In 2009 offshore installation contractor Heerema Marine Constractors (HMC) started planning the overhaul of the slewing rings of its two largest cranes in the fleet. These 7100mT cranes of crane vessel Thialf mounted on a 28m diameter base each rotate on 1127 rollers and twelve rail circles with a total length 2.4 km making up the slewing ring. TrustLube was approached to design an automatic grease system for these slewing rings and provided their first concept back in 2009 after which several changes were made in consultation with HMC.
The main reasons TrustLube was awarded this contract are the reliable metering system and tailor made solution custom designed for the Thialf. Besides that the new system will cut grease consumption significantly. Besides a manpower and cost saving this is also positive for the environment.
Once the final concept was agreed and a site visit was made onboard TrustLube started detailed design and fabrication. Installation was executed towards the end of the slewing ring overhaul end of 2010 and early 2011 in the Caland Canal (port of Rotterdam, The Netherlands). This was a joint effort between HMC and TrustLube who had their mobile workshop located onboard of the vessel.
Simple but effective
Grease is now dispensed through custom made skids mounted in cut outs in the rail circles. These cut outs were made in low loaded sections of each slewing ring. Every roller that passes the skid is supplied with grease. In order to get the correct amount of grease the pumps are linked by a PLC to the command system of the crane. As every roller is greased the contact between each roller and the rails is always lubricated, a simple but effective approach. With smoothly rotating cranes, the Thialf left the Caland Canal in 2011 - ready for its North Sea campaign of installing and removing oil and gas platforms.