Different Types of Oil Seals

Are you looking to keep your machinery free from any unwanted leakages but aren’t sure which rotary shaft seal is right for your needs? This guide will provide you with everything you need to know in order to select the right one for your application.

Oil seals, which are also known as rotary shaft seals, fluid seals or grease seals, play an important role in closing down the gaps between moving and stationary elements of mechanical equipment.

By preventing lubricants from escaping, they protect key components of machinery from being damaged by leaks of various fluids. Everything from car engines to assembly machines use these oil seals to remain free from any harmful interactions that can cause serious and expensive damage to any of their critical parts.

There are a wide range of oil seals to select from for any number of uses, so this guide will break down the most common seals to help you choose the right one for whatever piece of machinery you are working on.

What are rotary shaft seals?

Rotary shaft or oil seals are placed between moving and stationary pieces of machinery to ensure that contaminants, moisture, corrosive materials and abrasives do not damage the various components. They can also prevent unwanted mixing of fluids, including water and oil combining within a machine.

How are Oil Seals made?

First, an elastomer, most often nitrile, is vulcanised to a metal ring. This creates a stiffening effect that includes a specialised metal tension spring directly behind the sealing lip, keeping the oil seal firmly in place against the moving part.

Oil Seal Materials

There are many different materials used to manufacture oil seals.

Leather Oil Seals - Leather Seals, also known as Type L Oil Seals, are most common in components that are subject to dirt and poor lubrication. Since they come pre-lubricated and are able to absorb fluids, leather oil seals are able to provide sealing properties in conditions that synthetic rubber is unable to.

Synthetic Rubber Oil Seals - Styrene Butadiene Rubber oil seals, or just SBR oil seals, offer strong resistance to abrasions and lesions, making them an ideal seal for fast-moving machinery. With the ability to withstand extreme temperatures with its heat-aging qualities, they can be used in outdoor components. They are also seen as more cost-effective oil seals than natural rubber.

Nitrile Oil Seals - Nitrile oil seals, which is the commonly used term for acrylonitrile-butadiene rubber seals, is a very good general-purpose option due to the flexibility of use across a variety of components. The resistance is strong against fats, hot water, gasoline, mineral oils, grease and animal oils, making them the most often-used oil seals. They do not have a wide temperature range, making them a poor choice for machinery that can see extreme changes in temperature.

Viton Oil Seals - A synthetic rubber and fluoropolymer elastomer, Viton is used to make oil seals that provide resistance in both high temperature, up to 250°C and low compression set components. They also offer a high resistance to chemicals and abrasions, so they can be used in elements that regularly interact with petroleum and solvents.

Polyacrylate Oil Seals - Mostly selected for automotive and transmission uses, polyacrylate seals are able to withstand fuel, oil, ozone, sunlight and weather when used. With cars exposed to all these different fluids and elements, they are the perfect choice. However, they should not be used in low temperatures, as their flexibility weakens when cold.

Silicone Oil Seals - Designed to absorb lubricants in order to lessen wear and friction, silicone rotary shafts also offer high thermal resistance and a large temperature range. But, they do not handle abrasions well or interact with oxidized oils.

PTFE Oil Seals - A relatively new and exciting oil seal, the use of polytetrafluoroethylene means that they can withstand dry or unlubricated operations. With a massive thermal range of  -130ºC to +200ºC and a strong resistance to chemicals, they are considered to be the future of rotary shaft seals.

How to Choose the Right Oil Seal

There are several key factors to consider when you are selecting the oil seals for your next project to ensure that you protect your machinery from immediate and long-term damage.

Pressure - Many oil seals can only withstand low-pressure applications, so understanding the compression set of your components is key.

Temperature - Just like pressure, the temperature that your oil seal will be operating in must be known so that you can choose one that can withstand the heat or cold. PTFE have the widest range of temperature, making them useful for machines who can see usage in extreme weather or elements.

Shaft Speed - Considering the speed that the shaft will be moving, the runout, the housing bore and the type of oil being sealed is vital to making sure you select an oil seal that will not suffer from abrasions or spiralling.

Fluid Types - Various oil seals are able to withstand interactions with oils, fuels, grease, water and more. Knowing what type of fluid the rotary shaft seal will be in constant contact with will ensure the longevity of the seal and surrounding components.

Lubricant Amount - Seals will always perform best when lubricated, however in some machines there are more likely to be dry spells. For these cases, selecting a leather or PTFE seal will be beneficial, as both can operate with less lubrication than others.

If you require any assistance in discovering the factors that lead to the right oil seal choices, the Simply Seals Team is happy to assist you!

Find the right Oil Seal for your needs with Simply Seals!

With dozens of specifically-designed oil seals made from a variety of materials, it can be very difficult to understand the best choice for their machinery.

That is why the Totally Seals team is always available to assist you with choosing the correct style, material, and size of oil seal for everything from commercial machinery to hobby car building.

Contact us today to make sure that you select the proper rotary shaft seal that will protect your components and lead to a long, healthy life for all of your machines!

