Ensuring that Pressure Relieving Devices function properly is a critical part of any fixed equipment Mechanical Integrity program. These devices, and their associated piping, must be inspected and tested at regular intervals to ensure that they are providing the over pressure protection required by the applicable Code of construction.
Atmospheric storage tanks (ASTs) also require both over and under pressure protection. Note that ASTs may experience external pressures (partial vacuums) during unloading operations. To avoid buckling it is critical that AST under pressure\vacuum breakers be kept clear of obstructions and in proper working order at all times.