The integrity of piston rods, bearings and seals is paramount to ensure the leak-free operation of hydraulic cylinders demanded for today's major industrial manufacturing and process lines.

The piston rod is most vulnerable part of the hydraulic cylinder, with damaged piston rods being, by far, the most common cause of rod seal failure.

Piston rods are at risk of damage from tools such as spanners and wrenches used in installation, falling objects, and even operators using cylinders as steps to gain access to machines! If the piston rod receives only a slight knock, denting can occur which can lead to fluid leakage even if the seal itself is not damaged: the size and shape of the denting may allow the hydraulic fluid to bypass the seal.

Severe damage can lead to tearing of the seal and a more obvious source of leakage.

Obviously, if oil can get out, then dirt can get in ã leading to even more damage.

Induction case hardening is recognised as the most appropriate treatment for piston rods.

As standard, all Parker Hannifin European industrial tie rod cylinder piston rods are manufactured from precision ground, high tensile carbon alloy steel, hard chrome plated and polished to 0.2um max.

Piston rods are induction case hardened to Rockwell C54 minimum before chrome plating, resulting in a dent-resistant surface.

"Other manufacturers often use non-induction hardened steel as standard", says Parker Cylinder Applications Engineer, Andy Lindgren, "and may only offer induction case hardened piston rods as an option - at extra cost! Piston rods manufactured from non-hardened steel ã even if they are chrome plated ã are prone to denting, which leads to early failure of bearings and seals." "Additionally", says Andy, "the process of induction case hardening is simple to undertake during piston rod manufacturing, and has very little effect on the final cost of the cylinder.

OEMs and end-users should bear in mind that a new piston rod is a made-to-order part and replacement requires a complete stripdown and rebuild of the cylinder.".

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