Disasters - Names		Disasters - Names

Date:	15th December 1905
Colliery:	Broughton Moor
Cause:	Electric shock
Lives Lost:	1

Case Of Electrocution At Broughton Moor Colliery, 15th December, 1905.

The deceased, whilst walking outbye from his work, on a self-acting haulage road, came in contact with a broken signal wire, one of the broken ends of which was resting on an armoured electric cable charged with a positive current of 500 volts. The insulation of the cable was defective near the point, allowing a short circuit to take place from the core to the armouring and thence through the broken signal wire and deceased's body to earth.

There are two electric plants here, one for coal cutting and the other for haulage. Two cables from each plant are carried down the shaft. The dynamos are in separate houses on the surface, and the plants are quite distinct. The haulage motor is near the pit bottom, and the dynamo actuating it was not running at the time of the accident, and this part of the plant had no connection with the accident and need not he considered further.

The accident happened in connection with the coal-cutting plant. There are coal-cutting machines in two districts of the Little Main seam actuated by one dynamo, which was made by the India-Rubber, Gutta Percha and Telegraph Works Co., Ltd. It is an under type, double pole, continuous current, compound wound machine, and was installed in June, 1903. It is belt-driven, 7½ to 1 by a pair of 18 inch engines, with 2 feet 6 inch and stroke 40 to 45 lbs. of steam pressure. The dynamo at 500 revolutions per minute generates a voltage of 500 volts, and is wound for 110 amperes. The voltage can be regulated by a resistance placed in the shunt field.

The cables from the dynamo are led into a distribution box 88 yards from the pit bottom. Two pairs of cables are taken thence, each pair about 1,500 yards long, into the Nos. 3 and 4 districts. The accident occurred in connection with the cables into No. 3 district.

The cables into No. 3 district pass from the distribution box into a switch box 9 yards away and thence along the haulage and intake air road for 344 yards to a junction box ; from the junction box they extend for 137 yards and up a self-acting incline which is also part of the return air road, then for 720 yards a road used as an intake airway only, they then rejoin the haulage road and pass for 300 yards to the gate end switch and fuse box to which are connected the trailing cables of the electric coal cutter, which is actuated by two 10-h.p. motors coupled in series, enclosed type.

Part of the roads along which the cables pass are damp, and in places water runs on the floor. The floor of the road where the accident happened is quite wet.

The cables were supplied by the makers of the dynamo, and those extending into No. 3 district from the distribution box are made up of 19/16 tinned copper wires surrounded by an insulation consisting of a covering of vulcanized rubber inch thick and upon this two layers of common cotton tape, then a layer of hemp tape. Over the insulation a layer of close single armouring is laid, consisting of 20 galvanized iron wires No. 14 S.W.G., and upon the armouring is a dressed hemp covering which was worn off at many points.

The cables are supported on insulators fixed 7 inches apart on each side of wooden plugs driven into the roof at distances varying from 4 to 6 yards. The armouring of the cables was not continuous ; at intervals varying from 3 to 30 yards, lengths of 12 inches to 24 inches of the armouring were cut out where defects in the insulation had been discovered and the contour of the cable made up at these points by insulating material. The various sections of the armouring were not earthed.

The point where the accident occurred is 533 yards from the shaft and at the top of the self-acting incline already referred to. The incline is 80 yards long and has a gradient of about 3½ inches per yard. The road is about 7 feet wide and 5 feet high and the cables are carried near the roof on the left side going inbye. A signal wire consisting of one galvanized iron wire No. 12 S.W.G. extended along the right side from the bottom of the incline to a hammer at the top. This wire broke about 44 yards from the hammer when used by a deputy about 1.30 p.m. on the day of the accident; he went up the incline and coiled the two broken ends round wooden bars stretching from side to side of the road next the roof. Shortly afterwards and before the dynamo started, four ponies were brought down the road and their harness may have caught and moved the wire along the bar so that its broken end came in contact with the positive cable.

The bell wire hung down as a loop near the floor at the top of the incline and the deceased and his son coming from their work at 8.15 p.m. came in contact with it after the dynamo was started and before the coal cutter had commenced work. Deceased's son was leading by 10 or 12 yards and while passing between some empty tubs and the side of the road along which the bell wire was hung, he came in contact with it and received a shock, He was thrown down and both his arms were slightly burned, but he managed to get free ; he shouted, and then heard his father shout ; both their lights were extinguished in the commotion, but another miner who was before them came back with a light and they went to deceased and tried to get him free from the wire which he was gripping with his left hand. They used an iron plate but received a shock, then deceased's son used his cap and also received a shock, then they tried to find a piece of wood but were unsuccessful. The other miner then ran down the incline to cut off the current at a switch 430 yards distant from the place of the accident. Near the bottom of the incline he met the deputy and informed him, and the latter ran to the switch and cut off the current. The deceased was then released but had received the current for twenty minutes and was then quite dead.

After the accident the current was again turned on and the coal cutter worked out the shift. At the time of the accident nothing unusual was noticed by the engineman in the generating house. The fuse did not blow.

The Under-Manager examined the place at 9.30 p.m. and found that the broken end of that portion of the bell wire extending from the hammer down the incline was in contact with the left side and positive cable at a point where the covering over the armouring was intact, but at the point of contact there was a small hole through it to the armouring and the covering near the hole was slightly blackened as though by heat and had a smell of burning.

Owing to an accident in the shaft the testing of the cable was delayed until the 20th December. A portable magneto generator worked by hand developing 300 volts was then connected to the armouring of the positive cable on that section of the armouring upon which the accident happened and was also connected to the copper core at one of the points where. the armouring had been cut out and replaced with insulation 15 yards away from point of accident. An Ohm metre was placed in the circuit to indicate any leakage. The cable was found to be defective and a short circuit was discovered six yards from where the bell wire had touched the armouring. The insulation of the defective part was found to have given way, the cable had not been mechanically damaged, its circular contour at the point not having been deranged in any way, but it was found that short-circuiting had been taking place between the conducting wires and the armouring, 'the two being very nearly connected by fine blebs of copper that had been fused off the conducting wires.

The plant has been in use for the past 2½ years and up to the present has been free from accidents.

The Special Rules for the Installation and Use of Electricity were in force at the Colliery but, as the plant was in use before they came into force, Rule 1 of Section XI. applied, which reads as follows :—

"Notwithstanding anything contained in these rules, any electrical plant or apparatus installed or in use before the coming into force of these rules may be continued in use unless an inspector shall otherwise direct, or subject to any conditions affecting safety he may prescribe."

My attention had not been directed to the plant and I had taken no action under the rule.

Had the exemption not applied Rule 1 (c) of Section I. would have been contravened; it reads "All metallic coverings, armouring of cables, other than trailing cables, and the frames and bed plates of generators, transformers, and motors other than portable motors shall, so far as is reasonably practicable, be efficiently earthed where the pressure at the terminals where the electricity is used exceeds the limits of low pressure."

Since the accident the armoured cable has been taken out of the portion of road along which the workmen "travel" and the remaining portion is being replaced by unarmoured cable.

Source:

1905 Mines Inspectors Report (Cd 2910)

	Hartley, Thomas, aged 48, Hewer, electric shock
	All names found

 

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