PCD-Series Dual-Valve Pressure Controllers

Saturday, March 1, 2014

Alicat's PCD-Series dual-valve pressure controller incorporates a second proportional control valve at its outlet to vent excess pressure. The PCD maintains a stable pressure through the central process port to the closed volume under test. This valve opens only when needed, so almost no gas is wasted.

If the system pressure becomes too great, the outlet valve opens to return the pressure to the chosen setpoint. Because this process happens a thousand times every second, the amount of gas lost while maintaining a constant pressure in a closed volume is exceedingly little. In this way, choosing a PCD for applications in closed volumes will save you a lot of money.

Ordering a PCD Pressure Controller

When Alicat builds a PCD, we have a number of valves to choose from for both the inlet valve and the outlet valve. Correct valve sizing for PCDs depends upon the following three parameters:

1. Inlet pressure (P1): Lower inlet pressures generally require larger inlet valve openings
2. Exhaust pressure (P2): Customers typically vent either to atmosphere or to vacuum. Generally, a vacuum will generate greater exhaust flow rates than venting to atmosphere
3. Process volume (Vol): We also ask for the volume of the closed process under test because greater volumes require larger flows to fill and vent in a timely manner

Once you have provided these three parameters, our engineers will select the valves that will allow the most efficient filling and evacuation of your process volume while maintaining excellent control stability.

For those who require high flow rates into or out of the process volume at low pressures, we may recommend our PCRD Series. This series uses the same Rolamite valve that we use in our larger mass flow controllers for larger flows.

Typical Applications where the PCD may be used

• High Efficiency Helium Leak Check
• High-Speed Aerodynamic Testing
• Fluid Dispensing Using Pressure Control
• Fuel Cell Testing
• Pressure Control with Sense Port
• Regulating Vacuum In Test System When Vacuum Source Varies

Our range of PCD dual valve pressure controllers

Alicat's range of PCD dual valve pressure controllers are available in four different versions

• PCD - Standard PCD version for common applications
• PCRD - Large Rolamite valve type for higher flow applications
• PCDS / PCRDS - All stainless steel and FFKM wetted parts for aggressive applications
• PCD3 / PCRD3 - Incorporates a remote sensor port onto the flow body.

Related article

Liquid Flow Controllers from Alicat

Get in touch

We can supply full case studies for these applications – please call us today on 01953 609930 and ask for details.

Posted by James Kybird, Managing Director