Normally Open Stainless Steel Piloted Solenoid Valve — SS304, NBR, 2/2-Way

Cematic's normally open stainless steel piloted solenoid valve combines the piloted operating principle—high flow with low coil power consumption—with the corrosion resistance of 304 stainless steel, making it the right choice for industrial processes where brass is not compatible with the fluid or where material purity in contact with the process is a requirement. Available in sizes from 1/2" to 2", it covers the flow range for medium and large installations where a direct-acting solenoid would require high-consumption coils and larger solenoids.

Its normally open configuration maintains free flow when the coil is de-energized and interrupts it upon receiving an electrical signal. Therefore, it is the standard choice when the process's safe state is continuous flow and cutoff occurs by controller signal—refrigeration systems, water distribution, HVAC, and processes where interrupting the fluid due to an electrical failure would cause equipment damage.

Why stainless steel over brass in a piloted solenoid

The piloted operating principle is identical in brass and SS304—the difference is exclusively in body material and its implications for the process:

• Fluid purity: SS304 does not contribute copper or zinc ions to the fluid—unlike brass. Therefore, it is the correct material for purified water, demineralized water, utilities in food and pharmaceutical plants, and any process where metallic contamination is unacceptable.
• Chemical resistance: SS304 resists moderate aqueous solutions, diluted acids, and process fluids that would degrade brass. Consequently, it expands the range of possible industrial applications without the need for higher-cost anticorrosive bodies.
• Diameter range: This SS304 version is available in 1/2", 3/4", 1", 1¼", 1½" and 2"—significantly wider than the brass version (only 1/2" and 1"). Therefore, it is Cematic's only piloted NO option for diameters from 1¼" to 2" in this catalog.
• Maximum pressure: 0.7 MPa (7 bar) vs. 1.0 MPa for the brass version. For pressures between 0.7 and 1.0 MPa in SS304, consult Cematic's technical team.

Operating principle — Piloted Normally Open (NO)

In the de-energized state (coil de-energized): the pilot is open, the pressure in the upper chamber of the main piston is balanced with the inlet pressure, and the spring keeps the piston in the open position—fluid flows freely. When the coil is energized, the pilot closes, the pressure in the upper chamber drops, and the inlet pressure on the lower face of the piston pushes it upward, closing the main passage. When de-energized, the pilot reopens and the cycle restarts.

Critical operating condition: A minimum differential pressure of 0.05 MPa (0.5 bar / 10 psi) between inlet and outlet is required for the piloted mechanism to function correctly. If the system can operate with zero differential pressure or start without pressure, the correct option is the direct-acting NO solenoid in SS304 →

Construction materials

• Body: 304 Stainless Steel (SS304) — corrosion resistance for process water, aqueous solutions, moderately aggressive industrial fluids, and applications where material purity in contact with the fluid is a requirement.
• Piston and pilot: Stainless steel — corrosion resistant to process fluid.
• Seat seal: NBR (Nitrile) — compatible with water, compressed air, and mineral hydraulic oils up to 80 °C. For fluids requiring Viton, consult Cematic's technical team.
• Coil: Encapsulated, IP65 protection — suitable for humid environments and with industrial dust. Low power consumption thanks to the piloted principle.
• Connection: Female NPT thread — industrial standard in Mexico, compatible with stainless steel, carbon steel, and PVC pipes with adapters.

Technical specifications

Voltage selection

• 24 VDC: Standard in industrial control cabinets with PLC and DC power supply. The most common option in new installations and modern automated systems.
• 24 VAC: For low-voltage AC control systems—common in residential and mid-range industrial irrigation and HVAC controllers. Available in 1½" diameters.
• 110 VAC: For 110 V single-phase circuits available in the field—the most widespread voltage in industry in Mexico and the United States.
• 220 VAC: For power distribution boards with bi-phase distribution or European standard voltage.

Fluid compatibility

• ✅ Purified water and demineralized water — no metallic ion contribution from SS304, suitable for processes requiring fluid purity
• ✅ Process water and cooling water — up to 0.7 MPa and 80 °C
• ✅ Compressed air — up to 0.7 MPa, pneumatic and instrumentation service
• ✅ Mineral hydraulic oils — compatible with NBR seal up to 80 °C
• ✅ Moderate aqueous solutions — compatible with SS304 and NBR; verify concentration and temperature with technical team
• ⚠️ Differential pressure less than 0.05 MPa: the piloted valve does not operate correctly—use direct-acting NO solenoid in SS304 →
• ⚠️ Pressure above 0.7 MPa: exceeds the limit of this piloted version—consult Cematic's technical team
• ⚠️ Fluids with suspended solids: install an upstream line filter—the pilot orifice is sensitive to particles
• ⚠️ Temperature above 80 °C: NBR seal degrades—verify availability of Viton seal version with the technical team
• ❌ Concentrated acids, chlorinated solvents, fluids with high chlorides: SS304 may be insufficient—consult need for SS316

When to choose this valve vs. other Cematic piloted NO valves

• Piloted NO Brass + NBR: For water, air, and general oils where brass is compatible. Pressure up to 1.0 MPa. Only 1/2" and 1". See piloted NO solenoid in brass →
• Piloted NO SS304 + NBR (this product): For fluids requiring a stainless steel body—fluid purity, moderate chemical resistance, or diameters from 1¼" to 2". Pressure up to 0.7 MPa.

Main industrial applications

Purified water and utilities in food and pharmaceutical industries
In plants where the fluid in contact with the valve is purified water, water for pharmaceutical processes, or food production utilities, the SS304 body ensures no copper or zinc ion contribution to the fluid. Additionally, the NO configuration maintains continuous flow in the event of any electrical failure, protecting processes from unscheduled service water outages.

Irrigation systems and industrial water distribution in large diameters
In irrigation installations with distribution through 1¼", 1½" or 2" pipes where brass is not the specified material or where greater corrosion resistance is required, this normally open stainless steel piloted solenoid valve is the only Cematic piloted NO option available in these diameters. Consequently, it allows controlling large flows with low-consumption coils without needing to escalate to higher-cost motorized valves.

HVAC systems and industrial refrigeration with process water
In cold and hot water circuits for air conditioning and industrial refrigeration where the material specification requires stainless steel—due to the corrosivity of the process water or regulatory requirements of the installation—this piloted NO solenoid valve controls the flow of each zone with low power consumption and continuous flow in case of control failure.

Flow control in medium and large flow industrial processes
In process lines with diameters from 3/4" to 2" where the differential pressure always exceeds 0.5 bar, this piloted solenoid handles significantly higher flows than a direct-acting solenoid of the same diameter, with lower power coils. Also, the SS304 body ensures compatibility with process fluids that exclude brass for chemical or purity reasons.

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

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