On the afternoon shift of 18th January, 1990 at around 5.00pm a Toro 500D LHD unit caught fire while being refuelled and was subsequently completely destroyed. Attempts by the loader operator to extinguish the fire were unsuccessful and it quickly reached an intensity such that withdrawal from the area was required.
Over a period exceeding 20 years the Broken Hill experience of diesel vehicles in underground mining has been, with respect to fire, one of relative safety. Although fires on diesel engined vehicles have not been uncommon, they are usually electrical due to overheating or due to a failure of items such as hydraulic hoses allowing fuel/oil to spray onto hot parts and ignite.
The practice of fitting fire suppression systems to vehicles is optional and restricted to loaders and dump trucks, since these work very hard, become extremely hot and have greater fire risk in case of leaking fuel/oil.
In 1984 an investigation was undertaken with a view to determining whether spillage at fuelling stations and/or placing of waste oil on roadways posed a safety threat. Samples of "worst case" material were conducted jointly with the then ZC-NBHC mine. The material tested could be induced to burn weakly upon application of intense heat, however the combustion was not self supporting. It was concluded there was not a significant hazard from ground absorption of minor fuel spillages at fuelling stations.
Underground personnel have related that there have been many instances where fuel has been accidentally spilt onto engines and exhaust manifolds with the production of white smoke being the only result. Hence fuel spillage during refuelling had not previously been seen as a serious problem.
Commencement of the Fire
The loader that caught fire had been used for tramming dirt up the incline for around 20 minutes before refuelling. The loader was reversed into the fuelling station at 6 Access such that the operator could reach the fuel line and the pump switch while standing on the gridding adjacent to the engine bay (see Figure 1). The loader was shut down, but the electrics were left on - this was a deliberate action to avoid having to wait for an electronic delay built into the starting circuit, which would have been activated by isolating the electrics.
The operator then:
Activated the electric pumps that feed fuel and oil up from the 36 Level through pipes in the ground;
Checked and topped up the engine oil;
Commenced filling the diesel tank.
During refuelling the operator had difficulty with the 90o on/off ball valve that controls the flow of fuel. The handle (approximately 75mm long and held on by a small nut) fell off and was discarded in favour of a shifting spanner. Once the fuel tank became full the operator was unable to shut off the fuel. Fuel began overflowing.
Returned to the other side of the loader and shut off the pumps;
Returned to the fuel tank side of the loader and saw flames below the gridding and running up into the fuel tank;
Returned to the driver's cabin and twice operated the on-board fire suppression system (Quell) activator - nothing happened;
Exited the cabin and took the fire extinguisher (dry powder) mounted in the articulation area, while doing so he observed flames spreading across the floor under the loader. He returned to the fuel tank side of the loader via the bucket end of the loader and observed the floor of the fuel bay in the vicinity of the engine end of the loader to be in flames (see Figure 1);
He used the extinguisher to quell the flames and get close to the loader, by which time the extinguisher ran out. He returned to the wall of the fuel bay and tried using a second fire extinguisher which failed to operate;
By this time the fire was burning strongly, flames were up to the backs and the electric cables were burning. The operator went for assistance.
The Fuelling Station
The fuelling station was located in a disused access to the 36 Level Stope known as 6 Access. The Access is a dead end which was unventilated except by diffusion of air from the incline. The diesel and hydraulic oil were piped up through the ground from the 36 Level fuel room located in the main access to the Level.
Hose reels were used to house the fuel and oil feed hoses in the fuelling station. Mushroom switches activated electric pumps located on 36 Level to pressure the lines up to the fuelling station (a height of 26m).
The floor of the fuelling station consisted of broken rock and fine material. This material would have, over a period of time, absorbed and stored spillages of fuel and oil.
The Ventilation Circuit
The ventilation circuit is schematically shown at Figure 2. This shows the basic circuit as air flowing in on 36 Level and down the internal shaft to 36 Level. Part of the combined resultant airflow is up the incline to the 36 Level stope and to exhaust. Air also comes down from 32 Level via the incline and two rises from the incline, one of which passes the air through the chilled water exhaust, Except for the incline in between 7 Access and the spray drive, the airflow is up the incline to 10/11/12 Access where the up flowing air meets the air coming down from 32 Level.
