Valve that can shut-off the flow in both directions. In fluid technology this valve is implemented in then form of a seated or ball valve.
One of the most important sources of contamination in hydraulic installations is the dirt drawn in by the piston as it moves inward. To prevent this contamination occurring, scrapers are used. They are primarily manufactured from wear-resistant, elastic materials with very high hardness (80-90 Shore A) and given a sharp edge to ease the stripping action.
There are scrapers made of pure elastomers or with a metal part vulcanised into the stripper to improve the retention in the groove. Scrapers made of metal are available for special cases (Figure A 7).