Self-Regulated Control Valve-FAQ

A self-regulated control valve is used for adjusting the flow by using fluid pressure in the pipe. The flow is adjusted by receiving the energy from the controlled system. It has a simple structure and is economical to use.

The self-regulated valves that control the pressure at its inlet are called self-actuated upstream pressure control valves. They control the pressure at its outlet are known as self-actuated downstream pressure control valves.

This guide will detail the self-regulated control valve, its benefits, drawbacks, specifications, and other properties.

1. What is a self-regulated control valve?

The self-regulated control valve is the pressure-reducing valve and maintains stable secondary pressure without disturbing the primary pressure. The self-regulated pressure valve does not depend on the external signal for controlling pressure; instead, the pressure itself acts as a signal for opening or closing the pressure valve.

A self-regulated control valve controls the pressure at the upstream or downstream side of the control valve. If the pressure upstream is used to accelerate the control valve, the upstream pressure is maintained at a specific set point called the backpressure control valve. This valve is responsible for maintaining the back pressure by the control valve.

If the downstream pressure valve throttles the control valve, then the downstream pressure is maintained at a specific set point called self-regulated control valves.

2. What is the working principle of a self-regulated control valve?

The self-regulated control valve is applicable in various throttling applications and on/off applications. The process fluid is put into the diaphragm or piston, passing through the pilot to maintain the pressure. The pilot controls the main valve’s motion of the system. The pressure control requires three functional units, the controller, the measuring equipment, and the final controlling equipment.

The self-regulated control valve is expensive and complex in differential pressure or temperature control tasks. With less downstream pressure, the more trim open, and more downstream pressure causes more trim closing. The spring has the setpoint valve, which can be replaced if a different setpoint is required.

There is a pilot-loaded pressure regulator that uses external gas pressure for getting the pressure regulation set point. The pressure regulator acts as a pilot device to load pressure into the primary.

Regulator’s actuating diaphragm. The external load pressure establishes the regulator’s setpoint instead of the internal spring of the self-regulated control valve.

You can smoothly adjust the pressure by turning the knob on the pressure regulator, which is also adjustable at this point. The function of the pilot mechanism is to control the primary gas throttling mechanism. The pilot-operated valve is used in liquid service rather than gas.

3. What are the types of self-regulated control valves?

High pressure self-actuated regulating pressure reducing valve

This self-regulated control valve has a forged valve body. It has a nominal pressure of 6.4Mpa, 10Mpa, and 16Mpa and is suitable for high-pressure applications. The high-pressure self-actuated pressure reducing valve has two types, upstream and downstream self-regulating pressure reducing valve.

The downstream pressure makes sure to keep pressure behind the valve constant. It is suitable for oil, water, and non-corrosive gas at a temperature below 350°C.

Self-actuated temperature control valve for steam hot water

It has two main parts, the temperature sensor, and globe valve. It uses the principle of liquid thermal expansion to control pressure. It has a temperature range from -20°C-350°C. The self-operated temperature control valve is categorized into heating type, cooling type, and mixing type.

With the temperature rise, the valve closes that reduces the flow rate. Whenever the temperature decreases below the set value, it increases the flow rate of the medium to increase the temperature.

Self-operated micro pressure reducing regulator

The self-operated micro pressure regulator is divided into a single seat and a double seat. It does not need any external energy, and the actuator controls the position of the spool. The actuator changes the pressure difference and flow and achieves pressure stability and relief for downstream and upstream types.

4. What is the structure of the self-regulated control valve?

The self-regulated control valve consists of a pilot tube that takes the process fluid to pressurize the diaphragm. The diaphragm opens the valve so that the process fluid can pass through. The pilot tube connects the diaphragm to the downstream of the control valve. When the downstream pressure increases in the self-regulated control valve, the pressure is exerted on the diaphragm and closed.

When the valve closes, the process fluid also stops, reducing the downstream pressure to the setpoint level. When it’s below the set point, the liquid from the diaphragm goes back to the process line, thus relieving the pressure on the diaphragm. However, it results in the valve opening, increasing the process flow, thus increasing the pressure to its set point.

