before designing the seals that are used in high-temperature and pressure situations.

• Aerospace

Fluoropolymer seals made of materials like PTFE are incredibly useful in the aerospace industry. These are high-temperature sealing parts that offer reliable protection during high-temperature situations that arise in many parts of the vehicle, from the engine to its surface. 

During re-entry into the atmosphere, the surface of the vehicle experiences immense levels of friction, leading to extreme temperatures. High-resistant seals can act perfectly in situations like these.

• Automotive

Mainly used in the engine compartment, rubber seals help in absorbing extra heat and compression. High-temperature seals also find applications in various parts of a vehicle ' for example, high-quality seals are an integral part of any transmission so as to avoid grime and other contaminants damaging the functioning of the transmission. Seals are also used for maintaining pressure within the compartment where the engine is placed.

• Mechanical Engineering

Be it refineries, chambers, or turbines, high-temperature situations are inevitable in the mechanical engineering industry. When it comes to systems that regularly deal with extreme pressure and temperatures, it is important to choose a reliable high-heat seal that can offer effective sealing properties. 

If proper seals are not used to seal high-temperature situations, they might lead to leakage and corrosion, causing hazardous accidents.

• Chemical Plant

Many chemical processes and reactions take place in extreme physical conditions like high or low temperatures. Seals used in chemical plants and industries need to be highly resistant because fluids of high temperature and pressure are transferred. 

Transfer of such fluids also eventually corrodes and wears off the mechanical parts used in the plants, so it becomes crucial to use high-quality high resistant seals and pumps.

• Oil & Gas

The drilling of wells for oil and gas involves working in high-pressure, high-temperature situations. Both on and off the field for refineries, high-temperature sealing parts such as seals and O-rings are used to carry out the necessary processes smoothly. In these circumstances, only rubber and polymer seals can perform and retain their characteristics, thus offering long life and minimal issues.

• Medical Engineering

Many people are not aware of the wide applications of seals in the medical engineering field. Rubber seals are used in many components like medical pumps, IV pipes, implant materials, lab equipment, and even temperature-controlling devices. 

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Also, high-temperature-resistant seals find wide applications in this field ' these components are an essential part of temperature-controlling and measuring devices.

• Food Processing

When it comes to the food processing industry, purity, and stability are two important characteristics that one should look for in the devices used. PTFE is one of the best materials to use for high-tolerance seals when it comes to food processing and related industries. 

Since these seals come in contact with chemicals and other dangerous fluids of extreme temperatures and pressures, it is important to choose the right type of seal.

Factors to Consider When Choosing High Heat Seal Materials

It is of immense importance to choose the most suitable material for a high-heat seal. The wrong material can cause the seal to malfunction in extreme temperature situations, thus leading to potential hazards and damage. Here are some factors to consider while choosing materials for high-temperature seals:

• Material Compatibility

High-heat seals are widely used in many industries. So, it goes without saying that throughout their life, seals come in contact with a variety of materials and fluids. Seals also come in contact with the environment and the other devices and components that are a part of the setup.

The material from which the seals are made should be compatible with the substances that they are going to interact with. For example, if a high-resistant seal is used in the chemical industry, it should be capable of withstanding corrosion as the seal will come in contact with dangerous chemicals.

• Temperature Limit

The temperature limit of the material of the seal you are choosing is the most important factor to look out for. High-temperature seals will be employed in extreme situations, so they need to have high resistance to temperature and pressure. 

Often, extreme temperature and pressure can alter the characteristics of the material ' this is not ideal for a seal. Also, the seals should be neutral to chemicals and other reactive materials.

PTFE material seals can be used in the temperature range of -180' to 260'. This makes PTFE the best option to use in both extremely low and high temperatures.

• Thermal Expansion and Contraction

The coefficient of thermal expansion is a material property that points out the extent to which a material will expand when it is heated. Elastomers in general have coefficients that are nearly ten times that of steel. In the case of PTFE, it has a high thermal coefficient, meaning that it expands when exposed to high temperatures.

When it comes to high-temperature seals, the coefficient of thermal expansion will determine the extent to which the sealing will grow or contract compared to its comparative metal components. High-quality PTFE seals like the ones offered by Dechengwang are capable of overcoming minor setbacks to perform a long life.

• Resistance of Compression and Load

The compression set resistance of a material can be understood as its capability to revert back to its original shape after enduring resistance for a given time. This property of a seal is very important because it determines the capacity of a seal to withstand pressure and other external factors.

Many elastomers and fluorocarbon-based polymers have a great resistance-of-compression factor, making them a reliable choice of material for making products like gaskets, seals, and O-rings. 

Carbon-filled PTFE is one of the best materials in which highly resistant seals can be made ' apart from excellent compressive strength, this material also exhibits resistance to corrosion.

• Application Scenario

Another crucial factor to think about before choosing the material for a high-heat seal is the application of the seal. Depending on the industry in which the seals are to be used, the materials will differ. 

