Gas Turbine Explosion Investigation

AGI Gas Turbine Explosion Investigation

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At approximately 1300 hours on Saturday, 14 December 2013, a loud bang resembling an explosion was heard at the exhaust ducting of Gas Turbine Generator (GT) 1 after eleven (11) attempts of ignition during the maintenance period. Further external inspection conducted on GT-1 revealed that a number of bypass ducting bellows had ruptured and deformation was observed at the economiser casing. This report presents the findings and results of the investigation and examination of the origin and possible cause of the explosion. The investigation was conducted through site visits, data-gathering and forensic study. During the visits, the investigation team conducted a thorough on-site investigation and examination of the scene. During the course of the investigation and examination, the Team performed damage analysis and scientific interpretation of the scene to determine the possible area of origin, and potential cause of explosion.

Photograph 1: View of the Gas Turbine Generator (GT) 1 and the Heat Recovery Steam Generator (HRSG). The relevant Machines were identified in the photograph. Photograph was taken from the Southeast.
Photograph 2: View of the exhaust ducting. The interconnection between the exhaust ducting was observed to be displaced due to explosion (red arrow). Photograph was taken from the Southeast.

Based on the Team’s overall inspection and damage analysis of GT-1 and the surrounding area, the flame front from the fire which had initiated within the combustion chamber during the gas ignition sequence had propagated through the interconnected bypass ducting which contained accumulated natural gas. An explosion ensued as the flames acted as the ignition source to the pre-mixed fuel air cloud (fuel load) within the bypass ducting when the concentration ratio of natural gas and oxygen reached the lower explosive limit.

Photograph 3: View of the exhaust ducting. The interconnection between the exhaust ducting was observed to be displaced due to explosion (red arrow). Photograph was taken from the Southeast.

Based on the evidence, damage analysis and from the process of elimination of all other possible causes, the Team found that the explosion had commenced as the result of defective gas control valves and insufficient purging time.

Photograph 4: View of the bypass exhaust ducting. The bellow ducting was observed to have sustained damaged due to the explosion. Photograph was taken from the southeast.

The Team recommend that the main and pilot control valves be replaced. It is also essential to increase the purging time from 40 seconds to the recommended 350 seconds.

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BY APPROVED GROUP INTERNATIONAL (AGI)

Our mission is to provide scientific approach to forensic investigation, failure analysis and non-destructive testing; professional and economical disaster restoration.

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