Lip seal, also called Plunger Seal or Rotary Seal, is used in cylinder products or reciprocating seal devices, which will rotate when device is working.
Plunger Seal is mainly made from high grade silicone, liquid silicone rubber, NBR, PU rubber etc.
Elastomer Silicone Rubber Lip Seal's cross section is Y shaped. According to different ratios of cross-section’s height to width, seal ring can be divided into wide shape, narrow shape and Y shape. According to the equality and inequality of two lips height, seal ring can be divided into universal Y ring for shafts and holes, Y ring with unequal height for shafts and holes.
Silicone Lip Seal & Ring is used in reciprocating seal devices, which has a longer life span than Silicone Rubber O ring.
Working pressure: < 25 MPa
Working temperature: -40~+120℃
Medium: hydraulic oil, water, air
Rubber Lip Seal Working speed ranges vary in different materials :
NBR: 0.01~0.6 m/s
FKM: 0.05~0.3 m/s
PU rubber: 0.01~1 m/s
Lip ring made of PU rubber is better in sealing, life span and working pressure limit without retain ring.
Silicone Lip Seal & ring properties:
Less friction and smooth movement
Good pressure resistance and wide applicable pressure range
Simple structure and low cost
Silicone Lip Seal & Y Shape Ring Sealing Principle
Relying on the open lip, Y ring attaches coupling surface in a linear contact, producing “peak” contact stress under medium pressure, the higher pressure, the
greater contact stress. When coupling parts do relative motion at working speed, a layer sealing liquid membrane forms between sealing lips and sliding coupling surface, thus producing sealing effect. After sealing lip worn, it has the automatic compensation ability caused by medium pressure.
Lip Seal & Y ring with side lip for shaft. After each reciprocating motion, a little liquid (work medium) remains between main lip and side lip. With increasing reciprocating motion, the remaining liquid will filled with the room between main lip and side lip, finally forming a special “siege area”.
While the main lip is in the state of work, its pressure is higher than working pressure in small chamber due to the incompressibility of liquid in “siege area”. At the moment, the contact stress between side lip and coupling surface is also stronger than the contact stress between main lip and coupling surface. Therefore shaft extension forces the liquid in “siege area” back to small chamber, forming the reliable sealing condition, which improves Y ring sealing performance. The higher pressure in “siege area”, the greater contact stress from side lip on coupling surface and the sealing will be better.
Y Ring Application
Lip mouth must be towards the side with higher pressure during installing Y ring. Only in this way, can Y ring produce sealing effect.
Fit clearance between sliding coupling parts must be controlled in order to prevent Y ring root from being squeezed into the intermittence of sealing coupling surface under high pressure because of material plastic deformation .
As for Y ring, whose working pressure is more than 16 MPa, for ensuring Y ring’s life span, circlip must be installed in seal ring’s root to prevent the root from being squeezed into fit clearance.
In order to keep the moving stability and avoid overturn & distortion during reciprocating motion, supporting ring can be installed to Y ring lip.
Lip Seal & Y ring with supporting ring
1. one-way compression 2. two-way compression
There are small diversion holes distributing uniformly on supporting ring, which is good for pressure medium affecting on sealing lip sides through small holes，distracting two lips and keeping the right dynamic posture of Y ring to ensure the good dealing.
As for wide Y ring, the width of its cross section is twice or above as long as the height. This kind of seal ring can’t turn over or twist in groove, so we can choose not to install supporting ring.