Types of Oil Seal Materials / Material Selection Guide for Oil Seals - FITCO

Which is the Best Material for Your Oil Seal? 

Application: 

Radial shaft seals, also known as lip seals, are used to seal rotary elements, such as a shaft or rotating bore. Rotary shaft seals play a key role in extending the operating life of bearing systems and reducing the overall costs of maintaining these systems. The primary function of a rotary shaft seal is to retain bearing system lubricants therefore allowing the bearings to operate in optimal levels of lubrication. The secondary function of a rotary shaft seal is to exclude contaminants from the system, contaminants that can both damage bearings and break down the effectiveness of lubricants. 

USP: 

The seal construction will consist of a sprung main sealing lip which has a point contact with the shaft. The point contact is formed by two angles, with the air side angle usually less than the oil side angle. “Depending on the seal type these two angles are varied to create a “pressure distribution” at the seal contact point which has a steeper slope on the oil side of the seal. “The shallower the slope on the oil side of the seal the wetter the seal will run” 

An oil seal normally consists of three basic components: Sealing Element, Metal Case, and Spring. The function of an oil seal is to prevent leakage along the shaft. This is mainly achieved by the sealing element. Materials normally used are Nitrile, Acrylic, Silicone, and Viton Rubber.

Fluorinated Rubber (VITON)

Fluorinated rubber is widely known under the DuPont trade name of Viton®. Temperature Ranging -30 to 200° C , It has the best resistance to chemicals, and superior performance to high temperatures. Though Viton® provides so many good prospects, it has the highest cost.

Nitrile Rubber (NBR)

NBR is most commonly used material. It has good heat resistance properties, good resistance to oils, salt solutions, hydraulic oils, and gasoline. Operation temperatures are recommended from -40 to 120° C. It also functions well in dry environments, but only for intermittent periods. The disadvantage is poor chemical resistance.

Silicone Rubber 

Silicone compounds operate effectively in a broad temperature range of -50 to 180° C. It is unsurpassed in its resistance to heat and low temperatures. The high lubricant absorbency of silicone minimizes friction and wear. It is usually used for crank shaft seals. Silicone has poor hydrolysis resistance. It should not be used in oxidized or hypoid oils.

Polyacrylate Rubber 

Acrylic rubber has better heat resistance than Nitrile. It is recommended for high surface speed environments. The operation temperatures are recommended from -20° C to 150° C. It should not be used with water or in temperatures below -20° C.

MATERIAL PERFORMANCE

	NITRILE	Polyacrylate	SILICONE	VITON
Temperature  Range (°C)	-40 to 120	-20 to 150	-50 to 180	-30 to 200
Hardness (Shore)	70/80	70/80	75/85	70/80
Wear Resistance	O	X	XX	X
Costs	Most economical	3rd costly	2nd costly	Highest

O: Applicable | X: Applicable but must be observed | XX: Applicable in a limited amount of time | XXX: Not Applicable

MATERIAL CHEMICAL RESISTANCE

	NITRILE	PA	SILICONE	VITON
Inorganic acids
Organic acids	XXX	XX	XX
Alkali	XX	O	O	O
Salt	O	O	O	O
Alcohol	XXX	O	O	O
Esters	XXX	XXX		XXX
Phenol	XXX	XXX	O
Ketones	XXX	XXX		XX

O: Applicable | X: Applicable but must be observed | XX: Applicable in a limited amount of time | XXX: Not Applicable

For Futher Details 

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