Views: 0 Author: Site Editor Publish Time: 2026-09-09 Origin: Site
In modern industrial automation, space is often at a premium. Equipment designers are constantly challenged to pack more functionality into smaller footprints, and pneumatic systems are no exception. Traditional solenoid valves, while reliable, often occupy too much space for compact machinery, medical devices, or textile equipment. The WAALPC 331 Series 15mm miniature solenoid valve addresses this challenge directly — delivering the performance of a full-sized valve in a package just 15mm wide.
The 331 Series is a family of 3/2-way direct acting solenoid valves available in both normally closed (NC) and normally open (NO) configurations. With a compact 15mm width, multiple orifice sizes (1.0mm, 1.3mm, 1.5mm, and 2.0mm), versatile voltage options, and a wide range of socket connection types, the 331 Series provides a flexible, reliable solution for applications where space, weight, and precision are critical.
This guide covers the 331 Series product family, including ordering code structure, technical specifications, working principles, application scenarios, installation guidelines, and maintenance best practices.
A solenoid valve is an electromechanically operated valve that uses an electromagnetic solenoid coil to control the opening and closing of the valve mechanism. In pneumatic systems, solenoid valves direct the flow of compressed air to actuate cylinders, valves, and other pneumatic devices.
The 331 Series is a 3/2-way (three-port, two-position) direct acting solenoid valve — meaning it has three ports (inlet, outlet, and exhaust) and two operating positions (energized and de-energized). The direct acting design means the solenoid directly operates the valve mechanism without requiring pilot pressure, allowing the valve to function even at zero pressure differential.
Compact 15mm width: Ideal for space-constrained installations
Direct acting operation: Functions at zero pressure, no minimum operating pressure required
3/2-way configuration: Available in normally closed (NC) or normally open (NO)
Multiple orifice sizes: 1.0mm, 1.3mm, 1.5mm, and 2.0mm options
Wide pressure range: Up to 10 bar (1.0 MPa)
Fast response: Open <10ms, close <12ms
Flexible connectivity: Multiple socket connection types and wiring options
Low power consumption: Down to 0.5W with energy-saving coil option
The 331 Series ordering code provides comprehensive information about the valve configuration. Understanding this code is essential for specifying the correct valve for your application.
331 - C 4 S J - L
Position | Symbol | Description | Options |
|---|---|---|---|
① | Series | 331 Series | 331 |
② | Function | Valve function | C = Normally Closed (NC), O = Normally Open (NO) |
③ | Voltage | Coil voltage | 4 = DC24V, 2 = DC12V, 6 = DC6V, 8 = AC24V, 1 = Special voltage |
④ | Socket connection | Connection type | Z = 90° Right Angle Type, S = 90° Horizontal Type, C = Insert Type, M = Insert Nut Type, X = Direct Lead Type |
⑤ | Circuit board type | Circuit board option | Blank = Without circuit board, P = With two-way indicator, G = With lamp + overvoltage protection, J = With energy-saving template |
⑥ | Wiring length | Cable length | Blank = No wiring, A = 125mm, B = 300mm, C = Special requirements |
⑦ | Plug type | Connector plug | Blank = No plug, 1 = A1, 2 = A2, 3 = A3, 4 = A4, 5 = A5, 6 = A6, 7 = A7, 8 = A8, 9 = A9 |
⑧ | Coil power | Power consumption | Blank = 2.5W, L = Energy-saving 0.5W, H = 1.0W, T = Special power |
Model | Configuration |
|---|---|
331-C4ZP | NC, DC24V, 90° right angle socket, with two-way indicator |
331-C4SJ-L | NC, DC24V, 90° horizontal socket, with energy-saving template, 0.5W |
NC, DC24V, insert type socket | |
331-C4XA1 | NC, DC24V, direct lead type, with A1 plug |
331-04ZP | NO, DC24V, 90° right angle socket, with two-way indicator |
Parameter | Specification |
|---|---|
Valve Type | 3/2-way (3-port, 2-position) |
Function | Normally Closed (NC) or Normally Open (NO) |
Operating Method | Direct acting (cut-off type) |
Operating Pressure (NC) | 0–7 bar (0–0.7 MPa) standard; 0–10 bar (0–1.0 MPa) available |
Operating Pressure (NO) | 0–6 bar (0–0.6 MPa) |
Orifice Sizes | 1.0mm (small power or 10 bar version), 1.3mm, 1.5mm, 2.0mm (large flow) |
Response Time | Open <10ms, close <12ms |
Working Medium | Filtered compressed air (ISO 8573-1:2010 [7:4:4] or equivalent)or inert gas |
Medium & Ambient Temperature | –5°C to 50°C (non-freezing) |
Installation Method | Free installation |
Work Cycle | 100% continuous operation |
IP Rating | IP50 (standard); IP65 (direct lead type) |
Note on Filtration: For reliable operation, the compressed air should be filtered to meet ISO 8573-1:2010 Class [7:4:4] or better.
