OGP, the International Association of Oil and Gas Producers, has issued a safety alert following the death of a worker at a construction/rig repair yard in Singapore in May this year. The worker had entered an enclosed space which was inerted with argon gas for a welding operation.
Argon does not do much which is why it is useful in processes like welding where a non-combustible atmosphere is needed to prevent fire and explosions. It can also kill, as this case shows.
Too often there is more than one casualty. The first victim is joined by those who follow attempting a rescue. About two thirds of casualties are would-be rescuers.
In this incident two cylindrical foam sponge pads had been inserted in a riser guide tube to form a plug. Argon gas had been pumped into the 60 cm space between the two sponges as shielding gas for welding on the exterior of the riser guide tube. After welding finished, a worker descended into the riser guide tube by rope to remove the upper sponge. While inside, communication with the worker stopped.
A confined space attendant entered the riser guide tube to investigate. Finding his colleague unconscious, he called for rescue and then he too lost consciousness. On being brought to the surface, the first worker received CPR; was taken to hospital; but died of suspected cardio-respiratory failure after two hours of descent into the space. The co-worker recovered.
The victims were unaware of the asphyxiation risk from the argon gas shielding creating an oxygen-deficient atmosphere. There was no gas test done immediately prior to the confined space entry. The act of removing the upper foam sponge itself could have released additional argon, so any prior test would not be meaningful.
Portable gas detectors were carried, but inside a canvas bag. The co-worker did not hear any audible alarm from the gas detector when he descended into the space.
As is often the case it took a relatively long time for the rescues. It took 20 minutes to bring the victim to the deck after communication failed.
Working in a confined space always present more risk than work elsewhere. One estimate calculated that it is 150 times riskier to work in a confined space.
Sadly, the lessons are not rare and although this incident occurred onshore avoiding it was not difficult.
If there is restricted access and no natural or forced air flow then you’re probably dealing with a confined or enclosed space. If in doubt, treat it as a confined or enclosed space.
Says the safety alert:
As a first step:
- Assess whether the nature of the work absolutely justifies personnel entering the confined space.
- Identify and communicate the risks to personnel carrying out the work.
- Define requirements, roles and responsibilities to control, monitor and supervise the work.
- Check gas presence; understand how the work itself may change the atmospheric conditions.
- Ensure adequate ventilation, lighting, means of communication and escape
- Ensure step by step work permits are issued and displayed for each work phase, together with specific job safety analyses
During confined space entry:
- Station a trained confined space attendant at the entrance to the space at all times
- Ensure that communication and rescue equipment and resources are readily available
- Carry and use portable/personal gas detectors throughout the activity.