Valve Basics, Sizing, and Actuators Books

The valve is a controlled device that regulates the flow of a liquid or gas in a system.

This regulation is accomplished by the varying resistance that the valve introduces into the system as the valve is stroked.

As the valve modulates to the closed position the system pressure drop shifts to the valve and reduces the flow in the system.

The valve is very important to the operation of the system. Without a properly sized valve, the system will never operate at an efficient level.

For valves that are over-sized, the result is poor controllability that may cause the system to hunt or cycle. Under-sizing a valve will require a larger pressure drop across the valve to maintain adequate flow and may not provide the required capacity.

This results in the pump working harder and leaves the valve susceptible to the effects of cavitation.

Valve Books

These valve books consist of information related to basics, sizing, and actuators. The below table shows the list of main topics.

Topic 1Control Valves
Topic 2Valve Components
Topic 3Valve Parameters
Topic 4Valve Flow Characteristic
Topic 5Pressure Shift at Valve
Topic 6Valve Gain
Topic 7Valve Plugs
Topic 8Rangeability
Topic 9Cavitation
Topic 10Coil Theory
Topic 11Valve Sizing
Topic 12Valve Flow Coefficient
Topic 13Pressure Drop Across the Valve
Topic 14Three Way Valves
Topic 15Valve Selection Summary
Topic 16Maximum Temperature and Pressure Ratings
Topic 17Glossary
Topic 18Pneumatic Actuators
Topic 19Electric Actuators
Topic 20Maximum Seating Pressure

The factor that is most useful in selecting a valve type for a given application is the flow characteristic.

This characteristic is the relationship that exists between the flow rate through the valve and the valve stem travel as the latter is varied from zero to 100 percent.

Different valves have different flow characteristics, depending primarily on internal construction. This flow relationship is usually shown in the form of a graph as in the below Figure.

Selecting a valve type

The characteristic that is usually graphed is the Inherent Flow Characteristic that is found under laboratory conditions with a constant pressure drop across the valve.

An actuator is a controlled device that provides the force required to move the plug in a valve, which regulates the flow of fluid in the system.

Different size valves require different size actuators, depending on the characteristics of the system.

Valve Basics, Sizing, and Actuators Books

An important characteristic to be considered is the pump head, also known as dynamic pressure. This is the pressure the actuator must overcome to close a valve.

The force generated by an actuator is directly proportional to the effective area of the actuator diaphragm.

Download the below books to read more details.

Title:Valve Basics and Sizing, Valve Actuators
Author:Johnson controls
Size:305 KB, 389 KB
Pages:32, 32
Download:File 1, File 2

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