In the backpressure regulator valve, the diaphragm connects with the upstream of the pressure control valve. The process fluid is responsible for the opening and closing of the valve due to high or low pressure.

5. What are the applications of a self-regulated control valve?

The self-regulated control valve is suitable for pressure, temperature, and differential pressure control in various applications. It is used in applications where there is the deviation of controlled variables from the given set point. These setpoints are usually constant for the entire equipment life. The self-regulated control valve needs auxiliary power to operate the electrical signal. It has an actuator that connects to the valve.

The self-regulated control valve is used widely in gas, clean water, and heat supplier applications. It is a very reliable tool in providing control functions. Even in applications with energy supply failure, the self-regulated control valve is ideal as safety equipment. These valves maintain the inlet and outlet pressure in hygienic applications for dairy, food, and beverage industries.

6. What are the features of a self-regulated control valve?

The self-regulated control valve consists of a control valve, actuator, and a spring for pressure control. It is used for controlling the downstream pressure in the pipes. The control valve is closed when the downstream pressure arises. Some of the features of a self-regulated control valve are as follows:

• It provides upstream and downstream pressure control of non-corrosive liquids and gases.
• There is a feature of automatic adjustment with no external energy.
• The diaphragm in the self-regulated control valve has sensitivity adjustment to the pressure change.
• The piston-cylinder has high-pressure resistance and adjustable travel.
• The control valves are single-seat and sleeve types that provide comprehensive control.
• It has the material of stainless steel bellows which provide zero leak and frictionless stem seal.
• The upstream and downstream pressure of the self-regulated control valve is balanced through stainless steel bellows.
• The wetted parts of the control valve have non-ferrous metal.
• There is a control line kit for direct pressure tapping.
• The self-regulated control valve is maintenance-free with low noise.

7. What are the advantages of a self-regulated control valve?

• It is simple, reliable, and durable equipment with energy consumption.
• The self-regulated control valve is easy to install and operate.
• It provides an accurate flow coefficient with excellent performance.
• It is cost-effective as a self-regulated control valve does not require energy sources. Therefore, there is no need for electricity or gas sources to run it.
• It has accurate flow characteristics and provides good sealing performance.
• You don’t need additional axillary energy such as pneumatic or air energy to operate and move the actuator.
• They are widely used to control the pressure of fluids and gases in pharmaceutical and food plants because of their accuracy.
• It is medium controlled with self-operated regulators. It has an easy set point adjustment of the valve.

8. What are the technical specifications of the self-regulated control valve?

• The range of low pressure reducing valves for pressure setpoints ranges from 0.075 to 0.75 psi.
• There is a condensation chamber for liquids or streams to 350°C.
• A safety pressure control valve prevents the leakage and sealing or any rupture indication of the diaphragm.
• The control line kit of the self-regulated control valve provides pressure tapping at the valve body.
• For remote adjustment of the setpoint, there is an actuator.
• The bellow actuator has a set point ranges from 75 to 145, 145 to 320, 290 to 400 psi. The bellow actuator housing has the material of AISI 304, AISI 316Ti.
• The self-regulated control valve has an armored seat or plugs for better wear.

9. What is the principle of operation of the self-regulated control valve?

The medium flows through the valve, and the flow rate is determined by the position of the valve plug and the free area between the plug and seat. The plug stem is connected to the stem of the actuator. For controlling pressure, the diaphragm is joined by the positioning springs and the adjustment nut.  The self-regulated control valve is opened by the positioning spring once both the pressures are balanced.

The downstream pressure P² is controlled downstream of the valve. It is transmitted to the operating diaphragm through the control line, changing it into the positioning force. This force adjusts the valve plug and is adjustable at the set point adjustment nut. When the downstream pressure P² rises above the setpoint, the valve closes, and pressure changes.

The valves have the balancing bellows where the downstream pressure acts on the inner surface of bellows, while the upstream pressure works on the outer bellow surface. Thus, it balances the forces produced by the upstream and downstream pressure.

