Angle Seat Valve Working Principle

Angle Seat Valve Working Principle

examples of angle seat piston valves

Figure 1:Common angle seat valves

Angle seat valves, also known as angle body piston valves or pneumatic angle seat valves, are 2/2-way pneumatically actuated piston valves. The piston actuator provides a linear motion to lift the seal off its seat. Because the seat is positioned under an angle, the flow is minimally impeded in the open position, resulting in an excellent flow rate and a low pressure loss. They are used to regulate the flow of liquids, gases, steam, vacuum, and even aggressive fluids. They can also operate with high temperatures and high viscosity media, even under zero differential pressures.

The robust design makes angle seat valves a popular choice for harsh applications, and they have very high cycle lives. Therefore, they are excellent long-life alternatives to ball valves. These valves are also suitable alternatives for solenoid valves, especially with contaminated, viscous media where typical solenoid valves would fail. They may be operated using a single-acting or double-acting configuration, which has an influence on its pressure rating. They can also be designed as manually operated or electrically operated, but in this article, we will focus on the pneumatic angle valve.

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Construction and design

Angle seat valves have a robust construction similar to globe valves but use a piston-operated angle type valve with a closure spring. The body is normally cast or die-forged in one piece. A plug is connected to the end of the piston which is seated on PTFE seats. The piston is designed to retract further from the seat, thereby providing maximum flow rate. They may be Normally Closed (NC), Normally Open (NO), or Double Acting. The piston actuator comes with threaded ports or with NAMUR ports which allows for direct mounting of NAMUR style solenoid valves.

section view of an of angle seat valve

Figure 2: Section view of an of angle seat valve.

Often, the actuator head can be rotated 360° to allow the optimum position of air and electric lines in tight locations. The valve body is generally made of brass or stainless steel. Connection types include threaded, clamped, or welded. Typically, a visual indicator on the top of the piston shows whether the valve is open or closed.

Working principle

Angle seat valves are operated pneumatically such that air pressure is used to control the piston actuator, which lifts the valve plug off its seat. Normally Closed (NC) valves usually have the valve closed in unpressurized conditions and use a spring to return the valve to the rest state. Normally Open (NO) valves have the valve opening always open unless air pressure acts to close it. A NO valve can be obtained if the spring is placed on the opposite side of the piston actuator. Double Acting valves can be used to handle flow in both directions. These valves have no spring and depend on the supply air to determine the valve position.

Flow up and under the valve (causing the valve to open) will reduce the water hammer effect but reduces the maximum working pressure of the valve by typically 50%. However, fitting a strong return spring will help increase the working pressure, but a larger actuator will be required to overcome this increased spring strength. With flow over the seat (causing the valve to close), full working pressure is achieved, and water hammer can be reduced by restricting the compressed air supply flow.

 

Controlling the angle seat valve with a solenoid valve

Normally, a three-way solenoid valve is used to operate NC or NO angle seat valves. These angle seat valves have one connection port to the piston chamber. The solenoid valve controls whether the chamber is pressurized or vented. Double-acting angle body valves have two connection ports and cannot be controlled with a single three-way valve. They can be controlled by a five-way solenoid valve that can pressurize one port while venting the other, and vice versa.

Application

These valves can be used to deliver millions of cycles of operation in demanding applications such as steam, water, and aggressive media. They are ideally suited for vacuum applications and can be used in fast-acting applications up to 1000 cycles per hour with an expected life of over 10 million cycles. They are used in many industries, including food & beverage, chemical, oil and gas, water and sewage, etc.

Angle seat valve selection

End connections and line size

Angle seat valves come in various sizes and end connections, ranging from 1/2 to 3 BSP or NPT threads, with some manufacturers offering flange options. The nominal diameter (DN) of the valve seat and the Kv-value, which indicates the flow rate of water at a pressure drop of 1 bar, are essential for selecting the right size. Use our valve sizing calculator to determine the minimum required Kv-value for your application, ensuring high and efficient flow with minimal wear and leakage.

Operating temperature, pressure and material properties

The maximum working pressure typically ranges from 5 to 20 bar. Consider both the media pressure and the compressed air circuit pressure range. Angle seat valves can handle temperatures up to 200 °C with PTFE (Teflon) sealing, while other materials like NBR, FKM, and EPDM have lower temperature ratings. The choice of housing material, such as bronze, stainless steel, brass, plastic, or gunmetal, affects the temperature and pressure rating, with stainless steel providing excellent corrosion resistance and material strength. For high-pressure or high-temperature applications, opt for a stainless-steel housing with PTFE seals.

Valve installation and maintenance

Proper angle valve installation is critical for performance and safety. Ensure that the valve is installed according to the manufacturer's specifications. Regular maintenance checks are necessary to prevent leaks and ensure the valve operates efficiently.

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