In an Oil seal environment, there is shaft that is rotating inside a housing or bore. Because of the friction, there must be some clearance between the shaft & the bore. The function of the rotary seal / oil seal is to stop whatever fluid is inside from leaking out from the clearance. The oil seal may also be used to prevent outside material such as dirt from moving in the through the surface.
"Dynamic sealing" is the relationship between the rotating shaft and the seal and is handled by the sealing element. A garter spring may used in the oil seal to increase the radial interference between the oil seal lip and contact point on the shaft. In order to achieve this interference, the oil seal's ID must be slightly smaller than the diameter of the shaft.
"Static sealing" is the relationship between the housing and the seal. In order to achieve this interference, the oil seal's OD must be slightly larger than the diameter of the housing or bore.
An oil seal normally consists of three basic components: the sealing element, the metal case and the spring. The purpose of the sealing element is to stop the fluid from leaking between the shaft and housing.
The metal case will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The spring will help make the sealing element more effective. All materials must be selected depending on the environment in which the oil seal will function.
Below mentioned are few of the Oil seals profiles based on the O.d design & Lip design of the Rotary shaft seal / oil seals.
Oil Seal Types:
Generally, seals with spring loaded lips are used for retaining oil lubricants and non-loaded lips are used for low speed grease retention. Metal O.D seals are more suited for steel & cast iron housings. A press fit metal O.D seal has greater holding strength & alignment. As a general rule, the shaft surface speed of “V” & “K” type seal should be less than 10M/S.
OIL SEAL O.D Design:
OIL SEAL O.D Design Contd.
Oil seal with Economical metal O.D design for standard application (B2).
Oil Seal with Metal O.D with rubber covering on fluid side for added protection (B).
Oil Seal with Metal O.D design with rubber nose for enhanced O.D sealing (BR).
Oil Seal with Rubber covered O.D design for excellent O.D sealing (C).
Oil Seal with Metal O.D design with an inner case for greater structural rigidity (A2).
Oil Seal Lip Design:
"S" Type Lip:
Oil Seal with this type Lip are meant for non pressure fluid sealing & severe grease sealing
"T" Type Lip:
Oil seal with this type Lip are meant for non pressure fluid sealing & severe grease sealing with light duty exclusions of contaminants.
"V" Type Lip:
Oil seal with this type Lip are meant for economical grease or viscous fluid retention.
"K" Type Lip:
Oil Seal with this type Lip are meant for economical grease or viscous fluid retention with light duty exclusions of contaminants.
"WP" Type Lip:
Oil seal with this type lip are meant for dirt wiping or scrapping in hydraulic cylinder applications.
The below mentioned table shows the basic operating limits of spring loaded & non spring lip seals of S,T,D,V,K & WP. These limits are based on the assumptions that the heat is being conducted away from the lip through the lubricating fluid and shaft.
Lip Material Selection:
The lip selection is generally based upon operating temperature of the sealing lip, fluid compatibility & the pressure in the cavity, shaft speed, cost, operating environment and seal life requirement.
The most common in use material for seals used are :-