Berth 2 crane slewing ring assembly replacement

October 2011

(1) On 23/6/11 it was found that the Schat Harding crane on berth 2 was having trouble slewing in either direction. Upon investigation it was found that the reason for this was that excessive wear was causing resistance and sag was allowing the gearbox mounting plate to bind on top of the geared part of the slewing ring assembly, as well as this a small crack was found on the base of the crane pillar.

(2) Alliance lifting were called in on 24/6/11 to inspect the crane to see if it was still fit for use and upon inspection were satisfied that the crane could be used to de-rig the vessel currently alongside the berth but after this should not be used until repairs had been carried out.

(3) Schat Harding were contacted and a site visit to inspect the crane was arranged for 1/7/11. After inspection a report was compiled by their technician which recommended that the slewing ring be replaced, (see appendix 1).

(4) Roger Gosling of Schat Harding sent a quote through for a replacement slewing assembly, (see appendix 2). This was due to be delivered to Sem on 8/10/11.

(5) Ashdale were contacted to see what the work entailed, as they carried out the work when the slewing assembly was changed last time. It was established that a scaffold was needed to allow the crane pillar to be hoisted above the pedestal in turn allowing the removal and replacement of the slewing assembly,

(6) The crack on crane was welded by SEM maintenance and MPI’d by Rhyals (see appendix 3).

(7) Ashdale in for inductions 10/10/11, risk assessment and method statement supplied.

(8) Slewing ring bearing delivered to site on Monday 10/10/11 and lifted on to crane platform, whilst this was being carried out it was found that the slewing had become even more laboured and in fact the jib completely came to a stop. Because of this it was decided that the slewing gearbox should be removed and inspected so that if there were any problems with it they could be fixed whilst the new slewing assembly was being fitted, nothing was obvious upon inspection of the internals:

Upon further investigation of the gearbox it was found that there was a slipping clutch assembly that was designed to avoid damaging the gearbox should there be too much resistance whilst slewing:

The slipping clutch is located on the primary drive onto the gearbox from the bottom of the air driven engine:

The clutch assembly was stripped, inspected for wear and after being found to be in good working order was re-assembled.

(9) Kitsons scaffolded crane on 16/10/11, it was based on the estimation that the pillar was around 4 tonnes in weight, a drawing was done for this before it was constructed (see attachment 4):

(10) The jib of the crane was removed and rested on wood in order for the next part of the job to progress:

Ashdale asked for the scaffold to have lifting beams mounted at two feet above the top of the pillar:

(11) Once work had commenced it was found that two feet was not enough pull lift travel and that another set of ladder beams had to be installed giving four feet of clearance above the top of the pillar. The reason for the extra clearance needed was that a central air manifold in the pedestal was approx two feet in height meaning that the pillar had to be hoisted higher than envisaged:

It’s important to note that due to the height that the pillar has to be lifted that no part of the scaffold fouls on the crane pillar or attached gearboxes and that there is plenty of slack on the jib wires and hook wire.

(12) Once the old slewing assembly had been removed the flanges it bolts to were cleaned and the new assembly was put in place:

(13) Lifting gear was used to ensure the new assembly was installed in a controlled

manner and blocks were used as a failsafe:

(11) There was an issue once the new assembly was in place of the internal diameter

having too much of an interference fit with the locating spigot. After consultation with Schat Harding’s technical department it was decided to dress the locating spigot in order to allow the correct amount of clearance for the installation of the new assembly

(12) Upon installation of the new assembly the work was certified by Schat Harding technician Mick Wood (see appendix 5).

(13) The pneumatics were re-connected and external slewing gear greased.

(14) The jib was reattached:

(15) Lastly, the slewing gearbox and associated pipework was re-attached and a

function and load test carried out (see appendix 6).

Appendix 1

Appendix 2

Appendix 3

Appendix 4

A larger version of this drawing is present at the end of this report.

Appendix 5

Appendix 6

Additional photos of scaffold and different stages of work