PLM cranes are manufactured in the Netherlands and are in service throughout the world. Several machines have recently been delivered to the USA for dredging and material handling. PLMs are extremely heavy cranes built exclusively for duty cycle work. They have been designed from a practice-orientedbackground to be uncomplicated yet exceptionally reliable. PLM is a four-rope, hydraulic, duty cycle clamshell crane with unsurpassed reliability and ease of operations, low operating cost, and low fuel consumption specifically designed for continuous duty cycle clamshell unloading of ships and barges.
Crane sizes range from 3m3 to 35m3. The main difference between a lift crane and a duty cycle
crane is its ability to dissipate heat. Lift cranes are lightweight with large counterweights designed for ease of mobilization and stability. Duty cycle cranes are designed for stability with oversized components that can withstand the shock loads of starting and reversing a counterweight and payload without overheating. PLM engineers have designed its cranes to move a payload without moving excess weight such as fabricated steel arms and hydraulic cylinders. The excess weight of these components at extended radiuses will result in excessive maintenance costs without contributing to payload capacity.
PLMs are built exclusively for dredging, barge/ship unloading, and drop ball applications. PLMs use three drums with two wire ropes from each drum. One drum is holding, one is closing, and the third is for the boom. One rope is right lay, the other is left lay with two wires for holding and two wires for closing. Using this system, the clam can be lowered to more than 100ft below the base of the crane without spinning and without any tagline. PLM cranes use only one layer on the drum for holding the wire ropes, including the boom hoist.
The PLM Pit Dredger is designed for shallow and deep recovery of material from submerged sand and gravel deposits replacing an outdated dragline arrangement. PLM four-rope clamshell cranes are built for shallow and deep recovery dredging operations up to 150 feet and are used throughout Europe for dredging canals, harbors and waterways.
Drop ball use is one of the most destructive crane applications; every cycle is a shock load. Lift cranes are generally used and are undersized for the work. In reality they are two- rope, friction machines built for lift crane service. They are not designed for duty cycle service and have historically incurred extreme maintenance expenditures. PLM Cranes has introduced a crane specifically designed as a drop ball and scrap handling machine. The PLM crane is able to work continuously in this service without damaging the structure, slew bearing, mechanical components, and without overheating.
Of primary importance is the PLM’s ease of operation. PLM Cranes have no frictions, no brakes, and no foot pedals. All functions are performed with two joystick controls, including but not limited to barge positioning. PLM Cranes are available on crawler, rubber tyres, pedestal, pontoon, gantry or fixed base platforms, and are available with electric or diesel power. Each crane is custom designed and manufactured to client specifications with their specific application and conditions in mind.
PLM cranes use standard parts supplied by Mannesman Rexroth, Cat, Cummins, and others. There are no parts specific to PLM machines. The part numbers included in the PLM manuals are the original equipment maker’s numbers, not PLM numbers; parts are available off the shelf almost everywhere in the world. PLM stocks parts for a complete crane of every size at their factory in the Netherlands. PLM Cranes USA has sales, parts, and service in Granville, Illinois, USA.
Following extensive research of coal unloading options, Gulf Power in Pensacola, Florida, USA took delivery of a new PLM model 3520 four-rope grab crane with a 30m boom and a 27m3 grab. The crane unloads 1,500dwt coal barges at a rate of one per hour including clean-up. Along with unloading, the operator manages conveyor and barge positioning with joystick controls in the cab. Demonstrations of unloading and intensive investigation of maintenance and service records were crucial in Gulf Power’s decision to purchase a PLM crane