What is “Dieseling” in Hydraulic Cylinders?

Learn how to prevent one common cause of hydraulic cylinder failure.

What is “Dieseling” in Hydraulic Cylinders?If you operate any kind of hydraulic equipment, it is important to be familiar with the many problems that can interfere with the proper performance of various hydraulic components within the system. This certainly includes dieseling of the hydraulic cylinders.

What is Dieseling?

The term dieseling is a reference to the combustion process in a diesel engine. In your average combustion engine, a spark is needed to cause the fuel to combust. However, in a diesel engine, pressure alone is sufficient to cause combustion.

Here’s how this can happen in a hydraulic cylinder:

Sometimes, when a double-acting hydraulic cylinder retracts, the volume of fluid needed on the rod side is more than has been provided by the pump. When this happens, it creates negative pressure on the rod side of the cylinder. This negative pressure can suck air past the rod seals and into the cylinder itself. Then, when the newly contaminated fluid inside the cylinder gets pressurized on the next stroke, it can explode or combust. This damages the cylinder and destroys the seals.

How Can Dieseling Be Prevented?

To prevent dieseling, we have to tackle the errors that can let air into the cylinder.

First, make sure hydraulic cylinder’s chambers were fully purged of air during commissioning. Otherwise, this air ingression will naturally lead to dieseling.

Secondly, there is the possibility of a faulty float valve causing the air contamination. This can happen in equipment like hydraulic excavators, where the float valve is supposed to allow for the boom to be lowered rapidly under its own weight and the cylinder to also be retracted at the same time. The valve is supposed to allow the fluid from the piston side of the cylinder to be directed with priority to the rod side rather than sent straight to the reservoir. If the valve malfunctions or is not set correctly, you end up with negative pressure and ergo with dieseling.

Need Help with Hydraulic Cylinder Troubleshooting?

If you are experiencing frequent premature cylinder failures in your hydraulic equipment, you should definitely investigate the possibility of a dieseling issue. Be especially suspicious if the cylinder itself seems in good condition but the seals are failing prematurely.

If you would like help troubleshooting your equipment, just call Bernell Hydraulics. We can provide expert assistance as well as fast onsite parts replacement and repair in our local service area.

Posted on April 29, 2015
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