FLUID POWER HANDBOOK
WWW.SEALINGANDCONTAMINATIONTIPS.COM
HYDRAULIC
SEALS
IMAGE COURTESY OF MFP SEALS
One of the arguments often used against hydraulic systems is that dreaded word, leakage. But with proper sealing, leakage won’t be a problem with your system. Sealing is a vital factor in the proper function of hydraulic applications. Leakage from the cylinder or across the piston, along with the ingress of unwanted contaminants, can not only decrease the lifespan of the components, but it will affect the efficiency of the entire application. MATERIAL OPTIONS Proper material choices will be determined by the seal’s environment. Different types of chemicals react differently to different fluids, while some materials have higher pressure and temperature limits. They also must be able to withstand extrusion, so materials are very application-specific. Polyurethane Polyurethane is an organic material whose chemical composition is characterized by a large number of urethane groups. Urethanes belong to the thermoplastic elastomers (TPE) family and close the gap between thermoplastic and elastomeric materials regarding hardness, deforming behavior and consistency. Within certain
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temperature limits, polyurethane possesses the elastic characteristics of rubber combined with the advantages of a rigid plastic. The composition of the material is determined by three components: polyol, diisocyanate and a chain extender. The type and amount of these materials used, and the reaction conditions, are decisive in determining the properties of the resulting polyurethane material. In general, polyurethanes possess the following properties: yy yy yy yy
high mechanical, tensile strength good abrasion resistance modulus of elasticity is variable wide range of hardness values, while retaining good elasticity yy good resistance to ozone and oxygen yy outstanding resistance to abrasion and tear Temperature range for use: –30 to 80° C; high performance types (compounds) up to 110° C in mineral oils (long-term exposure temperature).
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7/15/19 10:04 AM
