D A V ID L. M cCA RD EL, B.Sc.
(m e m b e r)
(Paper read 21 si March, 1931).
It is hardly an exaggeration to say that the spread of electricity has revolutionised mining, making itself an indispensable ally, and rendering possible the re
organisation of recent years. At the same time wc arc not to feel satisfied, for much still requires to be done, and the purpose of this paper is to suggest some methods by which colliery electricians can contribute to the further improving of their industry.
Biefly the thesis is that a system can be built up which will have as its aim the prevention of break
downs or delays. It is believed that the wastage of time due to miner breakdowns and short stoppages (not always of electrical origin) is but ill appreciated If that be not the case, then it is difficult to realise why more determined efforts are not made to eliminate them. Unfortunately these things do not appear directly on cost books, and they are not assessed at so many pence per ton; if they could be, the figures would be
¡Humiliating and perhaps disillusioning.
How then is this ideal to be worked out ? By giving attention to two things: The initial planning of the installation; and the organising of the subsequent maintenance.
Considering the first point, as briefly as possible, importance should be laid up on these heads:—
Provide good quality plant of a type suited to its work.
Keep the character of any future extensions in view.
Remember that at a future date, as electrical practice improves, radical modernising may be necessary.
Purchase plant which lends itself to easy maintenance because of its design, and the spares service its makers provide.
Proceeding to the main subject of organised main
tenance, it is proposed to deal with it under these headings:—
1. Make a thorough job of installation at first.
2. Maintain a chart and record book of plant.
3. Carefully investigate breakdowns with a view to determining how to prevent their recurrence.
4. (a) Give better instructions to workmen handling plant.
(b) Improve co-operation among the officials.
5. Have a definite system of routine examination and testing of plant with a written record of results.
Thorough First Installation.
The Law obliges the electrician to examine and test all new apparatus before it is put into use. This is very much in his own interest. The examination enables him to note: the general design; the special features;
that the assembly is correct; that any automatic, pro
tective or interlocking gear is properly adjusted; and, that the makers have conformed with their Specification.
The tests (the figures obtained should be compared with those of the makers) will shew that the plant has arrived in condition.
Then, after the installation has been completed, a further series of tests ought to be made. These give an initial set of readings for any future reference and also shew that the plant has been safely erected.
The actual work of installation requires knowledge and experience and should be thoroughly carried out.
Unfortunately, in pit work, such jobs are sometimes hurried, the intention often being to complete them thoroughly later on. This is a wrong policy. If the work is efficiently carried out to begin with, it enters the realm of “ something attempted, something done,”
gives a feeling of security, and leaves the way clear for the next job.
Chart and Record Book of Plant.
Regarding the scale plan, shewing electrical appara
tus, which the Law requires, little need be said, but it is felt that a diagrammatic lay-out embodying the following information is essential to good administration:
switchgear; starters, controllers, etc.; protective gear, from fuses to lfeakage tripping devices; motors; driven plant, e.g. compressors, haulages, etc.; transformers, con
densers, etc.; cables, with sizes.
This chart must be complete and up-to-date. It is compact and orderly, whereas the scale plans huddles certain parts together and scatters others abroad over the paper. It gives a clearer conception of the lay-out enabling the circuits to be easily traced.
The amount of detail under each heading is left to the judgement of the electrician; with this suggestion, that too much here is as bad as too litle. The place for a complete detailed record is in a book or file in which can be kept full particulars of all apparatus as it is purchased, together with any alterations made upon it, any large overhauls or repairs, the setting of switch
gear trips, etc. Ill this way what is really a “ medical history ” of each item of plant can be built up. The value of such a record is obviously very great, and it is easily kept once the habit has been formed of making an entry immediately after the plant is ac
quired or the repair carried out.
Investigate Breakdowns.
Broadly speaking breakdowns are due to one or both of these two causes: Defect in equipment; failure of the human factor.
Provided that equipment has been well chosen to begin with(i.e. well suited to its work), is the produce of reliable manufacturers and well installed, breakdowns of this character are not frequent, especially when the onerous duties of underground service are considered.
At the same time when a breakdown does occur it should, if possible, be traced to its source, and carefully considered to sec if a recurrence can be prevented.
There may be a defect of design which the ingenuity of the electrician can remedy, a defect of material which a replacement will cure, simple wear and tear which an inspection might have revealed, or poor workmanship for which little excuse can be found.
Turning however to consider the human element in relation to breakdowns, we come to a subject of far- reaching importance. No matter how perfect the equip
ment o r how capable the electrician, unless the workmen do what is required of them the best results cannot be obtained. Good administration must therefore assess the workman’s value in the scheme. More consideration should t e given to: worker’s point of view; more lucid instruction as to his duties, and how to do them;
supervision and discipline which will see that he carries them out as directed.
