Regulating valve diameter issue
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When selecting a valve, the diameter of the control valve is generally less than or equal to the diameter of the process pipeline. But has anyone ever encountered a situation where a control valve needs to be installed with an enlarged diameter?
So far, I have not encountered any control valves of the type mentioned by the original poster that require diameter expansion for installation. If such a situation does occur, it indicates that the flow capacity of the pipeline has reached its limit, and such a condition should not be allowed to exist.
I’ve only seen those with reduced diameter. The diameter of a control valve cannot be larger than that of the process pipeline.
It’s not possible to increase the diameter; if the calculated valve diameter is larger than that of the pipe, it means there’s an issue with the data provided by the process team. It could be due to an excessive flow rate or too low a pressure difference before and after the valve – especially the pressure difference, as sometimes the process team provides incorrect data
It cannot be expanded in diameter; if the diameter is increased, it means that the flow rate through the pipe exceeds the valve’s capacity to handle such flow. In that case, the control valve becomes useless and is unable to perform its regulating function, or the set values and actual conditions no longer match, making it impossible to achieve proper control.
What an excellent question – I’ve never encountered it before, and I’m not sure if there’s a standard answer.
I have never encountered a case where the diameter of the control valve is larger than that of the pipeline. If the diameter of the control valve is larger than that of the pipeline, it will definitely be impossible to achieve control. This post was last edited by jujiangliu on 2009-3-3 17:07]
I have seen Emerson’s vortex flowmeters installed with expanded nozzles. But why doesn’t the control valve work? If you say no, you need to provide a theoretical basis.
I haven’t seen one with an expanded installation for the control valve yet
First of all, it’s pointless to install control valves with an enlarged diameter; your pipeline already limits the maximum flow rate that can pass through it, so what’s the point of enlarging the diameter? Moreover, an enlarged diameter causes the control valve to operate at a low opening degree, which affects both its lifespan and accuracy.
The flow capacity of a control valve is greater than that of a pipe of the same diameter; therefore, only reduction in diameter is possible, not expansion.
I used to work on construction sites, and since the owner’s specifications called for larger diameter values, we had to use wider pipes. But why do the valve diameter parameters calculated by valve manufacturers be larger than the actual diameter?
Everyone I’ve met is thinking about by how much to reduce the diameter – whether by one grade or several grades.
Valve manufacturers generally calculate the diameter of the valve based on the pressures before and after the valve as specified in the process requirements, and they usually opt for a reduced diameter.
Give it a push; I hope to get more suggestions.
It’s usually a reduction in diameter; the larger the diameter of the control valve, the higher the price, right?
I strongly agree. The design institute couldn’t come up with any reasonable values for the maximum closing pressure difference of the control valves and shut-off valves in our project. Under pressure, they finally told us to use a pressure of 0.1 MPa in front of the valve as the closing pressure difference. However, I noticed that in the instrument data sheets provided by foreign manufacturers, the maximum closing pressure difference for many valve models is much higher than the pressure in front of the valve. This is relevant to the choice of actuator and to whether the valve can close properly. The parameters suggested by the design institute are arbitrary and one-size-fits-all; as a result, especially with shut-off valves, it becomes impossible to achieve a complete shutdown. Are all domestic design institutes this careless these days?
It’s possible for the diameter to increase; our company has encountered such a situation: lol :lol :lol Of course, the reason is that the design institute made a mistake in the design – the process engineering team reduced the diameter of the pipelines without informing the instrumentation team. We didn’t detect this issue during the ordering process, so we had no choice but to use them. Fortunately, that particular area isn’t extremely important, haha. ;P
I’ve only used reducers; I’ve never used expanders, haha