Practical guide to choosing between these two models of reducing valves

A self-actuated pressure reducing valve is an essential device in any fluid system.

Its function is simple, but critical: to reduce a high inlet pressure, which may be variable, to a lower and, above all, constant outlet pressure. All this is achieved automatically, without the need for external energy sources such as electricity or compressed air.

Choosing the correct valve is vital to protect sensitive equipment “downstream”, optimize process efficiency, and ensure operational safety. At Valfonta, two of our most reliable models for this task are the M1 and the M2.

Although both are reducing valves, they are designed with distinct characteristics to cover a wide range of industrial applications, from the control of high-purity gases to the management of high-temperature steam.

In this guide, we analyze their differences to help you select the ideal model for your installation.

What is a self-actuated pressure reducing valve?

The term “self-actuated” (or “without auxiliary energy”) means that the valve uses the fluid’s own energy to operate its internal mechanism. It does not require electrical wiring or instrument air lines, which makes them incredibly reliable, easy to install, and with zero maintenance cost in that aspect.

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The use of a quality pressure reducing valve offers direct benefits for any system:

  • Equipment protection: This is the most common application. They prevent pressure gauges, heat exchangers, reactors, delicate instrumentation, and other equipment operating “downstream” from being damaged by excessive pressure.

  • Process stability: Many industrial processes (chemical, pharmaceutical, food) require an exact and constant pressure to function correctly. The reducing valve ensures that, even if the inlet pressure fluctuates, the process always receives a stable pressure.

  • Efficiency and savings: In steam applications, reducing the pressure also reduces the temperature, optimizing energy use. By not consuming external energy for its operation, its operating cost is zero.

  • Improved safety: By keeping the pressure within the design limits of the line, they reduce the risk of system failures. However, it is essential to understand that a reducing valve is not a safety valve. Overpressure protection (such as a relief valve) should always be installed when the installation requires it.

The M1 model: robustness and high performance for steam and gases

When the application requires greater robustness, a higher pressure range, or continuous operation with high temperatures, the M1 model is the indicated solution.

Unlike the M2, the M1 is a self-actuated valve with diaphragm and springs, designed specifically for more demanding work with steam, compressed air, non-hazardous gases, and liquids.

Its internal design is intended for maximum durability and minimal maintenance in severe conditions. Its most distinctive feature is the shaft sealing by means of a double-layer bellows in stainless steel. This bellows completely isolates the fluid from the rest of the upper components, preventing leaks and wear on the shaft, a critical point in high-temperature steam applications.

How does the M1 work?

  • The outlet pressure (downstream) is transmitted through an external control line (L) to the diaphragm chamber (H).

  • This pressure exerts a force on the diaphragm that opposes the force adjusted in the springs (K) by means of the regulating nut (F).

  • This balance of forces moves the obturator (C), opening or closing the passage to maintain a stable outlet pressure.

  • In large sizes (from DN65), it includes a compensation piston (D) that cancels the effect of inlet pressure variations.

Outstanding features of the M1 model:

  • Robustness: Designed for high performance and rapid response to demand changes.

  • Bellows sealing: Maximum reliability and durability, especially in steam.

  • High temperature: Prepared to work up to 250 °C (with EPDM+PTFE membrane and condensation tank).

  • Wide pressure range: Capable of regulating the outlet pressure in ranges from 0.1 to 15 barg.

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The M2 model: precision and direct action for multiple fluids

The M2 valve is one of the most versatile and demanded models in our catalog. It is a pressure reducing valve with direct action, which means that the outlet pressure acts directly on the internal membrane for rapid and sensitive control.

Its design is optimized to work with a wide range of fluids, including gases (such as air, nitrogen, and others), liquids, and steam. Thanks to its high sensitivity, it is an ideal valve for applications that require very precise control, even at very low pressures, offering regulation ranges ranging from 20 mbar to 8 bar.

How does the M2 work?

  • The inlet pressure (upstream) reaches the valve and pushes the piston-plunger assembly, closing the passage automatically.

  • By turning the regulating screw, a spring is compressed that acts on the membrane.

  • The membrane opens the valve’s obturator (closure), allowing the passage of fluid until the outlet pressure (downstream) reaches the desired value.

  • Any variation in the inlet pressure is absorbed by the compensation plunger, and any variation in the outlet pressure is detected by the membrane, which readjusts the obturator to maintain a stable set pressure.

H4: Outstanding features of the M2 model:

  • Direct action: Rapid response and high sensitivity.

  • Materials: Interiors in AISI 316 and closure in PTFE, with actuator options in stainless steel and gaskets with a composition suitable for food applications.

  • Membrane: It has a membrane reinforced with intermediate fabric.

  • Pressure tap: The pressure tap is internal as standard, which greatly simplifies installation by not requiring an external control line (except in steam applications).

This precision makes it ideal for chemical laboratories, water distribution networks, sanitary installations, compressed air lines, fire protection systems, and inert gas control (tank inerting).

Features Valve Model M1 Valve Model M2
Operating Principle Self-actuated by membrane Direct action by membrane
Compatible Fluids Steam, compressed air, non-hazardous gases, liquids Gases (air, nitrogen…), liquids, steam
Outlet Pressure Range (P.out) 0.1 – 15 barg (Wide range) 0.02 – 8 barg (High precision)
Maximum Temperature Up to 250°C (with EPDM+PTFE membrane) Up to 180°C (with EPDM+PTFE membrane)
Shaft Sealing (Obturator) Stainless Steel Bellows Gaskets (NBR, EPDM, PTFE+GR, etc.)
Pressure Tap External (Mandatory control line) Internal (Standard) / External (For steam or optional)
Inlet Pressure Compensation Yes (Plunger from DN65) Yes (Compensated by plunger)

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Industrial applications: where to install each model?