For example, seals made of fluorocarbon-based materials have high resistance to compression and can withstand extreme temperatures. This makes them a reliable choice for oil and gas industries.

If the application scenario involves a chemical plant, then manufacturers have to look for materials that are neutral to chemicals and can withstand corrosion. Thus to seal high-temperature situations in different scenarios, seals made of different materials might be needed.

Instructions for High-Temperature Sealing

To achieve perfect high-temperature sealing, one should follow a series of steps. The process starts with choosing the most suitable seal for a particular application and proceeding with the sealing methods and procedures. Also, it is important to conduct regular inspection checks to ensure that the seals are working properly.

• Select Suitable Seals

There are many different factors one should consider before choosing a particular seal for an application. Some of the most important factors include:

• Fluid pressure range ' the range of pressure in which fluids will flow in a system
• Temperature range ' the maximum and minimum temperature sets in the system at which the seal will operate
• Dimensions ' the size and width of the pumps and cylinders will determine the size of the seal ' the seal has to fit perfectly to avoid leakage.
• Application ' based on industrial application, the seal has to be chosen, as different applications demand particular characteristics.

• Prepare the Sealing Surface

Now that the right seal is selected, it is time to work on a proper sealing surface. The sealing surface where the seal and the hardware of the machinery interact needs to be smooth ' it is very important that this surface is clean and uniform.

Instructions for High Temperature Sealing

• Choose the Appropriate Sealing Method

When handling high-temperature sealing, it is of great importance to pick the proper sealing technique. The most common kinds of sealing techniques for high temperatures one should be aware of are o-rings, sealants, gaskets, compression packings, and many more. 

For choosing the appropriate sealing method, it is best to pay attention to a wide variety of aspects, including pressure conditions, operating temperature conditions, kind of equipment used, chemical compatibility, etc. 

• Follow Proper Sealing Procedures

Following proper high-temperature sealing procedures is essential for safety and credibility. Start with cleaning the surface of the sealing using safe-to-use cleaning elements. Paste the sealing material considering the operating pressure and temperature needs.

There are different types of procedures, like curing, compression, and torquing. Thus, do not go overboard with the pressure and temperature ranges during the sealing procedure. Prior to putting the sealing under high temperatures, it is best to leave the sealing material after applying it. 

• Perform Regular Inspections and Maintenance

To make sure that the high-temperature seals are functioning properly, conducting routine inspections and maintenance is relatively vital. It is best to perform an inspection every now and then to check the seal's condition and inspect for any damage such as leakage, wear and tear, etc. 

If any components are damaged, make sure to replace them as quickly as possible. Check the operating conditions such as pressure and temperature to ensure they do not deter the performance of the seals. 

6 Recommended Materials for Heat Resistant Seals

High-resistant seals are put under extreme temperatures and pressure. So, it is necessary for the seals to be made of materials that have a high coefficient of thermal expansion, and also are neutral to chemicals and extreme atmospheric factors. Here are some of the topmost recommended materials for high-temperature seals.

• PTFE

Polytetrafluoroethylene (PTFE), also commonly known as Teflon, is a fluorocarbon-based polymer and is one of the most common materials from which rubber seals and gaskets are made. The color of the polymer is white. 

PTFE is a fluoropolymer that is well-suited for manufacturing high-temperature seals. Here are some of its properties.:

• Temperature Range: The working temperature range of PTFE is from -180' to 260'. Components made of this polymer function well at both extremely low and high temperatures.
• Inertness: PTFE is biologically inert ' it does not react to biological fluids, so it can be used in the medical field without any chance of mishaps. The material is also chemically resistant ' it does not react to chemicals or does not deteriorate even when exposed to harsh chemicals.
• Resistance to Compression: The polymer is highly resistant to compression, so it can retain its original shape easily.
• Other Properties: The polymer is non-flammable. Teflon also has excellent insulating properties.
• PTFE Compounds

There is a wide range of PTFE compounds like Carbon-filled PTFE, Glass-filled PTFE, Graphite-filled PTFE, etc. In general, all of the PTFE compounds exhibit excellent physical, thermal, and chemical properties that make them a suitable choice of material for making high-tolerant seals. Seals made of these materials also have reduced wear rates and friction coefficients when compared to virgin PTFE.

• Carbon-filled PTFE: Contains up to 35% of carbon and the rest is PTFE. The color of the material is black. Parts made of this material exhibit improved resistance to load and electrical and thermal conductivity. The temperature range is from -269°C to 315°C. 
• Glass-filled PTFE: Contains up to 40% of glass fiber. The color of the material is cream white. Properties include improved wear resistance, chemical resistance, and optimal performance in an oxidizing environment. The temperature range is from -260°C to 260°C.
• Graphite-filled PTFE: Contains up to 25% of graphite. The color of the material is black. Properties include improved sliding properties against soft metals and chemical inertness. The temperature range is from -73°C to 204°C.

