Pneumatic pressure relief test plug

A pneumatic test plug for use with a pipe having a generally cylindrical internal pipe wall, the pneumatic test plug comprising:

• an inflatable bladder formed by a bladder wall that is elastically deformable;
• and
• an inflation valve mounted in the bladder wall such that an interior end of the inflation valve is in fluid communication with an interior area defined within the bladder, the inflation valve defining a main air passageway through which air is introduced into the interior area, and a separate release channel having an inlet disposed toward the interior end of the inflation valve and an outlet in fluid communication with an exterior environment outside the bladder;
• wherein the valve is mounted in the bladder wall such that a sealing portion of the bladder wall when in a sealed position engages the interior end of the inflation valve and sealingly closes the inlet of the release channel, and when said sealing portion is elastically deflected by overinflation of the bladder, said sealing portion uncovers the inlet of the release channel to allow air to escape from the interior area of the bladder through the release channel to the exterior environment, said sealing portion elastically returning to the sealed position when sufficient release of air has occurred.