The chemical reactor shown below has a cover (called a head) that is held in pla
ID: 735219 • Letter: T
Question
The chemical reactor shown below has a cover (called a head) that is held in place by aseries of bolts. The head is made of stainless steel (SG = 8.0), is 3 in. thick, has a diameter of 24
in., and covers and seals an opening 20 in. in diameter. During turnaround, when the reactor is
taken out of service for cleaning and repair, the head was removed by an operator who thought
the reactor had been depressurized using a standard venting procedure. However, the pressure
gauge had been damaged in an earlier process upset (the reactor pressure had exceeded the upper
limit of the gauge), and instead of being depressurized completely, the vessel was under a gauge
pressure of 30 psi.
(What force (lbf) were the bolts exerting on the head before they were removed? (Hint:
Don't forget that a pressure is exerted on the top of the head by the atmosphere.) What
happened when the last bolt was removed by the operator? Justify your prediction by
estimating the initial acceleration of the head upon removal of the last bolt.
(a) Propose an alteration in the turnaround procedure to prevent recurrence of an incident of
this kind.
Explanation / Answer
The chemical reactor shown below has a cover (called a head) that is held in place by a series of bolts. The head is made of stainless steel (SG = 8.0), is 3 in. thick, has a diameter of 24 in., and covers and seals an opening 20in. in diameter. During turnaround, when the reactor is taken out of service for cleaning and repair, the head was removed by an operator who thought the reactor had been depressurized using a standard venting procedure. However, the pressure gauge had been damaged in an earlier process upset (the reactor pressure had exceeded the upper limit of the gauge), and instead of being depressurized completely, the vessel was under a gauge pressure of 30psi.
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