How did the Fire Start?
A possible scenario is that fuel ran over the side of the fuel tank and onto the jump start (standard caterpillar type) fixed to the side of the tank. These were connected by heavy duty cable to the batteries and were energised at the time as the electrics of the loader had been left on.
Assuming fuel ran over the two contactors and that arcing occurred, it is conceivable that sufficient current would pass through the fuel to generate diesel vapour and to heat that vapour to 77oC (the flash point of the fuel). Vapour at or above the flash point together with arcing would cause the initial flame.
An alternate scenario is that very hot metal on the machine, presumably part of the exhaust, heated fuel and the associated vapour above either:
(a) 77oC - measured flash point
(b) 270oC - measured auto-ignition temperature
In the case of (a) an ignition source is still required, this source being a flame or spark of sufficient temperature and energy to initiate a self propagating flame front.
Investigations into the temperature of exhaust gases entering ceramic filters have found temperatures of up to 530oC and typically in excess of 400oC for machines working hard. These temperatures suggest metal surfaces may be hotter than the auto-ignition temperature of diesel fuel (270oC) or hydraulic oil (395oC).
The existence of such temperatures, particularly in an unventilated area, could facilitate auto-ignition.
Location of Personnel at Commencement of the Fire
A large number of personnel were in the mine at the time of the blaze. Only those working in the 36 Level area in between 6 Access and up to 10/11/12 Access were directly affected by the fire. These were:
7/8 Access a loader operator and a fitter.
9 Access a loader operator
12 Access the operator of the cable bolter and a serviceman who had come up to install another cable cassette;
36 Incline The driver of the "taxi".
Events following the Start of the Fire
Having been unable to extinguish the fire the loader operator sought assistance, the first phone he tried ceased operating while he was trying to use it. He used a second phone, at the internal shaft (150m from the fire) to alert the storeman and the Shift Boss of the fire.
What Persons Below the Fire did
The Shift Boss, unaware of the seriousness of the blaze, took the fire extinguishers and assistants up towards the fire. They could not get further than the rock breaker drive, due to dense smoke. (See Figure 3). The Shift Boss, being the only person carrying a self-rescuer, tried to advance wearing the unit, but due to the poor visibility, the sound of falling ground from the backs and an explosion, he retreated.
The Shift Boss returned to the level and notified the Ambulance Room of the seriousness of the fire and proceeded to collect foam generating equipment and hoses to fight the fire. Meantime the loader operator and another employee, being aware of persons in the workings above the fire attempted to effect a rescue. Taking six oxygen self-rescuers and a jeep they attempted to drive up past the fire. While driving up to the fire each fitted an oxygen self-rescuer. The units were Auer SSR 16BB's, the men were untrained for these units and so did not activate the quick start mechanism.
Shortly after the jeep entered the smoke it struck a wall and tipped onto its side. The driver fell onto the loader operator winding him. The driver then preceded up the incline on foot. Once he recovered sufficiently the loader operator made his way back down the incline to fresh air (See Figure 1 for location of Jeep). Following this event one additional person was trapped by the fire.
When the Shift Boss returned with hoses and foam generating equipment he found the only water connection available was for a 1" hose. In any case personnel had difficulty getting close enough to the fire to play water on it without breathing apparatus. The Shift-boss returned to the level to isolate the fuel and oil lines from the level up to 6 Access. He also ordered evacuation of the bottom of the mine.
Up at the scene of the fire, a number of men including the loader operator decided that there was little they could do, and that they would return to the 36 Level Maintenance Bay (approximately 250m away) and await for help to arrive. (ie fire/rescue crews with breathing apparatus). They had also decided that no one would be able to get down past the fire. They had begun to move down the incline when they heard a noise. This was the loader driver from 9 Access. He had made his way down the decline, past the fire and staggered out of the smoke in a semi-conscious state. The Shift Boss was returning to the fire when he came across the loader driver (with others) sitting against the wall by the Internal Shaft. The man was assisted to the 36 Level store and placed on a stretcher.
By this time the backs were booting badly and the loader was still burning fiercely with explosions occurring. The Shift Boss reported to the Ambulance Room that he had an injured man who needed oxygen and that others were trapped and probably dying. He called for breathing apparatus to be delivered to the 36 Level (he had trained people on the level) and for a rescue attempt via 32 level.
