Can a single-seat valve be used with an enlarged diameter?
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The project has encountered some difficulties recently; although they have been resolved, there is one issue that I’d like to discuss with everyone. Now, a control valve needs to be installed on the DN300 pipeline, but the pressure difference is relatively low while the flow rate is high. Logically, only a butterfly valve should be used, but given the importance of the location, is it possible to use a single-seat valve with an enlarged diameter? The single-seat valve uses DN400, but the butterfly valve has a CV smaller than DN300. Does this work? Another minor issue that arises: Consider the situation where there is an expansion before the valve; this reduces the flow velocity, increases the pressure of the medium, and results in a slight increase in the pressure ahead of the valve. There is a reduction in diameter downstream of the valve, which increases the flow velocity and reduces the pressure of the medium; as a result, the pressure downstream of the valve decreases slightly. As a result, the pressure difference before and after the valve increased. . . Is that so?
Well, if it were me, I would first talk to the technical staff from the control valve manufacturer.
For ordinary media, it is possible to enlarge the valve, except for some special media (such as those that may cause phase changes). As for flow rate, it is related to both pressure difference and the valve CV; you need to calculate whether the flow rate is sufficient, as it’s not possible to determine this just by looking at the CV. This is because safety margins are always considered when selecting valves. If a DN400 control valve is used, both the inlet and outlet sizes will be large; therefore, for such a valve, the pressures at the inlet and outlet will not become very high. Moreover, the feedback signal of the control valve can also be used to adjust the opening degree. The use of Bernoulli’s equation is based on the ideal condition of constant flow. The flow rate changes through the control valve; therefore, sometimes the flow velocity has a slight impact on pressure during the adjustment process, but it does not have a significant effect overall. What has an overall impact are still the CV value of the valve and the pressure difference between the valve’s inlet and outlet. This is my personal opinion for reference only.
Single-seat DN400? It is a low-pressure application – why not choose a butterfly valve? Poor reliability of butterfly valves? Moreover, it is merely for adjustment; unless very high precision in adjustment is required, butterfly valves should not be discarded! Also, the pressures before and after the valve refer to the total pressure before the valve and the total pressure after the valve; these are mainly related to the system! But I’ve never heard of the bracket diameter before!
Have you seen any examples of diameter expansion for control valves? Are there any relevant materials available? Fisher control valves are affected by diameter changes. I mean, have I failed to consider something?
It is normal for control valves to experience diameter expansion and contraction. We are the manufacturer and do this regularly. However, it is necessary to discuss the ingredients at the time of purchase.
Are there any guided materials or something? I’m looking for advice