Original inventor of M ü ller Co ax AG coaxial valve

Full solution to coaxial valve technology: pressure balance design leads to new heights in fluid control

Since the invention of coaxial valves in 1960, M ü ller Co ax AG has been committed to providing reliable valve solutions for controlling gaseous, liquid, highly viscous, particulate, and corrosive media. From simple on-off valves to application specific special valves, and then to complete modular systems, coaxial valves demonstrate excellent performance in harsh operating conditions such as vacuum, high pressure, and high-frequency switching due to their unique pressure balancing structure. The company is headquartered in Fuchtenberg, Germany and has subsidiaries such as m-tech and cx tec. It also has distribution offices in over 25 countries and regions worldwide. Its products are certified according to DIN EN ISO 9001:2008 and 97/23/EG PED, and meet special industry standards such as DVGW, ATEX, and T Ü V.

Core technological advantages of coaxial valves

The essence of coaxial valve design lies in pressure balance - the force on the valve core is independent of system pressure and pressure difference. Whether controlling vacuum or high pressure, its operating characteristics always remain precise and reliable. Unlike traditional valves, coaxial valves do not require a minimum pressure difference to function properly, achieving zero pressure start-up.

1.1 Pressure balance design/normal operation from 0 bar

In the closed state of traditional lift valves, the inlet pressure will act on the valve core to generate a large closing force, which needs to be overcome when opening. The coaxial valve, through a special flow channel structure, allows the medium pressure to act on both ends of the valve core in opposite directions, thereby canceling each other out. Therefore, no matter how high the system pressure is, the required opening and closing force is almost constant. This feature allows coaxial valves to operate in a wide pressure range from full vacuum to several hundred bars without the need for a minimum working pressure difference.

1.2 Backpressure sealing performance

When the valve is closed, the pressure on the outlet side can be higher than that on the inlet side without leakage. This is crucial for piping systems that require prevention of backflow or back pressure.

1.3 Maintenance free/dirt resistant

A coaxial valve has only one moving component (valve core), no valve stem seal, and no external actuator. This minimalist design minimizes wear points to the greatest extent possible. Even if the medium contains a large number of solid particles or fibers, the valve seat will not fail due to particle jamming. Under extreme working conditions, the lifespan of coaxial valves can be more than 10 times that of traditional valves.

1.4 Quick Response

The pressure balance structure allows the electromagnet to overcome only spring force and minimal frictional resistance, so the opening and closing action of the valve can be completed within 30 milliseconds (depending on specifications). This makes coaxial valves an ideal choice for applications that require high-speed circulation control.

1.5 Bi directional flow

Valves allow media to flow in any direction without the need to install multiple valves to achieve bidirectional shut-off. This feature simplifies pipeline design and reduces pressure loss.

1.6 Compact size

Due to the elimination of large pneumatic or electric actuators (coaxial valves typically use direct acting electromagnets or small pilot valves), the overall length and height of coaxial valves are much smaller than traditional valves.

Overview of Product Series

M ü ller Co ax offers 2/2-way and 3/2-way valves, with drive modes divided into direct actuated and externally controlled. The diameter range is DN 1.5-250, the pressure range is PN 0-500 bar, and the connection methods include threads, flanges, SAE, etc.

2.1 Direct acting 2/2-way valve (MK/FK series)

Direct acting valves drive the valve core directly through DC electromagnets, without the need for a pilot air source. Suitable for small caliber (DN 8-50) and medium low pressure (PN 16-100 bar) applications. The Kv value of the typical model MK 10 (DN 10) is 2.6 m ³/h, with a switching time of approximately 25 ms. The valve body material can be selected from brass, galvanized steel, stainless steel without non-ferrous metals, etc; Sealing materials include NBR, PTFE, FPM, CR, EPDM. The temperature range of the medium is -20 ° C to+160 ° C, and the ambient temperature is -20 ° C to+80 ° C.

