How does a control valve work?
Control valves automatically regulate pressure and/or flow rate, and are available for any pressure. The valve modulates flow through movement of a valve plug in relation to the port(s) located within the valve body. The valve plug is attached to a valve stem, which, in turn, is connected to the actuator.
Which valve is better for on off control?
Which of the following valves is better for on/ off control? Explanation: Butterfly valve is for flow regulation. Plug valve involves pressure drop during on/ off control. Ball valve involves on/ off control without pressure drop.
What is the difference between control valve and on off valve?
On-Off Valves An on-off valve is a much less precise instrument than the control valve. It either allows for unimpeded flow or it shuts off flow completely. Gate valves and plug valves use conical pieces that slide down through the channel, sealing it securely shut.
What are the parts of control valve?
A control valve consists of the following parts:Body. It is a type of a pressure vessel containing an orifice or an opening. Trim. Besides the body, trim is one such part of the valve that comes directly in contact with the fluid. Actuator. Bonnet.
How do you design a control valve?
The valve design equation relates the pressure drop ΔPv Δ P v across the valve to the volumetric flow rate q . The Cv is a measure of the size of a valve and valve suppliers have different valve body sizes, each with a different Cv value. The valve position or lift l is adjusted to regulate flow through the valve.
What are the factors to consider when selecting a control valve?
5 Factors to Consider When Choosing a ValveMedia Type. The characteristics of the liquid or gas type being controlled will determine the valve material that should be used. Application Conditions. Valve Function. Actuation Method. Maintenance Requirements.
How do I choose a control valve?
Control Valve SelectionGive careful consideration to selecting the correct materials of construction. Consider the operating temperature and pressure the control valve will be exposed to. Consider the degree of control you require and ensure the selected valve is mechanically capable of achieving the desired operating conditions.
What is turndown ratio of control valve?
Turndown Ratio refers to a valve’s installed characteristic; it is the ratio between the normal maximum system flow and the minimum controllable flow. Having a control valve that provides fine pressure control at a low percent open, as well as capacity for high flow rates, can be very advantageous.
Under what conditions would an equal percentage control valve be used instead of a linear control valve?
If most of the pressure drop is taken through the valve and the upstream pressure is constant, a linear characteristic will provide better control. If the piping and downstream equipment cause significant resistance to the system, equal percentage will provide better control.
How do you specify a valve?
How to Specify and Order the Correct ValvesCare should be taken to select the most suitable valves for your service(s). Exact specification of each valve should be made to avoid possible ambiguity. Selecting the Valve Size.Nominal size of the pipeline into which the valve will be placed must be determined.Valve Material.
What are the units for CV?
In the U.S. system of units, the Cv coefficient is the number of U.S. gallons per minute of water that will pass through a given orifice area at a pressure drop of 1 PSI. An orifice or valve passage which has a Cv coefficient of 1.00 will pass 1 GPM of water (specific gravity 1.0) with a pressure drop of 1 PSI.
