This article was originally published at KHL.com and written by Alex Dahm. You can view the original article here.
Changes in the design and material used in the booms of telescopic cranes has made repairs a lot more difficult and complicated, as Colin Sowman finds out
Thankfully the incidence of cranes suffering boom damage has reduced over the last few years – partly through lower workloads during the recession and partly because of the increasingly sophisticated warning systems that prevent modern cranes from being damaged by overloading.
While repairing booms by welding in a new section was relatively easy on older cranes, on the modern generation of machines things are less straightforward. Gone are the old mild steel box section telescopic booms and in their place are half-round or ‘D’ profile booms made from high-tensile steel. The steel in this new generation of booms is heat treated to provide the optimum balance between lightness and strength, allowing heavier loads to be lifted to greater heights than ever before.
While the in-use benefits of these newer designs are self-evident, if the boom becomes damaged the complication and level of skill required to repair them is now far higher than in the past. “The older stuff with box section booms is very repairable; you can easily insert new mild steel plates as it gets its strength from the box section,” says John Miller, aftersales manager for mobile cranes at Manitowoc in the UK.
“With anything built in the last eight years or so, if there is damage in the lower [half round] part of the boom section then it may not be repairable. It is a case-by-case situation. The lower section may look semi-circular but it is created by around 36 carefully spaced and controlled bends to create that profile and it relies on its shape and steel integrity to maintain its strength,” Miller adds.
There is no doubt that the number of independent repairers has reduced but they do still exist with the likes of Crowland Cranes in the UK, Avezaat, Köhler and Rusch in mainland Europe, Wheco in America and Pollisum Engineering in Singapore, all still active.
Variations exist between the crane manufacturers’ views of boom repairs and independent repairers. These can also differ between countries depending on the regulatory framework and the available skills. However, both Miller and Ed Hudson, general manager of crane aftersales at Liebherr Great Britain, describe the same damage evaluation process. The length, width and depth of the damage is measured along with its position in the boom’s profile and how far along the telescopic section it occurs. This information is then fed back to the design engineers at the factory who calculate if it can be repaired and, if so, how that repair must to be carried out.
From this point on views and procedures diverge by company and by country. Within Europe, for instance, if Liebherr’s engineers decide the boom can be repaired the company will carry out the work itself at its own dedicated premises in Germany. If the Manitowoc boom can be repaired then it will issue a repair specification listing the physical dimensions, material specification(s) of any section to be inserted into the boom along with the required filler rod.
This work can be carried out by an independent repairer as the specification also includes any requirement for pre- and post-welding heat treatment and the extent of post-repair testing but not the required coding for the welder. “The repairer must look at the materials and processes involved and satisfy themselves that their company has the necessary skills, certification and equipment to undertake that repair,” says Miller.
In the USA Jay Shiffler, vice president of business development at independent crane repairer Wheco Corporation, believes there is much mis-information about whether a repair (or repair process) which has not been approved by the crane manufacture has to be considered a modification. In the USA, repairs and adjustments to machinery fall under OHSA (Occupational Safety &Health Administration) 1926.1412(b) whereas modifications are covered by the more rigorous 1926.1412(a) and 1926.1434 standards.
Not only is Shiffler adamant that non-OEM approved repairs are not modifications, he also says that the repairs carried out at his company can be much quicker than those done by the manufacturer, resulting in a cost saving to the customer of between 30% and 80%.
Wheco repairs and refurbishes all makes and types of cranes and is an approved repairer for Manitowoc machines. It works from five locations and has invested heavily in new equipment and training cope with the new steels, Shiffler says. At any one time the company will have around 30 cranes in for repair or refurbishment.
Dave Dimelow, head of engineering at the UK arm of global loss adjuster Crawfords, says insurers usually require two quotes for the repair of any crane that is out of warranty. Dimelow says that some manufacturers refuse to divulge the specification of the material in the booms of their newer cranes. To get a second estimate a steel sample is sent for analysis to determine the grade(s) of steel used.
