What is the lowest possible pressure drop of a control valve in KPa?
Thread Content
What is the lowest possible pressure drop of a control valve in KPa?
This can be specifically asked to the manufacturer, and it varies from manufacturer to manufacturer.
10KPA was selected during the calculation
Depending on the process requirements, the pressure behind the control valve is designed accordingly during the design phase; the pressure difference across the control valve can range from several tens of kilopascals to several megapascals, depending on the specific process conditions
Not necessarily; if there is no reduction in diameter, it can be very small!
What is the lowest level that can be achieved? The lower the process requirements, the better. Ask me what the minimum pressure drop of the control valve I can use is
It’s been explained very clearly; I think 10 KPa is more than enough!
We can’t select this process. You can only choose by gauge; it’s frustrating
It should be the process conditions (materials, flow rate, pressures before and after the valve), along with the selection of instruments
We have also encountered this problem; you can set a differential pressure yourself, as long as it is approved by the process engineers. The key principle is that we need to be able to purchase such valves!
Well, those in charge of control must discuss matters with the process engineers based on the actual circumstances. Sometimes decisions have to be made, and this requires confirmation from the process engineers.
Have you thought about it? The minimum pressure drop when a spherical control valve is fully open can be made to be 1–2 times the fluid flow pressure drop in the valve length pipeline section; can the process engineers calculate this? ? Isn’t Kpa enough?
What about 100 Pa? Is that low enough? A regulated butterfly valve with a low load can be used.
For a selected control valve, is its pressure drop a fixed value? For example, in the case of a flow control valve, the smaller the flow rate, the lower the pressure difference
Our company has also purchased an electric butterfly control valve, which is used in the oil pipelines for crude benzene in coking operations. This valve is described as a \"versatile valve\", with 9 advantages listed in its manual. The original valve is having problems, and we plan to replace it with this one after some time.
Relative to the flow rate, as long as the pipe size is large enough, the pressure difference can theoretically be reduced to the pressure loss across the valve. It has been calculated for a control butterfly valve with a pressure difference of 100 Pa when the medium is gas. If the process does not provide conditions for differential pressure, the minimum differential pressure can be calculated using software based on parameters such as flow rate, upstream pressure, no diameter reduction, opening degree, and temperature. Additionally, to keep the pressure difference as low as possible, a V-ball valve or butterfly valve should be chosen.
There are specific requirements regarding the pressure drop of control valves. For gas media, when the pressures upstream and downstream remain constant, this pressure drop should be greater than 33% of the difference between those pressures, or 70 kPa. For liquid media, there is a requirement regarding the valve’s resistance ratio S; relevant design specifications can provide details on this. It cannot be said that the lower the value, the better, as otherwise the control valve will not be able to perform its regulating function.
Both V-type ball valves and butterfly valves seem to be good options. How should one choose between these two types of control valves?