Miracle workers
21 November 2007Installing lifting equipment in existing, and sometimes operational, factories is one of the biggest challenges for crane builders and manufacturers alike. Richard Howes finds out how they do it.
For US firm North American Industries (NAI), the ratio is different (50/50) but still large enough to present regular problems, as it explains later. It says it often begins work on a Friday, working nights and weekends to complete a major portion of the installation when the plant would normally be closed.
Of course, the people ordering the installation will rarely be crane-minded and the crane will often be an after-thought when the problem of lifting something too heavy to do so manually arises.
Put simply, existing buildings cannot handle the stresses enforced by modern day lifting gear, and the sometimes huge weights they can carry.
"Sometimes it's possible to get a structural engineer in to assess the strength of the building," says Sidwell, and it is possible to bolt new steel structures to existing framework, "but this is rare and tricky in itself," he adds. Inadequate foundations also create problems.
Ingo Ruehl, materials handling boss at CERN (the European Organisation for Nuclear Research), agrees that the biggest obstacle to overcome is the building conformity, "the dimensions (mainly the height) for calculating clearances and the structure and foundations regarding the SWL," he explains. He says when there is a lack of clearance space "we make sure that all access to the crane rails and the crane itself are locked and set up a procedure that regulates the access."
Up to a certain limit, Ruehl agrees that the building structure and foundations may be reinforced to increase the SWL. "On some metallic structures," for example, "it was enough to weld steel plates over the entire length of the vertical beams in order to increase the crane capacity," he says.
He gives an example where a 25t EOT crane was added to the same rails on which a 16t EOT crane operates. Both can operate at the same time but have to respect a certain distance.
"It is in general more difficult for civil engineers to evaluate the SWL for concrete buildings (especially if they are more than 20 years old)," says Ruehl. "In the past we even had to downgrade several EOT cranes due to the ageing of concrete buildings where crane rails were mounted on concrete slabs."
Portal frame buildings are essentially erected as economical, multi-purpose warehouses, marketable, say, to storage and light fabrication firms. So when a firm requires the lifting of heavy marble sections, for example, a more robust framework must be installed within to support cranes, whether it be a jib crane in one corner, or an overhead crane spanning the whole factory floor.
If concrete footings are necessary, the manufacturer can inform the customer for what load capacity they need to be rated in order to support the crane.
Lifting Equipment Engineers Association (LEEA) chief executive Derrick Bailes recalls the case of a new building where, during construction, it was realised that an area needed to be served by an overhead crane. It was too late to make the gantry integral with the building frame so a semi-independent structure was added. This took the vertical loads imposed by the crane but was tied into the building frame for lateral stability.
The building frame was in-filled with brickwork and the structural engineer clearly thought it would be adequate. However the day soon came when the crane hit the long travel end stops and the entire 80ft wide brick gable end shattered from top to bottom. An expensive error, to say the least.
Bailes explains that forces on structures arise not just from the payload but also the weight of crane hoist or crab and the crane bridge (depending on direction of travel). Moreover there is the possibility of shock loading arising from accidental collision into the travel end stops at speed. Essentially every structural element deflects under load.
Added problems can arise as a company will be required to scale back their own operations while an installation takes place. For example, a mobile crane may be required to lower box girders through the roof, in which case areas will need to be kept clear both within the factory and in the yard.
However, when Kuli Hebezeuge Helmut Kempkes GmbH fitted cranes at a chemical plant recently, the roof could not be opened because the inside temperature of the building could only be dropped by a few degrees.
Another example of the calamity installations can cause is when a customer ordered a 480 volt crane, but only had 240 volts in their building (perhaps due to a miscommunication between the customer and their electrical contractor).
Mark Sidwell says such problems should be overcome during what he describes as a "pre-site installation meeting," where the customer is informed of its requirements and for what period of time they will be on site. At the same time, drilling methods (and why they were chosen), access and fire protection and the restrictions of each are all outlined.
NAI says it sends customers engineering clearance drawings which provide all important measurements and details. The customer either signs the drawing as it is or works with the crane engineers requesting adjustments until the drawing is approved. Only then does the manufacturing process begin.
Additionally, pre-installation letters are composed, clearly stating the expectations and responsibilities of both the customer and the manufacturer. For example, it may be agreed that the customer must have anchor bolts in place prior to the installation.
However this never sets things in stone and customers often insist installations are delayed when their own product is due shipment or large orders come in at short notice. Money talks.
