Diaphragm Steam Pressure Reducers

Compact, cost-effective pressure control for individual equipment and small to medium steam loads. Simple direct-acting design with minimal maintenance.

Simple, reliable pressure reduction

Diaphragm pressure reducing valves use a flexible membrane to sense downstream pressure, balanced against an adjustable spring. No external pilot, no auxiliary power — just physics.

The result: a compact, reliable valve ideal for individual process equipment, steam tracing, small heating loads and applications where space is limited. Maintenance is straightforward — diaphragm and seat can be replaced without removing the body from the line.

Roffia distributes Spirax Sarco DP and DRV series — proven designs with millions of installations worldwide.

Diaphragm steam pressure reducer Spirax Sarco — Roffia srl

Technical specifications

DP Series (compact)

  • Max inlet pressure: 17 bar
  • Outlet pressure: 0.1 – 10 bar (adjustable)
  • Temperature: up to 200°C
  • Connections: Screwed DN 15-50
  • Accuracy: ±0.3 bar

DRV Series (medium capacity)

  • Max inlet pressure: 17 bar
  • Outlet pressure: 0.2 – 10 bar (adjustable)
  • Temperature: up to 232°C
  • Connections: Flanged DN 15-80 (PN 16/25)
  • Accuracy: ±0.2 bar

Advantages

  • ✓ Compact — fits in tight spaces
  • ✓ Simple — fewer parts to fail
  • ✓ Cost-effective — lower initial cost
  • ✓ Easy maintenance — in-line service
  • ✓ Self-contained — no external sensing lines

Considerations

  • • Droop: outlet rises 0.2–0.5 bar with flow
  • • Capacity limited vs pilot-operated
  • • For high accuracy, use pilot-operated
  • • Best for stable, predictable loads

Applications

Individual equipment

Single jacketed vessels, small heat exchangers, autoclaves. Dedicated pressure for each unit.

Steam tracing

Process pipe tracing where low-pressure steam prevents freezing or maintains product temperature.

Small heating loads

Unit heaters, coils, humidifiers with steady demand and moderate accuracy requirements.

Related products

Pilot-operated reducers

High accuracy, large capacity

Steam traps

Condensate removal

Isolation valves

Maintenance access

Spirax Sarco

Full catalogue

Domande frequenti

How does a direct-acting diaphragm pressure reducer work?
A flexible diaphragm senses downstream pressure and balances it against an adjustable spring. When downstream pressure drops (load increases), the spring pushes the diaphragm down, opening the valve. When pressure rises, the diaphragm lifts against the spring, closing the valve. Simple, reliable, no external pilot or power required. The trade-off: outlet pressure rises slightly with flow ("droop"), accuracy ±0.3–0.5 bar.
When should I choose a diaphragm reducer over a pilot-operated one?
Diaphragm (direct-acting): compact, lower cost, simple maintenance. Best for: single equipment, small to medium flows, non-critical applications, tight installation spaces. Pilot-operated: higher accuracy, stable pressure at all loads, larger capacity. Best for: main lines, critical processes, variable loads. If your application tolerates ±0.5 bar variation, diaphragm is often the cost-effective choice.
What is "droop" in a direct-acting pressure reducer?
Droop (or proportional band) is the increase in outlet pressure as flow increases. In a diaphragm PRV, the valve opens more as demand rises — and the spring must compress further, meaning higher pressure is needed to balance it. Typical droop: 0.2–0.5 bar from zero to full flow. Pilot-operated valves eliminate droop by using an external pilot to sense pressure independent of valve position.
What is the maximum temperature for diaphragm steam reducers?
Standard diaphragm reducers handle up to 200°C — suitable for saturated steam up to approximately 15 bar. For higher temperatures or superheated steam, special high-temperature diaphragms (PTFE-faced) extend the range. Check the datasheet; Spirax Sarco DP series is rated to 200°C standard, DRV up to 232°C with appropriate trim.
Which Spirax Sarco models are diaphragm reducers?
Spirax Sarco offers two main direct-acting ranges: DP series — compact, screwed connections DN 15-50, for small loads and individual equipment. DRV series — larger capacity, flanged DN 15-80, for medium loads. Both feature stainless steel internals and are suitable for steam, air and industrial gases. Roffia stocks common sizes; special configurations on request.
Can diaphragm reducers be used for air and gases?
Yes. Diaphragm reducers work on any compressible fluid — steam, air, nitrogen, CO₂, inert gases. Ensure the diaphragm and body materials are compatible with the gas. For corrosive gases, stainless steel bodies and PTFE diaphragms are available. Compressed air reducers are often diaphragm type for simplicity and cost.

Need diaphragm steam pressure reducers?

Contact us for sizing assistance or stock availability. We carry the most common DP and DRV sizes for fast delivery.

Richiedi preventivo Chiamaci ora
Privacy Policy Cookie Policy