CRANE CRITIQUE
Mobile Crane Structural Repairs What are the proper procedures?
A monthly crane and rigging informative column for all personnel directly or indirectly involved with crane safety. Each month we will attempt to explain a different technical issue pertaining to crane operations here on Guam, addressing the sometimes over-looked or misunderstood topics by management and operators alike. By Dave Barnhouse
This month’s topic: Performing structural repairs on a mobile crane.
So you found a crack in your hydraulic crane’s outrigger beam or maybe that light corrosion on the boom that you have been hoping would go away has turned into heavy metal loss. How are you going to repair this damage and be assured that the repairs are safe and compliant with safety and crane standards? Best advice and first thing you should do is contact the manufacturer, explaining the damage as detailed as possible. Include plenty of photos with accurate measurements. If the damage was caused by a crane accident, detail the accident also, including the load on the crane when it occurred, boom length, radius, boom angle, etc. The manufacturer will evaluate the damage and will determine if the part can be repaired sufficiently to maintain the original structural integrity of the part while maintaining the original operating parameters of the machine. It will then provide you with the proper repair procedure, but may very well inform you of the price of a new component as opposed to a repair procedure. If the latter is the case and the decision is made to repair the damage, you have just put you and your company in a liable position for the life of the crane. The repair procedure will specify a step by step procedure on how to perform the repair and a list of the required parts. If the repair is completed per the instructions and all welding is per-formed by a qualified welder, the manufacturer will stand behind the de-sign of the repair. This will maintain the original structural warranty on the product and maintain the machine’s structural integrity, as well as complying with ASME and OSHA standards and also maintain the resale value of the crane. Let’s look at what we might find in that repair
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Non-compliant boom truck turret repair, poor weld workmanship procedure. We will assume a deep dent was found on the side of a boom section, deep enough that it pre-vented an annual certification, therefore preventing the crane from operations. Assuming the manufacturer received accurate information from the crane owner and it has determined the dent can be repaired, the procedure will out-line precise steps to take for a compliant repair. The damaged component will require removal, torch cut, saw cut, or grind the welds off? Minimum and maximum dimensions, radiused corners, beveled edges, steel specs, filler metals, welding process, pre-heat or post heat, NDT requirements. These are all important parameters of a structural repair and no one should assume he knows how to repair a
CONSTRUCTION NEWS BULLETIN
repair such as this because ‘I’ve done it before and it worked”. Starting with the first step, removing the damaged part, it may not seem obvious but the method and procedure for removing the part may be very critical. Alloy steels react to heat just as mild steel but may not be as forgiving. In specific conditions and high stress areas overheating may cause stress cracks, which are never good. Dimensional characteristics must be adhered to also for the same reason. This includes radiused corners, weld spacing, etc. Another important step in this repair would be to replace the steel with the manufacturer’s recommended steel specs. Not what you think
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