What Happened to the Trapped Persons
The man in the Taxi had been to the 32 Level to pick up some detonators. As he was returning to 36 Level he ran into smoke, about 20m past 9 Access (see Figure 4). This smoke was initially a haze but quickly thickened. He reversed up past 9 Access and into the entrance to 10 Access (this area was still clear). From the phone (see Figure 4) he called the 36 Level store and reported the smoke and was told a loader was burning in 6 Access. He considered travelling through the smoke and into 9 Access to direct the man there away from the fire. He decided against this because if he couldn't find his way back he would only be adding to the number caught in the smoke.
The entrance to 10/11/12 Accesses was still clear, he could however see that smoke was coming up the dump hole (see Figure 4) and going into 12 Access. While he was deciding whether to go looking for the two men in 12 Access he saw them coming out. He waited for them and then took them and travelled a suitable distance up the incline from the fire.
The men in 12 Access were working on the cable rig when they smelt smoke. At first they thought it must have been the IT 12 Caterpillar forklift. They went to check the vehicle and observed smoke entering the area, it was hazy and up towards the backs at first. Quickly the smoke became thick and filled the drive. The serviceman reacted strongly to the smoke and commenced vomiting, with assistance from the operator of the cable bolter he opened and fitted his self-rescuer. The operator's self-rescue unit was back on the rig so he had to proceed without one. The operator led the way out and was followed by the serviceman who was still vomiting. The men report that the smoke was acrid and caused a burning sensation to the eyes and smelt like electrical wires burning. They found their way out of 12 Access and towards the incline. As they got closer they could see a vehicle which was the taxi. They travelled up the incline with the taxi driver to a safe point. As the men were feeling all right the taxi driver decided to remain in position and prevent further persons travelling down. A short time later an off duty Shift Boss arrived with visitors. The Shift Boss took the men from 12 Access up to the 32 Level and the taxi driver remained in position.
The Loader Driver in 9 Access was loading dirt in a cabin equipped Toro 500D. He stopped to remove his cap-lamp battery, and after doing so he went to move off but found he had nil visibility, He turned the air-conditioning off and waited to see if the smoke would clear.
When the smoke didn't clear he put on his cap-lamp and self-rescuer and left the loader. By the time he got to the end of the loader he could not see anything and the smoke was burning his eyes.
Due to difficulty in breathing through the self-rescuer he took it off and began breathing through his sweat rag. By crouching down low he managed to follow the air and water hoses out of the access. He noticed everything was quiet and that no help had arrived and concluded that nobody knew about the fire and that it was coming from 32 Level. He decided to head down to the 36 Level fresh air base. He commenced making his way down the decline and felt himself beginning to be overcome by the fumes but managed to convince himself to keep going.
When he was alongside the spray drive (chilled water sprays cooling down-cast air from 32 Level) he heard the spray motors and went in thinking he would get fresh air. The smoke didn't change (this reinforced his earlier impression that the fire was above) and thinking that time was critical, he continued down.
While moving down the decline he thought of finding an air valve to breathe from but he couldn't see one and thinking that he didn't have time to find one he continued on.
He came across two men at 7 Access (see Figure 5), they were calling out "help". He had a conversation during which he was told to go up, though the reason for doing so was not conveyed.
At this point it should be understood that all three men were suffering smoke inhalation, breathing air with unknown concentrations of CO and subject to extreme heat. They had difficulty talking and the very act of doing so caused them to feel more overcome and as if they were losing their breath.
Thinking to himself that "talking is useless", he said "I'm going down", and left. At the time he thought he was leaving them for dead. Continuing down the decline, by crouching low and running his arm against the wall, he got to the point where he could see the headlights of the jeep. He then took this to be the cause of the fire and thought if he could get past he would be O.K. He got past only to be hit by the intense heat of the fire. He continued on and finally staggered out of the smoke in between the zinc stub and the rock breaker. (See Figure 3)
The men in 7/8 Access. There were two men in the area, a miner and a fitter. The miner was on dirt and proceeding out of the access when he saw a smoke cloud the full size of the drive rolling in at him. He stopped and only had time to flash his light at the fitter and wave him to come over before he was engulfed in smoke.
