During routine maintenance, the fitter on one of our vessels was engaged in changing the leaking gland packing of a valve on a steam return line. Before commencing the task, he isolated the line by shutting off the main distribution valves as well as the inlet valve for the steam heating coil from where the return line issued. The main stop valve of the boiler remained open to maintain other auxiliary services. After loosening and separating the valve flange, the fitter did not notice any pressure in the line, and continued his work. All of a sudden and without any warning, a jet of steam and hot water spurted out of the open flange, scalding the fitter's face.
Result of investigation
1 It was established that despite being shut, the steam distribution and inlet valves were not holding. Consequently, steam slowly built up pressure on the condensed water in the heating coil, and when it was sufficient to overcome the internalresistance and head of the water, it spurted out of the open flange resulting in the accident.
2 No formal risk assessment was carried out before commencing the work on the steam line.
1 In order to avoid recurrence of such accidents, it is imperative that, apart from isolating the branch lines, the main stop valve on the boiler should be kept shut or the line blanked off upstream at a suitable point before opening any part of the steam lines;
2 Risk assessment must be carried out without fail before commencement of such jobs.
Source: Mars/Nautical Institute