2.2 External Control 2/2-way Valve (VMK/VFK, VSV Series)

For large diameters (DN 10-250) or situations that require remote pneumatic/hydraulic control, external control valves are used. The pilot valve interface complies with NAMUR/ISO 1 standards and can use 5/2-way or 4/2-way pilot valves. The Kv value of VMK 15 (DN 15) can reach 5.7 m ³/h, with an adjustable switching time of 50-3000 ms. The VSV series covers DN 40-250, with a maximum Kv value of 650 m ³/h (DN 250), suitable for high flow process pipelines.

2.3 3/2-way valve (MK/FK DR series)

The 3/2-way valve has three interfaces (A, B, C) for diverting or selecting the flow direction. It has a switching overlap function inside, which prevents all ports from being closed or opened simultaneously at the moment of switching. DR NC type is normally closed (A → B), DR NO is normally open (A → B). The technical parameters are similar to those of the same specification 2/2-way valve, but with a slight increase in length.

2.4 High pressure valves (KB, A 45, VMK-H series)

High pressure applications require valves to have extremely high strength. The KB 15 series (DN 2-8) adopts a direct acting type, with a single coil operating pressure of up to 300 bar and a double coil operating pressure of up to 400 bar. The A 45 series (DN 2-6) has a maximum pressure of 130 bar. The externally controlled VMK-H series (DN 15-50) has a maximum pressure of 200 bar, and the valve body is made of galvanized steel or stainless steel. For ultra-high pressure of 500 bar, the PCD-H series (DN 10-15) and KBS Ex explosion-proof valve (DN 1.5-3) can meet the requirements.

2.5 Certified valves (DVGW, ATEX, T Ü V)

DVGW certification: compliant with DIN 3394 part 1, used for combustible gases (G260), medium temperature -15 ° C to+80 ° C, and maximum pressure PN 40. MK/FK 15 DVGW Ex can be used for explosion-proof zones 2 and 22 (ATEX).

ATEX certification: The valve body is marked with II 2 G Exe me II T4 and II 2 D IP65 T130 ° C, suitable for potentially explosive environments. The maximum medium temperature for KB 15 Ex and MK/FK series Ex versions is 40-70 ° C.

T Ü V certification: Complies with DIN EN ISO 23553-1 and E DIN 32725 for liquid fuels (such as fuel oil), with a maximum medium temperature of 140 ° C.

2.6 Control Valve (Pressure Regulation and Proportional Control)

Coaxial valves are not only used for switch control, but can also integrate pressure regulation functions:

HPB series pressure limiting valve: manual stepless adjustment, achieving low-pressure circulation mode through a 3/2-way pilot valve. Pressure regulation range 10-200 bar, DN 8-65.

SPB series proportional pressure limiting valve: It achieves stepless pressure regulation through a 0-10V control signal, and the pilot valve is a proportional valve. DN 8～65， The maximum pressure range is 200 bar.

HPI/HPP series pressure reducing valve: manually adjustable, DN 8～32， The pressure range is 5 to 100 bar.

SPP series proportional pressure control valve: 3/2-way, used for closed-loop pressure control, DN 15， Pressure range of 5 to 100 bar.

2.7 Special valves

Develop for specific industrial needs:

V2 type high temperature valve: used for hot gas filtration and gasification processes, with a maximum medium temperature of 400 ° C, and sealed with graphite or metal bellows (1.4571). DN 15～100， Pressure PN 64.

LVP 06 High Pressure Valve: Used for gas filling and petrochemical processes, with pressures up to 500 bar and DN 6.

PCB-1 10: Used for adhesive and coolant supply, with external sealed bellows that can withstand viscous and particulate media.

PLB 05: Used for bonding laminated timber beams with corrugated pipe sealing technology.

IV series vacuum valve: pulse type bistable design, used for vacuum engineering (maximum vacuum degree of 98%), DN 20～32。

Modular and manifold installation

For systems that require centralized control of multiple valves, M ü ller Co ax provides a manifold solution. For example, models such as CFM 08, MCF 08, VMK 10-32 can be installed on aluminum or stainless steel modules, supporting 2 to 8 workstations and even expandable to more. The manifold integrates a common flow channel inside, reducing pipeline connections and leakage points. Segment module design allows users to freely combine according to their needs.

