Table of Contents
What are the characteristics of control valve?
A few other inherent valve characteristics are sometimes used, such as parabolic, modified linear or hyperbolic, but the most common types in manufacture are fast opening, linear, and equal percentage. Each application will have a unique installation characteristic that relates fluid flow to heat demand.
How do you determine control valve characteristics?
Valve characteristics selection guidelines
- Type of fluid to be controlled.
- Temperature range of fluid.
- Viscosity range of fluid.
- Specific gravity range of fluid.
- Minimum and maximum flow required.
- Minimum and maximum inlet pressure at the control valve.
- Minimum and maximum outlet pressure at the control valve.
What is FL and xT in control valve?
ANSI/ISA liquid sizing Equations use a pressure recovery factor, FL, to calcu- late the ∆Pch at which choked flow is assumed for sizing purposes. For compressible fluids, a terminal pressure drop ratio, xT, similarly describes the choked pressure drop for a specific valve.
How do you calculate control valve size?
The basic valve sizing equation Q = Cv√∆P can be used to calculate pressure drop, flow rate, or the flow coefficient. For solutions other than water, a correction for a difference in specific gravity of the solution is necessary. This revised formula would be: Q = Cv[√∆P/Sg] with Sg = specific gravity of the liquid.
Why are characteristics of control valves installed?
The installed characteristic is the relationship between valve position and flow in the specific system being considered, taking into account any changes in the pressure differential available to the control valve due to the approximately flow squared relationship between flow and piping pressure losses and/or a …
What is Cv value of a valve?
What is Cv value? The valve flow coefficient according to the JIS standard, represents the flow capacity in US gallons/minute of 60° F pure water when it is flowing through the valve with a pressure difference of 1 psi at the specified travel (operation range).
What is flow characteristics?
Flow Characteristic describes the relationship between the valve coefficient (Cv) and the valve stroke. Each throttling valve has a flow characteristic. As a valve opens, the flow characteristic allows a certain amount of flow through the valve at a particular percentage of the stroke.
What are 3 characteristics of fluids?
Fluids have common properties that they share, such as compressibility, density, pressure, buoyancy and viscosity.
What is Cv and KV in control valve?
The Valve Coefficient (Cv – in Imperial unit) – the number of US GALLON PER MINUTE of water at 60 °F that will flow through a valve at specific opening with a pressure drop of 1 psi across the valve. The flow factor (Kv – in Metric unit) – the amount of water that will flow in m3/hr.
How do you convert SCFM to Cv?
To obtain scfm output at a particular pressure, divide the valve Cv by the appropriate factor shown below. To convert scfm into Cv, simply reverse the process and multiply the scfm times the factor.
How is valve CV calculation?
The volume flow rate for liquids can be calculated by multiplying the fluid velocity times the flow area. Thus, Cv is numerically equal to the number of U.S. gallons of water at 60°F that will flow through the valve in one minute when the pressure differential across the valve is one pound per square inch.
What is the flow characteristic of a control valve?
The flow characteristic of a control valve is the relationship between the flow rate through the valve and the valve travel as the travel is varied from 0 to 100%. Inherent flow characteristic refers to the characteristic observed with a constant pressure drop across the valve.
How reliable are control valves?
Control valves are supposed to deliver reliable, repeatable control of process fluid flow rate over a wide range of operating conditions. As we will soon see, this is something of a challenge, as the rate of fluid flow through a control valve depends on more than just the position of its stem.
What is Chapter 6 of the control valve manual?
Chapter 6addresses the selection and use of special control valves. Chapter 7explains desuperheaters, steam conditioning valves, and turbine bypass systems. Chapter 8details typical control valve installation and maintenance procedures.
What is the operating medium of a control valve?
This is typically accomplished by placing the controller in the manual operating position. Operating Medium: This is the fluid, generally air or gas, used to supply the power for operation of valve positioner or automatic controller. Operative Limits*:The range of Control Valve Handbook | Chapter 1: Introduction to Control Valves 30