Industrial Solenoid Valves

Automated on-off control for water, compressed air, steam, gas and process fluids. Direct-acting and pilot-operated. Interchangeable coils, ATEX versions, wide DN range and voltages.

How solenoid valves work

Solenoid valves are electrically operated valves that use a solenoid (electromagnet) to open or close the fluid passage. When the coil is energised, the magnetic field attracts the movable core, shifting the plunger from its seat and allowing fluid to flow (NC configuration) or vice versa closing it (NO configuration).

They are the fundamental component of every industrial automation system: they receive an electrical signal from PLCs, thermostats, pressure switches, timers or sensors and translate this command into mechanical opening or closing of the flow. Response is fast (typically 10–100 ms), control is binary (on-off) and reliability is high for millions of cycles.

Roffia distributes solenoid valves in brass, stainless steel and engineered polymer, with coils in various voltages (24 V DC, 230 V AC, 110 V AC) and protection ratings up to IP67. Available in 2/2 way (isolation), 3/2 way (diversion), normally closed and normally open configurations.

Industrial solenoid valves — Roffia srl

Direct-acting

  • Opens with solenoid force alone
  • Works even at zero pressure
  • Ideal for viscous fluids and vacuum
  • Typically DN 6–25
  • Very fast response times (<20 ms)
  • Higher power consumption

Pilot-operated (servo-assisted)

  • Solenoid pilot + main plunger
  • Requires minimum differential (0.3–0.5 bar)
  • High flow rates with compact coils
  • DN 10–80 and beyond
  • Low power consumption
  • Ideal for water, air, pressurised fluids

Types and configurations

  • 2/2 way NC — isolation, fail-safe closed
  • 2/2 way NO — fail-safe open
  • 3/2 way — diversion/mixing
  • Bi-stable (latching) — holds position without power
  • Proportional — modulating opening 0–100%

Body materials

  • Brass CW617N — water, air, neutral gases, oil
  • Stainless steel AISI 316 — steam, aggressive fluids, food
  • Engineered polymer (PA, PVDF) — chemical fluids, demin water
  • Cast iron / Carbon steel — high flow, high pressure

Seal materials

  • NBR (Buna-N) — air, water, mineral oils (–10/+90 °C)
  • EPDM — hot water, steam, oxidising fluids (–30/+140 °C)
  • FKM (Viton) — high temperatures, solvents, synthetic oils (–15/+180 °C)
  • PTFE — universal, maximum chemical resistance (–40/+200 °C)

Typical applications

HVAC and building automation

Automatic control of hot and cold water in HVAC systems, fan coils, radiators, irrigation systems and sanitary circuits. Solenoid valves receive commands from room thermostats, BMS systems and timers to manage building comfort and energy efficiency.

Compressed air systems

Control of pneumatic cylinders, actuators, tools and automatic machines. 3/2 and 5/2 way solenoid valves control piston movement in both directions. Fast response times (<50 ms) and high switching frequency are essential for production efficiency.

Process plants and steam

Control of process steam, condensate and thermal fluids in chemical-pharmaceutical, food and manufacturing plants. Steam service requires specific solenoid valves with PTFE/FKM seals and stainless steel bodies.

Fire protection and safety systems

NC solenoid valves on sprinkler and deluge circuits: normally closed, they open on command from the fire control panel to flood the protected area. UL/FM certified versions available. For combustible gases (natural gas, LPG), solenoid valves with EN 161 approval for safety shut-off.

Roffia solenoid valve range

Water and air
Brass/stainless, DN 6–50
Steam
Stainless, PTFE, DN 10–40
Combustible gases
EN 161, NC, manual reset
Aggressive fluids
PVDF, PP, PTFE
High pressure
Up to PN 40
ATEX
Zone 1 and 2, explosion-proof
Proportional
0–10 V / 4–20 mA control
Isolated diaphragm
Ultra-pure fluids, pharma

Frequently asked questions

What is the difference between direct-acting and pilot-operated solenoid valves?
A direct-acting solenoid valve uses only the force of the solenoid to open or close the orifice — it can operate even at zero pressure or with viscous fluids, but is limited to small sizes (typically up to DN 25) due to the finite force of the coil. A pilot-operated (servo-assisted) solenoid valve uses the differential pressure of the fluid itself to move the main plunger; the solenoid only controls a small pilot valve. This allows large flow rates with compact coils and low power consumption, but requires a minimum differential pressure (typically 0.3–0.5 bar) to function. For vacuum or low-pressure applications, choose direct-acting; for normal-pressure process lines, pilot-operated valves are more economical and compact.
How do I choose the voltage and IP rating for a solenoid valve?
Coil voltage depends on the available electrical system: 24 V DC is standard for PLC control systems and industrial automation (low power, inherently safe); 230 V AC is common in European civil and industrial installations; 110 V AC is used in systems following US/ANSI standards. For wet environments, outdoor installations or where water jets are possible, select IP65 or higher protection. For potentially explosive atmospheres (petrochemical, biogas, solvents), ATEX-certified coils are required. Roffia supplies solenoid valves with interchangeable coils — you can order the valve body and then select the coil suited to your voltage and IP rating.
Can I use a standard solenoid valve for steam?
No. Generic solenoid valves for water or air are not suitable for steam service for several reasons: (1) standard NBR or EPDM seals degrade quickly at high temperatures; (2) water hammer from flash condensate can damage the plunger; (3) the coil may overheat if not designed for radiated heat. Steam service requires specific solenoid valves with: brass or stainless steel body, PTFE or high-temperature FKM seals, piston design (more robust than diaphragm) and class H coil insulation (180 °C). Roffia stocks solenoid valves for saturated steam up to 180 °C and 10 bar, with coils certified for continuous duty.
What does NC (normally closed) and NO (normally open) mean?
NC (Normally Closed): the valve is closed when the coil is de-energised; it opens when powered. This is the most common configuration — fluid flows only when the control system commands it, and in case of power failure the valve closes automatically (fail-safe closed). NO (Normally Open): the valve is open at rest and closes when the coil is energised — useful when flow must continue in the absence of power (fail-safe open), such as emergency cooling systems. Bi-stable (latching) valves also exist: they hold the last position without continuous power, controlled by pulses.
How often should a solenoid valve be replaced?
Service life depends on construction type, fluid and switching frequency. Quality industrial solenoid valves have a typical life of 1–10 million cycles. Wear parts include: diaphragm or plunger (mechanical fatigue, chemical attack), seat (erosion), coil (overheating). To extend life: (1) install upstream filters to prevent particles blocking the plunger; (2) verify chemical compatibility of seals with the fluid; (3) avoid excessive switching frequencies with coils not designed for continuous duty. Roffia supplies seal replacement kits and spare coils for all major solenoid valves in our catalogue.

Request a solenoid valve quote

Please provide fluid, DN, pressure, temperature, coil voltage and NC/NO configuration. We will recommend the most suitable solenoid valve with a quotation within 24 hours.

Richiedi preventivo Chiamaci ora
Privacy Policy Cookie Policy