By the time the miner got off and reached the back of the loader he couldn't see one metre. He followed the wall up towards the spray drive assuming the fitter was following. He walked into the door of an Anfo dumper and continued up the incline to the spray drive. Initially the air coming from the spray drive (40m long) was fairly clear, this quickly changed and the miner had to enter the chilled water sprays to get away from the smoke and fumes.
Because the smoke/fumes layered and followed the backs in he had to move right to the end of the spray drive. When the situation continued to deteriorate he considered climbing up into the rise (over a 19m drop) using the rock bolts, in order to get clear air.
Before retreating to the back of the spray drive the loader operator made two attempts to rescue the fitter after hearing his cries for help. Breathing through his dampened sweat rag he twice made his way down towards 7 Access in an attempt to reach the fitter. On each occasion he was driven back by heat and smoke. The fumes were acid tasting, caused a burning sensation to his eyes and throat and the heat was so intense that his skin felt all prickly.
Meantime the fitter, who had intended going up to the spray drive also, had become disorientated, and not knowing where he was he lay down in the drive and breathed through a rag (his self-rescuer was in his tool bag on the Tamrock in 8 Access). He was actually in the incline close to 7 Access. He called for help a few times, all he heard in reply was the sound of the loader in 7 Access idling. He thought this loader was the source of the fire.
After a time the fitter heard a cry for help and was soon joined by the driver of the overturned jeep. After leaving the jeep the driver had commenced running up the incline but soon he was crawling and following the wall because of the heat and fumes and because he couldn't see. He reported that the fitter, who seemed just conscious, thought he had been unconscious and had just come round. While they were both lying in the drive the loader driver (referred to earlier) from 9 Access came along and spoke with them. When he continued down, the other two attempted to follow but couldn't, becoming dizzy when they attempted to stand. The jeep driver reported feeling himself "going" and reported experiencing flashbacks throughout his life. He said he gathered a little extra will to live and decided to make for the spray drive as the only hope of survival.
The jeep driver was unable to find his way up the incline and became lost. He did realise he had started going down and not up, he also found a pipe which he recognised as a sandfill pipe. Next he found a gate end panel and saw 7A upon it. Having orientated himself as being in 7A Access he crawled to the other side of the drive and located an air hose he knew was there. He cut the hose and lay near it so he could breathe. His recollection is that up until that point he had continued wearing the oxygen self-rescuer. Clearly something was wrong with the self-rescuer or with the way it was used, in that he had, within a short time of entering the fire, became quite affected by fumes - when he should have been breathing good oxygenated air.
The fitter had remained where he was and had started vomiting. Also he had shed his hard hat and boots because they were too hot to touch. He heard 2 explosions and rocks falling. After a time he heard a noise which he thought was either water or air coming from down near the Wagner loader (7 Access). He thought there may have been someone putting the fire out. He then commenced crawling backwards down towards the noise, taking frequent stops to regain strength. He had started to dry-retch. Having got close to the Wagner he called for help. The jeep driver came over and assisted him to the air hose at a point close to him - he did this because neither man had the strength to move further than necessary. The jeep driver again cut the hose and both men breathed from it.
After a time the jeep driver decided to go for help as he didn't think anyone knew they were there. With a combination of crawling and walking he found his way up the incline towards the spray drive. He came within about 10m of the spray drive and reported feeling giddy and having difficulty walking.
The loader driver was meantime able to come to the front of the spray drive as the smoke and fumes had abated. He was also extremely cold from the time in the chilled water. While waiting there he saw a cap-lamp and heard a person mumbling, the person was going round in circles. He went down and assisted him to the spray drive where he collapsed.
The jeep driver was having difficulty breathing, once he recovered a little he got into the chilled water to cool off as he was extremely hot.
Both men waited at the spray drive until help arrived a short time later and they were taken up to a vehicle above 11/12 Access (ie to the clear air above the smoke) by one of the rescue party.
Two further members of the rescue party proceeded to the location where they had been told they would find the fitter. He was located and assisted to clear air and later to the surface.
The Action the Company Took
The fire commenced around 5.00pm. The Ambulance Room Attendant heard calls on the radio and knew a fire had started underground. A couple of minutes later, at approximately 5.15pm he received a call from the 36 Level storeman reporting a fire on a Toro in 6 Access.
