Kinshofer KM602 Hydraulic Ram Repair – Piston Wound Off the Rod

When the piston winds off the rod inside a Kinshofer KM602 grab bucket ram, it can be extremely dangerous. As the piston reaches the last few threads, the hydraulic pressure blows it off the rod with force and the bucket can slam shut like a guillotine. Simply Welding repaired a Kinshofer KM602-500lt clamshell bucket hydraulic cylinder after its piston wound off. We repaired it in-house with a new rod, piston and seal kit, rebuilt it within the hour and had it back on the machine the same day.

Job Description

The Kinshofer KM602-500lt clamshell bucket hydraulic cylinder had failed after the piston wound off, damaging the hydraulic rod and piston threads. We stripped the cylinder, replaced the rod and piston, then resealed and tested the ram. We hold all Kinshofer KM602 and KM622 parts in stock, so a repair like this can usually be completed the same day, with the rebuild itself often done within an hour.

Parts Used

A Kinshofer KM602 hydraulic rod, piston and a full seal kit, including piston and gland seals.

Stripping the Cylinder

The rod had already come away from the piston. We drained the remaining hydraulic oil, removed the gland nut from the Kinshofer hydraulic cylinder and pulled the piston out of the tube.

Inspection

The tube was checked for damage to the bore and threads, and for hairline cracks around the inlet and outlet ports. Any suspected cracks were checked with penetrant dye and developer. The gland nut was checked for impact damage, particularly around the wiper seal groove.

Re-assembly

A new seal kit was fitted to the gland nut, which was then slid onto the new rod. A new piston was fitted with its own seal kit, and a specialist Loctite was applied to the rod-to-piston thread. The piston was wound on quickly before the Loctite could cure, torqued to the set value and loaded into the pre-lubricated cylinder tube. The gland nut was fitted without Loctite and torqued to the set value.

Pressure Testing

The ram was first run on air to check for low-pressure leaks, then given an operational test. It was taken to full working pressure plus 15% and held on the pump for 30 minutes, and three full test cycles were completed.

Result

The ram was rebuilt within the hour and was back fully working on the machine the same day.

Frequently Asked Questions

What happens when a grab bucket ram piston winds off?

The piston gradually unwinds along the rod thread. When it reaches the last few threads, hydraulic pressure blows the piston off with force, damaging the rod and piston threads. The bucket can then slam shut like a guillotine, which makes it very dangerous for anyone nearby.

Do you stock Kinshofer KM602 and KM622 ram parts?

Yes. We hold Kinshofer KM602 and KM622 hydraulic rods, pistons, glands and seal kits in stock, so most Kinshofer ram repairs are completed the same day.

What do you check when a Kinshofer ram is stripped?

The tube is checked for damage to the bore and threads, and for hairline cracks around the inlet and outlet ports, with any suspected cracks checked using penetrant dye and developer. The gland nut is checked for impact damage, particularly around the wiper seal groove.

How is a rebuilt ram tested?

The ram is first run on air to check for low-pressure leaks, then given an operational test. On this job it was taken to full working pressure plus 15% and held on the pump for 30 minutes, and three full test cycles were completed.

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Leaking or broken hydraulic ram? We repair them in-house. Call 07747 682451 or send us some photos via WhatsApp.