How to choose valves for steam systems

Steam is one of the most widely used energy carriers in industry, but it demands components designed specifically for its unique characteristics: high temperature, phase changes and the presence of condensate.

Key valve types in steam systems

Control valves regulate steam flow to heat exchangers, maintaining precise temperature control. 2-way and 3-way globe bodies with pneumatic or electric actuators are the standard. Correct sizing (Kv calculation) is critical — an oversized valve hunts, an undersized one cannot deliver enough steam.

Pressure reducing valves (PRVs) maintain constant downstream pressure regardless of upstream fluctuations and demand changes. Direct-acting PRVs suit small loads; pilot-operated types offer tighter regulation for larger, variable loads.

Safety valves protect boilers and pressure vessels from overpressure. They must be PED-certified, correctly sized to discharge the full boiler capacity, and tested regularly.

Isolation valves — gate or ball valves for on/off duty. For steam, use metal-seated or high-temperature PTFE seats. Butterfly valves are suitable for low-pressure steam and condensate.

Materials matter

Steam valves must withstand temperatures from 100°C to over 250°C at pressures up to 40 bar or more. Cast steel (WCB) is the standard body material. Stainless steel internals improve erosion resistance. Bronze is acceptable for low-pressure saturated steam only. Never use PVC or brass above 100°C.

Common mistakes

• Oversizing control valves (leads to hunting and poor control)
• Using water-rated valves on steam (different pressure-temperature ratings)
• Forgetting to install strainers upstream of control valves and PRVs
• Not accounting for condensate at startup (water hammer risk)

Roffia's technical team can assist with valve selection and sizing for your steam system. Contact us for expert support.