DuPont Co. required a valve that would eliminate pressure spikes over 65 psi in a 4” water line flowing as much as 350 gpm.  Because this was a critical cooling application, the valve had to fail open, and minimal pressure drop across the valve was required. 

A conventional control valve could not be used, due to the slow response time; and any spring-loaded regulator would have too much droop.

A Jordan 4” Mark 66 Air Loaded Pressure Regulator was selected with a Controlair Mite 73 air relay switch installed in the instrument air feed line.  The Jordan Valve provided excellent control with pressure drops at 3 psi or less and rapid response to any pressure spikes.  The air relay switch was set at 55 psi so that in the event that instrument air supply was lost, a static load of 55 psi was locked into the dome of the Mark 66.  This allowed the valve to fail open on loss of air, but still control at 55 psi.  When the air pressure was restored, normal operation would resume, all without the need for electric power.