PEEK

Abbreviated as polyetheretherketone, this is a high-performance plastic that possesses impressive chemical resistance and mechanical strength. This material is highly recommended for manufacturing seals because they have high dimensional stability ' the coefficient of thermal expansion for the material is high. The color of the plastic is light brown or black. 

• Temperature Range: At very low temperatures, like below -70°C, the plastic is brittle. As for high temperature, it can withstand up to 260°C, making it a great choice for high-temperature seals.
• Inertness: Chemically resistant to common chemicals including acids, oils, solvents, and salts. It's also biocompatible.
• Resistance to Compression: PEEK boasts high wear resistance and tensile strength. 
• Other Properties: It's a lightweight material. Considered to be the ideal replacement for stainless steel. The material also has excellent mechanical strength and stability.

Virgin PEEK is a common choice for making laboratory and medical equipment, thanks to its biocompatibility and chemical resistance.

• PVDF

PVDF, which expands to polyvinylidene fluoride, is a fluoropolymer that has many special characteristics. For instance, the material is resistant to nuclear radiation, making it the perfect choice for use in nuclear reactors and related areas. 

PVDF also has high creep resistance ' it can endure mechanical stress for a prolonged time in a given environment without losing its sealing properties. 

• Temperature Range: PVDF has a wide temperature range: -50°C to 150°C. Due to this range, it is a reliable material for manufacturing high-resistant seals.
• Inertness: PVDF has resistance against common chemical solvents like acids and oils.
• Resistance to Radiation: PVDF is resistant to ultraviolet and nuclear radiation. This makes the material a great choice for use in the nuclear power industry.
• Other Properties: This material has impressive dielectric properties. It also has low permeability.
• PCTFE

Polychlorotrifluoroethylene (PCTFE) is a homopolymer of Chlorotrifluoroethylene (CTFE) and is a fluoropolymer that is known for its dimensional rigidity and stability. 

Translucent in appearance, this material is better than other fluoropolymers when it comes to mechanical properties and strength. PCTFE is also preferred for its low permeability.

• Temperature Range: The working temperature of PCTFE is from -240°C to 150°C. While seals made of this material can be used in both low and high-temperature situations, it is usually employed in cryogenic applications.
• Inertness: The material is resistant to all inorganic corrosive liquids.
• Mechanical Properties: Impressive creep resistance, thus making it a great option for applications where there is a chance for high wear and tear. It retains dimensional stability over a wide temperature range.
• Other Properties: PCTFE exhibits a great stress-crack resistance factor. It has really low gas permeability. Another specialty of this material is that it has near-zero moisture absorption.
• PFA

Perfluoroalkoxy (PFA) also goes by the name vinyl ether. This is one of the few plastics that is suitable to employ in both extremely low and high temperatures. Apart from being used to make seals that seal high-temperature situations, this material is also used to manufacture pipes, fittings, and corrosion-resistant lining for vessels. 

• Temperature Range: The working temperature of PFA is very impressive: it works in temperatures as low as -200°C and is also effective in extreme temperatures up to 260°C. 
• Inertness: PFA is chemically inert to a wide range of chemicals including solvents and industrial chemicals.
• Mechanical Properties: PFA is surprisingly stable at high processing temperatures. It has a low coefficient of friction and also a low dielectric constant. The material possesses impressive stress-crack resistance and creep resistance. 
• Other Properties: The material is capable of resisting ignition, thus avoiding the spread of flame in case of an accident.

A Reliable High-Temperature Seals Services Provider: DECHENGWANG

When it comes to the manufacturing of seals used to seal high-temperature parts and situations, it is highly necessary to choose the right material for the seal and follow all the protocols during the manufacturing process. Dechengwang is one of the most trusted providers of high-temperature seals internationally and here are some reasons why: 

• Offering Customized Design and Manufacturing

If you need to find a reliable seal manufacturer, Dechengwang is here to help you. We specialize in custom design and manufacturing of seals, O-rings, gaskets, and other machined parts. Our long experience in this field has helped us perfect our processes and achieve high-quality custom designs.

• Providing A Wide Range of Sealing Materials

Dechengwang specializes in fluoropolymer materials and manufactures a wide range of products using the same. We use fluoropolymers for manufacturing machined components because of their excellent mechanical strength, chemical inertness, and resistance to corrosion. 

It should also be noted that these materials are the perfect choice for high-temperature sealing parts in applications that involve extreme temperature and pressure situations.

• Available With No Minimum Order Quantity

Whether you are interested in placing a small order or big order, everything is possible with Dechengwang. We as manufacturers understand the needs and necessities of our clients and customers, so we do not keep a cap on the minimum order quantity. All of our products are available to order in any quantity the client requires ' there are no delayed processes for generating the order either. 

Conclusion

When it comes to choosing high-temperature seals, there are many factors one should consider, ranging from temperature range to durability. The application of the seal also determines the material from which it should be made. PTFE, PEEK, and PVDF are some of the common materials from which high-resistant seals are made.

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