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Big Returns from ention to Pumps
Page 64
Page 65
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By W. C. WILSON
M.Inst.T., M.I.R.T.E.
THE first two articles in this series were concerned with the mechanical maintenance of diesel power units at a reasonable and practical level of efficiency. My approach was based on the presumption that a system of preventive maintenance is the only way of avoiding the mechanical deterioration which leads to offensive exhaust and crankcase emissions—which are the subject of so much concern. A considerable number (probably the majority) of operators would accept this attitude as proper and reasonable; but there are far too many vehicles which are run to death and, in their last stages, certainly justify the attention given to the subject by the Government on numerous occasions.
A recent exchange in the House of Commons could be said to crystallize the situation when a Member of the Opposition asked what was being done to minimize the effect of diesel exhaust and to bring about an improvement in engine efficiency, operation and maintenance. The Government reply made it quite clear that the real remedy was considered to be the correct maintenance and operation of these engines.
At the same time that this exchange was reported, it was also revealed that investigations are proceeding into possible adverse effects of exhaust emission and the measures which can be taken to ameliorate it. Unfortunately, however, all the work done by the most skilled and competent backroom boys will not bear fruit if a high percentage of operators ignore the findings or fail to make themselves aware of them, and it seems reasonable to suppose many small operators might not even consider that the findings of such learned bodies could apply to the day-to-day working of their businesses.
The most effective target for an independent research organization would be the improved design of fuel-injection equipment and combustion characteristics. If this can be done at manufacturer level, and the effect is to decrease the call for servicing, then unquestionably vehicles in the hands of even the most casual user will be less likely to nine offence.
For the operator, there are financial as well as moral rewards in seeking to operate clean vehicles; but how can we hope to get this point across when one considers the facts revealed by the recently issued Annual Reports of the Licensing Authorities? Surely it could be expected that the factors affecting reliability, and therefore full employment, of vehicles would receive attention whatever else was neglected. There must be a great number of owner-drivers whose persona! safety is dependent on an adequate standard of braking, steering, lighting and even the general state of the chassis. In spite of these very good reasons for the employment of a comprehensive system of maintenance and repair a very high proportion of all vehicles examined were found to be sub-standard, and this at a time when road safety and accident prevention campaigns are a part of our daily life.
If this reflects the attitude of so many vehicle operators, how can the Government hope to impress upon them a sense of duty in regard to exhaust fumes other than by tightening-up and implementing the regulations which are available to control this admitted nuisance.
Whilst it may not be true of all areas, there will be parts of the country where an official " blitz " on smoke control could place an overload on repair facilities and bring about a position where offenders who had been warned would have to face the possibility of risking proceedings or having vehicles off the road. Even the best repair facilities are 410 hardly good enough in terms of quality of workmanship and speed of repair. There will be some small service stations that could be held up as an example of excellent organization and workmanship, but there must be a great number who are merely "getting by" because they are not subject to competition.
Diesel equipment repair stations will need to offer exchange facilities, highly skilled technical staff, an adequate reserve of the faster-moving spare parts and a quick supply from a central source of those which are in less frequent demand. Parking space will be required for large vehicles to be driven in and parked whilst under repair, and many of the small workshops set up in shops where normal trade has moved away (or in buildings which have become too obsolete for ordinary businesses) may find themselves sadly handicapped, though any increase in the demand for diesel equipment repair facilities will ensure that few specialized repair depots will ever be short of work.
Critical Standards Necessary Critical standards of reconditioning and repair, together with meticulous care and adjustment, are necessary if fuelinjection equipment is to offer reasonable standards of efficiency. These standards are difficult enough to achieve where skilled staff is available, suitable plant has been provided, and no limitations are placed on the time required for work to be carried out. How much more difficult is it, then, for repair depots taking in quite a variety of makes and types of fuel pumps, and who therefore need staff with exceptional degrees of skill and a wide range of experience—in addition to patient and orderly minds, if dependable components with an adequate potential of service are to be sent out.
Yet, all too frequently, suitable staff cannot be obtained, and an excessively high proportion of juveniles have to be trained into the work. There can be little doubt that the floating labour problem will affect this section of industry as well as any other, though here it can be afforded less than in most. Very large, nation-wide fleets whose vehicles are dispersed into small depots where repair facilities are quite properly reduced to the absolute minimum, will presumably have to depend on specialized local repair for fuel pumps and similar equipment, or to collect them into a central source where the total numbers will justify the provision of a well-equipped pump shop with staff engaged entirely on the repair of diesel engine equipment. Unfortunately, such a system has far too many loose links, and the results can be observed all too frequently.