Parameter | Specification |
|---|---|
Voltage Options | DC6V, DC12V, DC24V, AC24V (other voltages available upon request) |
Voltage Tolerance | ±10% |
Power Consumption (Standard) | 2.5W |
Power Consumption (Energy-saving) | 0.5W (L option) |
Power Consumption (1.0W option) | 1.0W (H option) |
Electrical Connections | Socket type (Z/S/C/M) or direct lead (X) |
Protection Class | IP50 (standard), IP65 (direct lead type) |
Model Type | Width | Height | Depth |
|---|---|---|---|
331-C4SJ-L (horizontal socket) | 15.2mm | 26.5mm | 20.6mm |
331-C4ZP (right angle socket) | 15.2mm | 20.6mm | — |
331-C4C (insert type) | 15.2mm | 20.6mm | — |
331-C4XJ (direct lead) | 15.2mm | 30.2mm | 20.6mm |
Port Identification:
Port 1 (P) : Pressure inlet
Port 2 (A) : Working port (outlet to actuator)
Port 3 (R) : Exhaust port
The 331 Series operates on the direct acting principle. Unlike pilot-operated valves that require a minimum pressure differential to function, direct acting valves use the electromagnetic force of the solenoid coil to directly move the valve mechanism.
How it works (Normally Closed – NC):
De-energized state (default): The valve is closed. A spring holds the valve mechanism against the valve seat, blocking the flow from the inlet (P) to the outlet (A). Port A is connected to exhaust (R).
Energized state: When the solenoid coil is energized, the electromagnetic field attracts the armature (plunger). This overcomes the spring force and lifts the valve mechanism off the seat.
Flow path: With the valve open, the inlet (P) is connected to the outlet (A), allowing compressed air to flow to the actuator. The exhaust (R) is blocked.
De-energization: When power is removed, the spring returns the valve mechanism to its closed position, reconnecting port A to exhaust (R) and blocking the inlet.
How it works (Normally Open – NO):
The normally open configuration operates in reverse:
De-energized: The valve is open (P → A)
Energized: The valve closes (A → R, P blocked)
A 3/2-way valve has three ports and two positions:
Port | Function |
|---|---|
1 (P) | Pressure inlet (supply) |
2 (A) | Working port (to actuator) |
3 (R) | Exhaust port (to atmosphere) |
NC Configuration:
De-energized: P blocked, A → R (actuator exhausts)
Energized: P → A, R blocked (actuator pressurizes)
NO Configuration:
De-energized: P → A, R blocked (actuator pressurizes)
Energized: P blocked, A → R (actuator exhausts)
With a width of only 15mm, the 331 Series is one of the most compact solenoid valves available. This miniature footprint enables integration into densely packed equipment where traditional valves cannot fit — such as textile machinery, medical devices, and electronics assembly equipment.
