Seals – The MVP of Team Cylinder
There are several components that make up the anatomy of a hydraulic cylinder. They function together as a team, and are all collectively responsible for successful performance in some way. As the saying goes, “We win as a team, and we lose as a team.” Although each team member is important, the seals in a hydraulic cylinder could easily be considered the MVP of the team. After all, success depends on the seal’s ability to withstand pressure, temperature, contaminants, and imperfections in mating components. Respecting the limitations of the seal package is key to the success of Team Cylinder.
Cylinders enter our repair facility for every reason you can imagine (and some you can’t) but the leading cause is leakage. Internal leakage degrades performance and eventually means that the cylinder becomes unable to perform its task. External leakage usually begins at the rod gland and appears on the piston rod as a film of oil that progresses into droplets of oil. This is readily apparent as the oil attracts dust and pools in areas around the machine. Aside from the obvious environmental concerns, it’s just plain messy. Even though the cylinder may continue to perform its task with a gland seal leak, no one feels comfortable with a leaky cylinder moving a load. Time for repair.
Tear down and inspection quickly identifies the cause of the failure, and usually places the blame in one of four categories: contamination of fluid, extreme temperature, extreme pressure, or physical damage.
Contamination can be in the form of a foreign fluid that is incompatible with the seals and attacks the elastomers; gases that impregnate the seals and cause issues such as explosive decompression; and, most commonly, particulate that embeds itself into the seal inhibiting its performance and causing abrasive wear to other components.
Extreme temperature can be problematic whether hot or cold. There are a wide variety of seal materials available to suit specific applications where extreme temperatures are known to exist. The problem occurs when seals are unexpectedly exposed to extreme temperatures outside of their normal range, such as abnormally cold ambient weather or a system malfunction that causes the machine to overheat. These types of circumstances can cause the seal to crack and fail (extreme cold) or become hard and brittle (extreme heat).
Extreme pressure can also be managed with the correct seal if this is a known system requirement, but can be a source of failure if the design pressure of the seal is exceeded due to a system malfunction.
Physical damage is the most common cause of seal failure and can typically be traced back to defects in the surface of mating parts. The piston rod is exposed to the work environment each time the cylinder is extended and can often sustain damage during service. Minor bumps and bruises can be managed by seals that are in good condition. However, once the bumps and bruises become nicks and gouges the sharp edges gnaw away at the seal surface and erode the seal’s ability to maintain a leak-free boundary. Oil is allowed past the damaged seal surfaces and appears as a film on the piston rod, which attracts dust particles. Some particles become imbedded within the imperfections on the rod surface and are carried past the wiper and rod seals into the cylinder, where they cause abrasive wear.
Regardless of the application or environment, the success of Team Cylinder will always rely on the abilities of its MVP to overcome the challenges of contamination, pressure, temperature, and the imperfections of its other teammates.
RHK Hydraulic Cylinder Services Inc. are one of the most valued hydraulic cylinder manufacturers in Canada. If you need a custom hydraulic cylinder or hydraulic cylinder service – including hydraulic ram repair – contact us today!