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Installing piston seals

Piston seals installed in closed grooves must be expanded or stretched into position. Seals with step cut slide rings such as CUT or SCP (→ Piston seals with rigid split slide rings) are relatively easy to expand into position. Non-split profiles should not be expanded to a material deformation of more than 20% for TPU or 30% for rubbers. Otherwise, the permanent deformation would be too large. Heating the seal, e.g. in an oil bath, decreases the required expansion force, but cannot increase the maximum material deformation.
Piston seals with a TPU slide ring can usually be installed by hand or with simple tools (fig. 1). PTFE seals or those with thicker radial sections may require special assembly tools to save time or avoid seal damage (fig. 2). For additional information about such special installation tools, contact SKF.
The recommendations cannot substitute for careful installation tests in the particular application.
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