A slewing ring at the end of its life. How long could it keep running like that? Liebherr A906

A 2009 Liebherr 906 excavator drove into our workshop and it was immediately clear what needed doing: there was about 2 cm of play in the slew. This time the culprit was not chipped teeth but a worn-out slewing bearing. With that much play the ring has to be replaced, no question.

Preparation

The machine was covered in a thick layer of mud, so we started with a thorough wash using chemicals and a pressure washer – when replacing a slewing ring, a clean joint area is essential. Then:

• we cracked the bolts loose with a wrench and extension bar (they were very tight) and then removed them with a pneumatic wrench,
• at the swivel joint we disconnected and plugged the travel lines, the return line from the hydraulic motors to the tank and the gear change line – so the machine could still be started and supported on its boom,
• we lifted the upper carriage with a forklift at the rear and with the boom at the front.

One bolt had been missed and the upper carriage lifted together with the ring – fortunately, once the forklift was in place, we simply removed it and took out the old ring.

Fitting the new ring

The new ring went in straight after the old one came out – the machine was secured, so no time was lost. We also replaced the full set of bolts: 40 in the upper row and 48 in the lower row, 88 in total. Every bolt was coated with copper grease, which protects the thread from corrosion and seizing – so that at the next replacement, many years from now, they can be removed without trouble.

After pre-tightening we torqued all bolts with a torque wrench to 620 Nm as specified by the manufacturer – one after another, marking each, in both the upper and lower rows.

Result

The play is gone and the slew runs smoothly without knocking. After refitting the covers the machine was ready to be handed back to the customer.

Takeaways

• Slewing play increases gradually – the longer a machine works with it, the greater the risk of damaging the structure and bolts.
• When replacing a slewing ring we always replace the complete set of bolts and torque them to specification.
• Copper grease on the threads makes the next repair easier.

We replace slewing rings in our workshop and, if needed, in the field. See our construction machinery service.

Watch the repair video: A Slewing Ring at the End of Its Life. How Long Could It Run Like That? Liebherr 906