Wiper Seals
Modern hydraulic seals are just as much constructed to close tolerances as the remaining hydraulic components for efficiency and longevity in service. What is more, these are the components that get the hardest life as they slide past or rotate at high speed round precision manufactured high-grade steel alloy components, namely shafts, bearing casings or piston chambers.
When a hydraulic machine is repaired, there are usually some parts that can be re-used after they’ve been reworked using processes such as cleaning, re-plating, machining, honing, lapping and grinding. These can be and often are offered as “Refurbished” and “As new” or even “Genuine second-hand” which always makes me smile. This is a contradiction in terms and which usually means cheap and risky to use.
“Can you use second-hand hydraulic seal components?” I hear you say. The answer is quite clear in that there is absolutely no second-hand market (or “after-market” in some parts of the world) in hydraulic seals (as any repair manual will tell you). This is the item that is routinely replaced when the hydraulic equipment is dismantled. After all it is the hardest-working part in the whole machine. However, few people go back to the machine manufacturer for these parts as this is often where the manufacturers make their money.
What is absolutely true is that hydraulic seals are, in themselves, precision items made for specific purposes but to standard sizes and are often multi-component items using high-tech materials. These hydraulic seals are invariably made by specialist companies with a significant R&D operation and thus are separate from manufacturers of equipment that use hydraulic seals.
These hydraulic seal manufacturers nearly always use distributors with huge ranges around the world to get their products to market. Accordingly, to save money, the answer is a no-brainer. Never use anything other than such reputable distributors recommends as the best priced item for the highest quality. It goes without saying to never use cheap non-specific items that may be knocking around the workshop. They may seem to fit but they are unlikely to last and they will cost you much more in the long run.
A page about other related products can be found here http://engineeringface.com/suppliers/Spring-Energised-Seals-From-FTL-6
And here http://engineeringface.com/suppliers/Dynamic-Seal-47