Structure, Operating Principle and Classification of Pressure Reducing Valves.
What is a pressure reducing valve?

Pressure reducing valve is also known as pressure regulating valve, pressure stabilizing valve, pressure regulating valve, etc. It is a type of industrial valve installed on the pipeline, with the function of reducing pressure and stabilizing the output pressure, so that the output pressure is always smaller than the input pressure of the system, helping the fluids to be easily transmitted to different devices. but the pressure is not too different.

 

Pressure Reducing Valve allows the operator to adjust the output pressure to approximately the desired number, as long as that number is compatible with other connections. From there, whether the fluid has a strong or weak flow, the pressure through the valve will still be adjusted appropriately, without changing.

Pressure reducing valves are usually made of alloys such as cast iron, copper, steel, stainless steel, etc. Depending on the needs of use and budget, there are suitable choices.

This device is widely used in air compressor plants, water pipelines, mining industry, etc.

Video introducing Pressure Reducing Valves from manufacturer OCV - USA. High quality Industrial Pressure Reducing Valves.

What is the pressure rating of a pressure reducing valve?

When the fluid is introduced into the system, the effects inside the pipe as well as the flow rate will create high pressure, causing the flow pressure to increase and be higher than the inlet pressure.

However, at some point, the system is required to divide the fluid into different branches or devices. Each branch will have a different type of pressure and is usually lower than the pressure of the pipe. Therefore, to ensure that the output pressure of these branches is compatible and suitable, without too much difference, a pressure reducing valve will be attached to the pipe to create a rated pressure.

When passing through the valve, the pressure of the fluid, whether high or low, will be changed to this rated pressure, depending on the number desired by the operator. This type of valve can be adjusted for both direct-acting and indirect-acting reducing valves.

Structure of the pressure reducing valve

Pressure reducing valves have many different structures and shapes. However, according to the operating principle, there are two basic types: Direct Operated Pressure Reducing Valve and Indirect Operated Pressure Reducing Valve.

There are two types of pressure reducing valves: direct-acting pressure reducing valves and indirect-acting pressure reducing valves.

 

Structure of direct-acting reducing valve

• Valve body: Has the task of containing and protecting the components inside the body. Connected to the system by threading, welding, flange connection... together with the valve cover to form a complete, closed device.

• Valve cover: Directly connected to the valve body to seal the device, preventing the fluid from flowing back out during operation.

• Valve pressure spring: Includes adjusting spring, main valve spring.

• Valve shaft: Directly connected to the valve disc, has the task of receiving force from the handwheel, then acting on the valve disc, making the valve disc operate.

• Valve disc: Has many different shapes from ball, pin disc, cone,... When acted upon, the valve disc will perform the action of lifting and lowering, helping to reduce pressure for the system, with good corrosion and oxidation resistance.

• Pressure adjustment screw: Responsible for adjusting the rated pressure for the output.

 

Indirect-acting valve structure:

• Main valve: Where the valve body and main valve disc operate. Directly connected to the pipe, it has the function of adjusting the output and inlet flow pressure of the valve.

• Adjusting screw: Where the valve output pressure is adjusted.

• Adjusting spring: When performing the adjustment action, the adjusting screw will exert force on the spring, thereby transmitting the signal to the controller.

• Regulator: Automatic regulator, which receives the output pressure signal. The regulating valve has the task of adjusting the pressure acting on the valve disc, creating a balance between the pressure in the valve and the valve output pressure.

• Controller: Has an important task, directly affecting the spring of the main valve, helping to adjust the opening of the main valve, thereby increasing or decreasing the output pressure so that the fluid can flow easily to other devices without any difference.

 

Working principle of pressure reducing valve

Because of the different structures, the direct-acting reducing valve or the indirect-acting reducing valve will also have different working principles. However, they also have in common the pressure adjustment based on the compression of the adjusting spring.

Working principle of direct-acting pressure reducing valve

In the normal state, the valve is fully open, the width of the valve port will be set by the adjusting screw, which will directly affect the valve spring, just need to increase or decrease the compression of the spring to increase or decrease the pressure. The rated pressure will always keep the output pressure value stable and unchanged.
Increase the output pressure of the valve: Turn the screw clockwise, the valve spring is affected, leading to increased compression. This action will reduce the direct aperture of the main valve, increase the clearance between the valve seat and the valve disc. The flow rate of the fluid through the main valve increases, thereby increasing the output pressure of the valve.
Reducing valve outlet pressure: The operator simply turns the screw counterclockwise to reduce the spring compression. This will narrow the gap between the valve seat and the valve disc. The flow rate of the fluid through the valve will decrease, thereby reducing the valve outlet pressure.

