Three checks on a pneumatic solenoid valve
Solenoid valves look identical from the outside across a wide range of part numbers. Three attributes separate them.
Port size and thread
Usually 1/8, 1/4, 3/8 or 1/2 inch, often expressed in metric equivalents. State the thread standard (BSPP, BSPT or NPT) as well — the same nominal size in a different thread will not seal.
Coil voltage and power
Common values are 24 V DC, 110 V AC and 220 V AC; DC and AC coils are not interchangeable even when the body is the same. Note the wattage too, because a lower-power coil on the same body is a different part number.
Valve function
Written as ports (ways) then positions — 5/2 means five ports and two positions. Getting this notation wrong is how a working valve ends up doing the wrong thing:
- 2/2 — two ports, two positions; simple on/off.
- 3/2 — three ports, two positions; used to drive a single-acting cylinder.
- 5/2 — five ports, two positions; drives a double-acting cylinder and exhausts the unused side.
- 5/3 — five ports, three positions; a centre condition (closed, exhausted or pressurised) holds or frees the actuator.
What the label will not tell you
Manual override type, flow coefficient (Cv/Kv), response time and the electrical connector standard are usually only in the datasheet. If the label is worn, send a photo of the connector and of the machine it is mounted on — the model family is often recognisable from the manifold.
Fitting the wrong function is the most expensive mistake here: a 5/2 substituted for a 5/3 removes the ability to hold the actuator mid-stroke, which on a press is a safety issue, not a convenience one.
Other guides
- How to read an industrial nameplate before asking for a price
- Bearing suffix codes: what ZZ, 2RS, C3 and N mean
- Four measurements before ordering a hydraulic hose
- How to measure an O-ring or oil seal correctly
- How to describe a part you cannot identify
- Compatible, OEM or genuine: what the word on a quotation actually commits you to