What is hydraulic seal? Types of hydraulic seals

Hydraulic seal

Hydraulic seals is a non metallic ring located in the grooved piston which separate the  fluids and prevent leakage of cylinder in reciprocating motion application is known as hydraulic seal. 

Hydraulic seals are made with Rubber, PTE material or polyurethane. Materials are selected based on their application of uses, fluid type, pressure and temperature. 

Types of hydraulic seals

According to motion

Static seal: Static seals is located into the housing where no motion are required and sealing are also within limited space. 

Dynamic seal: Rod seal and piston seals are dynamic seals. In the dynamic seal, a motion are created into the inner diameter along the shaft or rod of hydraulic cylinder. Rod seals creates the motion into inner diameter along the rod and piston seal creates the motion into outer diameter along the barrel or tube. 

According to type of work (Hydraulic seal)

Hydraulic Piston seal: Piston seals are located in the groove of cylinder piston and In the piston seal, sealing lips are contact with entire bore housing. Piston seals maintain the position and control of cylinder motion.It prevents the fluid leakage across the cylinder piston during the system pressure pushes the piston.  

Hydraulic Rod seal: Rod seal is located in the rod end port of hydraulic cylinder.This seal hold the pressure and prevent it from leaking out.

Hydraulic Wiper seal: Wiper seals are also be called as a scrappers or dust seal. Wiper seals are used to cylinder rod end port to prevent dust and contaminants entering into the cylinder  when the piston shaft is retract.Usually one pieces of wiper seal are used in a single cylinder.

Difference between Piston seal, Rod seal and wiper seal

Piston seal	Rod seal	Wiper seal
1.Works like pressure restrictor.	1. Rod seal prevents the fluid from leaking out.	1.Work like a dust protector
2.Prevent passing the fluids through the piston.	2. Prevent the corrosion of rod	2. Wiper seals prevents external contaminants entering inside the cylinder.
3.Control the cylinder motion and maintain the position of hydraulic cylinder	3. Rod seal generates lubrication film during the cylinder retraction.	3. It makes lubrication films for the cylinder during the retraction of rod.

Cause of hydraulic seal failures

Hardening: Hydraulic seals are became hard due to high fluid operating temperature and high speed stroking operation. Due to Seal hardening they lose their elasticity and resulting to failure

Improper installation: Improper installation damages the seal lips and it is the cause of seal failures. 

Contamination: When the seals are dirty with the contamination like mud, tiny elements and powder resulting seals losses ability to prevent contamination from the piston. 

Fracture: Fracture is the another reason of seal failures. It causes from burn and long brakes which are created by high pressure, shocks and low quality manufacturing material quality of seal.

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Hydraulic seal