Cobra Middlesbrough Limited has been operating Liebherr wheeled loaders at their rock salt processing facilities in North Road for a number of years and these highly specialised materials handlers are fully equipped and protected for what is an extremely corrosive working environment. Proof of the success of these machines is that Cobra has taken another Liebherr loader on a three-year equipment supply and maintenance contract. A new generation L 5502plus2 ZK-HL wheeled loader joins an existing L 566, replacing an L 544 which has come to the end of its long, productive and trouble-free working life.
Cobra Middlesbrough Limited handles and processes around 500,000 tonnes of rock salt a year under contract to Cleveland Potash Limited and which arrives on site by rail from Boulby Potash mine. The main uses for this product are road treatment during the icy winter months and, in a finer screened form, for animal feed salt. The incoming bottom-dump rail wagons discharge the rock salt into conveyors below ground, from where it is conveyed to the main stockpiles and subsequent processing. Cobra distributes nationwide, with some of the rock salt destined for export to continental Europe and America. The crushed rock salt is stored in open storage and under cover and, in another part of the same building, the fine screening and stockpiling of the animal feed salt is also carried out prior to selling on to specialist animal feed suppliers.
The Liebherr wheeled loading shovels carry out numerous tasks, including stockpile management, loading trucks and spreaders and conveyor hopper loading for feeding specialist dry bulk tankers. The winter time is undoubtedly the busiest period, when large volumes of salt need to be handled and loaded onto trucks and specialist vehicles for the vital task of ensuring that roads are treated against icing. The loaders work predominantly outside but also undertake stockpile management and conveyor hopper feeding inside the processing sheds.
The Liebherr L 5502plus2 ZK-HL is a high-lift version with Z-pattern bucket linkage and is an articulated, hydrostatically driven wheeled loader in the 16 tonnes class with a tipping load of 11,650kg. Power is supplied by a Liebherr made en-gine which develops 130kW and is fully compliant with Stage IIIA / Tier 3 emissions. The standard general purpose bucket has a capacity of 3m³ and, combined with the HL arms, provides a superb load-over-height of 4.3 metres – ideal for loading material into bulkers and a combination that gives excellent productivity in a simple and cost-effective package.
An important feature of the L 550 is a high level, isolated cooling system which is equipped with an automatically reversing fan to maintain radiator cleanliness and efficiency; cyclonic engine air pre-cleaners are also included to combat the dusty environment. The hydrostatic driveline system on the loader contributes to considerable fuel consumption benefits, which the customer particularly appreciates and, with limited slip differential in both front and rear axles, produces good efficient pushing power when stockpiling whilst, at the same time, prolonging tyre life. Automatic central lubrication is standard and greatly contributes to reducing maintenance time; the system on the machine has been specially adapted with stainless steel fittings for this salt application.
The operator’s cab is air-conditioned, equipped with an adjustable steering column, joystick control for the attachment, air-sprung operator’s seat and tinted glass. Convex mirrors are also included and Liebherr’s own colour rear view camera system has been factory installed, with the monitor built-in to the instrument panel, offering full screen or split screen imaging as required for all-round visibility and optimum operational safety.
To overcome the corrosion problems encountered when handling salt, the L 550 was subjected to some very special treatment and adaptations, all of which were carried out at Liebherr’s wheeled loader factory in Bischofshofen, Austria which is extremely experienced in these kinds of specialist modifications.
The paint specifications are highly detailed and include pre-treatment of steel panels, with post assembly of the structural parts as sub-assemblies being degreased and primed with a special epoxy zinc phosphate, prior to finishing with special polyurethane paint. When total assembly has been completed, all the relevant areas of the loader are polyurethane painted again and various cavities are treated with a preserving agent and, where necessary, sealed. The cabin is primer coated using an electrophoretic process, with the surface finish of powder coating. This is the same process as used in car production and proves to have highly effective anti-corrosion properties. Rubber tabs are fitted to the pedals and stainless steel is used for all pedal “mechanics”. Protective sprays and coverings are applied to all electronics. All radiators and condensers for the air-conditioning units are constructed from Teflon-coated aluminium; the engine, pumps, hose systems and engine compartment are all specially painted. Cable looms are sealed, contacts are sprayed with Dinitrol 77 B after assembly and, where necessary, rubber caps are fitted or sealed with special silicone as required. VCI coverings are applied to enclosed electronics, headlights and controls. Stainless steel is used for the bucket positioning guide and screw connections; wheel pins and shiny contact surfaces are rust-proofed and sealed with Dinitrol 4010.