Be fair to yourself and your pocket – take care of your booster pumps
CDC Technical Paper

How many times have you said "bloody booster pumps"? – not as many times as we have heard it! – and we agree with you.

Repair costs for booster pumps in some of the mines are unacceptably high and whilst in the short term that might be good business for CDC, in the long term it is bad business and the sooner we can put it right the better, since good long-term relationships with customers are far more important than any short-term profits.

More recently we have been analysing all the aspects of booster pumps on continuous miners, and in particular the factors that affect their performance, their service life and the reasons for their failure, and some interesting facts have emerged.

Pump failures are not peculiar to any particular make or model of pump. They are more prevalent in some mines than others and more frequent on some machines than others, and pump failures are generally less common where pumps are regularly serviced.

An analysis of the causes of pump failures from our own records show that we hardly ever get a pump to repair that is just plain worn out. Nearly half the pumps returned to us look as though they have had a severe argument with a Sherman Tank and the balance show severe signs of a real lack of TLC (tender loving care), with either no oil in the crank case or dirty oil, or oil and coal dust and occasionally just grease, hydraulic motors that have failed due to dirty hydraulic oil, and very often the pump units arrive back with no accessories, the motor and pump connections open and full of coal dust and with no indication of the cause of failure.

In a situation like this and taking into account the fact that all pumps are returned with a three-month guarantee and ready for immediate service, we have no option but to completely strip the pump, replace all the bearings, packings, seals, gaskets and any other part that shows signs of wear, the hydraulic motor has to go for complete overhaul and all the accessories have to be replaced (relief valve, over-pressure valve, accumulator, coupling, pressure gauge and all the fittings).

The minimum cost for this would be R20 000 and yet the cause of failure of the pump initially may have been nothing more than a broken relief valve spring, costing a few rand.

An analysis of the cost of repairing the average pump shows that 55 per cent is for the repair of the pump itself, 25 per cent is for replacing the accessories, 12,5 per cent is for labour, including strip, repair, test and collection and delivery. The balance of some 8 per cent is for the repairs to the hydraulic motor.

Prevention of failure of the booster pump comes down to two simple factors. First and foremost, the position of the pump on the CM is vital. It must be mounted in a protected position where it will not be damaged by roof falls or bumped during the normal operation of the CM. At the same time it must be accessible for the other important factor and that is regular service.

'We have proved beyond doubt
that regular service can all but
eliminate booster pump failure'

We have proved beyond doubt that regular service can all but eliminate booster pump failure. The first mine that employed CDC on a service contract basis went for over 18 months without a booster pump failure at a cost of less than the average cost of a repair to a pump.

When a pump does fail in service, then try at all costs to keep the pump on the machine by checking that the simple things are still okay and a typical example of this is failure of the relief valve spring. This can be replaced in the field quickly, easily and for a few rand. If the pump unit has to be removed, then care should be taken to block all the connections to eliminate the ingress of coal dust and the unit should be returned to CDC, complete with all the accessories, and if possible, some indication of the cause of failure.

If the problem is a relatively minor one and can be fixed without stripping the pump and a full guarantee is not required, then pump repair costs could be slashed dramatically. Remember also that the failure of a hydraulic motor does not mean the replacement of the whole unit and that CDC offers service exchange hydraulic motors that can be fitted in the field quickly and easily without the need to strip the whole pump out.

Whilst the costs of pump repairs may seem high, the cost of the loss of production are infinitely higher and with the minimum of effort in maintaining the pump on a regular basis, hundreds of thousands of rands could be saved each year.

It is for this reason that a CDC service contract is offered at a very low rate and covers not only the pump but also the whole of the dust suppression system. More and more mines are making use of this service and have found that the payback outweighs the cost many, many times over.