Operating principle of indirect-acting pressure reducing valve

This type of valve will have a difference compared to the direct-acting valve, which is to adjust the balance between the output pressure and the pressure acting on the main valve diaphragm. Then set the large or small opening of the main valve to achieve the desired pressure.
Increase output pressure: Turn the screw clockwise, this will create a torque that affects the spring, causing the spring compression to increase. In this way, the aperture of the regulating valve is expanded, reducing the pressure on the main valve diaphragm, helping to expand the gap between the valve seat and the valve disc. From there, the flow rate through the main valve will increase, increasing the output pressure of the valve.
Reduce output pressure: Turn the screw counterclockwise to reduce the spring compression. The spring compression force decreases, the aperture of the regulating valve will become smaller, the pressure on the main valve diaphragm increases, causing the gap between the valve seat and the valve disc to narrow. Reduced flow through the main valve will reduce the valve outlet pressure.

Technical specifications of some pressure reducing valve brands.
Each type of pressure reducing valve will have different technical specifications depending on the usage needs, below is the technical specifications table of some pressure reducing valve brands:

OCV pressure reducing valve from the US:

• Model/Series: 127

• Cv range: 2.3 ~ 6210

• Size: From DN32(1.1/4") – DN600 (24")

• Material: Ductile iron, Cast steel, Copper, Stainless steel.

• Connection type: ANSI150# and ANSI300# flange

• Maximum operating pressure: 740 psi

• Output pressure range: 5~740 psi (depending on size, depending on material, choose spring range when ordering.)

• Maximum temperature: 400 degrees F (~204 degrees C)

• Fluid used: Water

• Origin: USA

 

VENN Japan Pressure Reducing Valve:

• Model/Series: RP6-B

• Cv range: 1 ~ 256

• Size: From DN15 (1/2") – DN200 (8")

• Material: Gray cast iron

• Connection type: JIS10K FF flange

• Maximum operating pressure: 1.0MPa

• Output pressure range: 0.03~0.8MPa

• Maximum temperature: 184 degrees C.

• Using fluid: Steam

• Origin: Japan

 

 

Pressure reducing valve from Yoshitake Japan:

• Model/Series: GP-1001V

• Cv range: 1 ~ 256

• Size: From DN15 (1/2") – DN100 (4")

• Material: Ductile iron

• Connection type: JIS10K FF flange

• Maximum operating pressure: 1.0MPa

• Output pressure range: 0.05~0.9MPa

• Maximum temperature: 220 degrees C.

• Usable fluid: Steam, Air

• Origin: Japan

Samyang Korea Pressure Reducing Valve:

• Model/Series: YPR-1S

• Cv range: 1 ~ 256

• Size: From DN15 (1/2") – DN200 (8")

• Material: Gray cast iron

• Connection type: KS 10K RF flange (~ JIS10K RF)

• Maximum operating pressure: 10 kgf/cm2g

• Output pressure range: 0.35~8 kgf/cm2g

• Maximum temperature: 220 degrees C.

• Usage fluid: Steam, Air

• Origin: Korea

SPECIFICATIONS (mm))

 

Classification of Pressure Reducing Valves

There are many types of Pressure Reducing Valves on the market with their own characteristics. Therefore, for the convenience of users, based on some criteria, this device is divided into many different types such as:

Classification by operating method
Direct-acting pressure reducing valve

This type of valve is often made of solid alloys such as stainless steel, copper, cast iron, steel, etc. and is often simpler in structure than the indirect valve.

When a force is applied by rotating the screw, it will directly affect the valve spring, which will increase or decrease the compression of the spring, helping to expand or narrow the gap between the valve seat and the valve disc, thereby increasing or decreasing the output pressure of the system.

 

Indirect Pressure Reducing Valve

This type of valve operates on an indirect mechanism and has a more complex structure than a direct pressure reducing valve. The operating mechanism is based on adjusting the balance between the outlet pressure and the pressure acting on the main valve diaphragm. Then set the large and small opening of the main valve to achieve the desired pressure. Although the pressure reduction ratio is high, the flow control valve only allows a small amount of pressure adjustment at each adjustment.

 

Classification by usage environment

Water pressure reducing valve

Also known as water supply pressure reducing valve. This type of valve has the function of reducing pressure and stabilizing the output pressure for the system, protecting the safety of pipes and equipment, and is often used in industrial and civil water supply systems.

Usually, too large a flow rate will create quite high water pressure in the system. Therefore, the pressure reducing valve is a great tool to help balance the output water pressure, avoiding high pressure that will damage the pipes and affect the user.

 

Pneumatic pressure reducing valve

Also known as pneumatic pressure regulator, pneumatic pressure regulator, ... has the task of adjusting air pressure, to ensure stable output pressure to other applications and equipment, helping the system and other machines to operate normally.

