Explosion of Liquefied Petroleum Gas (LPG) in a Supermarket

Two workers were killed and nine injured on December 2009 when an explosion occurred inside a new shopping complex somewhere in Malacca. During the accident, the workers were making final preparations for the official opening of the complex. The LPG was channeled from the bulk storage tanks through a gas piping network and controlled by a shut-off valve at each of the shop-lot- which is used as a food and beverages outlet. Forensic engineering investigation found out that the explosion happened when a shut-off valve in one of the shop-lots was inadvertently left opened.

Photo 1: Gas supply from two LPG tanks

Photo 2: Damages caused by blast effect in the supermarket

The LPG leakage was detected and discovered by the one of the workers working near the shop-lot. However no was taken to evacuate the building and the shut-off valve inside the shop-lot cannot be turned off because the door was shuttered and locked. The LPG which had escaped and accumulated in the shop–lot can be easily ignited by any sparks from the on-going work outside the shop.

The combination of accumulated LPG and spark caused a confined vapor cloud explosion [VCE] resulting in building walls cracked and damaged, window glasses shattered and ceilings collapsed. Death and injuries were due to flying debris from the explosion acting like shrapnels.

Methods Of Improvement

1. A comprehensive LPG safe system of work need to be established. On top of that the management must ensure that the system is implemented and followed through by anyone who works with LPG.
2. Thorough inspection on the LPG pipings and fittings need to be done before the commissioning process to ensure that all shut-off valves in the shop-lots were properly turned off.
3. The gas piping contractor shall ensure that the end pipes were closed with ‘end caps’ to prevent any leakage of gas even though the shut-off valves were closed.
4. The contractor should be briefed about the dangers of LPG and the safety evacuation measures to be taken in the event of any leakage.
5. To ensure good ventilation in the building, especially for enclosed and confined places where LPG could accumulate if a leakage occur.
6. The location of the LPG main emergency shut-off valve shall be easily and readily accessible.

Reference:

1. Examples of Chemical Data Sheet (CSDS) for Liquefied Natural Gas (LPG) from Gas Malaysia can be read at www.gasmalaysia.com/docs/datasheet/datasheet_lpg.pdf