M any of the requirements of the standards for vehiclemounted handling machinery
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• have been spelt out in Continental CEN and homegrown BS equivalents. But from 1 January 1995 they will take on the force of UK law, with a scale of penalties for infringement.
Lorry-loader cranes and tail-lifts are classed as workplace machinery and become subject to rationalised European safety standards, set out in 1989 and 1991 EC directives.
When lifting capacity is not less than one tonne or not less than four tonnes per metre/jib extension, says the EU directive, a means must be provided of warning the operator (usually the driver) as the equipment's designed safe working load (SWL) is approached or exceeded.The CEN standard working party oil tail-lifts ignores the one-tonne lower capacity limit, calling for overload warning buzzers on all tail-lifts.
Because the geometry of a lift lacks the variable jib radius factor of a crane, a less elaborate means of overload warning is implied. Alan Milne, engineering director of the Ray Smith Group, says tail-lifts will nevertheless have to have additional labelling which reminds the user not only of the safe working load, but of the effective reduction in rate capacity if the load is positioned too far back beyond the centre of the platform.
But because a crane's mode of operation frequently involves lifting a load and then extending the jib radius so that a hazardous condition could be reached in mid movement—cranes of the Atlas and Hiab type are being required to have a more elaborate overload indicator device.
Visual display indicators of actual working load have long been fitted to heavier-duty hydraulic cranes from Atlas, Hiab and others—those beyond those usually categorised as lorry-loaders. Such indicators will now be required on lighter models, whose price sensitivity has hitherto inhibited their fitting.
As often occurs in legislation, manufacturers have to make their own interpretation of the new requirements. The strategy at GCM 600, the UK Hiab distributor, is well advanced, with the adoption of a rate capacity indicator developed over the past two years and produced by Loughborough Projects. It will add about £750 to a Hiab's list price. GCM applications engineer Charles Babbington says an in-house indicator may be offered as an alternative.
They are devices which simply monitor the pressure in the first (base) stage boom's hydraulic cylinder. The pressure reading, which provides a direct indication of the load x jib radius factor, is shown in a display panel of 10 warning lamps, which are progressively illuminated as the pressure approaches and then exceeds the safe working load point.
The colour of the lamps changes progressively, traffic light style, from green, through amber, to red. Annotation alongside the lamps indicate 70, 90 and 100% of SWL. At 96% SWL an audible warning is activated and beyond 110% the display flashes. Such detail is not in compliance with specific legislative requirements but is GCM's and Loughborough Projects' response to user comments as well as to the new legal provisions.
To what extent the newly demanded load rapacity warning indicators (be they labels or sensor-fed display devices) will contribute to real life safety is debateable. Commercially available lorry-loader cranes, tail-lifts and other hydraulic equipment have long been equipped with pressure relief valves which physically prevent the kind of overloading which could cause either a structural failure or, in the words of the directive, "cause the machinery to tip up or overturn".
As far as cranes are concerned, they typically also incorporate an interlock device which stops one or both of a lorryloader's stabiliser legs being retracted while the crane is in use. All reputable, big-name, crane and tail-lift makers have for many years conformed to codes of practice embodied in safety-related British and European standards.
The voluminous requirements of the new Supply of Machinery (Safety Regulations) 1992 coming into force next year confirm the need for such relief overload prevention. They also call for a form of load check valve so that in the event of a hydraulic pipe burst (possibly through an external cause) the load will be held.
But a load capacity warning, in the form of an illuminated display on a crane, or a prominent label on a tail-lift or demountable system, does of course make triggering of an overload pressure valve less likely.
It means that fruitless attempts to lift over-heavy loads can be minimised, and the tedious remedial measures needed when an overload valve has immobilised the equipment—with a load possibly suspended in mid-lift can be avoided. It is proposed that for existing installations, the statutory safety requirements for vehiclemounted machinery will come into force two years after their implementation on new installations.
Though the exact requirements remain open to different interpretation, the new laws are likely to he given teeth by insurance companies providing industrial injury cover. They will insist that insured parties take every reasonable precaution through compliance with the spirit as well as the letter of the new machinery safety regulations.
by Alan Bunting