Near Miss: steam and water released from filter

What happened?

A mechanic was given a work order to clean out strainers from a boiler circulation pump. The mechanic was got to loosening the last two bolts, and stopped to wait to hear a “pop” indicating the lid coming up. The “pop” was a little bit more than was expected. As the mechanic waited for approximately 10 seconds, it was noticed that the pressure started getting more volatile with more air and water coming out. The mechanic moved out of the way, and called the control room to let them know what was going on. An operator and a supervisor responded and went to a valve that they thought might still be partially open. They attempted to try and close it. The supervisor tried with a bigger valve wrench and was able to turn the valve two more turns to close it off.

What went right 

• The employee moved out of the way when they noticed increased pressure from the filter;
• The supervisor was able to close the valve two more revolutions after the incident.

What went wrong? 

• The valve did not fully close when operations attempted to isolate it.

Lessons learned

• Procedures were changed so as to open the bypass on the filter first, then isolate the inlet and outlet of the filter. Open drain valves upstream and downstream and then open the purge upstream and downstream, ensuring zero energy is exhausting.

Members may wish to refer to:

• Crewman badly scalded during tank cleaning
• LTI: person crushed in watertight door