All protective equipment should be tested

This section lists some protective equipment that has often been overlooked and not included in testing schedules. 

After a low-temperature trip on a nitrogen vaporizer failed to operate, it was found that the trip was never tested. The equipment was rented, and the user assumed—wrongly—that the owner would test it. 

A pump leaked and caught fire. It was impossible to reach the suction and delivery valves. But there was a second valve in the suction line between the pump and the tank from which it was taking suction, situated in the tank dike. Unfortunately this valve was rarely used and was too stiff to operate. 

All valves—whether manual or automatic—that may have to be operated in an emergency should be tested regularly (weekly or monthly). If completely closing a valve will upset production, it should be closed halfway during testing and closed fully during shutdowns. 

Emergency blowdown valves are among those that should be tested regularly. Reference 5 describes in detail the measures necessary to test emergency isolation valves when very high reliability is needed. 

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All protective equipment should be tested regularly, or it may not work when required. While it is sufficient to test relief valves every year or every two years, instrumented alarms and trips are less reliable and should be inspected every month or so. 

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