Oil seals are rotary shaft seals that close a gap between stationary and moving components and prevent lubricant to escape and thus stop contamination through the clearance. There are different types of oil seals that fit a different application and surroundings and are made out of different materials. The right material and type of oil seal is determined by the application and the medium that will be used with the oil seal.
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The DIN standard specifies dimensions and requirements for materials, marking, use and installation of rotary shaft lip seals used for retaining fluid or grease in unpressurized equipment, or equipment with a low differential pressure, that has rotating shafts. DIN defines standards for rotary shaft lip type seals for automobiles.
The standard oil seal consists of a metal ring as the inner skeleton which provides the structural stability to the oil seal. The outer part is made of rubber or metal - based on the requirement and the application of the oil seal. The spring on the lip of the oil seal provides support to the lip and prevents the lubricant from leaking outside and also prevents contaminants from entering.
The oil seal consists of a metal ring as the inner skeleton which provides the structural stability to the oil seal. The outer part is made of rubber or metal - based on the requirement and the application of the oil seal. The spring on the lip of the oil seal provides support to the lip and prevents the lubricant from leaking outside and also prevents contaminants from entering.
Tip for greasing oil seals with dust lips: If oil seals with fixed dust lips are being used, the space between the sealing lip and the dust lip may also be filled entirely with grease. The medium to be sealed will dissipate the heat.
A garter spring is a coiled steel spring that is connected at each end to create a circular shape. It maintains the radial force exerted by the sealing lip around the shaft surface.
The most commonly used oil seals in most applications are rubber cased or metal cased oil seals.
Metal-cased oil seals are used when installed to a housing bore made of the same material. This allows for equal contraction and expansion of the materials during operation, preventing leakage from occurring. Typically metal-cased seals are more cost efficient than rubber seals.
Rubber-cased oil seals are the most common oil seal execution, used when a metal-cased seal has the potential to fail (for example because of thermal expansion). Oil seals with a rubber case cannot rust, in contrast to oil seals with metal cases. Moreover, oil seals with a rubber case can seal a lightly damaged housing much better than metal cased oils seals. In high temperatures and high pressures, fast expanding rubber can provide a tight fit and more stable sealability.
The most commonly used type is type R. This type has a carbon steel insert and has rubber outside diameter. The rubber gives a good sealing capability, even when the housing is not fully in tolerance. The sealing lip with spring provides interference on the shaft for effective sealing. The outside diameter, with inner metal reinforcement case, allows press-fitting in the housing, with sufficient interference on the rubber to provide static sealing.
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.
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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.
can be difficult to get right, especially if you do not have the original machine specifications. Thankfully, there are a few ways to identify oil seals; from their design, size and material. As there are hundreds of different oil seals available on the market, this guide will cover the four most common design types. Typically available with either a single or double lip, in Nitrile or Viton Rubber Material.
Firstly, the oil seals covered in this guide classify the single lip as the inner diameter at the bottom of the component. The single lip is vital to the function of the seal by containing the oil, grease or lubricant. The only difference between a single and double lip is the additional rubber lip on the top of the oil seal which helps prevent dust or dirt from coming close to the shaft. Identifying the oil seal lip can be misinterpreted with a visual inspection alone. For or this reason, you should press along the inner diameter at the top of the seal, if you feel a ridge with a slight movement or give it is highly likely you have a double-lipped oil seal.
Fully covered outer diameter for excellent sealing. This oil seal is fully enclosed in a rubber material and is the most widely used type of oil seal. Great resistance to thermal cycling, temperatures and different chemical resistance.
Economic metal outer diameter for standard applications. This is an economical oil seal where the metal is exposed on one side and offers a closer fitting between the oil seal and housing or bore. Due to this, it has limited use with sealing thin liquids or gases.
The same design as type B with an additional inner case for greater structural rigidity. This type of oil seal is typically used in heavy-duty engineering machinery or large diameter sized seals
The same design as type A with corrosion protected metal case and stainless-steel garter spring. Suitable for use with a wide range of fuels and chemicals.
We can&#;t emphasise enough how important it is to choose the right oil seal to keep your application functioning, and functioning well.
Not every oil seal is the same. Manufactured using various material elastomers and to suit a range of dimensions, seals are as unique as the application they are intended for.
However, oil seals do all aim to perform the same function &#; to prevent leaks and stop contamination entering the application.
These seals also typically have a single or double lip, and the most common materials used in the makeup of these types of sealing products include Nitrile, Viton, or rubber.
Helping to close (seal) the gap between stationary and moving parts, oil seals prevent leaks and stop contamination due to the flexible lip rubbing against the shaft as it rotates.
The DIN is the standard that specifies a seal&#;s dimensions, requirements for materials, use and installation, and more.
Therefore, helping to find the right seal for the intended application, all seals and gaskets come with a unique coding system to help identify the type of seal and its features and properties. This is necessary to allow you to choose the correct seal and to record what seals work best in certain applications.
The most popular types of oil seals that we see are the single lip 21 and the double lip 23.
A single lip seal is what contains the oil, grease, or lubricant. Primarily, it does exactly what it is intended to do as an oil seal. A standard oil ring will consist of a metal ring as the inner to provide stability, with the spring on the lip providing additional support and preventing leaks from occurring.
A double-lip seal is a seal that has an additional rubber lip to prevent dust or dirt from entering the shaft, increasing the seal&#;s longevity. This second additional layer will feel like a ridge along the inner diameter at the top of the seal itself, ultimately providing extra protection.
The most common types of oil seals are rubber or metal cases.
Rubber-cased seals (A) = an excellent sealing solution encompassing a rubber-covered lip seal, with the oil seal fully enclosed. This type of oil seal is the most popular as it provides great thermal resistance, as well as temperature and chemical resistance. Often used when metal-cased seals have the potential to fail, this type of seal can&#;t rust, provides a tight fit as it is fast expanding, and can seal even when housing is slightly damaged.
Metal-cased seals (B) = a seal with a metal outer diameter; this type of seal is suitable for more standard applications. As the metal is exposed on one side, you can achieve a closer fit; when used with the same material application, it can provide equal contraction and expansion, and this type of seal can be more cost-effective than rubber seals. However, these seals should be used cautiously as they aren&#;t suitable for sealing thin liquids or gases.
C = with a reinforced metal insert, similar to seal type B, this seal has the extra benefit of an additional inner case, making it incredibly robust. Often found in heavy-duty machinery or equipment that requires a larger-size sealing solution.
F = a seal that operates as a stainless-steel garter spring, with a similar design to seal type A, but with the added benefit of a metal case that provides corrosion protection; this type of seal is most suitable for a range of fuels and chemicals. Connected at each shaft end to create a circular shape, garter springs help maintain the radial force around a shaft&#;s surface.
R = a rubber seal with a carbon steel insert and a rubber outer; this type of seal provides an effective sealing solution; with press fitting, it can also provide static sealing and comes with a good lifespan.
Bearing isolators = a dynamic seal that offers protection from a range of external contaminants.
There are various lip materials available for oil seals, some of the most common:
Installation of oil seals depends on the seal aim, direction, intention and also placement within the shaft and housing itself.
You will also need to consider dimension requirements. For example, inner and outer diameters, diameter of the housing, seal thickness, cross sections, and more.
Then, there are also service limits such as application operating speed, applied pressure, vacuum rotation, fluctuating temperatures, external influences etc.
There are various types of oil seals to fit a range of applications, and it&#;s vital that you find the right oil seal for you.
For specific requirements, speak to a member of the SSP team today, call 274 776, or your requirements to ; we&#;d be happy to help.