FESTO 7959 (MFH-3-1/4-S) Solenoid Valve

Full Product Name: MFH-3-1/4-S, Order No.7959, Tiger Classic Series 3/2-way Normally Closed Single Solenoid Solenoid Valve

⚠️ Valve body does NOT include solenoid coil; coil must be ordered separately

✅ Key Specifications

📌 Model Code Explanation

MFH: Tiger Classic series solenoid valve

3: 3/2-way valve

1/4: Main port thread G1/4

S: External pilot supply version

🛠️ Application Scenarios

Single-acting cylinder control, vacuum circuit, air blow-off/shutoff, packaging machinery, machine tool pneumatic circuits, air switches for automated production lines.

External pilot: Cannot be driven directly by low-pressure vacuum. Pilot supply must be independently supplied with ≥1bar control air.

🔁 Same Series Reference (Order No.)

7958: MFH-3-1/8-S (G1/8)

7959: MFH-3-1/4-S (G1/4)

7960: MFH-3-1/2-S (G1/2)

⚠️ Selection & Maintenance Notes

1. Solenoid coil must be purchased separately (e.g. MSFW series, AC220V / DC24V). Valve body comes without coil;
2. External pilot structure, independent pilot air supply, works reliably even when main circuit is under negative pressure;
3. Poppet valve design with soft seal: excellent sealing performance, but vulnerable to wear if medium contains heavy dust;
4. Second-hand inspection focus: manual button operation, air tightness test (pressurize port 1: no output at port 2 when de-energized, air output at port 2 when energized).

FESTO 7959 (MFH-3-1/4-S) Application Cases

Core advantage: External pilot 3/2-way normally closed poppet valve, compatible with vacuum in main circuit, high flow rate 800L/min; independent pilot air supply via M5 port ≥1bar. This is the biggest difference from standard internal-pilot MFH valves.

Case 1: Packaging Machine｜Single-acting Clamping Cylinder Control (Most Common)

Equipment: Horizontal form-fill-seal machine, vertical bagging machine, carton folding machine

Circuit: 7959 → Single-acting spring return clamping cylinder

Coil energized: Valve shifts, compressed air enters cylinder cap end, workpiece clamped;

Coil de-energized: Valve resets, cylinder chamber exhausts, spring releases workpiece.

Selection Reasons

1. G1/4 high flow, fast clamping response; detent manual button allows manual clamping test during commissioning;
2. Soft seal poppet valve, low leakage after long frequent cycling;
3. PAL rail manifold mountable, multiple valves mounted side-by-side for centralized air supply and exhaust.

Note: Pilot air shall be taken from a separate clean air source, not shared with main cylinder air supply.

Case 2: Vacuum Pick & Place Circuit (Representative Application of This Valve)

Equipment: PCB mounter, carton feeding manipulator, plastic part handling suction cup module

Circuit: Vacuum generator → 7959 valve → Vacuum suction cup

De-energized: Valve closed, suction cup disconnected from vacuum source, suction cup vented to atmosphere, workpiece released;

Energized: Valve opens, vacuum connected to suction cup, workpiece picked up.

✅ Key point: External pilot version allows vacuum in main circuit. Internal-pilot MFH cannot be directly used for vacuum circuits (negative pressure in main circuit causes unreliable shifting). This is the core value of 7959 (suffix -S).

Note: M5 pilot port must be continuously supplied with ≥1bar clean compressed air. Vacuum cannot be used as pilot supply.

Case 3: Machine Tool｜Chip Blow-off & Workpiece Ejection

Equipment: CNC lathe, machining center, stamping machine workpiece blow-off, material bin air separation

Circuit: Main air supply G1/4 → 7959 → Air nozzle

Energized: High-flow air jet blows away metal chips or eject finished workpieces out of station;

De-energized: Air supply cut off, nozzle pressure relieved.

Selection Reasons: 800L/min high flow for high intensity short pulse blowing; poppet valve tolerates minor dust for machine tool cutting environment; IP65 allows mounting outside machine cabinet.

Case 4: Rubber & Plastics Industry｜Single-acting Lifting/Ejection Mechanism

Equipment: Injection molding machine mold ejection, rubber molding machine demolding, hot pressing tool lifting

Circuit: 7959 driving large bore single-acting spring return cylinder for mold ejection.

Features: Die-cast aluminum housing tolerates oil contamination and elevated temperature in mold environment; valves can be assembled on manifold rail;

Safety merit: Automatic spring reset upon power loss, mold retracts automatically for safety redundancy.

Case 5: Conveyor Line｜Pilot Control for Pneumatic Valves (Used as Pilot Valve)

Equipment: Sorting conveyor, pallet stopper, large bore pneumatic shut-off valve

Circuit: PLC drives 7959; 7959 outputs pneumatic signal to actuate large-size main pneumatic valve.

