What Is a Schiedrum Pressure Control Valve?

Schiedrum pressure control valves (such as the 20DR series) regulate downstream or upstream pressure in hydraulic and pneumatic systems. A pressure-reducing (or pressure-control) version holds a preset secondary pressure regardless of fluctuations in the supply, protecting components and stabilising process conditions.

How to Size and Select

• Function: Decide reducing (downstream control), relief (over-pressure protection) or sequence — each has a distinct symbol and porting.
• Flow capacity: Check the rated flow at the set pressure; undersized valves cause excessive drop and heat.
• Pressure range: Match the adjustment range to your working setpoint.
• Port size: The 20DR-400 uses a DN/flange style port — confirm mating dimensions.
• Medium and seal: Mineral oil, HFA/HFC fluids or air each demand compatible seal and body materials.

Installation and Setting

1. Install in the correct flow direction; a reducing valve is not bidirectional.
2. Mount where the adjustment is reachable and protected from shock loads.
3. Set pressure with the downstream isolated or at zero flow: turn the screw until the gauge reads the target, then open the circuit.
4. For remote control, some models accept a pilot pressure instead of the mechanical adjustment.

Maintenance and Common Faults

These valves are robust but sensitive to contamination. Symptoms and causes:

• Pressure drifts up: seat or spool contaminated — flush and clean.
• Cannot reach set pressure: supply below required, internal leak, or wrong spring range.
• Hunting/instability: oversized for the flow or trapped air in the pilot line — bleed and resize.

Service by replacing the cartridge seal kit; avoid lapping seats in the field. Keep the tank breather and filter in good condition — most failures trace back to dirty oil.