He then rang the Mine Environment Superintendent who is in charge of the Fire Department and was told to call in the Fire Control Coordinator. He did this and then notified the Security staff and the Ambulance and Security Superintendent. He then proceeded to prepare the rescue trolley and the Ambulance for transport to underground.
The Mine Environment Superintendent, The Fire Control Coordinator and the Ambulance and Security Superintendent were all at the mine by about 5.40pm. Attempts at that time to find out the current status of the fire and safety of personnel were not fruitful. Before going underground the Fire Control Coordinator requested the Ambulance Room Attendant to call in a fire/rescue team consisting of North Mine personnel. At about 6.00pm the Delegated Manager for North Mine was called and he proceeded to the mine to coordinate the mine actions.
At around 6.00pm the Ambulance Room Attendant, the Mine Environment Superintendent and the Fire Control Coordinator loaded the cage and proceeded underground with rescue and fire fighting equipment. They proceeded to 32 Level because the 36 Level Shift Boss had asked for a team to come to 32 Level since he regarded access from the 36 Level as impossible due to the intense heat of the fire. They found this difficult to understand because their knowledge of the ventilation indicated 36 Level as the only place to get access to the fire. They later learned that the Shift Boss was referring to means of access to the trapped persons.
The equipment was unloaded at 32 Level. Here the level Shift Boss informed them that a wall of smoke was at 10 Access and it may be better to tackle the fire on 36 Level. The fire control people proceeded down the 32 Level intake decline to check the situation. Having been informed of a casualty on 36 Level, the Ambulance Room attendant proceeded to that level with the rescue trolley, a compressed air set and the oxy-viva equipment. He arrived on 36 Level at about 6.20pm, and proceeded by train the 950m distance to the store area where the casualty (the loader driver from 9 Access) was given treatment.
The fire control people meantime travelled down to the 10 Access area with the 32 Level Shift Boss and found a wall of dense black smoke coming up the incline and entering the 10 Access area. The 32 Level Intake Decline was relatively clear down to 10 Access by virtue of the downflowing ventilating air.
A decision was made not to enter the smoke at that stage due to:
the intensity of the black smoke;
lack of suitable breathing apparatus;
the lack of people having a sound knowledge of the area.
A decision was taken to fight the fire from 36 Level until the intensity of the smoke and fumes abated.
At approximately 6.15pm the Mining Superintendent for the 36 Level Area was calling in trained persons who knew the area well to form a rescue/fire fighting team. These men came to the mine and prepared to go underground wearing Dräger BG174 sets (minimum of 4 hours).
On 36 Level the arrival of the Ambulance Room Attendant with only one compressed air set caused frustration for the trained rescue personnel on the level who wished to attempt a rescue but could not; as rescue teams must consist of at least two persons.
Shortly after, four extra compressed air sets arrived on 36 Level and the Shift Boss organised a team to investigate above the fire. The Ambulance Room attendant went up to the fire with some other men. By this time the intensity of the fire had apparently abated, as the smoke had moved back from the rockbreaker and persons could approach 6 Access from the incline and see the overturned jeep. The fire was still burning though the source may have been mainly the tyres of the loader at this stage. A hose was feeding water onto the fire. The Ambulance Room Attendant and another man proceeded to check the overturned jeep. Finding no one they proceeded up the incline laying out a line of bell wire as they went. After going up 60 - 70 metres the Ambulance Room Attendant suggested to the other man that they turn back, he disagreed and they went on. The heat and the smoke were intense and it got to the point that the Ambulance Room Attendant decided it was foolish to continue. They went back and arrived below the fire at approximately 6.50pm. By this time the fire control people had arrived.
When they arrived they found a 1" hose being used to apply water to the fire. Two lengths of 38mm fire hose were fitted to another 1" valve, however as both flow and pressure were inadequate the line was broken and repaired to obtain a better flow. Prior to this a third valve had been located and this was being used to apply water to the fire from two lengths of 38mm fire hose. Once the flow was restored to the original point through unrestricted piping, that supply fed a branch to two 38mm hoses - a total of three fire hoses.
