Normally Closed Steam Solenoid Valve — Teflon/Viton, 0 to 180 °C, Class H Insulation

Cematic's normally closed steam solenoid valve is an electrically actuated valve specifically designed for ON/OFF control of steam in industrial systems operating up to 180 °C and 1.0 MPa. Unlike general-purpose solenoids, this model incorporates three exclusive design features for steam service: a double seal of Teflon and Viton, a coil with Class H insulation (the highest thermal class in the catalog, capable of operating in contact with steam at 180 °C without winding degradation), and a G1/2" (BSP) thread connection — the most widely used European standard in industrial steam lines. Therefore, it is the correct choice when the fluid is steam and the application rules out any general-purpose solenoid.

Its normally closed configuration ensures automatic steam shut-off in the event of any electrical failure — the mandatory safety state in steam lines where a power outage should not leave the passage open. Additionally, its direct action operates from zero pressure (0 bar), so it works correctly in low-pressure steam systems or during startup when pressure has not yet been established.

Why this steam solenoid valve — differences vs. general-purpose solenoids

Standard solenoids with NBR seals fail in steam service within weeks or months. Cematic's steam solenoid valve addresses the three typical failure points of a general-purpose solenoid in steam service:

• Teflon + Viton Seal: Teflon (PTFE) is the most steam-resistant seat material in terms of temperature and purity — it does not introduce contaminants into the steam. Viton (FKM) complements it as a secondary seal with chemical and thermal resistance up to 180 °C. Consequently, the combination of both ensures a hermetic seal in saturated steam for years of continuous operation, where NBR would degrade in weeks.
• Class H Insulation in the Coil: Class H is the highest thermal class in the family — it withstands winding temperatures up to 180 °C. Standard class coils (Class A, B, or F) degrade when in contact with hot steam. Therefore, Class H is the minimum requirement for coils in full-temperature steam service.
• G1/2" (BSP) Thread: The BSP (Gas) thread standard is the most widely used in industrial steam lines in Europe and in industrial installations in Mexico that follow European standards or use imported equipment. Unlike NPT thread — which seals by thread interference — BSP thread seals with a flat gasket, which is more suitable for high-temperature steam where tapered threads can develop micro-leaks.

Operating Principle — NC Steam Solenoid from Zero Pressure

In the de-energized state (coil de-energized): the steam solenoid valve remains in the closed position — the spring holds the plunger against the Teflon seat, blocking the steam flow. When the coil is energized, the electromagnetic field directly displaces the plunger and opens the steam flow. When de-energized, the spring automatically returns the plunger to the closed position.

Direct action operates from zero pressure — without a minimum differential pressure — making it suitable for low-pressure steam systems and during startups when pressure has not yet reached operating values. Consequently, it avoids the problem of pilot-operated solenoids that do not open until the required minimum pressure is reached.

Construction Materials

• Body: Stainless steel or steam-resistant alloy — mechanical support for steam temperatures and pressures up to 1.0 MPa and 180 °C.
• Plunger: Stainless steel — resistant to corrosion from steam and condensates.
• Seat Seal: Teflon (PTFE) + Viton (FKM) — the combination with the highest thermal and chemical resistance in the catalog. Teflon as the primary seat and Viton as the secondary seal, ensuring a hermetic seal in saturated steam up to 180 °C.
• Coil: Class H insulation — highest thermal class available, supports continuous operation in contact with full-temperature steam. IP65 protection against moisture and steam condensates.
• Connection: G1/2" (female BSP) thread — BSP standard for industrial steam lines.
• Orifice: 8 mm — sized for steam flow in 1/2" nominal diameter.

Technical Specifications

G1/2" BSP vs. NPT Thread — why it matters in steam

This steam solenoid valve uses G1/2" BSP (British Standard Pipe) thread, not NPT thread. The distinction is technically important in steam service:

• G (BSP) — parallel thread: Seals with a flat gasket or washer — not by thread interference. Consequently, the seal does not depend on progressive thread tightening and is more reliable in applications with thermal cycles (thread expansion and contraction due to steam heat).
• NPT — tapered thread: Seals by thread interference with sealant. In high-temperature steam, thermal cycles can gradually loosen the thread, leading to micro-leaks.
• G-NPT Adapters: If the installation has NPT threads, Cematic can advise on certified adapters for steam service. Consult with the technical team before installation.

Compatibility and Installation Conditions

• ✅ Saturated steam up to 180 °C and 1.0 MPa — the main application for which it is designed
• ✅ Hot water up to 180 °C — with the same maximum pressure conditions
• ✅ Pressure from zero — suitable for low-pressure steam systems and startups
• ⚠️ Mandatory vertical installation with coil upwards: steam condensate inside the valve must drain into the line; installing with the coil downwards can accumulate condensate and damage the coil
• ⚠️ System purge before first startup: remove accumulated condensation water from the line before energizing the coil to prevent water hammer
• ❌ Superheated steam above 180 °C: exceeds the valve's limit — consult with Cematic's technical team

Applications of the Steam Solenoid Valve

Industrial Steam Heating Systems
The normally closed steam solenoid valve is the standard control and shut-off component in steam heating systems in industrial plants — textile, food, pharmaceutical, paper, and cardboard — where steam distribution to radiators, heat exchangers, or heat coils is controlled by an automation system. Its NC configuration ensures steam shut-off in the event of any electrical failure in the control system, protecting the process from uncontrolled overheating.

Manufacturing Processes with Steam
In food, beverage, canning, and pharmaceutical production where steam is the heating, pasteurization, or sterilization medium, this solenoid valve controls the steam flow to autoclaves, kettles, heat exchangers, and reactors with automatic safety shut-off. Additionally, the Teflon seal ensures that the steam controlled by the valve is not contaminated by seal materials — a requirement in processes where steam directly contacts the product.

Temperature Control in Curing and Drying Processes
In curing ovens, industrial dryers, and drying tunnels where steam is the heat transfer fluid, this NC solenoid regulates the steam inlet to temperature exchangers with immediate response to the temperature controller signal. This allows maintaining process temperature within tight tolerances with high-frequency ON/OFF control.

Industrial Cleaning and CIP/SIP with Steam
In Clean-in-Place (CIP) and Sterilize-in-Place (SIP) systems where steam is the sterilizing agent, this steam solenoid controls the steam flow to process lines with automatic shut-off at the end of the cycle. Consequently, it ensures that the sterilization process is correctly interrupted without manual intervention and without risk of overexposure to steam.

Power Plants and Power Generation
In cogeneration plants, steam turbines, and steam distribution systems in power plants, this NC solenoid acts as an automatic shut-off valve in auxiliary steam lines where the working pressure does not exceed 1.0 MPa. Likewise, its Class H insulation ensures reliable operation in the demanding thermal environments of a boiler room or turbine hall.

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