Modernisation is a broad range of activities encompassing alteration or modification of existing cranes to enhance their safety, reliability, functionality, performance and/or capability.
Minor modernisation activity is simple refurbishment or modification of one or more components. Examples include replacement of steel bar or bare wire cross-conductors with festoon systems, changing cab operation to a fixed or travelling push-button pendant, adding radio or infra-red remote controls. It could also include modifying the gear reducers or the addition of lighting. These activities are relatively inexpensive, readily identified and easily justified.
Major modernisation activity is altering the original basic design. This tends to be expensive and requires analysis of the return on investment. Examples of major modernisation include complete control upgrades such as: replacing “manual, across-the-line controls” with magnetic or electronic controls (AC variable frequency or DC variable voltage); replacing magnetic controls with electronics; and changing capacities and/or speeds. It can also be modification of the crane configuration, replacement of major components such as entire trolleys, hoists or end trucks.
Why modernise?
Consideration for modernisation comes from internal or external sources. Internal can be continuing problems with excess gear wear, wheel wear, or a safety concern with bare wire cross conductors. External sources occur with changes in codes, crane location or use. Examples include increasing maximum lifted loads, a need for more accurate control and increased operating speeds.
Common internally initiated modernisation activities include taking advantage of technological advances. Replacing manual, across-the-line controls with magnetic controls for example removes full line voltage from the vicinity of the operator, increases reliability and enhances performance. The modern controls give smoother operation, more precise load spotting and reduced maintenance costs. Electronic controls (AC variable frequency or DC variable voltage) feature inherent load limiting of the hoist for eliminating crane overloads. Custom programming is offered for speed points to suit the application, adjustment to acceleration and deceleration of travel motions for elimination of load sway, and to have constant operating characteristics, regardless of the weight on the hook. One version constantly monitors the hoist motor encoder and will hold the load in if the holding brake fails (available, for example, on Ace Tronics AC VF flux vector controls). Elimination of contactors and solenoids means fewer electro-mechanical parts to maintain, thereby reducing down time by protecting against operator abuse by preventing reverse plugging and overloading. These controls also use the motor to decelerate which means reduced brake wear. Maintenance cost reduction is achieved using built-in diagnostics that quickly isolate and identify problems.
Replacing bare wire or angle iron cross-conductors with a festoon system gives the advantages of safety (eliminates the potential for accidental contact with live electrical conductors), increased reliability and better performance (corrosion build-up on bare wires is a constant problem). Old style collectors tend to disengage from the conductors when load sway or quick crane movements occur.
Relocating the push-button pendant from a fixed point on the bridge or trolley to a festoon system allows the operator to be positioned at any point under the length of the bridge and thereby avoid dangerous locations such as between the load and a wall. Positioning for a better view of the load is also possible. An operator placing a load onto a truck, for example, can move to see both sides of the truck when setting the load in place. Well positioned operators tend to eliminate plugging and move loads more efficiently. They cause less damage to buildings and machinery and there are fewer injuries. Radio or infra-red remote control has similar advantages of more flexibility in choice of operating position.
Externally initiated modernisation activities often include change of use such as lifting heavier loads. In the case shown in the picture at the bottom of page 27 a special low-headroom, eight-wheel trolley allowed an existing 20 ton capacity crane to be used for handling 30 ton loads. End trucks were replaced with low profile extended wheelbase versions to meet building column loading restrictions. As the crane is located in the middle of the factory, replacing the girders would have meant snaking them through adjacent buildings, widening doorways and interrupting operations. The cost of equipment was 40% of that of new equipment, and the cost of installation was 30% of installing new equipment. Value of not interrupting operations is higher than the cost of the modernisation.
Obsolete equipment and unavailable parts are also major reasons for modernisation. Take the example of six cranes in operation over burning tables at a US shipyard. Since their purchase, more than twenty-five years ago, the manufacturer has gone out of business and parts became unavailable. These were the only metric dimensioned cranes in the factory and standard parts inventories could not support them. Replacement parts had to be reverse engineered as needed. The process took several days and maintenance costs averaged $104,000 per year. Crane down time exceeded 14 hours per three-shift five-day working week at $5,000 an hour. A replacement trolley costing $120,000 solved the problem and the result of this modernisation was 98% availability. The return on investment including down time cost was less than six months.
Another Ace World customer with a crane from a defunct manufacturer, had a problem with hoist gearing that was failing every six to eight months. The hoist has a 40hp motor but analysis revealed that the intermediate and final reductions were only good for 12hp. The rest of the hoist was in good shape and was salvaged by reworking the gearbox by replacing the 320 Brinell hardness spur gearing with 40 Rockwell hardness helical gearing.
Enhanced productivity is one of the most common reasons to modernise. An example is a US mini-mill, an electric furnace/slab casting operation, with a full ladle weight of 209 ton. Limitations of the crane were affecting productivity – the ladle could holding an extra 6 ton of metal per heat. The furnace could produce the additional metal with little additional cost. Net value of the increased productivity was approximately $1,200 per heat, multiplied by 24 heats per day, multiplied by five days a week, multiplied by 50 weeks a year ($1,200 x 24 x 5 x 50 = $7,200,000).
The crane manufacturer no longer exists and replacement parts and service averaged $15,000 a month. Crane availability was averaging 90% due to the strenuous efforts of maintenance staff but lost production was estimated to be worth $12,000 per hour. Modernisation of the crane would have included replacing the trolley, end trucks and controls, while retaining the girders (with minor reinforcement) as well as the cab, walkways and cross conductor systems. Modernisation costs would have been 60% of a new crane but the modernisation process would have taken a full two weeks longer than the installation of a new crane. In this case lost production and interference with operations dictated that the entire crane be replaced with a new one.
Modernise or not?
Factors to be considered vary but many are common to almost all situations. All factors must be identified and qualified by establishing values to determine the best course of action.
• Safety – there is an economic value to reduced claims and reduced damage to products and equipment
• Overall cost of down time – if a crane is unavailable 10% of the time, it is time to start analysing costs and evaluating a plan of action. Establish a value for reliability and identify the actual cost of lost or restricted production
• Future needs – are there identifiable increases in crane demands on the horizon? If so, these should be considered when looking at options and justifications
• Cost of parts and repair – track maintenance personnel expenses as well as parts
• Total cost – be sure to consider all factors including cost of money and restricted production. In other words, establish the total cost of ownership for not modernising as well as modernising.
You might not be able to make a silk purse out of a sow’s ear but, if you are clever, you can make that sow’s ear into a functional wallet.