The choice between one model or another will depend on the specific pressure, temperature, and fluid conditions of your installation.

When to choose the M1 valve

The M1 model is the ideal choice for more severe processes, where robustness, high temperatures, and a greater outlet pressure capacity are decisive factors.

Its design is intended for:

  • Steam circuits: It is its star application. The stainless steel bellows seal guarantees a much longer service life and almost zero maintenance compared to traditional gaskets in high-temperature steam (up to 250 °C).

  • High outlet pressures: When a higher regulation range is needed, the M1 reaches up to 15 barg.

  • High demand lines: Ideal for main compressed air or gas lines with large demand variations, where its response is quick and effective.

M1 pressure reducing valve

When to choose the M2 valve

M1 pressure reducing valve

The M2 model is the perfect choice for most general service applications and installations that require very fine control at low or medium pressures.

Its high sensitivity makes it preferable in:

  • Chemical and pharmaceutical laboratories.

  • Water distribution networks and sanitary installations.

  • Compressed air lines for instrumentation.

  • Fire protection systems.

  • Inert gas control, such as the protection of tanks with nitrogen, where it is necessary to reduce the pressure to very low values (millibars) with great precision.

Installation guide and best practices (M1 and M2)

Correct installation is the best guarantee of optimal performance and a long service life. Although the M1 and M2 have differences, both share fundamental installation principles that must be respected.

Before installing the valve, it is essential to clean the inside of the pipe very carefully to prevent any impurities or installation residue from impairing the correct functioning of the closure.

For this reason, it is almost essential (and highly recommended) to install a strainer filter (Y-type) just in front of the reducing valve. This action protects the seat and the obturator from erosion and blockage, avoiding excessive maintenance and extending the service life of the equipment.

Both models must be installed respecting the arrow located on the valve body; this arrow must always coincide with the direction of fluid circulation.

The standard and preferred mounting position is in a horizontal pipe.

  • For most fluids (gases and liquids above 0°C), the actuator (the upper part with the membrane and spring) must be installed in a vertical position, pointing upwards.
  • For gases and liquids up to 80°C, mounting on a horizontal pipe with the actuator in a vertical position, pointing downwards, is also possible.

Important! Mounting is not allowed with the valve “lying down” (that is, with the actuator shaft in a horizontal position), as the valve would not behave correctly.

This is one of the most important considerations for high-temperature applications.

The condensation barrel is mandatory whenever the fluid is steam or for liquids with temperatures above 125 °C.

Its function is to protect the membrane (the component most sensitive to heat) from overheating. The barrel creates a “water seal” (condensate) that is interposed between the hot fluid of the main line and the membrane, ensuring that it always works at a safe temperature. Before start-up, this tank must be filled with water to overflowing.

Here we find the main installation difference between both models:

  • Model M2: It is supplied as standard with an internal pressure tap. This means that, for most liquid and gas applications, it is not necessary to install an external pipe, greatly simplifying assembly.
  • Model M1: It always requires an external control line.
  • Exception (M2 in Steam): When the M2 valve is used for steam, the use of the external pressure tap, which will be connected to the condensation barrel, is mandatory.

When an external control line is used (either in the M1 or in the M2 for steam), it must be connected in the reduced pressure zone (downstream). To avoid incorrect readings due to turbulence, it must be located at a minimum distance of 1 meter from the valve outlet (or approximately 6-10 times the nominal diameter, DN).

Frequently asked questions about M1 and M2 pressure reducing valves

The main difference is the application. The M1 model is designed for more robust and demanding applications, especially high-temperature steam (up to 250 °C) and higher outlet pressures (up to 15 barg). It uses a stainless steel bellows seal for maximum durability. The M2 model is ideal for general services and applications requiring high precision at lower outlet pressures, and can regulate from 20 mbar.

Yes. It is a critical safety point. A pressure reducing valve controls the pressure, but it is not a safety valve. If there is a possibility that the valve will fail (for example, due to dirt in the seat) and the inlet pressure passes “downstream”, it could damage the equipment. Therefore, whenever necessary, overpressure protection, such as a Valfonta pressure relief valve, must be installed downstream of the reducer.

The most important maintenance is preventive: install a strainer filter at the inlet. Apart from this, the seals and parts subject to normal use must be checked periodically and replaced if necessary, depending on the severity of the working conditions. It is essential to always use original spare parts recommended by Valfonta.

It is the operating principle of the M2 model. It means that the outlet pressure (downstream) acts directly on the valve diaphragm. This force is what, in equilibrium with the regulating spring, moves the obturator to open or close the passage of fluid. This design provides a very fast and sensitive response to pressure changes.

Valfonta: your expert partner in fluid control

The M1 and M2 models are just a part of our specialty in pressure reducing valves. At Valfonta we have an exceptional technical team that will help you from the outset to choose the exact valve that your system or installation requires.

Our catalog also includes a complete range of solutions for fluid control, such as pressure relief valves, control valves, injectors and ejectors for liquids and steam.

If you would like us to contact you to see what type of valve and which model is right for you, just take a few seconds to fill out this form. You can also call us by phone at 93 37 208 88.

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