To eliminate breakdowns directly or indirectly due to the failure of this human factor is very difficult. For instance the real causes are, naturally, often camouflaged
by the men themselves. O r again the malpractices are not done when an official is near; a machineman does not start up on delta when the manager is working with him. Very often however, wrong ways of doing things leave evidence which affords a clue, enabling the officials to be on the look-out. For example, burnt ends of contacts or punctured shields in the instance just mentioned.
On the other hand, many workers are anxious to do the right thing, and appreciate instruction.
Instruction to Workmen.
The law demands that “ authorised persons ” are to be “ competent,” and it is evident that the electrician must help to teach this competence. There is an opinion abroad to-day that mining has become less skilled, in reality the need for trained workmen was never greater. The variety of jobs below ground is wider than ever before, and there is, as yet, no older generations to teach the present one, for the methods employed are of recent introduction. Hence the burden falls upon the officials, not only to master new methods themselves, but also to impart knowledge to their men.
An instance was given recently at a meeting of this branch of a lad controlling a conveyor gear, and who was starting and stopping it by screwing the B.E.S.A.
plug in and out instead of going to the gate end box It was a typical case of ingenuity and ignorance of consequencies; instruction should aim at fostering the one and curing the other.
Included under this heading should be the answer
ing of workmen’s queries and the investigation of their complaints. This encourages good men, interests them in the plant and helps to disclose incipient dangers.
In a concern like a colliery, maintenance requires and depends upon co-operation among those who or
ganise it. During recent years the responsibilities of the mining electrician have increased, his relation to the management has become increasingly important until now he is an indispensable official of the mine. In the past the colliery manager was accepted as the expert in all the departments under his control. In these days of specialisation, however, very few can have the know
ledge or the time sufficient to enable them to fulfil the work of such a dictatorial nature.
How does this affect organisation ? The work of the electrician being electrical in character his whole energies can be concentrated upon electrical problems.
With the manager, however, electrical engineering is but one of the facets of mining, and, were he evei so anxious, he could not allow himself to become ab
sorbed by it. It is obvious, therefore, that from co
operation between these two officials good results will come.
Mention should also be made of co-operation between the mechanical and electrical staffs. There can be no definite boundary to their respective spheres; otherwise efficiency is impaired and time wasted. For example, who should line up haulage and motor in erection ? W ho is responsible for the coupling bolts thereafter ? These are questions which co-operation can best answer.
Definite System of Examination and Testing.
This is perhaps the most important aspect of the subject, and it is a phase of the mining electrician’s duties and responsibilities which has been so well dis
cussed that it is impossible to break fresh ground.
However, in view of its extreme importance, some re- pitition may be justified.
Considering the examination of plant, Section 66b of C.M.A. 1911 requires this to be done weekly so far as mechanical defects of an external character are con
cerned. As to the wider and fuller examination that maintenance demands no limits can be put to its com*
pletness, but it should embody:—
Earth connections at joint boxes, bonds, frames, tanks, carcases, etc.
Trailing cables, their plugs and sockets. These were responsible for 64°/o of the fatal and non-fatal accidents of electrical origin in 1929.
Contacts at fuses, line switches, controllers, liquid starters, sliprings, commutators.
The state and level of oil in switchgear and trans
formers.
Flame-proof enclosures, looking out for cracks, miss
ing bolts, wing nuts, etc.
Pressure relief valves.
Fuses, overload settings.
Automatic, protective and interlocking gear.
Motor air gaps.
Cabling.
Earth plates.
Lightning arresters, etc.
Meters.
Power station switchboard.
While these examinations are being made it will be possible to carry out many adjustments, thus pre
venting failures and learning about the cause and nature of defects. Naturally some parts of the plant will require much more attention than others, e.g. coalcutter and conveyor switches. With frequent attention contacts are kept in better order, insulating shields are re
placed before being punctured, particles of copper or moisture are removed before they are sufficient in number to form a continuous short circuit path. Thus are vexa
tious delays prevented, safety ensured and replacement costs reduced.
Coming to the testing of plant, which roughly means the carrying of the above principles of examination further by taking actual readings from which records can be built. These latter are very essential, not only to reveal deterioration, but also to safeguard the electrician himself in the event of mishap. In addition to being entered in the log book, they should be tabulated in a separate record book.
Essential Tests.
The chief tests to be made are: Tests of Insulation Resistance, using the Megger or similar apparatus, of:
Installation in its entirety, or up to transformers or motor generators.
On the secondary side of transformers and motor generators.
(For both of these tests consistent values are more im
portant than high readings—less than one megohm is to be expected).
Districts by themselves. The degree of sub-division depending on the results obtained.
Individual items of plant: e.g. Trailing cables (there are special instruments for this). Motors. Switches, etc.
Separate circuits, such as that of the rotor of a slipring motor.
In making these experiments the effects of temperature and moisture must be kept in mind.
