What is control valve capacity?
Valves need to be measured on their capacity to pass fluid. To enable fair comparison, valves are sized on a capacity index or flow coefficient. Control valves adjust processes by altering: Flowrate – For example, the amount of steam or water that enters the process equipment.
What is a steam control valve?
Steam control valves not only control the pressure, but also the temperature in process applications. The steam control valve can be used simply as an on and off device, or any combination of controlling to include regulation, modulation, mixing, or even isolation.
How do you calculate steam flow through a valve?
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 difference between CV and KV in control valve?
Same model valve has different coefficient for each diameter. Kv is the flow coefficient in metric units. Cv is the flow coefficient in imperial units. It is defined as the flow rate in US Gallons per minute [gpm] of water at a temperature of 60 fahrenheit with a pressure drop across the valve of 1 psi.
How do you calculate control valve size?
Control Valve Sizing – FluidFlow
- Control Valve Sizing.
- When sizing a control valve, the most common approach is to calculate the flow coefficient, Cv which is a measure of the capacity of the valve body and trim.
- C = Q/N1 * √ (ρ1/ρ0) / (∆P)
- ρ1/ρ0 is the relative density.
- Fluid Density: 965.4 kg/m3.
How do you size a control valve?
So, how do you size a control valve anyway? When sizing a control valve, the rule of thumb is to size it so that it operates somewhere between 20-80% open at maximum required flow rate and whenever possible, not much less than 20% open at the minimum required flow rate.
What type of control valve is used in a steam turbine?
A control valve is supplied with dry saturated steam from a separator at 12 bar g and used to drop steam pressure to 4 bar g at full load. The full load flowrate is 1300 kg/h requiring a Kvr of 8.3. A DN25 (1”) valve is initially considered for selection, which has a Kvs of 10 and a valve outlet area of 0.000 49 m2.
How to calculate the safety capacity of a steam power plant?
The plant should size the safety capacity according to the control valve’s maximum flow by calculating the inlet steam pressure (PI) at the maximum steam pressure, which is the safety valve setting of the steam supply source. The plant should not calculate the maximum steam pressure using the steam system’s nominal operating pressure.
How are control valves sized?
To enable fair comparison, valves are sized on a capacity index or flow coefficient. This tutorial explains the different types of flow coefficient in use, how they are established, how they compare, and typical values for different sized valves. A control valve must, as its name suggests, have a controlling influence on the process.
When considering a safety valve downstream of a steam pressure control valve?
When considering a safety valve downstream of a steam pressure control valve, the total capacity of the safety valve at the set point must exceed the steam