Basic guide for regulating this type of valve

Regulating a pressure reducing valve is a simple but critical maintenance task.

The objective is to adjust the internal force of the mechanism so that the outlet pressure (“downstream”) remains stable at the desired value, regardless of inlet fluctuations.

The quick answer: In the vast majority of industrial valves, including the M and PRV series from Valfonta, regulation is achieved by modifying the compression of the main spring using an adjustment screw or nut.

To do it correctly, just remember this golden rule:

  • To increase the pressure (+): Turn the screw clockwise (to the right). This compresses the spring and exerts more force on the diaphragm or piston.

  • To decrease the pressure (-): Turn the screw counterclockwise (to the left). This decompresses the spring and reduces the opposing force.

Although the concept is simple, performing the adjustment safely and accurately requires following some essential prior steps that we detail below.

Table of contents

Before starting: preconditions for safe regulation

It’s not just about grabbing a wrench and turning. Before manipulating the valve, it is essential to ensure that the installation meets minimum conditions to guarantee that the reading is real and we do not damage the equipment.

1. Installation of pressure gauges (essential)

It is impossible to regulate what cannot be measured. For a correct adjustment, you need to have visibility of what happens inside the pipe. As indicated in our installation diagrams, it is necessary to have two pressure gauges:

  • Inlet pressure gauge: To verify that sufficient pressure reaches the valve.

  • Outlet pressure gauge: This is the critical one. It must be located “downstream” of the valve to see in real time how the pressure changes when turning the screw.

2. Cleaning and filtering

Before attempting to regulate a new or recently maintained valve, make sure that the pipe is clean. A small metallic chip or dirt lodged in the seat can prevent the valve from closing tightly, causing the pressure to rise uncontrollably and preventing fine regulation. Therefore, we always recommend installing a Y-strainer filter just before the reducer.

3. Avoid water hammer

Never regulate the valve by opening the flow suddenly. Shut-off valves (inlet and outlet) must be opened slowly. A sudden change in pressure can damage the internal diaphragm or bellows of the valve even before starting to regulate.

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Step-by-step guide: the standard adjustment procedure

Once the installation has been verified, we can proceed with the regulation. This procedure is valid for most of our self-actuated spring valves.

  • Step 1: Relax the spring (recommended); if it is the first start-up, it is advisable to start with the valve “relaxed”. Turn the adjustment screw or nut counterclockwise until you notice that the spring exerts hardly any pressure. This ensures that the valve is closed or at its minimum pressure point when starting the flow.

  • Step 2: Open the fluid passage slowly; open the shut-off valves (inlet and outlet) very slowly. This is vital to avoid water hammer that could damage the internals of the valve. If the valve requires a condensation tank (for steam or fluids >125 °C), make sure it has been filled with water until it overflows before this step.

  • Step 3: Fine adjustment, with the fluid circulating (or with the valve in static, depending on the process), start turning the regulating element, observing the outlet pressure gauge closely.

    • To increase the pressure: Turn clockwise (right). By doing so, you are compressing the spring, which forces the valve to allow more fluid to pass through to balance that force.
    • To decrease the pressure: Turn counterclockwise (left). By decompressing the spring, you reduce the adjustment value.

  • Extra tip: If you need to lower the pressure and you have gone too far, sometimes it is more effective to “loosen” the screw a little more than necessary and then “tighten” it again until you reach the exact point by going up. This helps to seat the spring correctly.

  • Step 4: Verification; once the desired pressure has been reached on the pressure gauge, secure the position (if the model has a lock nut) and observe the behavior of the valve when there is flow consumption and when consumption is closed.

Particularities according to the Valfonta model (M Series vs. PRV Series)

Although the physical principle is the same, the tool and the element that you must touch change depending on the model you have installed. Here we detail what to look for in each series:

M Series (Industrial Models M1 and M2)

These models are usually installed in higher flow and size applications.

  • Model M1: The adjustment is made by turning the adjustment nut located on the top, above the spring.

  • Model M2: Features a hexagonal head adjustment screw on the top of the tower.

    Remember that, after adjustment, the outlet pressure acts directly on the diaphragm for compensation.

PRV Series (Stainless Steel Valves)

This range has more compact or hygienic designs, and in some cases requires specific tools:

  • Model PRV20: It is adjusted by turning the upper adjustment nut.

  • Model PRV30 and PRV45: The design is more specific. To adjust the setpoint, you will need an 8 mm Allen wrench to turn the internal adjustment nut/screw.

  • Model PRV44: It uses a conventional adjustment screw located on the top of the cap.

Some of our most requested valves:

Quick reference table: tools and direction of rotation

To make your job easier, we have compiled in this table what tool you need exactly for each model in our catalog and how you should act on it.

