In the most basic sense, a hydraulic seal is a pliable, non-metallic ring that is placed in a groove or other fixture to form a seal that blocks a fluid pathway. They are used extensively in machinery as a vital tool as they provide the critical function of allowing fluid power to change to linear motion.
What are they made out of?
Two of the most common materials that hydraulic seals are made out of are nitrile rubber and fluorocarbon rubber or otherwise known as VITON.®
Nitrile rubber, or NBR, is one of the more common materials used for hydraulic sealing applications. It is comprised of a copolymer of butadiene and acrylonitrile and is typically inexpensive to manufacture. It demonstrates a superior resistance to petroleum-based hydraulic fluids. However, one of the drawbacks of using NBR hydraulic seals is the fact that they are vulnerable to environmental complications. If you intend to use this kind of hydraulic seal, keep in mind that the adequate temperature range for proper sealing is between -57 degrees to 100 degrees Celsius. It can withstand temperatures up to roughly 121 degrees Celsius, but it will most likely fail after any long duration of exposure. It is compatible with propane, butane, petroleum oil, mineral oil and other greases. However, it should be stressed that it is not compatible with any chlorinated or aromatic hydrocarbons.
Fluorocarbon rubber or FPM is estimated to be the second most common material used in hydraulic sealing systems. It is a combination of both vinylidene Fluoride and hexafluoride propylene and demonstrates that it has a noticeably higher temperature range of endurance than NBR. It is also resistant to weathering much more than NBR. It can withstand temperatures between -46 degrees and 204 degrees Celsius that makes it ideal for situations involving extreme temperature changes. It is compatible with many of the same petroleum based hydrocarbons as NBR but can also work with organic solvents and chemicals. It does not fair well with any glycol-based brake fluids, alkalis, ammonia, various other acids and extremely hot steam.
How do I install a hydraulic seal?
Here are some step-by-step instructions to guide you when installing a hydraulic seal:
1. Find a clean working area and place the parts in an easy to reach area.
2. Thoroughly clean and dry any parts that will be part of the seal. Make sure to inspect the parts for signs of damage or cracks.
3. If there are any rough patches, use an emery cloth and smooth them down.
4. Carefully slide O-ring seals over the components you intend to seal.
5. If there are backup rings needed with the O-rings, make sure to install those next. Keep in mind that the pressure should be on the initial O-rings, not the backup rings.
6. Slide the piston seals on just as you did the O-rings. Sometimes, if the seals are too rigid, you will need to soak them in hot water to make them pliable for installation.
If you have any questions or concerns regarding hydraulic seals or their installation, be sure to contact your local mechanic or hardware store to avoid unnecessary complications.