The direct acting design offers several advantages:
Zero minimum operating pressure: Functions even when the supply pressure is zero
Fast response: Open <10ms, close <12ms
Simple construction: Fewer moving parts than pilot-operated valves
High reliability: Consistent performance regardless of pressure fluctuations
The 331 Series is available with four orifice sizes to match different flow requirements:
Orifice Size | Best For |
|---|---|
1.0mm | Small power applications, high-pressure (10 bar) versions |
1.3mm | Standard flow applications |
1.5mm | Medium flow applications |
2.0mm | Large flow (high flow capacity) applications |
The 331 Series offers five socket connection methods to suit different installation requirements:
Connection Type | Code | Description |
|---|---|---|
90° Right Angle | Z | Compact, low-profile connection |
90° Horizontal | S | Side-entry connection |
Insert Type | C | Push-on connection |
Insert Nut Type | M | Screw-lock connection |
Direct Lead | X | Wired connection, IP65 rated |
The 331 Series offers three circuit board options:
Option | Code | Feature |
|---|---|---|
Standard | Blank | No circuit board |
With indicator | P | Two-way LED indicator for visual status |
With protection | G | LED indicator + overvoltage protection circuit |
Energy-saving | J | Energy-saving template for reduced power consumption |
The 331 Series offers energy-saving coil options down to 0.5W (L option), significantly reducing heat generation and power consumption — ideal for battery-powered or energy-sensitive applications.
With a 100% continuous duty cycle and fast response times, the 331 Series is designed for demanding, high-cycle applications.
The 331 Series 15mm miniature solenoid valves are used across a wide range of industries where compact size, fast response, and reliability are essential:
Sock knitting machines: Controlling yarn tensioners, pattern selectors, and needle actuators
Carpet weaving machines: Pneumatic control of loom mechanisms
Hosiery machines: Precise air flow control for high-speed knitting operations
Oxygen generators: Controlling oxygen flow in concentrators
Respiratory equipment: Precise air pressure control
Diagnostic instruments: Pneumatic actuation in analyzers
PCB assembly: Controlling vacuum pick-and-place systems
Semiconductor equipment: Clean air flow control
SMT (Surface Mount Technology) : Component placement systems
Pilot control: Directly operating larger pilot-operated valves
Compact machinery: Space-constrained pneumatic systems
Robotics: End-of-arm tooling control
Packaging equipment: High-speed pneumatic actuation
Industry | Application |
|---|---|
Automotive | Assembly line pneumatic tools, test fixtures |
Food & Beverage | Packaging machinery, filling equipment (with appropriate filtration) |
Printing | Paper handling, registration systems |
Laboratory | Analytical instruments, sample handling |
Before installing a 331 Series solenoid valve:
Verify the model: Confirm function (NC/NO), voltage, connection type, and orifice size match your requirements
Check the air supply: Ensure air is filtered to ISO 8573-1:2010 Class [7:4:4] or better
Inspect the valve: Check for any shipping damage
Verify electrical supply: Confirm voltage is within ±10% of the coil rating
Mount the valve: Install in any orientation (free installation)
Connect piping: Connect port P (1) to the supply, port A (2) to the actuator, and port R (3) to exhaust
Apply thread sealant: For threaded connections, use PTFE tape on male threads only, leaving the first thread bare
Tighten connections: Do not overtighten
Select connection type: Choose from socket (Z/S/C/M) or direct lead (X)
Connect wiring: Follow the wiring diagram for the specific connection type
Verify polarity: For DC models, ensure correct polarity
Check grounding: Ensure proper grounding for safety
IP rating consideration: For IP65 protection, use the direct lead type (X)
Do | Do Not |
|---|---|
Use filtered air (ISO 8573-1 Class [7:4:4] or better) | Use unfiltered or contaminated air |
Match voltage to coil specification | Apply incorrect voltage |
Use proper thread sealant | Allow sealant debris to enter the valve |
Depressurize before maintenance | Disassemble under pressure |
Keep within temperature range (–5°C to 50°C) | Exceed the rated temperature |
Frequency | Task |
|---|---|
Daily | Visual inspection for air leaks; check electrical connections |
Monthly | Verify valve operation; check for unusual noise or heat |
Quarterly | Inspect for signs of wear or contamination |
Annually | Replace seals if showing signs of aging |
