Inspection of the hydraulic cylinder rod is a crucial part of maintenance. The rod is a critical component for the proper functioning of the cylinder and is also highly susceptible to damage – it scratches easily, and external impacts can leave dents.
Here’s a short guide to inspecting a cylinder rod:
Test the surface with your fingernail: If scratches can be felt with a fingernail, the rod likely needs to be repaired or replaced.
Visually inspect the surface: Are there small, dot-like marks that resemble weld spatter? These are also grounds for repair or replacement.
Is the chrome layer worn?: Use a chrome thickness gauge to measure the coating. The recommended minimum thickness is 0.016 mm. Surface roughness should also be checked using a roughness meter—standards vary depending on the cylinder, but a general recommendation is Ra 0.2.
HL Hydraulics recommends:
Piston rods under 90 mm in diameter should be replaced with new ones. Piston rods over 90 mm can be re-chromed. In this case, the old chrome layer is removed using acid, the piston rods are ground, and then re-chromed.
We also advise checking the straightness of the piston rod—either with a straightedge or by clocking it in a lathe. If the piston rod has more than 1 mm of runout per 1000 mm (i.e., the piston rod is bent by a millimeter per meter), we recommend replacing it. In such cases, the cylinder tube should also be measured and inspected, as a bent piston rod indicates excessive radial force, which likely caused damage to the inner surface of the cylinder tube.
We strongly advise against attempting to straighten a bent piston rod using a press. This will damage the chrome layer and lead to rapid corrosion
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