The total generating capacity of the D.C. generating plant was 700 kW. from a 500 kW. turbo-generator set and a 2 kW. A.C. motor driven motor-generator set which usually served as a stand-by. The main switch board in the power house was at the coke-ovens and was a multi-panel board, open type single pole air-break circuit breakers and single pole knife switches. The overhead line feeder to the Nos. 1 and 2 Pits was protected by a 500 ampere circuit breaker on the main switchboard. This was fitted with a single series connected overload coil and a dish-pot time lag which at the time of the accident was short of oil and therefore acted instantaneously. The rating of the overload coil was 500 amperes and it was set to operate at this value. Transmission from the coke-oven power house to the colliery surface switchboard, a distance of 160 feet, was by two overhead lines, each of 0.2 square inches in cross sectional area.

In the colliery surface switch-house there was a group of switches and circuit breakers. One circuit breaker controlled the supply to the No.1 Pit and two others the supply to No.2 Pit. Other switches controlled the supply to the surface plant. The switch protection the No.1 feeder was an open circuit breaker with an overload trip rated at 125 amps with an adjustable tripping plunger, capable of being set to 100 per cent overload, with a time delay of unknown value.

The No.2 Pit was usually fully manned to wind coal on Sundays. It was usual for the brushers at the No.1 Pit on the back or afternoon shift on weekdays to work on Sunday morning to avoid working on a Saturday afternoon. Thirteen brushers and two firemen came to work in the No.2 Pit on Sunday, 30th January.

The fireman, Joseph Campbell, who was in charged of Kelly’s Section, descended the pit about 5.30 a.m. and the thirteen brushers with Thomas McDermott, the fireman in Archinvole’s Section, descended about 6.45 a.m.. Four brushers went with McDermott down the main haulage to Archinvole’s Section. Nine, including Thomas Martin, the brushing contractor who worked in Kelly’s Section, followed their usual custom and went in by the main return as far as the air-crossing over Waddell’s Brae. They passed through the doors into the overcast into Waddell’s Brae, down the brae and into the side haulage road and up Kelly’s Brae to Kelly’s Section. The distance from No.1 Pit to the foot of Waddell’s Brae was 300 yards shorter by the return airway and Waddell’s Brae than by the intake endless rope haulage road. The return was also easier to travel than the haulage road. They were met at the lamp station at the foot of Waddell’s Brae by Joseph Campbell.
It was customary for Campbell to travel inbye by the same route as the men and the side haulage road, outbye of Waddell’s Brae was not travelled by anyone after the end of the day shift on the Saturday. The pit bottomer in charge of the No 1 Pit bottom on Sundays had failed to come to work and no one was appointed to take his place. This was a contravention of Section 53 (2) of the Act. Two shiftsmen were employed all morning examining No.1 shaft.

The current was on in all the A.C. and D.C. cables in the pit as well as on the surface. According to evidence, there was no interruption of the current until the D.C. plant, both on the surface and below ground, failed about 10.15 a.m. The breaker in the coke oven power house tripped, which indicated a considerable load.
David Campbell, acting pithead man, found that the current had failed to the screening plant and had received a signal bell from the No.2 Pit bottom for the current to be switched on again, went with William Stewart, the lampman, who acted as switch board attendant, to the switch house and after opening all the switches, he telephoned the coke oven power house attendant to close the circuit breaker. This was done and Stewart and he closed all the surface and underground switches one by one. The power house attendant noted that the current was normal and the No.1 Pit circuit breaker remained closed so that no reading was shown on the ammeter. No signal or message was received from No. 1 Pit bottom as there was no one in attendance there.
At some time between 10.30 and 10.45 a.m., the assistant electrician, James Wilson, entered the switch house and noticed that the circuit breaker for No.1 Pit was off. He pointed this out to William Stewart and Wilson closed the switch without making any further inquiry at the time but later reported what he had done to the head electrician, William Patrick. The switch remained close and the ammeter indicated that there was no current in the circuit. As was the usual practice, both men made no attempt to find the cause of the switch being tripped.

There was no disturbance of the current in the No.1 Pit. About 12.30, the supply outside haulage was cut off at the ‘Circle’ by William Patrick.