All About Oil Seals

 Oil seals go by many names, such as shaft seals, dirt seals, grease seals, lip seals, and many other variations of these. They are essentially simple devices used in rotary shaft equipment to prevent lubricant from escaping and for excluding contaminants such as dust, dirt and water. An oil seal’s most important function, however, is that it protects every type of ball, sleeve and roller bearing in the rotating shafts. The seals also prevent the integration of two different fluids that shouldn’t mix, such as oil and water.

How do oil seals work?

The basic principle of an oil seal is fairly straightforward. It is installed adjacent to the bearing, with the flexible lip against the rotating shaft and the casing pressed into the housing to hold the seal in place. It’s important that the sealing lip is lubricated to prevent it from overheating as a result of any generated friction. It’s also crucial to understand which type of seal is appropriate for your particular machinery. Before selecting your seal, consider the environment, temperature, pressure and shaft speed of your machine, as well as the type of medium the seal will come into contact with during operation. These considerations will all determine the size, colour, and type of lip material or sealing element to choose, and whether it can be sealed in or sealed out.

What material are oil seals made from?

Oil seals are made from multiple compounds and materials. Some of the oldest, still in use today, are leather and felt compounds. The trend in mass production, however, has seen a move towards synthetic rubber or elastomers. Nitrile is by far the most popular material but developments in PTFE have created a surge of interest in buyers needing seals for high-speed shaft rotation applications. Viton is taking over from the polyacrylic and silicone, as it works better in high-temperature applications and has a high-resistance to abrasion and harmful chemicals.

There are various sizes of industrial and ordinary oil seals, ranging from 0 to 33cm (13in). These varieties are also designed for different temperatures. As long as your seal matches the original equipment it’s intended for, you can be sure your machine will perform at its best. For further guidance and information regarding oil seals, don’t hesitate to contact our knowledgeable team. We are always available to assist you with your bearing, seal and gasket needs.

Posted by on 31st May 2019

Oil seals are often called grease, fluid, or dirt seals. These seals close spaces between stationary and moving components in mechanical equipment. Oil seals are designed to prevent the escape of lubricant. They also block contaminants from entering machinery. This is especially important in severe environments where heat and foreign objects may be frequently present. They also prevent the mixing of different mediums like lubricating oil and water.

What is an Oil Seal?

Oil seals come cataloged as metric oil seals or imperial sized oil seals. The seals can also be custom-made to match the bearings in new types of machinery. They are installed in practically every type of machine including vehicles, protecting all kinds of precision, precisely-fitted ball bearings, sleeve bearings, and roller bearings.

The oil seal gets its structural stability from an interior metal ring which serves as an inner skeleton. The outer skin is made of a more flexible material like nitrile rubber or other materials based on the physical environment of the seal. A spring on the lip of the seal supports the lip and keeps the lubricant from leaking. The lip construction is what blocks contaminants from outside.

Where loads are light, the outer skin layer can be made of silicone. It can be made of Fluroelastomer (orViton) to protect under high temperatures (more than 120 degrees Celcius). The skin can also be made of Poly Acrylate or Polytetra-FluroEthylene.

The shaft on which the oil seal is mounted has to be ground to a rough surface finish. The shaft also should be hardened to prevent grooves forming on the shaft when the pressure is exerted by the spring on the seal. The area where the seal is fitted also has to be ground to prevent grooves that tend to wear out the lip of the oil seal faster than normal.

Oil seals have a flexible lip that actually rubs against the rotating shaft or housing to prevent leakage. The spring keeps the lip in contact with the shaft. Bearing isolator oil seals are dynamic seals that incorporate a rotor or rotating member and a stator or stationary member. The rotor actually turns with the shaft. Some oil shafts are bearing isolators with a "labyrinth" construction. Others incorporate simpler O-rings.

Types of oil seals include:

• single and double lip
• metal cased
• rubber or polymer
• internal, external and axial orientation
• spring loaded

A patent for an oil seal was filed by Nelson Thomas Edward on August 12, 1937, and published a year later. There were two purposes described. The device was to provide an oil seal between a fixed housing and a rotating part. The seal is described as

made of a yieldable resilient material having flat sealing faces and comprising two ring portions connected together by an annular portion substantially v-shaped in cross-section which may yield or expand as the mounting requires.

The oil seal would seal one face against a rotating member and the other face to a stationary housing. It would prevent dirt from coming between the hub or shaft and the seal.

Old School O-Rings

Early engines used O-rings (also called packing rings or toric joints) as seals (first patented in 1896). These are just mechanical gaskets in the shape of a torus (a circular ring--like a lifesaver), seated in a groove and compressed during assembly between two or more parts. It creates a seal at the interface. However, O-rings require a fluid film to lubricate them. They have limited usefulness in vacuum application and at extremes of temperature. The modern oil seal represents a significant improvement over the simple O-ring because it effectively seals in lubrication and prevents contamination from outside under a wide range of pressures and temperatures.

If you're looking for quality oil seals, bearings for industry or agriculture, ATV parts, and plenty more, check out The Big Bearing Store. With low prices and same day shipping in most cases, there's no reason to spend time searching the internet when everything you need is all in one place.