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.
Figure 1: Types of sealing devices
An oil seal, also known as a shaft seal or dirt seal, prevents lubricants such as oil and grease from escaping along a rotating shaft. Oil seals are an important component in preventing leaks and contaminants from clogging various engines, pumps, and pipelines.
Installing and replacing oil seals can be a daunting task. But with the right knowledge, the results can be good. Here are 8 tips to guide you on what to look for when working with oil seals. Read on for more information.
An oil seal, also known as crankshaft retainer, is a small device, but essential to ensure the proper engine operation. It plays a key role in all moving parts of an engine, acting as a physical barrier. This mechanical seal fulfils the dual purpose of sealing a rotary shaft to maintain the necessary lubrication (avoiding leaks) and preventing other foreign matter from contaminating shafts and bearings in the rotary shaft equipment.
Materials used
Among the most common causes of oil seal failure are:
The most common oil seals are the ERIKS types R, RST, M and MST, which correspond respectively to types A, AS, B and BS according to DIN 3760/ISO 6194.


Valve cover gaskets and head gaskets play pivotal roles in maintaining the proper functioning of the engine. The valve cover gasket prevents oil leaks and contaminants from compromising the lubrication and performance of the engine, while the head gasket ensures the proper sealing of the combustion chamber, allowing for efficient fuel combustion and preventing the mixing of oil and coolant. Both gaskets are critical for the overall efficiency, performance, and reliability of the engine.
What material are oil seals made from?
How are they used?
Additionally, lubricants can be used on both sides of the oil seal to reduce friction and enhance sealing performance. The sealing process is crucial for preventing contaminants from entering machinery or equipment while keeping essential fluids contained within.