Hydraulic seals, basic materials In hydraulics, all the components have internal cavities that are sealed mostly by metal to metal contact, because a little internal leak is allowed for lubrication purposes, but in other cases the leak should be zero, for example in cylinders or in pumps to avoid external leakage. The use of elastomers or flexible materials is mandatory.
The following is a summary of the most used materials for sealing purposes in hydraulics.