Another piece of equipment used in my fleet is something that, for the small operator, could well bridge the gap between guesswork and the need to call in the specialist. This is a gauge to check injection efficiency. In our own conditions, it cannot be used to the best advantage for the standard of maintenance has always been high. There are relatively few serious defects to detect, and we have a pump shop with most of the equipment needed to ensure that the hands of our fitter (who was selected by reason of having a naturally tidy and painstaking disposition) are used to good effect. We have also taken full advantage of the excellent training facilities offered by the manufacturers.
are circumstances in which the equipment could be to much better advantage than in our own case. gh I am trying to avoid all supposition or reference to nobserved experience of others, I shall come back to le the possibilities offered in different conditions.
is device which we utilize is a pressure gauge ing in kilos and pounds per square inch a range of are adequate to cover the whole requirements regisby even the most indifferent of injectors and the most ive pump elements. It is obviously quite a simple mentally to convert one of the scales so as to facilinterpretation in atmospheres. Fitted between a fuel ■ delivery valve and the appropriate injector, the ing of the injector, its operative pressure and sharpness Ieration, can be seen quite clearly on the gauge.
our case, however, with a non-adjustable injector, the )enefits of a check in these conditions cannot be ed. It will be appreciated how easy it is for injectors can be adjusted in situ to be tuned to perfection. .ter valves are provided so that the injector may be ed and the pressure then read is that of the pump !nt. In this phase of checking, the condition of the :ry valve can be ascertained; the gauge shows readily gh what is happening and it is probable that even men who are not specializing in the servicing of njection equipment could quickly become adept at its ad employ it to advantage.
must be admitted, however, that my own staff (who early phases of its use were employing the equipment ently) could always read far more into it than I was ,o do, and the results achieved satisfied me that their osis was accurate and dependable. Though in the days this was most helpful in enabling us to establish ; faults were most prevalent (how quickly injector ires could fall off, for instance), its principal use with lwadays is in association with the pump, test bench, ! it enables pump condition to be ascertained without ing.
type of engine upon which we are standardized is, nderstand, to be supplied in future with adjustable ors; when these units are in service there can be no that the gauge will come back into its own and be by those craftsmen on the workshop floor who are rned with the servicing of injectors.
estic Research Work
rnestic research work in my department (if it could be led by such a description) followed a period when the enance system for fuel-injection pumps had been ned up, so defects had already been reduced to a turn. Therefore, few startling results were achieved, h ample opportunity was afforded of appreciating could be done where it was the only equipment yed for the assessment of fuel injection efficiency.
the hands of diligent and inquiring craftsmen some sing results could undoubtedly be achieved. It is like the doctor's stethoscope, I fancy. Never having privileged to use one on the human anatomy, I can
■ uppose that the uninitiated would hear all sorts of )s, gurgles and other noises which would mean ig; but the doctor, with his mental blue prints of the
human physiology, can sort out the noises and deduce what is going on—or at least we are comforted by thinking that this is so! Such equipment will not do away with the need for test benches for the precise adjustment of fuel pumps; but it seems reasonable to suggest that, with the elimination of faults in injectors, delivery valves, and an indication of the condition of elements, continued. indifferent performance will point to big defects.
It would seem that pressure-gauge equipment really comes into its own when distributor-type pumps are employed, and I refet to this only to stimulate the interest of those who, using this type of pump, are experiencing difficulties that may be resolved more readily.
Labour demand for the maintenance of fuel-injection systems will inevitably increase if improved standards of exhaust cleanliness are to be demanded. Economy, personal satisfaction and public duty are likely to be the rewards (in that order), though it could be said that the reverse should be the case. So let us consider the economy which will justify the effort to the most hard-headed of business men.
Reference has already been made to a drive for improved fuel pump condition. This came about as the result of a personal inquiry in my own fleet into the cause of excessive exhaust smoke, and the close co-operation which resulted between the pump shop staff and myself at workshop level. One disconcerting discovery was that hydraulic governing systems, which we had been led to believe (working in admirable conditions) would be almost free from wear, were in fact far from durable and reliable: a much better system of maintenance was required than we had been led to suppose.
Wear in Fuel Pumps Wear in fuel-pump-control mechanisms can prove very costly indeed. For example, when fuel pumps which had been undisturbed for long periods and appeared to be working satisfactorily were removed, it was found that a 'surprising degree of wear had taken place in the pumps, and in the governor in particular; 13 per cent of the fleet dealt with in this way showed a consumption improvement of 0.43 mile per gallon. This improvement has been sustained, though it cannot be over-emphasized that the most accurate adjustments tend to be lost with long-term operation; we find that the economic pump setting which we can afford to employ always tends to become more generous. For example, eight pumps checked to ascertain what variation had occurred in a period of approximately one year showed an average increase of 0.8 c.c.—and it should be appreciated that the original setting offered an adequate performance Now that attention has been given to every 'pump with mileage in excess of 100,000 (and some, it must be admitted, needed relatively little attention), we shall aim at removal for examination, calibration, phasing and renewal of worn governor parts every second year, which means approximately 70.000 miles.
Where this work can be associated with routine repair, such as the preparation for the Ministry of Transport's annual examination, little cost is incurred. Even with annual mileages much lower than our own, an improvement in m.p.g. of the order referred to can repay quite handsomely in hard cash the cost of the work carried out— and the smoke problem is licked.