Normally open passes flow when the coil is not energized. Apply power and the plunger seats to stop the flow. Direct-acting designs don't need a line differential, so they work on low-pressure, vacuum, or gravity feed. Many allow bidirectional flow, which helps with simple fill, vent, and drain circuits.

Choose normally open when you want flow to continue during outages, cooling loops, tank breathers, and safe-to-fail vents.

If you need the opposite behavior, pick a normally closed model. For efficiency and quick actuation, direct-acting stainless steel or brass with seals (EPDM, FKM, PTFE) suit air, water, and light oil. Ask about the duty cycle if the coil stays energized.

Part numbers are the most helpful. If you do not have part numbers, there are a few numbers that prevent misorders:

– Media and temperature range.
– Min/max pressure and required Cv.
– Port size/thread for your normally open solenoid valve (1/81/2 NPT).
– Body/seal materials (brass, 303 SS; EPDM, FKM, PTFE).
– Coil voltage/connector (12 VDC, 24/60 VAC, 120/60 VAC; DIN or ½ conduit).

Yes – if the specific normally open 2-way solenoid valve is rated. Match materials and seals to the media, then confirm temperature/pressure limits and orifice. Mount the coil upright, and add an upstream strainer. For combustible gas, verify the leakage class and approvals. When in doubt, share the tag or part number for a quick check.

Most issues trace to setup, not the valve:

– No strainer; debris keeps the seat from sealing.
– Reverse flow; follow the body arrow.
– Voltage drop on long runs; upsize wire.
– Orientation ignored; condensate soaks the coil.