There are also the tests of continuity of the earth
ing system using battery variable resistance, low read
36 THE MINING ELECTRICAL ENGINEER. July. 1931.
ing voltmeter and ammeter—or special instrument. This is particularly important as it is only upon the occur
rence of a defect that the earthing system is called upon for its intended purpose. If its condition then proves faulty disaster may follow. Hence confidence is best secured by frequent testing.
In this case the tests are carried out upon individual items of plant, as well as upon districts, since it is necessary to have a minimum current carrying capacity of 50°,» of that of the largest conductor used to supply the apparatus in question (Reg. 125b). The tests should give low resistance readings, which, by these tests should be shewn as not tending to increase. In other words they are exactly the opposite of what insulation tests should be.
In carrying out inspections or tests, the provisions of Reg. 131 g regarding the discharge and protection of apparatus whilst working at it, must be borne in mind.
How often are these tests to be taken? Reg 131c says ‘ ‘ as often as may be necessary to prevent danger.’- Naturally this depends on the character of the equip
ment and the nature of the working conditions. Also the more important it is to prevent stoppages of any particular plant the more frequently should it be tested.
When can these tests be made ? In a modern colliery organisation is necessary here. As a rule the only suitable times are during change of shifts, idle days, or week-end shifts.
Rccords.
A diagrammatic lay-out should be made in such a form that prints can be taken from it and distributed to the electricians concerned. A new chart will be re
quired generally every two years.
A record book of plant may be merely a foolscap notebook, a double page being allotted to each item of plant.
The examination and test record book may be of a similar character; a double page to each piece of plant with its tabulated results.
Illustrations have not been included in this paper for two reasons: the electrician should be encouraged to design his own records, because he is then more likely to take a keen interest in keeping them; illustrations have already been given regularly in The Mining Elec
trical Engineer from time to time and modifications oi those can be made to suit particular requirements.
This short paper is an attempt to outline a method of organising the electrical maintenance of a colliery (hat will increase its effective working hours by eliminat- ting breakdowns and consequent delays. It may be challenged as involving too much work or as being too idealistic.
To this there are two replies:—
A breakdown brings work to the officials. Instead of waiting until the failure occurs let them expend the same energy trying to prevent it. The one way service is interrupted, the other way work goes on smoothly. They expend the same labour in each case, are saved worry and get the satisfaction of things having gone on well into the bargain. The gain is obvious.
Carrying out any phase of the organisation suggested will bring its own benefits, independently of the carry
ing out of the others. Without the ideal being actually reached, substantial improvements could be made. If the expeditions to Mount Everest set out to reach the pinnacle, they failed; but if their aim was to explore
on the way up to the peak, then they gained a worthy measure of success.
Discussion.
Mr. McGLASHAN.—The initial planning of an in
stallation, when carefully and thoughtfully carried out, is a great boon, and relieves the manager and electrician of many worries and anxieties. Though there may be grumbles at the stringency of present-day regulations, many of those regulations were introduced to counteract the rule-of-thumb haphazard layouts installed at mines in days gone by. In fact it was just possible that those regulations had been the biggest and strongest incen
tives to keeping and extending the use of electricity in mines.
In the general lay-out, the interlocking of the wiring system and operating machinery should be so arranged that failure of any one part would not necessitate a com
plete shut down. The conditions at a colliery under which electrical machinery has to be equipped and main
tained were nearly always of a difficult nature. Pre
cautions had to be taken against unforseen forces likely to endanger the lives of those in the mines, and machines placed where there was the least likelihood of damage.
It was false economy to instal second-rate machines, which were not of robust make with easy maintenance.
Whilst a system may be thoroughly and most effi
ciently installed, the heavier loads, larger plants, and higher voltages made conditions more exacting, neces- istating diligent, conscientious supervision and inspec
tion, and if that was to be done satisfactorily it must be done systematically and by a properly trained skilled elec
trician. The tabulating of motors and machines with the results of their tests and inspection was simply to put matters on a business-like footing, and to enable the elec
trician to have everything at his finger ends. Spasmodic examinations and attentions were of little use. If the time of the electrical staff were entirely taken up in the repair shop, and examinations made hapazard, then the staff would certainly be kept busy on repairs.
Regarding the question of closer co-operation of staff, Mr. McGlashan said that was a point which \yas gradually finding its bearings, as without a doubt the manager, the mechanical and also the electrical engineer must travel in step with each other if they were to get the best results from their united efforts, but he would feel disposed to say that the electrician should have a closer grip over the men who operate the machines for which the electricians were mainly res
ponsible.
Mr. M URRAY, while agreeing that records should be kept said it was very difficult at the present time to keep up-to-date the records actually required by legis
lation. It was better to prevent a breakdown than to effect a repair, and the mining electrician had to learn that before he could realise the importance of organised
lation. It was better to prevent a breakdown than to effect a repair, and the mining electrician had to learn that before he could realise the importance of organised
