Boiler Explosion (Exxon Singapore)
Boiler Explosion (Exxon Singapore)
Boiler Explosion (Exxon Singapore)
INTRODUCTION
On 9 Dec 2000, at about 2:30am, three personnel were trying to re-start the boiler when an explosion occurred inside the furnace of the boiler. The three personnel were badly injured with more than 50% 2nd degree burns on their bodies. Two of them subsequently passed away later in the hospital:
DESCRIPTION OF ACCIDENT
Boiler was on LPG firing. Night Order was given to light up diesel burner in Boiler. The three personnel attempted to light up the diesel burner at about 12:30am. They made several attempts but were unsuccessful. At 2:20am, they attempted to light up the diesel burner. However, the boiler experienced a master fuel trip which shut down the boiler totally. While restarting the boiler on LPG, an explosion occurred.
Investigations revealed that the startup team encountered some difficulties in lighting the boiler with LPG some time back. To overcome the problem, they devised a temporary manual bypass method.
This bypass method was not the same as the operational procedures.
Pre-Startup Safety Review (PSSR) was claimed to be carried out on the Boiler. But the PSSR document was not available for our review during the investigation.
It was found that the bypass valves did not have any sealed wire when the startup team first implemented the bypass method. However, the team did not find out further why there was no sealed wire on these valves.
SITE FINDINGS
Site investigations after the accident confirmed that the 2 bypass valves were 50% open. This confirmed that the bypass method was utilised to restart the boiler.
Data records confirmed that the LPG control valve was about 66% open just before the explosion. The block valves before and after the control valve were fully open.
A direct path was therefore established to allow LPG to enter the firebox, resulting in the explosion of the boiler.
100% open
Block valve 100% open
Block valve
100% open
CAUSE OF ACCIDENT
Use of temporary bypass method to restart the boiler after it had tripped. Two bypass valves of the trip valves were opened without first closing the two block valves, downstream of the LPG control valve Non-compliance of the company internal S.M.S.s safety requirements: - The use of unauthorised temporary bypass method - The removal of sealed wire on the bypass valves.
CONCLUSION
Air (Oxygen)
FIRE
TRIANGLE
LPG
LESSONS LEARNT
All personnel who are operating boiler must follow Safe Operating Procedures. Authorisation must be obtained before introducing change to the boiler system or procedures. Ensure all personnel who are operating boiler received adequate training and supervision. Ensure proper documentation.
ACTIONS TAKEN
The company had been instructed to carry out a thorough inspection and examination on the remaining Boiler and carry out necessary rectification works to restore the boiler to safe operating condition. The company had also thoroughly reviewed the BMS and carried out rectification to improve the system. They had also reviewed and audited their internal S.M.S. to identify weaknesses and to close such gaps.
Don't Neglect Your Boilers Operation Just Because They Operate Automatically
THANK YOU