Incident
During rounds, a cruise ship’s third engineer discovered a leak on the drain valve for one of the vessel’s four economisers. There was an open-ended pipe running from the valve to a tundish drain in the deck. The chief engineer (C/E) was briefed and a decision was taken to conduct a repair. The economiser’s circulating pump was stopped and the inlet and outlet valves were shut; the plan was to leave the system to cool down overnight before the repair.
However, after the isolations were in place, the second engineer (2/E) decided to check the system by opening the drain valve. Leaning over the valve, the 2/E cracked it open and pressurised hot water and steam burst out of the drain pipe.
The force of the discharge caused the hot water to deflect upwards off the tundish, severely scalding the 2/E’s face. After initial medical treatment on board, he was evacuated to a nearby hospital for specialist burns care.
Lesson Learnt
- Hazard → The opening of drain lines on pressurized systems must be undertaken with extreme caution. The 2/E intended to check that the drain line and valve were unobstructed before the economiser was drained the following day when the system had cooled. It is a reasonable practice to use residual system pressure to check a drain line, but it must be done in a controlled manner. The economiser’s working pressure was 8 bar. It is good practice to allow the working pressure to lower and the system to cool sufficiently before opening the drain valve.
- Risk → The 2/E leant forward over the pipework that ran to the tundish to open the drain valve. As a result, his upper body was directly in line with the deflected water and steam. When venting or releasing stored pressure, it is vital to ensure that your body is not in the path of any predictable discharge.
- Equipment → Caution must be exercised when opening valves that are infrequently used. A valve that has become seized in the shut position may require excess force to manoeuvre it and lead to the valve suddenly and unexpectedly opening, causing an uncontrolled fluid flow. The use of a correctly sized wheel key can provide appropriate torque and increase the application of controlled force to the valve wheel.
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Source: SAFETY DIGEST
