Aug. 04, 2023
You may not need to know much about oil seals, but there is a good chance the components in your car engine do. This blog explains the basics of oil seals and how they work.
Oil seals are devices that are used to seal oil. They are typically made of metal and have a rubber or synthetic rubber sealing element. Oil seals are used in various applications, including automotive, aerospace, and industrial.
The primary function of an oil seal is to prevent the escape of lubricating oil from a bearing or other moving part. Oil seals also keep contaminants out of bearings and other sensitive components. In automotive applications, oil seals are found in the engine, transmission, and differentials. In aerospace applications, oil seals are found in hydraulic and pneumatic systems. Industrial applications for oil seals include pumps, compressors, and gearboxes.
Oil seals consist of three main elements: the body, the lip, and the spring. The body is typically made of metal and has a groove that houses the lip and spring. The lip is made of rubber or synthetic rubber and is what comes into contact with the shaft or housing to create the seal. The spring helps to keep the lip in contact with the shaft or housing.
Oil seals seal lubricating oils in engines, transmissions, and other mechanical systems. The oil seal has two main functions: to keep the oil in and the contaminants out. Many different types of oil seals are available on the market, but they all serve the same purpose.
The most common type of oil seal is the lip seal. Lip seals have a metal or plastic lip that presses against a mating surface to create a seal. This type of seal is commonly used in engine applications with high pressure and temperature. Another type of oil seal is the v-ring seal. V-ring seals have two lips that form a V-shape when installed. This type of seal is used in lower-pressure applications such as transmissions.
Oil seals are important to keep your engine and transmission running smoothly. Without them, your engine would be susceptible to contamination and leaks. If you notice an oil leak, it is important to have it repaired as soon as possible to avoid further damage to your engine.
Oil seals are used to keep oil in and contaminants out. They are found in various applications, such as automotive engines and transmissions, hydraulic cylinders, and pumps. Oil seals have two main functions: sealing and wiping. Sealing keeps lubricant in and keeps contaminants out. Wiping helps remove debris that may have gotten past the seal.
Oil seals work by being pressed against a surface by the pressure of the fluid they are sealing. This creates a tight seal to prevent leakage but still allows the fluid to move freely. The seal can also withstand many applications’ high temperatures and pressures.
If you’re looking for information about oil seals, check out Ariiz’s portfolio. They have a wide range of oil seals perfect for any application. From National Oil Seals to other top brands, Ariiz has the right oil seal for the job. With over years of experience in the industry, they’re sure to have the knowledge and expertise to help you find the perfect oil seal for your needs.
Jan 5, 2015
Hydraulic seals prevent leakage and loss of fluids from systems. When seals shrink or harden, they can crack and may lose elasticity, leading to seal failure. This can be caused by:
High operating fluid temperatures
Fluid degradation
The use of incompatible hydraulic fluids can cause swelling, and/or shrinkage of the seal or chemical attack that can lead to the failure of lip seals as well as O rings.
The most commonly used material is acrylonitrile or nitrile butadiene rubber (NBR). Relatively inexpensive, NBR exhibits excellent resistance to petroleum-based hydraulic fluids for the temperature range -50°C to 120°C (-60°F to 250°F), but is not resistant to weathering. NBR can be used at temperatures up to 150°C (300°F) but service life will be shortened.
Compatible fluids: Petroleum-based hydrocarbons including mineral oils, diesel and fuel oils; vegetable oils and greases; HFA, HFB and HFC hydraulic fluids; dilute acids, alkali and salt solutions up to moderate temperatures.
Incompatible fluids: Highly aromatic hydrocarbons; ketones, acetic acid, and other polar solvents; strong acids, and glycol-based brake fluids.
The second most common material is fluorocarbon rubber (FPM/FKM), commonly known under the DuPontTM trade name VITON® *. It can be used over a wider temperature range of -40°C to 200°C (-40°F to 400°F). There are two main classes of Viton materials, type A and type G. Type A is more common and lower cost than type G, but type G offers improved compatibility with most fluids and resistance to both weathering and ozone.
Compatible fluids: Petroleum-based hydrocarbons, synthetic hydraulic fluids, fuels, including gasoline/alcohol fuels, aromatics; many organic solvents and chemicals.
Incompatible fluids: Glycol-based brake fluids; strong alkalis, amines, ammonia, formic and acetic acids, and superheated steam.
Other materials are used for specialised applications such as thermoplastic polyurethanes (TPU) with bio-hydraulic fluids.
To evaluate the interaction of hydraulic fluids and the sealing materials, it is important to understand the differences between hydraulic fluid base oils.
API Group I base oils are commonly used for hydraulic fluids. They are refined by a solvent extraction method.
API Group II and III base oils are refined by hydroprocessing techniques that convert waxes into iso-paraffins without using solvents. These base oils are water white in color and have superior oxidation resistance.
API Group IV base oils are polyalphaolefins (PAO) whilst API Group V fluids include naphthenic mineral oils, polyalkylene glycol (PAG), natural triglyercide and synthetic esters and other synthetic products.
The majority of base oils used for hydraulic fluids need additives to enhance specific properties. These additives also introduce an additional set of potential interactions with the seal material.
It is possible to predict the swelling or shrinkage behavior of a seal material with reasonably accurate results under normal operating temperature conditions.
Comparing the aniline point of the fluid in question to the aniline point of standard ASTM International reference oils produces a useful indication of the oil/ seal compatibility.
More accuracy can be obtained using the Elastomer Compatibility Index (ECI) method that compares the behavior of a standard NBR compound in a variety of petroleum-based oils to the behaviors of various other nitrile compounds. The results of the compatibility tests are plotted on a graph and used to determine the Swelling Behavior (SB) of the compound in question. Knowing the ECI of the fluid and the SB of the seal material, one can calculate the expected physical interaction of the pair.
Given the wide range of variables, it is wise to seek guidance from the manufacturers when selecting seal materials for either a new build or maintenance replacement.
It is particularly important to consider the likely impact of any change in hydraulic fluid on the seals already in use before proceeding with a replacement.
For API Group I based fluids operating at temperatures below 100°C (212°F), NBR seals are the most cost-effective choice. Fluoroelastomers (FKM) increase the maximum operating temperature to 200°C (400°F), which is well above the recommended range for ordinary fluids, whilst only slightly reducing low temperature performance. All the other materials exist to fill application niches not covered by NBR or FKM materials.
For applications currently using NBR or FKM seals that are not exhibiting unusual failure modes or unexpectedly short service lives, it is unlikely that changing to a higher performance – and usually more expensive – material will reduce operating or maintenance costs enough to offset the cost of the premium seals.
For new designs that operate with the same fluids in the same temperature ranges as existing systems, the same seal materials will probably work in the new system too. For new systems that don’t duplicate existing designs, either NBR or FKM is a logical elastomer to start with, unless there is something very unusual about the system or known issues with the fluid that will be used.
For more information on hydraulic fluids, elastomer or seal performance, contact your Lubrizol representative.
* Viton is a registered trademark of the E.I. du Pont de Nemours and Company
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