Pressure reducing valves (PRVs) regulate and minimize fluid or gas pressure in a pipeline or system. Typically installed where high-pressure fluid or gas enters the system, PRVs lower the pressure to a safe and manageable level for downstream components.
Pressure reducing valves use a spring-loaded mechanism or pilot-operated design to detect and control the pressure in the system. When the pressure exceeds the valve's set point, the valve opens to allow fluid or gas to flow through and lower the pressure to the desired level. The valve then closes once the pressure is stabilized at the set point.
Pressure reducing valves are commonly used in many applications, such as water supply systems, heating and cooling systems, and industrial processes. They are essential for maintaining pipelines and systems' safe and efficient operation by preventing overpressure and potential damage to equipment or personnel.
Pressure Reducing Valve Features
Self-Contained Pressure Control
PRVs control pressure through fully automatic self-contained operation by using a combination of mechanical and hydraulic components. Pressure reducing valves are typically equipped with a diaphragm or piston that senses the upstream pressure of the fluid or gas. When the upstream pressure exceeds the valve's set point, the diaphragm or piston moves to open the valve and allow fluid or gas flow. As the fluid or gas flows through the valve, it encounters a restriction orifice that reduces the pressure and maintains a constant downstream pressure.
A spring within the valve applies a force on the diaphragm or piston to keep the valve closed when the upstream pressure is below the set point. The spring is adjustable, allowing the set point to be changed as needed.
In addition to these mechanical components, pressure reducing valves may also be equipped with hydraulic components, such as a pilot valve or pilot line, that help to control the valve's opening and closing. The pilot valve or pilot line is connected to the diaphragm or piston. It uses a pressure signal to modulate the valve's position, allowing for precise downstream pressure control.
Precise Control of Downstream Pressure
By using a combination of sensing, regulating, and feedback mechanisms, PRVs precisely control downstream pressure. The valve senses the upstream pressure of the fluid or gas using a diaphragm, piston, or another sensing element. When the upstream pressure exceeds the valve's set point, the valve opens to allow fluid or gas to flow through and reduce the pressure to the desired level.
Water Hammer Protection
A pressure reducing valve can eliminate water hammer protection under defined conditions by combining design features and operational controls. Water hammer is a hydraulic shock that can occur when a fluid is rapidly forced to stop or change direction, resulting in a sudden increase in pressure that can cause damage to pipes and equipment. Pressure reducing valves are designed to minimize the risk of water hammer by controlling the pressure and flow of fluid in a pipeline.
To eliminate water hammer, pressure reducing valves may incorporate features such as slow-closing or quick-opening mechanisms, which can reduce the sudden changes in pressure that can lead to water hammer. Slow-closing mechanisms can be particularly effective in reducing water hammer by gradually closing the valve and reducing fluid flow rate in a controlled manner.
Adjustable closing speed or opening speed, which can allow the valve to be set to operate at a speed that minimizes the risk of water hammer, may also incorporate. These controls can be particularly effective when the fluid flow rate in the pipeline is subject to sudden changes, such as during the start-up or shut-down of pumps or other equipment.
System Saving
In the event of a power failure or other interruption to the supply of electricity, the valve may be unable to operate as intended, resulting in a loss of pressure control and potential damage to the system. To prevent this, pressure reducing valves can be designed with a bypass valve or feature that allows fluid to bypass the valve and flow freely through the system. This can help to maintain a minimum flow rate and pressure in the system, preventing damage to equipment and ensuring that the system remains operational until power is restored.
Rapid Action
A pressure reducing valve provides rapid action by immediately sensing and adjusting based on downstream pressure through its internal sensing, regulating, and feedback mechanisms. This allows the valve to respond quickly and effectively to pressure and flow rate changes, helping maintain a stable and safe operating environment for the pipeline and its associated equipment.
Types of PRVs
There are several types of pressure reducing valves, each designed for specific applications and operating conditions. The most common types include:
Direct-Acting Pressure Reducing Valves
These valves use a diaphragm or other sensing element to directly regulate the position of the main valve and control the downstream pressure. They are simple in design and suitable for low-flow applications.
Pilot-Operated Pressure Reducing Valves
This type of valve uses a pilot valve or pilot line to sense the downstream pressure and provide feedback to the main valve. As a result, they are capable of regulating higher flow rates and pressures than direct-acting valves.
Proportional Pressure Reducing Valves
Proportional pressure reducing valves use electronic or hydraulic controls to provide precise, proportional downstream pressure control. They are often used in industrial and process applications where precise pressure control is critical.
Differential Pressure Reducing Valves
These valves regulate the pressure differential between two points in a pipeline rather than maintaining a constant downstream pressure. As a result, they are often used in applications such as heat exchangers, where a precise temperature differential is required.
Back-Pressure Regulators
This type of valve maintains a constant pressure upstream of the valve rather than downstream and is typically used in applications such as fuel systems and chemical processing, where maintaining a constant upstream pressure is critical.
Pressure Relief Valves
These valves are designed to relieve excess pressure in a pipeline rather than regulate the pressure in safety applications, such as steam boilers and pressure vessels.
What is the difference between a pressure reducing valve and a pressure relief valve?
