Reactor bypass case

By The Brainy Engineer Friday, January 18, 2019

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A reactor was fitted with a bypass
(Figure 1 ), The remotely operated valves A, B, and C were interlocked so that C had to be open before A or B could be closed.

It was found that the valves leaked, so hand-operated isolation valves (a, b, and c) were installed in series with them (Figure 2).

After closing A and B, the operators were instructed to go outside and close the corresponding hand valves a and b. This destroyed the interlocking.

One day, an operator could not get A and B to close. He had forgotten to open C. He decided that A and B were faulty and closed a and b. Flow stopped, The tubes in the furnace were over- heated. One of them burst, with no lives loss



 Lesson Learned

Any Plant Modifications even minor ones shoukd undergo only through the Plant MOC ( Management of Change ) Procedure Only and the human error should be taken in consideration when you do the MOC PHA, also Updating the SOP is part of MOC Implementation process ( Document Update ) and training of all concerned about the New Changes,
also the PSSR ( Pre Start Safety Review ) should be done prior the actual implementation of the MOC to address any human or process hazards