10. What are the components of a self-regulated control valve?

In letdown pressure regulators, no power supply is required, and the failure position is the position it takes if any of the components fail. If the diaphragm or downstream pressure breaks, the regulator opens. The regulator closes when the spring breaks. For overcoming the diaphragm failure, you need to place a relief valve.

Cavitation occurs between the two valves when the pressure inside the valve drops below the vapor pressure of the flowing fluid. It can be overcome with the pressure recovery coefficients of the regulators and cavitation coefficients.

11. How to calibrate a self-regulated control valve?

For testing the proper functioning of the self-regulated control valve, you need to have a regulator and test gauge. First, check the instrument data and pressure requirement. Check the specification sheet of the vendor and the maximum allowable pressure. Open valve A and check the pressure indication on test gauge B with the set pressure.

If the set pressure does not meet the specifications, you need to remove the setpoint adjustment screws of the self-regulated control valve. Adjust the screw until the desired pressure is achieved. This procedure is used for pressure reduction in the control valve.

The second method is the backpressure regulator method, in which the regulator and test gauge are needed as the testing equipment. In this method, you first need to check the instrument data and vendor’s specification sheet. The instrument is set up for testing.

Repeat the same procedure by opening valve A and note down the pressure indication of valve B as the set pressure. If the set pressure is not per the specifications, remove the set point adjustment screw and adjust it until the test gauge reaches the desired pressure.

12. What are the essential parts of a self-regulated control valve?

The self-regulated control valves are used to control and maintain pressure in various applications. The self-regulated control valves are standard in the gas industry, while the pilot regulated control valve is suitable in high flow situations. The self-regulated control valve consists of three main parts:

• A measuring element
• A loading element
• A restrictive element

The loading element is weight, spring, or pressure from some external source. When you compress the spring, it produces a loading force. The diaphragm connects to the process fluid, which creates a force against the loading force.

The restrictive element is connected to the spring. The diaphragm regulates the flow through the regulator. In the self-regulated control valve, the downstream pressure decreases the spring force. This force overcomes the gas on the diaphragm causing the valve to open and increase the flow. The increase in pressure closes the valve and reduces the flow.

13. How to best use a self-regulated control valve?

The self-regulated control valve is a cost-effective and optimized pressure measuring solution used in various distribution networks. The tricky task is to purchase a suitable self-regulated control valve for your application. When there are changes in the physical environment of the valve, the self-regulated control valve responds by opening or closing.

A differential pressure regulator applies the pressure of the fluid against the diaphragm. The diaphragm uses a spring to get force balance with the diaphragm at the set pressure. You need to maintain higher differentials between temperature and flow in heating systems to get the most out of energy.

If you want to achieve the high efficiency of the self-regulated control valve, the balanced flow control system is preferred, ensuring a balanced supply of heating and cooling in all installation parts. In addition, the control valves use downstream to maintain accurate performance.

The pressure-independent control valves are successful in providing cost-effective control within the distribution networks. Another important factor is considering the low supply and centralized distribution factors for getting the balanced heating system. The self-regulated control valve is the self-controlling valve that does not need any further input. Therefore, it provides the best performance and proper levels.

14. What are the safety precautions of using a self-regulated control valve?

• Some preventive measures need to keep in mind while you are operating a self-regulated control valve. Some safety precautions are as follows:
• Before using a self-regulated control valve, inspecting the regulator and valve before using it is essential.
• It is recommended to avoid connecting the valves and regulators to the supply source, which has a higher pressure than the regulator’s maximum rated pressure.
• Read the product label specifications carefully. If there is no rate pressure, contact your representative for the rated pressure installation and use.
• Before the installation of regulators and valves, establish the flow direction of the fluid. It is the primary duty of the user to install the equipment properly.
• When you are installing the self-regulated control valve, do not over-tighten the components in the pressurized system.
• If there is any malfunction in the self-regulated control valve or case of any leakage, immediately take it out of service.
• While applying pressure, make it gradual to avoid any sudden pressure shock to the equipment.