A pressure reducing valve and a pressure relief valve are similar types of valves used in piping systems to regulate pressure, but they serve different purposes.
A pressure reducing valve (PRV) is designed to regulate and lower the pressure of a fluid flowing through a pipeline to a predetermined level. This is typically done to ensure that excessive pressure does not damage downstream equipment or processes. As a result, a PRV maintains a constant pressure downstream of the valve, even if there are fluctuations in the inlet pressure. PRVs are commonly used in steam and gas pipelines, water distribution systems, and industrial processes where precise pressure control is necessary.
On the other hand, a pressure relief valve (also referred to as a PRV) is designed to protect equipment and piping systems from overpressure conditions by releasing excess pressure into the atmosphere or a low-pressure system. The valve is set to open at a predetermined pressure level and relieve the excess pressure until the system pressure returns to a safe level. These PRVs are commonly used in applications such as pressure vessels, pipelines, and storage tanks, where overpressure can cause catastrophic equipment failure or damage to the surrounding environment.
Learn more about Pressure Relief Valves
Pressure Reducing Valve Applications
Pressure reducing valves are used in a wide range of applications where precise pressure control is required. Some of the most common applications are:
- Water Distribution Systems – PRVs reduce high incoming water pressures to safe levels for use in homes, businesses, and other facilities. They can also help prevent damage to water mains and other distribution system components.
- Steam Systems – When used in steam systems, PRVs regulate the pressure and prevent damage to pipes, valves, and other components. They are often used in industrial applications, such as power generation and manufacturing.
- Gas Distribution Systems – Pressure reducing valves regulate pressure and prevent damage to pipelines and other components in natural gas distribution systems. They can also help to improve the efficiency of gas-fired equipment.
- Hydraulic Systems – PRVs are used in hydraulic systems to regulate pressure and prevent damage to pumps, valves, and other components.
- Process Industries – Pressure reducing valves help maintain precise pressure control and prevent damage to equipment in a wide range of process industries, including chemical processing, oil and gas refining, and food and beverage production.
- Fire Protection Systems – PRVs regulate the water pressure and prevent damage to fire hydrants, hoses, and other components while also helping to ensure that firefighters have access to a reliable water source in the event of a fire.
Overall, pressure reducing valves are an essential component of many different systems and applications where precise pressure control is critical for safe and efficient operation.
Advantages of Using a Pressure Reducing Valve
There are several advantages to pressure-reducing valves, including enhanced safety, improved efficiency, longer equipment life, consistent performance, reduced noise and vibration, and improved system stability. Pressure reducing valves provide a range of benefits that help ensure the safe, efficient, and reliable operation of pipelines, equipment, and systems in various applications.
Examples of Pressure Reducing Valves by Manufacturer
Bell & Gossett Pressure Reducing Valves
Bell & Gossett pressure reducing valves fill the system to a preset pressure for optimum performance. Combination dual unit valves include a pressure reducing valve and a relief valve.
- Fast fill feature reduces start-up time and labor
- Low inlet pressure check valve help prevents system pressure loss if the supply water drops below system pressure
- Convenient cleanable strainer prevents dirt and sediment from entering the system
- Union connection available with 1/2" male NPT thread and 1/2" female sweat tail-piece for fast, flexible system connection
- Brass body construction is highly resistant to corrosion and ideal for water systems
- Lead-free brass body/construction is ideal for potable water systems
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Taco Pressure Reducing Valves
The Taco 3350 valve is used to automatically feed water to a hydronic system whenever pressure drops below the valve's pressure setting. The 3350 PRV reduces incoming pressure and automatically maintains system pressure to the valve's adjustable set point. If the system pressure drops below the valve's set point, it will automatically add water. The 3350 is suitable for systems with fill pressure requirements between 10-50 psi and features a fast-fill button with automatic reset. The valve automatically exits the fast-fill mode once the system is full and the desired set pressure is reached.
All parts in the cartridge-style pressure reducing valve are contained in a one-piece cartridge that can be easily removed and serviced without reducing system pressure. The device offers a fast-fill mode that automatically returns to normal mode when the set pressure is reached. It also delivers increased flow to speed system fill times. Its unique dial-in pressure setting allows for easy adjustment throughout the 10-50 psi range without needing an external gauge.
The unique one-piece cartridge design significantly reduces diaphragm load, extending the overall product life. A stainless steel coaxial strainer prevents system debris from affecting the valves' performance. An integral check valve allows the cartridge to be removed under system pressure for replacement or servicing. The 3350's body is made of forged brass. Wetted parts inside the cartridge are made of stainless steel, engineered plastics, and bronze.
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Armstrong Pressure Reducing Valves
Armstrong low pressure reducing valves feature the same unit as Armstrong combination valves. All working parts are brass with an easily cleaned built-in strainer. They are factory adjusted at 12 lbs and are suitable for 1, 2, and 3-story buildings. Model RD-11 is equipped with either a sweat or threaded tailpiece on the inlet side and an integral check valve.
Armstrong high pressure reducing valves are factory adjusted for 150 lbs initial and 45 lbs delivery pressure. They feature all working parts brass, a built-in strainer, an extra large diaphragm, and a check valve.