Learn About Self-operated Pressure Regulating Val|Fleyenda

Learn About Self-operated Pressure Regulating Valve

Nov.07.2024

The self-operated pressure regulating valve is a control device that does not require external energy and relies on the pressure or temperature or flow changes of the measured medium to automatically adjust according to the preset value. It is an energy-saving instrument. It integrates control and execution of many functions. It is an independent instrument control system. It integrates the functions of transmitter, controller and actuator. It is different from the control valve in the general sense.

Composition of Self-operated Pressure Regulating Valve

Self-operated pressure regulating valve is a self-contained pressure controller valve. Generally speaking, the medium pressure changes with the change of the medium flow rate. When the medium flow rate changes, in order to ensure constant pressure, a self-operated regulating valve is required to control it.

The self-operated pressure regulating valve is composed of three major elements, namely:
1. Current limiting elements: valves, etc.;

2. Measuring elements: pressure gauge, valve diaphragm, piston, etc.;

3. Load elements: springs, heavy objects, human power, etc.

Classification of Self-operated Pressure Regulating Valve
1. According to the control behind the valve and before the valve, it is divided into: self-operated behind-valve (pressure reduction) control valve and self-operated front-valve (pressure relief) control valve.

2. According to whether it has a commander or not, it is divided into:

a. Direct-acting self-operated regulating valve

The direct-acting pressure regulating valve directly controls the valve through the medium itself to achieve the function of pressure regulation. Direct-acting pressure regulating valves have pressure-taking modes behind the valve and pressure-taking modes in front of the valve.

Take the pressure behind the valve and keep the pressure behind the valve within the set range to achieve the effect of pressure reduction behind the valve.

Take the pressure in front of the valve and keep the pressure in front of the valve within the set range to achieve the effect of pressure relief in front of the valve.

b. Pilot-operated self-operated regulating valve The pilot-operated regulating valve achieves automatic pressure regulation through mutual control between two valves.

Working Principle
1. Working principle of pressure adjustment behind self-operated valve (see figure below)

pressure adjustment behind self-operated valve

The pressure P₁ in front of the valve becomes the pressure P₂ behind the valve after being throttled by the valve core and valve seat. P₂ is input into the upper membrane chamber through the pipeline and acts on the top plate. The generated force is balanced with the reaction force of the spring, which determines the relative position of the valve core and valve seat, and controls the pressure behind the valve. When P₂ increases, the force P₂ acts on the top plate also increases. At this time, the force on the top plate is greater than the reaction force of the spring, causing the valve core to close toward the valve seat. At this time, the flow area between the valve core and the valve seat decreases, the flow resistance becomes larger, and P₂ decreases until the force on the top plate is balanced with the reaction force of the spring, thereby reducing P₂ to the set value. In the same way, when P₂ decreases. The direction of action is opposite to the above, which is how post-valve pressure regulation works.

2. Working principle of self-operated valve front pressure adjustment (see figure below)

self-operated valve front pressure adjustment

The difference between self-operated pressure regulating valve and control valve

The main difference between these two types of products is that the control valve not only requires external energy (such as power or air source) for driving energy, but also needs to receive external control instrument signals to change the relative position of the shutoff parts in the valve, thereby changing the fluid flow. The self-operated pressure regulating valve neither requires external energy nor receives signals from external control instruments. It can realize pressure regulation only by relying on the pressure signal of the medium to be adjusted.

Main Feature

1. The self-operated pressure regulating valve does not require external energy and can work in places without electricity or gas. It is convenient and energy-saving.

2. The pressure segment range is thin and crosses each other, and the adjustment accuracy is high.

3. The pressure setting value can be set continuously during operation.

4. For pressure adjustment after the valve, the ratio between the pressure in front of the valve and the pressure after the valve is 10:1~10:8

5. Rubber diaphragm type detection, the actuator has high detection accuracy and sensitive action.

6. The pressure balance mechanism is adopted to make the regulating valve sensitive and control precise.

Installation Precautions

1. The pressure point should be taken at the appropriate position of the pressure regulating valve. The pressure regulation in front of the valve should be greater than 2 times the pipe diameter, and the pressure regulation behind the valve should be greater than 6 times the pipe diameter.

2. The calculated diameter of the self-operated valve can be smaller than the diameter of the pipeline, while the stop valve, cut-off ball valve, bypass valve, and filter cannot be smaller than the diameter of the pipeline.

3. To facilitate on-site maintenance and operation, appropriate space should be left around the pressure regulating valve.

4. When the medium is clean gas or liquid, the filter in front of the valve does not need to be installed.