FIRE DOWN BELOW

We are often reminded that “safety is the first priority.” In maintenance, we have to provide the means to practice this. Preventive programs vital to safety must be implemented and kept functional. A good indication of the necessity of such programs is the alarming number of fires involving underground mobile vehicles.

Each year in Ontario alone, between 1984 and 1988, more than 40 fires involving underground mobile vehicles were reported to the Mining Health and Safety Branch of that province’s Ministry of Labour. (The branch publicizes accidents and their causes.) And according to an interim report, 1989 is expected to have continued the trend. The causes?:

* electrical fires, generally from short-circuited wiring;

* hydraulic fires initiated by leaks from hoses spraying a hot engine surface;

* brake fires occurring when grease and oil ignite, caused by heat from dragging brakes;

* fuel fires from fuel leaks; and

* compressor fires caused by air hoses becoming blocked by oil and carbon.

A glance at the following cases involving underground vehicle fires will serve to illustrate just how easily such accidents can occur:

— A JDT 426 haulage truck caught fire because a worn transmission hose leaked and sprayed transmission oil on to the hot turbo-charger. The fire was extinguished with the fire suppression system. To prevent such calamities in the future, a new procedure has been initiated whereby the operator and a mechanic inspect the equipment daily. In addition, the mine is replacing its turbo-charged engines.

— On a boom truck, a fire was put out with the truck’s portable extinguisher. The starter cable had contacted the scrubber, which melted the cable cover. The resulting short caused a spark, which ignited oil from a leaking hydraulic hose. A load-haul-dump machine (LHD) being used to hang pipe in a ramp was moved about 10 times, with the park brake being operated each time. Eventually, smoke began to come from the park brake area, and the LHD (though difficult to move) was driven into a nearby shop. Flames then broke out, but when the fire suppression system was triggered, it failed to work (the dry chemical, used to extinguish fires, had become packed down in the fire suppression canister). A hand-held extinguisher from the LHD was used to douse the fire. A check of the brake showed no mechanical failure — it may have been activated accidently or it may have been left on by mistake (there was buildup of grease and oil around the brake).

— In another accident, the right rear back-up light of a JDT 426 was crushed, short-circuiting the positive wire in the light. The circuit-breaker in the instrument panel failed to take out the fault and started to burn. The operator put out the fire with the portable extinguisher.

— On another occasion, a fire broke out in the battery compartment of a LHD. The operator shut down the machine and extinguished the fire with a 20-lb. extinguisher.

— A bolt that secures a hinge had worked loose on a battery compartment cover. The cover dropped on the positive post of the battery and the resulting arcing ignited the insulation on the battery lead.

Many of these fires (cited in a Mining Health and Safety interim report) could have been prevented had the equipment been inspected properly beforehand.

A mark of well-organized maintenance is the reviewing of checklists for the routine inspections of the systems that are installed. Increasing the frequency of the inspections should also be considered.

The above is an example of part of a checklist for the routine inspection of underground vehicles.

It is also advisable that certain work orders be processed. For example, fusible links should be installed, instead of circuit-breakers, in the instrument panels. Also, the hinge bolts of the battery compartment covers should be welded.

Such work orders are routine in a well-executed maintenance program. The simplest step is drafting them. They should receive high priority and be completed in fewer than three weeks. Updating checklists for fire suppression systems may require discussions with the personnel who keep them maintained and with suppliers.

Adding items to the existing checklists requires endorsement, and the first-line foreman must explain to his crew why items are being added. There should be no chance of items being bypassed if there is a formal system of careful and accurate inspections of all underground mobile equipment.

Effective programs are hard to come by and are the result of carefully executed effort. This is probably why there are still mines that pay only lip service to routine inspections. You can be sure that they will be among those that will be submitting fire reports in 1990.