Series / Model Adjustment Element Usual Tool To increase pressure (+) To decrease pressure (-)
Model M1 Upper adjustment nut Open-end / adjustable wrench Clockwise Rotation (Compress) Counterclockwise Rotation
Model M2 Adjustment screw (Hexagonal head) Open-end / adjustable wrench Clockwise Rotation (Compress) Counterclockwise Rotation
Model PRV20 Upper adjustment nut Open-end wrench Clockwise Rotation (Compress) Counterclockwise Rotation
Model PRV30 Internal adjustment nut Allen wrench (8 mm) Clockwise Rotation (Compress) Counterclockwise Rotation
Model PRV44 Upper adjustment screw Open-end wrench Clockwise Rotation (Compress) Counterclockwise Rotation
Model PRV45 Internal adjustment nut Allen wrench (8 mm) Clockwise Rotation (Compress) Counterclockwise Rotation

*Note: In all Valfonta models, the principle is universal: Compressing the spring (clockwise rotation) always increases the adjustment pressure.

Common problems during regulation

Sometimes, no matter how much we turn the screw, the pressure does not behave as we expect. These are the three most common problems we encounter in the field and how to solve them:

1. The pressure rises on its own when I close the consumption

If you regulate the valve to 3 bar with the tap open, but when you close it the pressure on the pressure gauge starts to rise slowly until it equals the inlet pressure, you have a sealing problem.

  • Probable cause: Dirt or impurities lodged between the seat and the obturator, preventing a tight seal. It may also be due to an obturator eroded by use.

  • Solution: Disassemble the cover, inspect the seat and clean or replace the closure if it is damaged. Remember: the previous filter is vital to avoid this.

2. The pressure fluctuates a lot (Instability)

If the pressure gauge needle constantly goes up and down (cycling), regulation is impossible.

  • Probable cause:
    • The tapping of the control pipe (if it is external) is too close to the valve, in a turbulent area.
    • The valve is oversized for the actual flow that passes through.
  • Solution:
    • Make sure that the pressure tap is at minimum 1 meter from the valve outlet.

Install a needle valve in the control pipe to “cushion” the signal and stabilize the reading.

3. I can’t reach the desired pressure

Turn the screw to the maximum, but the pressure does not rise enough, or loosen it completely and the pressure is still too high.

  • Probable cause: The installed spring does not correspond to the pressure range you need. Reducing valves work with different interchangeable springs to cover specific ranges (e.g. from 1 to 8 bar, or from 4 to 12 bar).

  • Solution: Check the valve’s characteristics plate to confirm the spring range (“RANGE”). If it is out of range, contact Valfonta to acquire the appropriate spring.

More frequently asked questions about valve regulation…

The general recommendation is to perform the fine adjustment in dynamic conditions, that is, with a flow consumption representative of your usual process. Reducing valves have a slight difference between the pressure at zero flow (closing pressure) and the pressure with flow. If you adjust it in static, the pressure may drop slightly below what is desired when you open the taps or machines “downstream”.

If you have reached the end of the screw’s travel and the outlet pressure is still low, do not force the mechanism. The most likely thing is that the spring installed in your valve does not cover the range you need (for example, you have a 0.5-3 bar spring and you need to reach 5 bar). You should contact Valfonta to acquire the appropriate spring for your new working range.

In steam applications or fluids at more than 125°C, the barrel (condensation tank) acts as a thermal barrier. If you try to regulate the valve without having previously filled it with water until it overflows, the steam will come into direct contact with the elastic diaphragm of the actuator, and may burn or deform it instantly, which would render the regulation useless.

Yes. Although models such as the PRV series allow some flexibility, the standard position (horizontal pipe, vertical actuator) guarantees the best sensitivity and less wear. Installing the valve with the actuator “lying down” (horizontal axis) is not recommended, as the weight of the internals and lateral friction can cause erratic regulation or hysteresis.

The control line transmits the actual pressure from the outlet pipe to the diaphragm, allowing the valve to “know” when to close or open. In models that require it externally (such as the M1 or M2 in steam applications), it is vital to connect it at least 1 meter from the outlet. If connected too close, fluid turbulence will distort the reading, causing the valve to oscillate and not regulate stably.

Self-operated valves are very stable and do not require continuous maintenance. However, the springs may undergo slight relaxation after years of service or intense cycles. It is recommended to periodically check the pressure on the outlet pressure gauge and, if a deviation is observed, make a small adjustment to the regulating screw to compensate.

Do you need assistance from our technicians to regulate your valve?

Correct regulation not only ensures that your process operates at the exact required pressure but also extends the lifespan of the entire installation, protecting pipes, filters, and sensitive machinery.

Contact us

If, after following these steps, you are unable to stabilize the pressure, or need to modify the working range of your valves (spring change), do not hesitate to consult with our specialists.

At Valfonta, we have been designing and manufacturing pressure reducing valves for decades. Contact our technical team to resolve any issues or advise you on the exact replacement your equipment needs.