Cylinder Failure – Contamination

One of the most common causes of hydraulic cylinder failure is contamination. A contaminant is defined as “a polluting substance that makes something impure.” In other words, anything that is not supposed to be in your hydraulic cylinder is a contaminant. This includes air, water, chemicals, and of course particulate such as dirt, metal and other hard materials. Although the damage caused by any contaminant cannot be reversed, air, water and chemical contamination may be corrected without removing the cylinder from service – if addressed immediately. Particulate contamination is more difficult to remove from the cylinder, and may require disassembly.

Air contamination is usually caused by improper bleeding of the circuit and cylinder during installation and commissioning. It may also be introduced into the cylinder through the hydraulic pump circuit if a leak in the inlet line allows air to be drawn into the fluid and carried downstream into the cylinder. Air contamination is quite noticeable, as it causes spongy and erratic cylinder performance and, in extreme cases, a phenomenon known as “Dieseling.” This occurs when the fumes within the air bubbles ignite when pressurized, causing burning of the seal face.

Effects of Dieseling on Seal

Water contamination may be introduced through the pump circuit if there is water in the hydraulic reservoir or through a failed rod wiper seal. Water reduces the lubricity of the hydraulic fluid, accelerates wear and corrosion and leads to degradation of the seals. Water can be difficult to remove from the hydraulic system and requires immediate and thorough flushing to purge from the cylinders.

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Chemical contamination is usually introduced into the hydraulic system accidentally by someone using an incompatible fluid to top up the reservoir. Fluid that is incompatible with seal materials will cause the seals to degrade and fail. As with water contamination, the solution requires immediate and thorough flushing of the system.

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Particulate contamination is the most common cause of hydraulic system component failure – and cylinders are no exception. Hydraulic cylinders operate under high pressure, dynamic conditions that often involve high cycle rates. Hard particles of dirt and metal material within the hydraulic fluid become embedded in the seals and bearing materials. These hard particles score the smooth sealing surfaces of the rod and barrel, creating leak paths for fluid to bypass, and degrading the performance of the cylinder. Even if the contamination is identified and the fluid is filtered and cleaned, the embedded particles remain in the cylinder and continue to cause scoring with each stroke. The cylinder must be disassembled and re-sealed to prevent further damage.

RHK Hydraulic Cylinder Services Inc. are experts in hydraulic cylinder service. We can repair cracked hydraulic cylinders and can handle any hydraulic cylinder rebuild. Contact us today to learn we can help you.                            


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