Golborne Colliery Disaster
March 18th, 1979 - the town of Golborne, Lancashire went about its’ business as usual. Nobody could have expected that the day would end in disaster after an explosion and fireball at the local colliery, resulting in 10 men dead and 1 injured. The victims included electricians who were working within the colliery to restore power to ventilation fans that had previously stopped working.
Cause of the explosion
It is believed that the explosion was caused by an ignition of built-up methane gas in a tunnel, which was 1,800ft underground. Initial reports released stated that 3 men had died at the scene, with 8 others seriously injured, primarily with burns and lung injuries. Methane is a naturally occurring gas and as such all collieries have ventilation systems in place to disperse it before it can build up and become a threat. It was not initially clear what had caused the methane to ignite, especially as all of the men involved were carrying methanometers and safety lamps.
Immediate aftermath
In the immediate moments after the explosion, the deputy-manager activated the emergency procedures to ensure all men currently underground were removed to a place of safety and summoned the Boothstown rescue brigade. Deputy McGuire and locomotive driver H Baxter then took a locomotive as far as they could into the tunnel, after which they proceeded by foot, and soon came across badly injured men trying to escape. Rescue teams arrived and together three separate operations were undertaken to rescue all 11 men, 3 of whom were considered dead at the scene.
Resulting investigation
Once the area had been cleared and deemed safe, the HM Inspectorate of Mine and Quarries started their investigation of the site, with assistance from the Safety in Mines Research Establishment (SMRE). This included interviews with all those involved to determine the circumstances surrounding the explosion, review of all paperwork and records pertaining to the running of the colliery and safety procedures and a thorough inspection of all the equipment and workings involved. Many items were impounded and inspected above ground. SMRE also took charge of establishing the source of the explosive mixture and the ignition source.
Findings & Cause
The findings of the investigation were as follows:
- The unventilated P1 Intake Drivage contained a high concentration of methane, or “firedamp” on the morning of the explosion. Air samples taken 2 days after the explosion (before it was de-gassed), showed a 75% firedamp content, which in turn indicates the firedamp content immediately before the explosion would be around 50%.
- It was suggested that this firedamp could have overflowed to the Plodder Dip Intake, where the ventilation fans were not operational.
- The firedamp-air mixture that had overflowed into the Plodder Dip Intake was too rich to burn, but was flammable when the rate of flow fell slightly.
- Electrical sparks then ignited this mixture, which resulted in a slow moving flame that passed down the Intake and reduced the rate of ventilation in the Drivage.
- Investigators concluded that, about 2.5 minutes after the first ignition, the firedamp-air mixture in the Dip Intake was also ignited, which they concluded was approx. 9% firedamp. The resulting flame would have been fast moving and caused the violent blast, producing the fireball that shot down the tunnel.
- Coal dust did not play a substantial part in the explosion.
The potential source for the electrical sparks that ignited the firedamp-air mixture initially was deemed to be two exposed live connector pins in an auxiliary plug on an interlock circuit cable attached to a section switch on which the electricians were working.
It was also found that the excessive delay in restoring power to the ventilation fans had resulted in the build-up of a high concentration of firedamp. A de-gassing operation was in process at the time of the explosion but had not had enough time to lower the concentration to a level to avoid the risk of explosion.
Resulting Recommendations
- The Switchgear that was deemed responsible for the sparks was located on on the return side of the P1 Intake Drivage. The report recommended that for all future colliery works, Switchgear that controls auxiliary ventilating fans should be located on the intake side of the drivages.
- Proper planning of all electrical works and installations needs to be closely coordinated by both the electrical and mining departments, ensuring reliability of electrical supply at all times!
- Alternative arrangements of ventilation need to be arranged should the fans stop working in known gassy conditions and areas.
- Early warning devices need to be used to ensure mechanical protection of ventilation fans, with further research work also required on the use of fans in parallel, electrical control and interlocking arrangements of auxiliary fans.
- The Colliery Manager needs to ensure the rules for de-gassing of drivages meet the following:
- Unless the firedamp concentration can be positively controlled to not exceed 1.25% all electrical power to apparatus on the return side of the place to be de-gassed should be isolated. This does not apply to apparatus which is certified intrinsically safe and is also approved under regulation 20 or regulation 21 A of the Coal and Other Mines (Electricity) Regulations 1956, as amended.
- All persons are withdrawn from places likely to be affected before the de-gassing operation is commenced.
- In places where regulation 22 of the Coal and other Mines (Electricity) Regulations 1956 applies
- No exposed live circuit should be tested unless the circuit and the method of test are certified intrinsically safe and the type of circuit used for the control and interlocking of auxiliary fans and section switches should be clearly identified and should be intrinsically safe.
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