4 Ways to Minimize Hydraulic Cylinder Failure and Repair Costs

hydraulic cylinder failureAs a product group, hydraulic cylinders are almost as common as pumps and motors combined. So if you operate a lot of hydraulic equipment, it’s likely that cylinder repair expense is a significant portion of your total operating costs.

According to some studies, up to 25% of mechanical equipment failures are failures of design. If we apply this to hydraulic cylinders, then as many as one in four hydraulic cylinders are not adequately designed for the application they’re operating in.

This doesn’t mean that the cylinder won’t do the job asked of it, it willbut not with an acceptable service life. So if you have any cylinders that don’t last like they should you may need to address one or more of the following four issues:

#1. Bent Rods

Bending of cylinder rods can be caused by insufficient rod diameter or material strength, improper cylinder mounting arrangement or a combination of all three. Once the rod bends, deforming load is placed on the rod-seal. This increases leakage and ultimately results in premature failure of the seal.

The allowable rod loading for a cylinder in an existing application can be checked using the Euler formula. The detailed procedure for doing this is explained on pages 58 and 59 of Industrial Hydraulic Control

#2. Rod Finish

The surface finish of the cylinder rod has a significant effect on the life of the rod seal. If the surface roughness is too low (smooth), seal life can be reduced as a result of inadequate lubrication. If the surface roughness is too high, contaminant ingression is increased and an unacceptable level of leakage past the rod seal can result.

In the context of extending cylinder service life, think of the cylinder rod’s surface as a lubricated, wear-surface and treat it accordingly.

In some applications, the use of an alternative rod surface treatment with superior mechanical properties to conventional hard-chrome plating, such as nickel-chrome plating or High Velocity Oxygen Fuel (HVOF) metal spraying, can increase the service life of the rod and its seals.

And in some cases, the installation of a shroud or bellows to protect the rod surface and its seals from impact damage and contaminants, can afford similar life extension benefits.

Hydraulic cylinder with protective shroud installed.

Hydraulic cylinder with protective shroud installed.

#3. Ballooned Tubes

Ballooning of the cylinder tube is usually caused by insufficient wall thickness and/or material strength for the cylinder’s operating pressure. Once the tube balloons, the correct tolerance between the piston seal and tube wall is lost, allowing high-pressure fluid to bypass the seal. This high velocity fluid can erode the seal and localized heating caused by the pressure drop across the piston reduces seal life—the end result of which is: premature failure of the piston seal.

#4. Insufficient Bearing Area

If the surface area of the bearing (wear) bands in the gland and on the piston are insufficient to adequately support the side thrust transferred to the cylinder, excessive load is placed on the rod and piston seals. This results in deformation of the seals, and ultimately, their premature failure.

Repair or Redesign?

To summarize the above: not all hydraulic cylinders are made equal. So if you have any hydraulic cylinders that suffer recurring failure, it’s likely that design modifications are required to break the vicious circle of failure and repair. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” available for FREE download here.

4 thoughts on “4 Ways to Minimize Hydraulic Cylinder Failure and Repair Costs

  1. That's really interesting that one in four hydraulic cylinders could have problems. I'll apply your tips to look for signs like bent rods that indicate a problem. I don't have much experience with hydraulics, but have always been fascinated by them. My uncle uses them a lot in his job and was showing me how they work the other day.

  2. It’s good to know that when it comes to keeping a hydraulic cylinder maintained, there are somethings that need to be done. I will have to remember to check the surfaces to make sure that they are staying smooth. This is something that will be good to know so that we don’t run the risk of contamination.

  3. Thank you for explaining the importance of the rod’s finish in making sure that you can extend its life. My friend has been wondering about what kinds of things he can do to make sure that his hydraulic cylinders stay in the condition they are currently. I’ll be sure to run this past him and see if he’s considered the finish and how it helps to keep everything running smoothly.

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