Normally Open Brass Solenoid Valve — Direct Acting, High Flow

Cematic's normally open solenoid valve is the ON/OFF control component for systems where the fail-safe state in the event of an electrical failure is the free flow of fluid — unlike NC (normally closed) solenoids, this solenoid valve maintains flow when the coil is de-energized and interrupts it when it receives an electrical signal. Therefore, it is the correct choice in refrigeration, irrigation, process control, and dosing applications where cutting off fluid in the event of a failure represents an operational or safety risk.

Its direct acting, high flow design allows it to handle significant flow rates in 1½" and 2" diameters without relying on system differential pressure to operate — consequently, it functions correctly even with zero differential pressure, unlike pilot-operated solenoids that require a minimum upstream pressure to open.

Operating Principle — Normally Open (NO)

In the de-energized state (coil de-energized): the valve remains open — fluid flows freely through the orifice. When the coil is energized, the electromagnetic field pushes the plunger downwards, closing the fluid path. When de-energized, the internal spring returns the plunger to its original position and flow is automatically restored.

Therefore, this configuration is suitable when:

• Flow must continue in the event of a power failure (safe state = open)
• The valve operates energized most of the time and opens when de-energized
• Automatic opening is required in case of an unscheduled power outage

For applications where the safe state is fluid cutoff, the correct option is the normally closed (NC) solenoid valve →

Construction Materials

• Body: Zinc-plated brass — corrosion resistance for water, air, mineral oil, and non-aggressive fluids. Robust construction for continuous industrial use.
• Plunger: Stainless steel with optimized mass for quick response and reliable spring-action opening.
• Seat Seal: NBR (Nitrile) — compatible with water, compressed air, and mineral hydraulic oils. For aggressive fluids, check compatibility with Cematic's technical team.
• Coil: Resin encapsulated, IP65 protection — suitable for humid environments and industrial dust.
• Connection: Female NPT thread — industrial standard in Mexico, compatible with steel, copper, and PVC pipes with adapters.

Technical Specifications

Voltage Selection

• 110 VAC: For installations in Mexico and the United States with 110 V single-phase circuits available on site. This is the most common voltage in local industrial installations without a dedicated DC source.
• 220 VAC: For power panels with bi-phase distribution or installations where a 220 V circuit is available at the installation point.

Fluid Compatibility

• ✅ Process water and potable water — up to 0.7 MPa (7 bar) and 80 °C
• ✅ Compressed air — up to 1.0 MPa (10 bar), industrial pneumatic service
• ✅ Mineral hydraulic oils — up to 0.7 MPa, compatible with NBR seal
• ✅ Cooling water — industrial cooling and HVAC systems
• ⚠️ Fluids with suspended particles: it is recommended to install an upstream inline filter to protect the seal and orifice
• ❌ Acids, chlorinated solvents, corrosive fluids: use a solenoid with a stainless steel body and Viton seal

Main Industrial Applications

Refrigeration and HVAC systems
In industrial refrigeration circuits, the normally open solenoid valve maintains the flow of refrigerant or cooling water while the system operates, and cuts it off when it receives a closing signal from the controller. Furthermore, in the event of an unscheduled power outage, the flow is automatically restored, preventing overheating of the protected equipment.

Industrial process control and dosing
In manufacturing lines where continuous flow is the normal operating condition and cutoff is the exception, this NO solenoid valve reduces coil energy consumption by being de-energized for most of the cycle. Therefore, it represents an energy advantage over NC solenoids in continuous flow processes with brief cutoffs.

Technified irrigation systems
In gravity or low-pressure irrigation installations where water supply must flow by default and be cut off in specific areas according to the irrigation schedule, the NO configuration is the standard choice. It also ensures that an electrical failure does not interrupt irrigation during critical crop stages.

Industrial washing and cleaning equipment
In washing tunnels, industrial washers, and CIP cleaning equipment, the NO solenoid valve controls the opening and closing of rinse water and cleaning solutions, allowing triggering from a PLC or timer with immediate response.

Dispensers and machine tools
In liquid dispensers and machine tools with coolant supply, this high-flow, direct-acting solenoid valve allows handling the required flow rates in 1½" and 2" diameters without significant pressure drops in the line.

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

Technical Data Sheet