The 40 tonne Hitachi SCX400T telescopic crawler crane was a runner up
15. March 2017
UK contractor St James Group has reported a serious incident - a near miss - with a 40 tonne Hitachi-Sumitomo SCX400T telescopic crawler crane on a London job site in January.
The crane was lifting a compressor when the boom dropped rapidly until it bottomed out in the horizontal position. Fortunately no one was hurt or injured. On inspection it became clear that a fitting connection to a pressure gauge on the pressure side of the lift cylinder had fractured, allowing hydraulic oil to escape, causing the boom to descend.
The incident was reported to the Health & Safety Executive and a joint investigation launched by the crane owner Eagle Crawler Cranes Hire and Hitachi distributor NRC. All parties confirmed the failure of an adapter that connected the pressure transducer and gauge to the cylinder. The adapter was fitted as original equipment by Hitachi Europe. An independent report by Penenden Engineering indicated that the failure was due to fatigue, although the part does not have a given service life.
The contractor is now bringing it to the wider attention of crane owners and users to highlight the fact that a misconception exists that in the event of such a failure the cylinder’s Holding/Lock/Check valves will still support the boom in the event of such a failure.
We hope to have a video of the incident shortly, however it is unlikely to show any further detail, but will show the speed that the boom descended.
It is good that this information has been made more widely available. Although a shame that it has taken two months to do so, it is a promising development all the same.
It would be useful perhaps to have more expert input to this, but by their nature pressure transducers need to be subject to the pressure side of the lift cylinders at all times which means a live connection. One method to prevent this being a major risk in the past was to make the connection as small as possible to ensure a slow descent, and on some machines to fit a ‘velocity fuse’ whereby the rapid passage of oil through the orifice would close the hole.
Whether this old technology has been improved on, replaced or deemed unnecessary I have no idea, but others will know of course.
Technically or theoretically this issue applies to all cranes that use hydraulic cylinders to raise the boom.
Comment by the Heavy Lift Specialist:
Very good initiative to explain what went wrong in this near miss. More contractors should take the courage to report near misses, from which the industry can learn a lot and make it a safer place to work in.