Failure of Solids: Markham Colliery Disaster - Case Study Example

Executive summary Eighteen men fell culprits and died in the 1973 Markham colliery disaster in which other eleven persons sustained serious injuries after a cage descending into the mine failed to stop while reaching the base of the mineshaft. Moreover, another person was reported to have sustained very bad injuries suffered during the rescue process. A fracture in the brake rod of the crane is what the report that was released after an investigation into the accident indicated to have been the cause to the crash. The braking system as was relied upon to slow down the cage as it descended people into the mine failed because of metal fatigue as was later discovered. The braking system as was used in the operation of the cage comprised of mechanical braking system as well as regenerative braking system using direct current kind of power as was used in powering the double deck descending cages. A system of levers as well as braking pads were relied upon in the mechanical braking process, besides, some steel rods were in use for transmitting braking pressure from the spring nests towards the main levers and as such, the steel rods would always be under tension whenever brakes were applied in the system. However, the system mechanical functionality has a standby system of braking which is applied in the event of an emergency. This is what the ‘winding engine man’ on duty (Kennan) claims to have failed simultaneously with the internal braking system, and hence resulted in the crash-landing of the cage. The investigation that ensued to determine the exact cause of the accident found nothing more to be associated with the accident except the fatigue and resultant breaking of the braking rod as was relied upon to produce the braking effect of the winding system. In fact the analysis showed that the materials used in manufacture of those breaking rod was the perfect type from industrial specifications and hence fatigue was blamed on causing the breakage and hence the failure. Report Outline of the accident: On the 6th of March in 1974, the ‘secretary of state for energy’, Varley Eric Graham tabled the findings of the investigations into the cause of the accident as was investigated with the direction by Peter Walker (the secretary of state for trade and industry)at the time after the accident. The report confirmed that eighteen persons lost their lives in the accident with at least twelve other persons sustaining serious injuries through the accident and during the rescue mission. The report was compiled from a public inquiry that was commenced immediately after the accident and fifty-five persons gave evidence of the account as to what transpired. The report established that the fatalities were caused by a crash into the bottom of the mine that happened after the cage in which the men were travelling in failed to brake upon nearing the base of the mine. Besides, there ensued a delay in reaching for the injured after the mine gates suffered distortion and they were rescued hours after the accident happened. Through the evidence presented by the public inquiry, the much sought after information in understanding the intrigues that would have caused the over-wind with the system of the cage was gotten. After the analysis, the accident was found to have resulted after the cage system that ferried miners into the mine failed to brake hence crash landing into the bottom of the mine. The failure resulted from material fatigue that affected the steel metal rods, which supported the breaking mechanism for the cages as they descended into the mine. Evidence: The investigation led to a number of revelations, which included that, all system of brakes; even the emergency braking system failed. The mechanical system functionality has a standby braking system, which is applied for emergencies. However, according to the ‘winding engine man’ on duty the system failed simultaneously with the system’s main braking system, and hence resulted to the crash-landing of the cage. According to Kennan, sparks were observed below the braking cylinder and he immediately ensued retarding the winding. The immediate action was to apply the regenerative system of brakes together with pulling to position the brake lever. After noting no effect from the systems of brake, he applied the emergency stopping system, which equally failed to the utter dismay of him, and this therefore caused the cage to crash to the ground hence causing the fatalities as were. Working practices and system design: the cage system comprises of the system through which a winding motor is powered through direct current motor. The winding rope has two cages wound at each end and which serves as the containers in which the people are transported through, to and from the mine. The operation of the system had the mechanical braking system released and gradual application of the DC power to the motor. After an initial acceleration, the system acquires and maintains a constant speed of 6m/s until the cages approach the bottom after which deceleration commences through reduction in power voltage supply. Deceleration is followed by a mechanical braking system, which is responsible of complete halting of the cages at the bottom. An 8 feet long steel rod was strategically placed between the ‘spring nests’ and the ‘main lever’ and had the main role of transmitting the force. The compression of then springs therefore yield pressure on the rod always and this explains the continued tension that the rod suffers. Besides, safety is ensured through automatic system of supply of power, which would disconnect the motor from the main power source whenever applied and automatically applies the mechanical braking system. This therefore shows that the working of the cage system in the mine is well designed and its effectiveness assured if not for such total system failure as was blamed for having caused the accident. At the time of accident, the cage had fifteen men on board with fourteen others in the lower compartment and after being loaded at the surface, the descent was normal until past the midway when Kennan noticed sparks and his efforts to retard the engine became fruitless. After applying all emergency control measures, Kennan notes that noting happened until the cages crash-landed at the bottom of the mine hence resulting to the deaths and the injuries. During the examination, metallurgical test on the steel rods revealed the breaking resulted from strain and fatigue. However, after crack detection through electromagnetic methods, only minor defects got detected but greasing and lubrication was shown to have lacked although these defects would not explain the accident. Conclusion and recommendations The report presented after the investigation of the cause of the Markham colliery accident was instrumental in establishing that total mechanical failure in the system caused it. However, the main weakness was found with the centre rod, which suffered fatigue and strain and hence broke thereby disabling all other systems in operation; even the emergency ones. Design problem was established in that the system did not consider spring nest high pressures and there had been no efforts to lubricate all the axles. This therefore explains the recommendations of this paper that proper system design should be emphasized while making such a system in the mine as this would have saved lives and such other fatalities as resulted from the crash. Proper lubrication and frequent stress analysis for the supportive rods is necessary in such a system and this would aid in early detection of possible breakages due to stress and fatigue and hence have timely repair and maintenance procedures. Finally, slow emergency response mechanism would equally be pointed out as to have been a feature in the rescue operation and this paper therefore recommends that a regulatory body should be constituted to oversee such prompt response to emergencies is ensured. Bibliography Calder J. W. 1974. “Accident at Markham Colliery Derbyshire: Report” Viewed April 2, 2014, Read More