Summary on valve shutdown and throttling
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This post was last edited by herozxg on 2009-8-7 22:35 (1) Shut-off: Almost all valves have a shut-off function. Gate valves and ball valves can be used when cutting off flow alone without the need for flow regulation; for rapid shutdown, plug valves, ball valves, butterfly valves, etc., are more suitable. A stop valve can both regulate flow and shut it off. Butterfly valves can also be suitable for regulating large flow rates. (2) Changing the flow direction: By using a two-way (L-shaped channel) or three-way ball valve or plug, it is possible to quickly change the direction of the material flow. Since one valve can serve the function of multiple straight-through valves, this simplifies operations, ensures accurate switching, and reduces the space required. (3) Throttling: Globe valves and plug valves can meet general flow regulation requirements ； For regulating large flow rates, butterfly valves are generally used as they are cost-effective ； Pin valves can be used for fine adjustment of minute amounts ； For regulating stability (pressure, flow rate) over a wide range of flow rates, a throttle valve is the appropriate choice. The above is a summary based on my research; feel free to add more! There’s one thing I’m not clear about: a control valve is a valve with an actuator used to regulate flow rate. Are globe valves or throttle valves generally used for this purpose? Is a control valve equal to an actuator + a shut-off valve (throttle valve, V-ball valve, etc.)?
Valves used to control flow are usually those that are easy to adjust for flow regulation. Such as control valves, throttle valves, and plug valves, because the size of their valve seats is directly proportional to the stroke of the moving part. Rotary types (plug valves, ball valves, butterfly valves) and flexibly-bodied types (clamp valves, diaphragm valves) can also be used for throttling control, but they are typically suitable only within a limited range of valve port sizes. In most cases, people usually use changing the valve disc shape of the stop valve for throttling. It should be noted that using the adjustment of the opening height of a gate valve or globe valve to achieve throttling is highly unreasonable. Because, under the throttling effect, the flow velocity of the medium in the pipeline is very high, which can easily cause erosion and wear of the sealing surfaces, resulting in a loss of their sealing function. Similarly, it is also unreasonable to use a throttle valve as a shut-off device. Valves for reversing and diverting flow: Depending on the requirements for reversing and diverting flow, such valves can have three or more channels; plug valves and ball valves are suitable choices. Under certain circumstances, other types of valves, when connected together in two or more appropriate units, can also be used for directional shunting. For media containing suspended particles, valves in which the closing element slides along the sealing surface while performing a wiping function are the most suitable. Such as flat gate valves
This post was last edited by cmt2098200 on 2009-8-7 22:14. When selecting a valve, functionality and cost should be taken into consideration. Of course, the fluid composition, design pressure, and design temperature also need to be considered. The main functions of valves are as follows: Block function: Gate, Slide Gate, Plug, Ball, and Butterfly valve (as it is inexpensive). Throttling function: Globe valve, Needle valve, Angle valve, and Butterfly valve. Block and throttling function: Globe valve, Butterfly valve, and Large Gate valve. Non-return function: Check valve and Non-Slam valve. Block, throttling, and non-return function: Stop Check Valve, Angle Check Valve, and Straight Check Valve. Block, layout in a downward direction, and throttling function: Intermittent (Y-pattern) blowdown valve and Continuous (Angle-type) blowdown valve. Emergency automatic block function: Excess Flow Valve. Special-purpose valves: Orbit valve, Diaphragm valve, three-way valve, four-way valve, and Jacketed valve, etc...