Stainless Steel Normally Closed Solenoid Valve — SS304, Viton Seal, High Temperature up to 180 °C

Cematic's normally closed stainless steel solenoid valve combines the two most demanding attributes of industrial automation: fail-safe closure in the event of an electrical failure (NC) and the chemical and thermal resistance of 304 stainless steel with a Viton seal. For this reason, it is the correct solenoid valve when the process simultaneously requires automatic cut-off in case of power failure and operation with aggressive fluids or at temperatures above 80 °C — conditions where the NC brass solenoid with NBR seal is not sufficient.

Its direct acting, high-flow design ensures reliable operation with zero differential pressure, without relying on line pressure to open — unlike pilot-operated solenoids. Consequently, it is suitable for systems with variable pressure or cold starts where differential pressure may be zero at the beginning of the cycle.

Operating Principle — Normally Closed (NC)

In the de-energized state (coil de-energized): the valve remains closed — the internal spring keeps the plunger on the seat, blocking fluid flow. When the coil is energized, the electromagnetic field lifts the plunger, opening the flow. When de-energized, the spring automatically returns the plunger to the closed position.

This configuration is correct when:

• The fluid must be cut off in the event of an electrical power failure (safe state = closed)
• The process operates with high-temperature or chemically aggressive fluids that rule out brass or NBR seals
• Automatic shut-off is required in steam systems, hot water, synthetic oils, or corrosive process fluids
• The process standard requires a stainless steel body for fluid purity (purified water, pharmaceutical utilities)

If your process requires automatic opening in the event of electrical failure with SS304 and Viton, the correct option is the normally open stainless steel solenoid valve (NO) →

Why SS304 + Viton over Brass + NBR in NC configuration?

The NC brass solenoid with NBR seal covers most standard fluid control applications up to 80 °C. However, there are process conditions where this combination is insufficient, and the SS304 + Viton alternative is the correct one:

• Temperatures above 80 °C: The NBR seal loses elasticity and begins to degrade above 80–90 °C. Viton, on the other hand, maintains its integrity up to 180 °C — which enables this valve for low-pressure steam, hot water, high-temperature oils, and thermal process fluids.
• Fluids that degrade brass: SS304 resists process water, moderate aqueous solutions, and many industrial fluids that attack zinc-plated brass. In addition, Viton is compatible with synthetic oils, fuels, and some solvents that would destroy NBR in a few weeks.
• Fluid purity requirements: SS304 does not contribute copper or zinc ions to the fluid. Therefore, it is the correct material for purified water, utilities in food or pharmaceutical production areas, and any process where metallic contamination is unacceptable.

Construction Materials

• Body: Stainless steel 304 (SS304) — corrosion resistance for water, steam, aqueous solutions, and industrial process fluids. No contribution of metallic ions to the fluid.
• Plunger: Stainless steel — corrosion resistance by the fluid and optimized mass for reliable spring closure and quick electromagnetic opening.
• Seat Seal: Viton (FKM) — compatible with temperatures up to 180 °C, synthetic oils, fuels, aggressive process fluids, and most non-halogenated industrial solvents. Significantly more resistant than NBR in high-temperature and aggressive fluid applications.
• Coil: Resin encapsulated, IP65 protection — suitable for humid environments, with condensation and industrial dust.
• Connection: Female NPT thread — industrial standard in Mexico, compatible with stainless steel, carbon steel, and copper pipes.

Technical Specifications

Voltage Selection

• 24 VDC: Standard in industrial control cabinets with PLC and DC power supply. Ideal safety voltage for new installations and modern automated systems. Available in all diameters.
• 110 VAC: For installations with 110 V single-phase circuits in the field — the most widespread voltage in industry in Mexico and the United States. Available in all diameters.
• 220 VAC: For power panels with bi-phase distribution or installations with European voltage standard. Available in all diameters.

Fluid Compatibility

• ✅ Low pressure steam up to 180 °C — enabled by Viton seal; standard NBR does not withstand this temperature
• ✅ Hot water up to 180 °C — heating systems, heat exchangers, and industrial thermal processes
• ✅ Purified water and process water — no contribution of metallic ions from the SS304 body
• ✅ Compressed air up to 1.0 MPa — high-pressure industrial pneumatic service
• ✅ Hydraulic and synthetic oils — Viton resists a wider range of oils than NBR
• ✅ Fuels and mineral oils — verify area classification before installation
• ⚠️ Fluids with suspended solids: install upstream line filter to protect seal and orifice
• ❌ Concentrated acids, halogenated solvents, high chloride fluids at high temperatures: SS304 may be insufficient — consult Cematic's technical team for SS316 requirements

Main Industrial Applications

Steam and high-temperature process fluid control
This is the differentiating application of this solenoid valve compared to the NC brass solenoid. The normally closed stainless steel solenoid valve with Viton seal operates reliably in low-pressure steam lines, superheated water, and thermal transfer fluids up to 180 °C, with automatic shut-off in the event of electrical failure. For this reason, it is the standard component in industrial heating, sterilization, and CIP/SIP processes where the fluid temperature exceeds 90 °C and the safe state requires closure.

Dosing of aggressive fluids in industrial processes
In chemical, petrochemical, and manufacturing plants where the process fluid degrades NBR or brass, the SS304 + Viton combination in NC configuration guarantees safety closure in the event of electrical failure and the necessary chemical resistance for continuous operation. Likewise, SS304 prevents metallic contamination of the process fluid in sensitive applications.

Purified water and utilities in the food and pharmaceutical industry
The SS304 body does not contribute copper or zinc ions to the fluid — unlike brass — so this NC solenoid valve is suitable for controlling purified water, water for injection, and industrial utilities in production areas where metallic contamination must be controlled and automatic shut-off in the event of failure is a process safety requirement.

CIP and SIP systems with hot solutions
In Clean-In-Place (CIP) and Sterilize-In-Place (SIP) processes with hot alkaline or acidic solutions, the NC + SS304 + Viton combination simultaneously solves the three requirements: automatic closure at the end of the cycle, chemical resistance to the cleaning solution, and thermal resistance to CIP/SIP process temperatures. Consequently, it reduces maintenance costs compared to solenoids with NBR seals under these conditions.

Control of synthetic oils and organic process fluids
In centralized lubrication systems, thermal transfer oil circuits, and processes with high-temperature organic fluids, the Viton seal resists chemical degradation that would render an NBR seal useless in a few weeks. In addition, the NC closure ensures that the fluid is automatically cut off in the event of any electrical failure of the control system.

For the complete range of solenoid valves, see solenoid valves collection →

Technical Data Sheet