Full definition
A scraper seal installed at the outer end of a hydraulic or pneumatic cylinder head (where the rod exits the cylinder), with the primary function of scraping contaminants — dirt, dust, metal chips, water, ice, paint — from the reciprocating rod surface before they enter the cylinder and damage internal seals, the cylinder bore, and the rod surface. Without effective wiping, abrasive particles carried past the wiper on the rod surface act as lapping compound, rapidly wearing the rod seal, scoring the rod, and contaminating the hydraulic fluid. Types: (1) Single-lip wiper — elastomer or PU lip (standard for indoor, clean environments). (2) Double-lip wiper — primary scraper + secondary wiper for dusty/outdoor environments. (3) Metallic scraper — hardened steel or bronze ring with interference fit (for the most severe contamination: foundries, steel mills, stone processing). Materials: polyurethane PU (best abrasion and scraping efficiency), NBR (standard, economical), and PTFE (lowest friction, chemical resistance). Wiper lip hardness: 90-95 Shore A for effective scraping. Per ISO 6195 (groove dimensions) and cylinder manufacturer specifications. The wiper is the first line of defense for the entire hydraulic system — a failed wiper leads to cascading damage to all internal components. Brands: Parker, Trelleborg, Hallite, SKF.