Green Series: Intelligent Control with 80% Energy Efficiency

M ü ller Co ax has launched the Green Line series based on the standard MK/FK series, with a patented electronic control system that can reduce the energy consumption of direct acting valves by up to 80%. This series has the following characteristics:

Adjustable damping mode (on/off) to eliminate water hammer phenomenon.

Integrated optical and electrical position indicator (on/off).

The energy of the fully automatic magnet decreases while the electromagnet remains in a cold state.

Spring reset ensures power-off safety.

This significantly reduces heating and energy consumption for valves that require prolonged opening or closing.

Interpretation of Technical Parameters

5.1 Kv value (flow coefficient)

The Kv value is defined as the flow rate (m ³/h) of water passing through a valve at 5-30 ° C under a pressure difference of 1 bar. The Kv value of coaxial valves is related to their diameter and structure. For example:

DN 10: Kv ≈ 2.5～3.0 m³/h

DN 15: Kv ≈ 4.8～6.0 m³/h

DN 25: Kv ≈ 11.2～13.3 m³/h

DN 50: Kv ≈ 28.2～43.0 m³/h

DN 250: Kv ≈ 650 m³/h

5.2 Switching time

The opening and closing time of direct acting valves (such as MK 10) is about 25 ms; the opening and closing time of external control valves (such as VMK 15) can be adjusted within the range of 50-3000 ms to meet different hydraulic impact requirements. The fast switch (30 ms) is suitable for precise measurement, while the slow switch (3000 ms) is used to reduce water hammer.

5.3 Range of work pressure

Coaxial valves can cover from full vacuum (<10 ⁻⁶ mbar · l · s ⁻¹ leakage rate) to 500 bar. For high pressure, double coil operation or external pilot control is usually used.

5.4 Temperature Range

Standard sealing (NBR) is suitable for -20 to+80 ° C; FPM (fluororubber) can be used for -20 to+160 ° C; PTFE (polytetrafluoroethylene) can be used for -20 to+200 ° C. The special high-temperature version (V2 type) uses graphite or metal bellows sealing, and the medium temperature can reach 400 ° C. The low-temperature version can be customized up to -196 ° C.

Application Fields and Selection Guidelines

6.1 Typical Applications

Oil and gas: Combustible gas cut-off (DVGW certification), emergency shutdown, venting.

Chemical and process industries: corrosive media, high viscosity polymers, slurries containing solid particles.

Power generation: boiler soot blowing, coal gasification filter blowback, cooling water control.

Mechanical manufacturing: machine tool coolant, lubrication system, hydraulic fixtures.

Vacuum technology: vacuum packaging, vacuum handling, coating equipment.

Adhesive and Coating: Glue laminated wood, automotive coating.

6.2 Selection Points

Medium characteristics: gas, liquid, high viscosity, containing particles? Do you need bellows sealing (to prevent leakage)?

Pressure and vacuum: maximum working pressure, do you need bidirectional flow?

Path and flow rate: calculated based on Kv value and allowable pressure drop.

Switching frequency: For high frequencies (>1 Hz), direct acting or fast pilot type should be selected.

Environment and medium temperature: Choose appropriate sealing materials and valve body materials.

Explosion proof requirements: Is ATEX Zone 2 or Zone 1 required? Do we need DVGW gas certification?

Control mode: direct electromagnet (24 V DC/230 V AC) or pneumatic pilot? Do we need proportional control?

Electrical connections: DIN EN 175301-803 A-type/B-type plugs, M12 connectors, junction boxes.

Quality and Certification

M ü ller Co ax strictly implements the ISO 9001:2008 quality management system, and all valves undergo final testing on a dedicated testing bench. The product complies with the European Pressure Equipment Directive (PED 97/23/EG). The main certifications include:

DVGW: German Gas and Water Industry Association, used for gas pipelines.

ATEX: Explosion proof Directive, applicable to potentially explosive environments (gases and dust).

T Ü V: German Technical Supervision Association, used for liquid fuel safety.

SIL: Safety integrity level assessment can be provided upon request.