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.

(a) What force (lbf) were the bolts exerting on the head before they were removed? 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.

(b) Propose an alteration in the turnaround procedure to prevent recurrence of an incident of thiskind.