(69e) Methods for Evaluating and Reducing the Risks of Pneumatic Pressure Testing of Vessels and Piping

Hydrostatic testing of piping and vessels designed to handle LNG or other cryogenic liquids is problematic because of the need to remove residual water.

Pneumatic pressure testing of piping and vessels at moderate-to-high test pressures is more hazardous than hydrostatic pressure testing because the stored energy is much greater with compressed gases. Hazards from loss of containment during pneumatic pressure testing include both blast overpressure and missiles.

In applications where pressure testing with liquids is undesirable, such as in cryogenic piping systems and vessels, pneumatic pressure testing can only be justified when care in fabrication and in non-destructive examination of vessels and piping reduces the probability of loss of containment to such a small value that risk is acceptable.

This paper outlines methods for evaluating the risks of pneumatic pressure testing of vessels and piping, as well as methods of risk reduction.