At the time the fire control people arrived three tyres were still burning while the fourth was all but burnt out. Once adequate water was available two of the three remaining tyres (which were probably two thirds consumed) were extinguished fairly readily. The fourth and least accessible tyre was very difficult to extinguish. It was apparently burning from the inside and despite getting water onto it, it kept burning.
The process of fighting the fire was extremely hazardous in any case, throughout the process the backs kept booting and frequent falls of ground took place. Any contact of water with the backs caused them to "explode" with associated falls of ground. Due to these problems and being hampered by insufficient pressure it was not possible to properly tackle the remaining fire which consisted of one tyre. Use of foam was tried, but again water pressure meant that insufficient could be generated to completely bury the tyre and extinguish it. Large amounts of ground fell in 6 Access, with smaller falls extending into the incline and endangering fire fighters.
At approximately 7.10pm a team of three men wearing BG174's left the surface and proceeded to 36 Level. They were told the fire was under reasonable control and to proceed to 32 Level. They travelled to 32 Level and were driven down to the 10 Access area by the Shift Boss. They proceeded into the smoke and arrived at the spray drive (at about 7.20pm) where they were hoping to find the men. They located two men at the spray drive, and after fitting them with oxygen self-rescuers, one of the team led the two back up to clear air while the others proceeded to 7A Access and found the fitter in the location given to them by the jeep driver.
Meanwhile a party of three men (including the Registered Manager) had travelled up past the now partly subdued fire. Two wore compressed air sets and a third a BG174. Although the heat from the fire was less intense there was still dense black smoke (tyres) and almost no visibility. This party proceeded up to the spray drive where they met two of the rescue team from above with the fitter who had been in 7A Access. One of the compressed air sets ran out indicating that this was a poor choice of equipment for the situation. The fitter was assisted up the incline to clear air and taken to the surface to a waiting Ambulance.
Some members of both rescue teams travelled back down the decline, and past the fire into clear air. One of these men knew how to activate the high pressure water supply to supplement the normal supply. This was done with considerable improvement in pressure.
All the injured men were on the surface by a little after eight and those seriously affected by smoke and fumes were conveyed to hospital by Ambulance. The fire crews reduced the fire to no more than smouldering tyres by about 8.30pm.
Injuries From the Fire
The principal physical injuries were to the three men who were trapped by the fire and who had to breathe the smoke and fumes for periods of up to two and a half hours. These men suffered exposure to heat, and smoke inhalation, that resulted in hospitalisation. The fourth trapped person was located in the spray drive (intake air) and exposed to the smoke and fumes that mixed with that air supply. His injury from exposure was significantly less. Fortunately no person suffered serious burns and the major injury was serious loss of lung function.
Two other men (in 11/12 Access) had a brief exposure to smoke and fumes, but quickly cleared the affected area.
The four men who were trapped by the fire all suffered severe post-traumatic shock. Many of the people associated with the fire fighting and rescue, and in particular the Shift Boss and the driver of the burnt loader experienced trauma to varying degrees. Following the fire the four men who had been trapped were off work, and three were initially hospitalised. From interviews with them the seriousness of the post-traumatic shock was self evident. An officer of the Department urged the Mine to provide counselling and recommended individually to the four men that they seek professional help to work through the problems that were affecting them and their families.
The company are to be commended for recognising the trauma effects of the fire and arranging debriefing sessions run by trained personnel from the Department of Health. While the concept of providing psychological care in the face of trauma or loss is at an early stage, it is an important recognition of the need to provide for the non-physical welfare of employees adversely affected by events in the workplace.
Of the four men trapped none will be returning to the underground environment. Three have already left the industry and the fourth expects to do likewise. Each of the four trapped men suffer from what could be described as a severe psychological allergic reaction to the mine. This allergic reaction is manifested in; the inability of the men to even contemplate return to their former workplace, their difficulty or inability to approach the mine site, (even going to the mine to pick up documents has resulted in the men getting no further than the gate) and even contact with mine personnel or officials has been a cause of distress.
How did the men Survive the Fire
No scientific evidence is available, however it seems logically compelling to conclude that the levels of carbon monoxide the men were exposed to were not quite high enough to cause unconsciousness and then death. The reason for this being the continual addition of ventilating air that both diluted and removed the fumes.
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