Everything You Need To Know To Find The Best s type oil seal manufacturer

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.

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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.

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Are you asking yourself what is a seal, and where do I find them? Today we're hopefully going to bring more clarity than Google when you search for "seal" which brings up cute animals and a British singer. Many people have heard of O-rings but many never realize that there are so many other important seals beyond a simple O-ring.
 
Seals are one of the most critical components that most people wouldn’t even think twice about. You can find seals in almost any application where you need to prevent leakage of liquids, or gases escaping or prevent outside contaminants such as dirt getting into the equipment.
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Where do I find seals?

So when I go visit my customers do they have seals in their equipment? In most cases, it will be yes because seals are one of the most critical components in equipment to prevent leaks, contamination, and damage from exposure to the environment.

​Some common examples of where you find seals would be in a shaft of hydraulics or pneumatics, pumps, engines, rollers at a steel mill, compressors, or preventing leaks at a chemical plant. The places where you find a seal are truly almost limitless, the easiest way to think of it is anywhere a liquid, gas, or solid could escape or get into the equipment there will be a seal ensuring safe and reliable operation.
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Types of seals

Okay so I can find these seals almost everywhere but what types of seals are in that equipment? Well, seals can be broken down into two main categories, static seals and dynamic seals. Static seals are found in mating glands where there is no motion on the sealing surface. Dynamic applications are used to create a barrier between a static and a moving surface. These seals are used to retain fluids, pressure and remove contaminants most commonly used in linear, oscillating, and rotating applications.
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Static seals

• O-rings: These are one of the most common seals that you can find anywhere because of the diversity of applications where they are utilized. O-rings are the most simple seal you can find on the market because it is a simple circle designed to seal around mechanical components or fill spaces along groves to prevent leaks. Due to the huge range of applications, you may find an O-ring in a massive range of sizes, materials, and hardness.
• Clamp Seals: Clamp seals are most commonly used to maintain hygienic standards during the manufacturing process in applications such as dairies, distilleries, bakeries, breweries, or other food and beverage production facilities.
• Gaskets: Gaskets are used to fill the space between mating components and prevent leakage between the two objects while under compression. These are extremely common seals to find in applications that don’t come into contact with movement such as a pipe fitting.

Dynamic seals

• Oil seals: Also called radial shaft seals are used in dynamic applications to keep oil, grease, and other harsh chemicals leaking out of moving applications. An oil seal consists of a metal case and rubber sealing lift that fits closely around the shaft. The rubber lip creates a barrier that prevents oil and other fluids from leaking and causing damage.
  Fluid power seals: are most commonly used in hydraulic and pneumatic applications and are designed to prevent fluids or gases from leaking into or out of the system. The most common fluid power seals are piston and rod seals.
• Other dynamic seals:
  • Rotary seals
  • U-cups
  • V-rings
  • Wipers
  • Guide rings

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Common sealing materials

There are truly a massive amount of different sealing materials and compounds but below are some of the most common you will see utilized.

• NBR (Nitrile Butadiene Rubber)
• FKM (Fluoroelastomer) 
• PTFE (Polytetrafluoroethylene)
• FFKM (Perfluoroelastomer)
• HNBR (Hydrogenated Nitrile Butadiene Rubber)
• Silicone

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Selecting the right seal

Selecting the right seal is critical to ensuring the efficient operation of equipment. When selecting what material to use in your application seal there are a few key aspects to consider.
 
The first thing to consider when selecting what seal is right for you is to know what the temperature range will be for the application. Every sealing material has a unique range of temperatures it performs best, and extreme heat, cold, or fluctuations affect the materials differently. It is critical to ensure the seal can perform in the temperatures you will be subjecting it to avoid a sealing failure and ensure it operates efficiently.
 
Next, you need to consider the environment that the seal will be in because this could greatly affect the lifespan or even cause a seal failure if the wrong material is utilized. You need to consider the pressures, chemicals, and outside environment such as exposure to sun, dirt, or water. Just like temperature certain materials perform excellently in certain chemicals but can begin to break down when subjected to the wrong contaminants.
 
You also want to consider what unique needs your industry requires. For example, if you are manufacturing pharmaceuticals or food and beverages you can’t just use any seal off the shelf. You need to take extra care in ensuring you are utilizing hygienic FDA seals to ensure you comply with the regulation.
 
We know that selecting the right seal is an incredibly important decision that isn't always easy without specialized knowledge. As a company that specializes in seals and sealing technology our experts at Freudenberg-NOK are here to support our partners at Fastenal, and your customers find the ideal seal for their unique needs.
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​Content originally from Freudenberg-NOK Industrial Services. Reused here with permission.