This type of valve is widely used for air compressors, adjusting the output limit of the system, so that whether the pressure in the system is low or high, the output pressure will be fully compatible with the device.

The valve usually has a gauge attached to both ends to display the input pressure and output pressure of the system, helping the operator to observe and monitor easily.

 

Hot steam pressure reducing valve

This type of pressure reducing machine is widely used in steam plants, boiler systems, steam boilers, drying and steaming systems in the food processing industry.

This type of valve is also used to adjust hot steam to the correct pressure and temperature to vulcanize products in rubber factories, helping to adjust and maintain the stability of the output pressure according to an available standard.

 

Hydraulic Pressure Reducing Valve

This is a type of valve that operates indirectly, the manufacturing material is usually cast iron with sizes from DN50 - DN500. The valve operates based on the flow pressure pushed into the system and the flow pressure is adjusted through the pilot

.

Classification by connection type

Welded joints

This is the method by which the valve will be welded tightly into the system pipeline, usually large pipes. This type of joint will help the valve have a solid connection, not falling or breaking when there is vibration. However, it will cause difficulty in disassembling and repairing.

Threaded joints

Usually operate on small pipes with sizes from DN50 or less, the main production materials are stainless steel, copper, steel, cast iron, etc.

This type of valve will be connected to the system by threaded joints, so the installation process is quite simple. This type of valve is extremely convenient and is used in many different environments. However, the ability to withstand pressure is relatively low, so it is only suitable for small systems.

Flanged joints

Used in systems with medium and large pipes from DN40 - DN300, the body is designed with a flange for installation into the system. Flanges usually comply with current standards such as ANSI, JIS, BS, DIN, etc. This type of valve has better sealing ability than the threaded type, avoiding leakage.

Designed from many different materials such as steel, cast iron, copper, stainless steel, etc., it can withstand high pressure and work in many harsh conditions. The advantage is that it can withstand high pressure, so it is often used in large systems.

 

Classification by material

Copper pressure reducing valve

Copper has high safety, heat resistance and good durability. The main design of this type of valve is usually threaded or flanged.

The advantage is that the pressure adjustment is quite easy, safe and durable, so it is used in clean water environments for apartment buildings, high-rise buildings, in the food and medical industries and some hot steam systems.

Cast iron pressure reducing valve

Cast iron has high mechanical strength, can withstand harsh environments such as high temperature, high pressure, so it is widely used in compressed air systems, hot air, industrial zones, etc.

The outer layer of cast iron pressure reducing valves is often painted with an epoxy layer to prevent dust and oxidation. However, the ability to resist corrosion by chemicals is relatively low.

Stainless steel pressure reducing valve

Stainless steel is a hard and relatively durable alloy, capable of working in harsh environments such as high pressure and temperature. At the same time, the ability to resist corrosion and oxidation is quite good. Therefore, the price of this type of valve is often higher than that of valves made of other materials.

Stainless steel valves are preferred for installation in highly specific systems such as chemical systems, gasoline, gas, compressed air, etc.

 

Advantages of pressure reducing valve

As a device with effective pressure protection and control functions, Pressure Reducing Valve always plays an essential role in many pipeline systems, receiving high appreciation for its outstanding features:

Reduce the output pressure of the system to be compatible with many different applications and devices, stabilize the system at a safe level, avoid vibration, cracking, reduce life, protect equipment on the pipeline, avoid explosion when overloading pressure causes damage to the system, dangerous for users.

Diverse in design, material and cost, suitable for different usage needs.

There are many popular connection types such as welding, threaded, flange, suitable for many types of pipes with different sizes and materials.

Can work automatically thanks to the pressure of the fluid in the pipe.

Withstand high pressure up to hundreds of bars.

Applied to many different types of environments such as liquid, gas, steam, chemicals, etc.

Made from hard alloys such as stainless steel, cast iron, copper, steel, etc. with good corrosion resistance, working well in environments with high pressure and temperature.

Compact design, simple working mechanism, quick operation.

Simple installation, easy to disassemble for maintenance and repair when necessary.

Many brands to choose from from Korea, Japan, China, Europe, etc.

In addition to the above advantages, the pressure reducing valve also has some limitations, affecting the valve's performance:

Not very effective when used for fluids in solid, granular form, with many impurities such as powder, cement, mud, wastewater, etc.

Due to frequent immersion in fluids, the sealing part will be easily damaged.

 

Application of pressure reducing valve

Today, with the superior features that this device brings, pressure reducing valves have been widely used in most different industries and fields. Especially in fields related to water pressure, air pressure, hot steam pressure adjustment, etc.