Job specifications can get pretty bizarre. Mark Sidwell recalls a job at a water treatment firm where they had to transport the crane parts across a beach. While they stopped short of taking their shoes off and rolling up their trousers, the shifting sand and incoming tide presented a logistical nightmare.
NAI says it overcame several obstacles on one memorable job in which they complied with a customer's request during manufacturing to shorten the span of the bridge beam on a custom overhead crane. However, during the normal procedure of taking final measurements at the job site prior to installation, NAI discovered that the customer had never communicated to the building engineer the same requested change. As a result, the crane span was built to the customer's specifications, yet it would not have been long enough to reach the runway attached to the building. The measurements taken by NAI also turned up another problem, that the supports erected by the builders, on which the crane was to be installed, were uneven.
In this case, the bridge girder extension was welded on site, lengthening the beam once again so that it would fit the new dimensions.
NAI more recently installed a crane in Utah about 40 miles from the nearest town, climbing rough hilly terrain with the lull machine in order to transport the bridge beam from the road to the installation location.
Heinz-Helmut Kempkes, managing director, Kuli Hebezeuge Helmut Kempkes GmbH, recalls a time when one of Germany's top chemical companies intended to restructure the production facilities in an old building erected in the early fifties. They required the modernisation and extension of the crane systems within 48 hours to prevent disruption of the production.
Although the common track was strong enough for the higher loads, revamping the two old cranes was out of the equation for time and economical reasons. The choice was to replace the two double lattice girder 10t units with two new box girder cranes of 15t capacity plus an additional 10t crane.
The erection and assembly could only be carried out outside the normal working hours, thus restricted to Friday night after 22.00 until Sunday night at 22.00.
The crane erection space was limited and mechanical installations could only be done in single parts. The 120m long bus bar power rail was to be replaced entirely. For the assembly of the new bus bar a lane of only 2.1m in width was available.
"To meet the tough time schedule it was arranged with the client to prepare the crane installation one weekend earlier," says Kempkes. Work started on Friday at 14.00 but without disturbing the operations of the two old cranes. First, the assembly of the new 120m long bus bar aside the old bus bar was arranged while the old bus bar was still in use.
Four mechanics/electricians installed the new one by using a 16m range aerial platform movable through the centre-positioned lane, just 2.1m wide. A new raising cable and a wall mounted main switch were installed too. The old cranes were connected to the new bus bar and the old bus bar was dismantled.
The actual installation began on schedule at 22.00 the following Friday.
The new cranes were equipped with a one-side catwalk as well as an accessible crab. "It had not been possible to assemble and install the cranes at the ground just to lift it to the track rail level," recalls Kempkes. "No space was available for using a truck mounted crane of sufficient capacity, so the three new cranes were erected with a part length of 40m out of 120m. The track rail was just 0.25m from the brick walls."
The end carriages of the first 15t crane were brought up to the track and provisionally fixed. Then, the two girders were lifted up and bolted to the end carriages. This was followed to lift up and position the hoist crab.
The whole electrical installation of the crane and connection to the power rail, commissioning of the crane functions and fine adjustment of the frequency inverters were completed with the further aid of a 12m working platform and a 40t compact truck mounted crane.
Based on estimation of the weight of the old lattice girder construction the dismantling of the first old crane could be done in single parts with the use of a 60t truck mounted crane.
The assembly of the second new 15t crane was done in same way followed by the disassembly of the second old crane. Finally, the new 10t unit could be assembled in the same way as the 15t crane.
The work was further impeded by a request, during installation, for modifications in the crane control to avoid hook entrance to a particular space where an additional small office building was planned.
Han-Tek Inc., a materials handling integrator which specialises in overhead cranes, systems automation and electrical controls, based in Victor, New York, supplied a custom built charging crane to fellow US firm Special Metals Corporation for its high performance nickel and cobalt alloys plant.
The project was originally targeted for 52 weeks, but with the client under both internal and external pressures to ship product, the schedule had to be substantially accelerated and the plant remained operational during installation.
The original crane and press were under production while the new charger was installed on the extended portion of the runways, while the DC hotrails were split to prevent the old crane from entering the expansion zone. The crane was shipped to site on five trucks with over-height, width, and length loads, a production task in itself.
Han-Tek had an average of eight people on site and double shifts were run whenever possible. This was necessary for two reasons; first, to accommodate the newly abbreviated schedule and, second, to receive and begin installing components of the staggered shipments.