Scenario: Main valve has huge flow capacity and cannot be directly driven by small solenoid valves; 7959 serves as secondary pilot valve to provide control air signal.

Advantages: 10ms fast response, stable pilot output, suitable for 2-stage control of large pneumatic circuits.

Case 6: Retrofit & Replacement for Legacy Equipment (Spare Part Application)

Many imported automated production lines manufactured from 1990s to 2010 adopt Tiger Classic poppet valves. Damaged MFH-3-1/4-S (7959) can be directly replaced.

Industry status: This classic legacy spare part. Specified on drawings of many packaging, printing and textile machines. Supports through-hole mounting or PAL rail mounting; no hole modification required during replacement.

Common Risk Reminders Across All Cases

1. Valve body without coil, MSFW coil must be ordered separately (DC24V most popular);
2. -S = external pilot, M5 pilot port pressure ≥1bar, pilot air filtration ≥40μm; insufficient pilot pressure causes no shifting or intermittent misfiring;
3. Medium must be filtered; dust particles scratch poppet seal and cause internal leakage;
4. In vacuum applications, main circuit negative pressure cannot be used for pilot supply; independent positive pressure air source required for pilot.

Industry Summary List

Packaging Machinery: Carton machine, horizontal packaging machine, heat sealer (clamping, vacuum material pick-up)

Machine Tool & Metal Working: Chip blow-off, workpiece ejection

Rubber & Plastics Injection: Mold single-acting ejection

Logistics Automation: Suction cup handling, sorting stopper

Printing & Textile: Fabric clamping, paper stack air separation

Legacy imported equipment maintenance & replacement (Tiger Classic valve)

Working Principle of MFH-3-1/4-S (Festo 7959)

Model breakdown: 3/2-way, normally closed, single-solenoid spring return, external pilot (-S) poppet solenoid valve

Important: This is an external pilot valve. The solenoid coil only controls pilot air and does NOT directly actuate the main spool, completely different from direct-acting solenoid valves.

1. Port Definition (3/2-way Valve)

Port 1: Main air supply inlet (G1/4)

Port 2: Working output port → Connect to cylinder / suction cup / nozzle

Port 3: Exhaust port (main circuit exhaust)

Port 12: Pilot supply port M5 (external pilot dedicated, must be supplied ≥1bar clean compressed air)

Port 82: Pilot exhaust port M5

Definition of 3/2-way: 3 air ports, 2 working states (de-energized / energized)

2. Two Operating States

✅ State 1: Coil De-energized (Home Position, Normally Closed)

1. Main poppet is pressed against main valve seat by return spring force;
2. Main circuit: Port1 (main supply) ↔ Port2 disconnected; Port2 ↔ Port3 (exhaust) connected;
3. Pilot circuit: Pilot control chamber exhausted via port82, no pressure inside pilot chamber;
4. Result:

For single-acting cylinder: Cylinder exhausts and retracts by spring;

For vacuum suction cup: Suction cup vented to atmosphere, workpiece released.

✅ State 2: Coil Energized (Shifted Position)

1. Solenoid coil pulls armature → opens small internal pilot slide valve;
2. Compressed air from external pilot supply (port12) enters control chamber of main poppet;
3. Pressure from pilot air generates thrust to overcome return spring and shift main poppet;
4. Main circuit switching: Port1 ↔ Port2 connected; Port2 ↔ Port3 exhaust port blocked;
5. Result:

Compressed air flows from port1 to port2 to actuate actuators;

Vacuum circuit: Port2 connected to vacuum source, negative pressure generated at suction cup for workpiece pick-up.

After de-energization, pressure inside control chamber discharges through port82 pilot exhaust port, spring pushes main poppet back to home position, returning to normally closed state.

3. Core Feature: Principle of External Pilot (-S) (Key)

Internal pilot valve: Pilot air is tapped from main supply port 1. If main circuit is under vacuum (negative pressure), no positive pressure available at port1 to generate thrust to shift poppet, cannot be used for vacuum circuits.

External pilot (-S): Pilot air is independently supplied from port12, fully isolated from main circuit (port1/2/3).

Main circuit port1 can carry compressed air or vacuum negative pressure. As long as port12 pilot supply maintains ≥1bar positive pressure, reliable valve shifting is guaranteed.

👉 This is the fundamental reason why 7959 can be used in vacuum suction cup circuits.

4. Structure Overview (Poppet Valve)

It is a poppet valve, not slide valve: Sealing is achieved by pressing rubber seal against valve seat.

Advantages: Excellent sealing performance, low leakage;

Disadvantages: Sensitive to dust in medium; solid particles may scratch sealing surface and cause internal leakage.

5. Manual Override Mechanism

The valve body is equipped with detenting manual pushbutton:

Press and rotate to lock, mechanically actuate pilot spool. Manual shifting available without power or coil energization, used for commissioning, air test and maintenance.

6. Concise Principle Comparison Table