pressure-regulating valve meaning

• [Engineering]
  "A valve that releases or holds process-system pressure (that is, opens or closes) either by preset spring tension or by actuation by a valve controller to assume any desired position between full open and full closed."

• pressure regulating valve (prv):    [Architecture]A de ...
• pressure regulating valve station, prv station:    [Architecture]An i ...
• regulating valve:    [Architecture]A va ...