In the UK, Section 6(1) of the Health and Safety at Work Act “places a general health and safety obligation on anyone in the supply chain, so far as reasonably practicable, for when articles for use at work are being used, set, cleaned or maintained.” Some in the industry interpret this as meaning crane manufacturers have an obligation to make the information required to repair a damaged machine available to the owner – others disagree. Again, the regulatory framework varies from country to country; even within supposedly common areas such as the European Union.
For the insurance companies, having got their cost and time estimates to repair a damaged crane, they do not usually stipulate if the manufacturer or an independent company should undertaking the work. It is, after all, in the insurer’s interest to get the repair done as quickly and as economically as possible. Dimelow is, however, quick to point out that crane jobs with latest high-tensile steel booms are still relatively new, so the repairs he has handled have gone back to the manufacturer which, he says, has a built-in advantage. “Especially if the crane needs other repairs such as a new cab, then the manufacturer has the advantage because they control the cost of replacement parts. It’s tough for the independents,” he says.
That said he sees no reason why specialists independent companies should not repair crane booms as an appropriately coded welder will know the processes required to join the steels involved. This may involve pre-heating the boom before the welding takes place, ensuring the weld does not cool too quickly and, even 24 hours of heat treatment, after the welding has finished.
“This is not rocket science,” says Dimelow, “it’s all laid down in various standards and, given the correct equipment, a suitably coded welder should be able to carry out the job satisfactorily. The company carrying out the repair must stand behind their work.”
Dimelow is quick to add that he has never seen an incident where a repaired boom on a telescopic crane has failed. “If it did, the potential consequences could be drastic and the legal claims would probably drive the repair company out of business,” he says.
Regardless of whether the manufacturer or an independent company undertakes the repairs, insurers will normally insist on an overload test to prove the repaired boom is up to the job. “The repaired section must be as strong as the original or stronger,” says Dimelow. For that reason the overload test required by the insurer may be equivalent to that undertaken during the type-approval. If the repaired boom passes the test then the insurance company will accept it as serviceable.
Peter Issitt, managing director at Crowland Cranes, believes his company can repair a boom for as little as half the cost of a replacement. “The real advantage is the time needed to complete a boom repair compared with the experienced lead times for a replacement boom,” Issitt explains.
Like other remaining crane repairers, his company has kept up to date with the new steel specifications and welding processes but, even then, it is not a straightforward process. A recent boom repair concerned a Terex Demag AC 100 from 2009 fitted with a half-round boom. While getting the repair specification was not a problem, the company had to source the specialised steel from Germany before bending it into the required profile and welding the replacement section into the boom.
While companies like Crowland and Wheco are well versed in repairing the new generation of booms, there are potential pitfalls out there for unwary crane owners – even removing an unwanted bracket from the boom can cause problems. “If somebody uses oxy-acetylene equipment to remove a bracket, that could create problems with the heat treatment and may even cause local changes in the steel’s composition,” says John Miller. Liebherr’s Hudson goes even further, saying, “Owners and repairers should always contact the manufacturer before doing any hot work on a boom.
Work carried out immediately after a crane incident has also become more important in the repair process. For instance if a crane has suffered a tip-over and is lying on its side, the boom is an obvious place to apply forces to right the unit. With the new booms crane owners must ensure that the recovery operators do this with the utmost care as the cross section of the new booms are designed to be loaded vertically. Even relatively small sideways stresses can cause distortion – especially if the boom is extended. A distorted boom, or a particular section or sections, may have to be replaced if it has obviously been stressed past the yield point.
Another area where problems could arise is if the crane suffers a fire in the engine bay as this is often adjacent to or just beneath the base of the boom. While the charred boom may look like it just needs a new coat of paint, the fire may have upset the heat treatment of the steel leading to a weak point – again the consequences of this passing undetected could be disastrous.
The message is that owners and operators must be aware that the new generation of booms are less tolerant of accidents, incidents and overloads but repairs are possible. Depending on the type and scale of boom damage a suitably equipped and staffed independent repairer may offer a time and cost-effective alternative to OEM repairs or replacement. Whichever option the crane owner decides to take, the insurance company will require an overload test on a repaired boom before the machine can be put back into service.