An article edited from a news item by ‘Troublespot’, the Marine Professional magazine #IMarEST
On 14 July 2020, a passenger vessel was anchored when a sudden release of steam in a feed water tank caused a crew member fatality.
Shortly after 10am on 14 July 2020 , three crew, including one junior seafarer, descended into a feed water tank as part of an inspection and routine maintenance operation to clean, scrape and re-paint the tank.
Work had already been done to isolate the tank in accordance with Lock Out Tag Out procedures (LOTO) and theoretically all procedures had been followed. On a blow-out line running from the boiler to the feed water tank, there were two manually-operated valves, V037 and V134, as well as one pneumatically operated valve V040; V037 and V134 were secured and tags fixed.
Simultaneously, a different team was working on preparing the vessel to leave anchorage. Working his way down the pre-departure checklist, the Officer of the Watch (OOW) requested that a second diesel generator be switched on.
An exhaust gas economiser, working to improve the efficiency of the vessel by recycling generator exhaust gas heat, began to feed its heat into one of the ship’s boilers. Very quickly, the water level in boiler 1 began to increase, coinciding with an increase in steam pressure.
As the boiler water level reached 80%, high-pressure steam surged towards the feed water tank, blowing through both the secured V037 and then the pneumatically operated valve (V040) on the blow-out line.
Though painstakingly secured by the crew, valve V134 provided no hindrance to the steam either, and it blasted through into the tank, at a temperature of 170°C and a pressure of 8 bar, directly above where two of the crew were working.
Both seriously injured, they and their uninjured colleague managed to climb from the tank, but it wasn’t soon enough for the junior seafarer, who died in hospital on 19 July, after sustaining serious body surface burns.
Investigations
Subsequent investigations, including destructive testing, identified major problems. Valve V037 – the first line of defence, between the boiler and the pneumatic valve – was so corroded that it was impossible to close.
Testimony from the crew indicates that the valve wheel could be turned a sufficient number of times to lead the operator to believe it was closed.
But valve V134 should have held. According to subsequent laboratory testing, the valve was in good condition, with no significant corrosion. “Considering the shipboard and bench test, it is concluded that the valve was not fully closed at the time of the incident”.
At the time the tank was being isolated, the second engineer had presumed that with two valves closed manually, isolating the pneumatically operated valve was unnecessary.
Therefore, three lines of defence were suspect before the crew entered the tank; V037 had rusted open; pneumatic valve V040 was left to operate automatically; and V134 – despite having been tagged – was not properly closed.
Next steps
It was noted that the LOTO procedure left much to be desired, with no set procedure for isolating the feed water tank – instead, this was left to an engineer’s discretion.
In fact, non-electrical systems were not subject to a LOTO policy. “The written procedure for isolating the boilers did not include identification of the valves on the blow-out line,” nor, indeed “a need to apply additional controls to systems incapable of being locked out.”
Leaving non-electrical systems out of the ship’s LOTO policy left much open to interpretation by crew. Under the impression that the relevant equipment had been turned off, and the valves had been isolated in accordance with the advice of the ship’s engineering staff, those going into the tank were not aware of the threat they faced.
“During interviews, the surviving injured crew member stated that he would not have entered the tank if he had known it was attached to an operational boiler,” said the report.
As is the case with many accidents, it would not have been possible had any one of a number of potential barriers to disaster been in place.
If, for example, the pneumatically operated valve had been deactivated, it would have prevented the steam getting as far as the unsecured V134. Had the boiler been shut down entirely, there would have been no risk to the crew.