15. How does the self-regulated temperature control valve work?

Self-regulated temperature control valves do not depend on external power sources to regulate the temperature in various systems. For example, these are commonly used for boiler temperature adjustment by maintaining a linear relationship between temperature and the valve.

For operating the self-regulated temperature control valve, the sensor is inserted into the pipeline—the change in temperature results in the opening of the valve. If the temperature rises, the sensor is heated and expands capillary to close the valve.

Once the temperature changes, the liquid volume changes. This change is transmitted through the capillary tube while the actuator acts on the valve stem. When the temperature is heated, it will close the valve. When the temperature is cooled, it opens the valve.

16. What is the installation method of a self-regulated control valve?

There are some techniques and strategies for installing the self-regulated control valve. While installing, make sure that the valve body is installed at the inlet of the primary heat medium. The valve stem is positioned upwards to make sure that the self-regulated control valve has a vertical position. Finally, you need to install a filter at the inlet of the self-regulated control valve.

Install on/off valve on the inlet and outlet of the control valve. Insert the sensor around the outlet and carefully observes the valve stem and capillary tube during installation.

17. What are the parameters of a self-regulated control valve?

The body type of the self-regulated control valve is single-seated and globe type. The trim material is made of stainless steel. The temperature ranges from -5°C to +70°C.

It is used widely for the pressure-reducing stabilization for gases, liquid, and steam. The design and manufacturing of the self-regulated control valve are manufactured according to the standard of AMSE/API/BS/GB.

The accuracy range is within ±5%, and the connection is flanged or socket welding. The pressure class of the self-regulated control valve is 1.6, 4.0, and 6.4 Mpa.

18. What is the difference between a self-regulated control valve and a pilot-operated pressure-reducing valve?

The self-regulated control valve uses flow pressure in the pipe to adjust the flow. It controls and manages the secondary stress without affecting the primary force. In contrast, The pilot-operated pressure-reducing valve allows flowing from inlet to outlet port in the system. The self-regulated control valve is operated by the diaphragm that adjusts the primary pressure to a piston.

The self-regulated control valve reduces and balances the excess pressure in the system. The essential function is to relieve stress from higher to lower. The self-regulated control valve is suitable in applications where precise pressure control is required for larger loads. It is famous for gas and steam flow control. If the medium is liquid, the liquid should be clean without dirty.

Pilot operating pressure valves reduce the pressure in the pipeline; they are cheaper. Its structure consists of a pilot valve for loading a diaphragm. It increases the force to open the valve. The pilot-operated pressure reducing valve has the advantage of tight downstream pressure control. It has a wide application for gas, liquid, oil, steam, etc.

The pilot-operated pressure deducing valve has the same components as the self-regulated control valve: diaphragm, plug, seat, and spring. It has the added component of a pilot, which separates  P2 from the loading force. The pilot connects with the downstream piping, which provides accurate measuring of the pressure conditions.

19. What is the Precautions for the installation of a Self-regulated Control Valve?

The main precaution of installation of a self-regulated control valve are:

• The pressure point should be taken at the appropriate position of the pressure regulating valve. The pressure regulation before the valve should be more significant than 2 times the pipeline’s diameter, and the pressure regulation after the valve should be greater than 6 times the pipeline’s diameter.
• According to the calculation, the diameter of the self-operated valve can be smaller than the pipeline’s diameter. In contrast, the stop valve, cut-off ball valve, bypass valve, and filter can’t be more modest than the distance across the pipeline.
• Appropriate space should be around the pressure regulating valve to facilitate on-site maintenance and operation.
• The filter before the valve may not be installed when the medium is clean gas or liquid.

Conclusion

A self-regulated control valve is an important tool for adjusting the flow in various applications. The self-regulated control valve is used widely in different industries, such as petroleum, electric power, food, metallurgy, textile, machinery, and construction buildings.

At BCST, we provide high-quality and reliable self-regulated control valves to meet the specific requirement of your application. You can contact us any time in case of any queries.