The reason this device is popular is because once the pressure exceeds the allowable limit, the system will not be able to operate effectively, damaging many devices, causing injuries to operators and causing great economic losses. Some of the fields where pressure reducing valves are most widely used include:

Applications in water and liquid systems
Water systems of high-rise buildings, adjusting the pressure for lower floors below to have stable water pressure.

Widely used in factories, industrial parks, machinery and equipment manufacturing.

Applications in industrial water treatment systems, domestic water, irrigation water, production.

Clean water treatment plants.

Factories producing soft drinks, wine, beer, milk, etc.

Applications in hydroelectric and thermal power plants.

Water supply and drainage systems for ships, oil pipeline systems, etc. help to minimize possible incidents due to water or gas pressure exceeding the allowable level, and keep the system pressure balance within a safe level.

Lake systems, swimming pools, water parks, fountains, etc.

 

Applications in the food processing industry

In the large-scale food processing industry, to ensure a certain level of safety in production, pressure cookers will be designed with a pressure regulator and a pressure relief valve. This helps prevent explosions, which can be dangerous in cases where it is necessary to maintain high temperatures and pressures to quickly cook food.

 

Applications in pneumatic systems
High temperature air compression systems.

Drying, steaming, cooking, ironing, pressure cookers, boilers, etc.

Garment factories, textile factories.

Wood factories.

Metallurgical factories.

Mineral, fuel, coal, oil mining systems, etc.

Widely used in industry to run supporting tools, blow clean, inflate tires, balloons or other types of airbags, etc., reduce pressure to avoid overloading the air, reaching a level that can be dangerous.

Applications in other fields of science - technology - life.

 

How to adjust the output pressure of the pressure reducing valve

Usually, the pressure reducing valve used for water will be set by default to 3 - 5 bar. However, if we need to change the pressure of the pressure reducing valve, we can perform the following steps:

Before adjusting, we need to close all types of valves and faucets installed after the pressure reducing valve first.

To easily adjust the output pressure of the valve, we need to install a pressure gauge. Installing the gauge will help us easily monitor the pressure fluctuations, thereby making appropriate adjustments.

Then remove the valve protection cap.

Use a wrench to loosen the locking screw.

Use a 2-sided screwdriver to turn clockwise to increase pressure and turn counterclockwise to reduce pressure.

When the desired pressure is reached, tighten the locking screw to fix it.

After completing the above steps, close the protective cap.

 

 

 

Some notes when buying a pressure reducing valve

Before buying a valve, you need to specifically research each type to make the right choice. A pressure reducing valve compatible with the system will bring higher operating efficiency. Things you need to keep in mind when buying a valve are:

Depending on the environment of use, there is a suitable valve choice. For example, stainless steel valves will be used in places with high temperature and pressure, corrosive chemicals. Cast iron or copper valves should be used in places with normal temperature conditions, not too high pressure, which will help save a lot of costs.

Choose a valve depending on the rated pressure of the system. The rated pressure of different systems will be different. Therefore, it is necessary to clearly understand the rated pressure of each system to have a suitable valve choice, helping to bring the best working efficiency. According to the manufacturer's recommendation, a pressure reducing valve with a safety pressure 8-15% higher than the system's rated pressure will activate the valve to open more easily.

Depending on each system, there are suitable designs and connections. Threaded and flanged connections are two types of connections that are highly effective, low cost and easy to install.

Choose reputable stores and guaranteed brands to avoid buying fake, counterfeit, and poor quality goods.

 

How to install a pressure reducing valve?

In order for the pressure reducing valve to operate stably and durably over time, without shaking or tearing the valve membrane, when installing, we need to follow all the safety instructions provided by the manufacturer.

Pay attention to the joints and connections to see if they are consistent, consider whether the length of the straight pipe when connecting directly to the Pressure Reducing Valve is reasonable. At the same time, it is advisable to install additional pressure gauges on both sides of the valve to control the pressure parameters of the valve, avoiding the case of being unable to control the pressure overload.

It can be seen that the pressure reducing valve is an indispensable device in most industries, especially the liquid and gas industry. Thanks to the Pressure Reducing Valve, industrial operations become easier, stabilize the pressure of the system, help the system operate efficiently, quickly and bring high safety.

Demo image of installation instructions for pressure reducing valves for steam systems

 

Demo image of installation instructions for pressure reducing valve for water system

Demo image of installation instructions for pressure reducing valve for steam (gas) system

 

If you want to know more information about pressure reducing valves or need to order, please contact us immediately via hotline for the most specific advice. Phuc Minh is proud to be one of the most reputable suppliers of genuine valves on the market today. We have many valve lines with diverse designs, quality and imported directly from abroad, bringing the best experience to consumers.