Symptom | Possible Cause | Solution |
|---|---|---|
Valve does not shift | No power; incorrect voltage; coil burned out | Check power supply; verify voltage; replace coil |
Air leakage | Damaged seals; loose connections | Replace seals; tighten connections |
Slow response | Low voltage; contaminated air | Check power supply; clean/replace filter |
Coil overheats | Incorrect voltage; continuous duty exceeded | Verify voltage; check duty cycle |
Valve chatters | Low voltage; insufficient current | Check power supply |
Internal leakage | Worn valve mechanism | Replace valve |
No flow | Blocked port; incorrect connection | Check port connections; clear blockage |
Factors affecting 331 Series valve service life:
Air quality: Clean, dry, filtered air extends seal and valve life
Operating frequency: Higher cycling rates may accelerate wear
Ambient conditions: Temperature extremes and contaminants reduce life
Power supply: Stable voltage prevents coil damage
Proper filtration: Meeting ISO 8573-1:2010 Class [7:4:4] or better is essential
Factor | Consideration |
|---|---|
Function | Normally Closed (NC) or Normally Open (NO) |
Voltage | DC6V, DC12V, DC24V, AC24V, or special voltage |
Orifice size | 1.0mm, 1.3mm, 1.5mm, or 2.0mm — match to flow requirement |
Socket connection | Z (right angle), S (horizontal), C (insert), M (insert nut), or X (direct lead) |
Circuit board | Blank (none), P (indicator), G (indicator + protection), or J (energy-saving) |
Wiring length | Blank (none), A (125mm), B (300mm), or C (special) |
Plug type | A1–A9 or blank |
Coil power | Blank (2.5W), L (0.5W energy-saving), H (1.0W), or T (special) |
Application: Controlling a small pneumatic cylinder in a sock knitting machine, requiring NC function, DC24V, moderate flow, compact installation with right-angle socket.
Recommended model: 331-C4Z (NC, DC24V, right angle socket, standard circuit board)
For energy-sensitive applications: 331-C4ZJ-L (NC, DC24V, right angle socket, energy-saving template, 0.5W)
Requirement | Recommended |
|---|---|
Valve should be closed when power is off (fail-safe) | NC (C) |
Valve should be open when power is off | NO (O) |
Most industrial pneumatic applications | NC (C) |
WAALPC 331 Series 15mm miniature solenoid valves offer a compelling combination of compactness, performance, and versatility:
✅ Ultra-compact 15mm width — Ideal for space-constrained applications
✅ Direct acting — Functions at zero pressure, no minimum pressure required
✅ Fast response — Open <10ms, close <12ms
✅ Multiple orifice sizes — 1.0mm, 1.3mm, 1.5mm, and 2.0mm options
✅ Wide pressure range — Up to 10 bar (1.0 MPa)
✅ Flexible connectivity — Five socket connection types and direct lead
✅ Multiple voltage options — DC6V, DC12V, DC24V, AC24V, and special voltages
✅ Energy-saving options — Down to 0.5W power consumption
✅ Circuit board options — Indicator, overvoltage protection, and energy-saving templates
✅ IP65 available — Direct lead type provides IP65 protection
✅ 100% continuous duty — Designed for demanding high-cycle applications
✅ Proven applications — Widely used in textile machinery, medical devices, and industrial automation
The WAALPC 331 Series 15mm miniature solenoid valve delivers the performance and reliability of a full-sized valve in a remarkably compact 15mm package. With its direct acting design, multiple orifice sizes, flexible connectivity options, and wide voltage and power choices, the 331 Series provides a versatile solution for a vast range of applications where space and precision are critical.
Key takeaways:
Type: 3/2-way direct acting solenoid valve
Functions: Normally Closed (NC) or Normally Open (NO)
Width: Only 15mm — one of the most compact valves available
Orifice sizes: 1.0mm, 1.3mm, 1.5mm, and 2.0mm
Pressure range: Up to 10 bar (1.0 MPa)
Response time: Open <10ms, close <12ms
Voltage options: DC6V, DC12V, DC24V, AC24V, and special voltages
Power consumption: Standard 2.5W, energy-saving 0.5W
Connection types: Z (right angle), S (horizontal), C (insert), M (insert nut), X (direct lead)
IP rating: IP50 (standard), IP65 (direct lead type)
Applications: Textile machinery, medical devices, electronics manufacturing, industrial automation
By selecting the correct configuration for your application and following proper installation and maintenance procedures, WAALPC 331 Series miniature solenoid valves will deliver years of reliable, precise control.
For more information about WAALPC 331 Series 15mm miniature solenoid valves or to discuss your specific application requirements, please contact our technical sales team or visit www.waalpc.com.
