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Pressure Ramp Up for Improved Pressure Control (2)

A direct-acting sequence valve SC*A can be used as a main stage relief. By applying pressure onto port 3, the setting and/or relief characteristics of the SC*A can be controlled separately from the main stage. An external orifice is used to limit the pilot flow to the relief valve RP*T

  • Direct-acting sequence:        SC*A, 
  • Relief valves as pilot:            RP*T, RD*A

Benefits of this circuit arrangement:

  • The direct-acting sequence valve SC*A as a main stage controls high flow rates well and has a good response time. Since the pilot valve (RP*T) has a high capacity, the main stage SC*A can open very fast.  Piloting a SC*A with a RP*T effectively produces a 3 stage valve
  • Fig.1 shows the step response of a standard direct-acting relief valve RD*A and an anti-shock relief RP*T.
  • The SC*A should be set to its minimum setting without pilot pressure. Approximately 300 psi is a good minimum setting for a fast reseat.
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