Seeking advice on the opening issue of Fisher pneumatic diaphragm control valves
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I have a question: For the Fisher pneumatic diaphragm control valve, the opening degree after installation is 80-90%. I used domestic control valves from Chuanyi in the past, and the flow coefficient CV of both types is the same. So why is the opening degree of the Chuanyi valves 50-60%, while that of the new Fisher valve is 80-90%? Is this opening too large? Could someone with expertise give me some advice?
CV refers to the volumetric flow rate, or mass flow rate, of the fluid in the pipeline passing through the valve, at a constant pressure within the testing conditions per unit of time. That is, the maximum flow capacity of the valve. Your situation may be related to the flow control curve of the control valve (whether it is linear or based on equal percentage changes), the opening degree of the shut-off valves before and after the control valve, and the pump’s flow rate.
It has no impact on operation, provided that the control valve can regulate the flow rate. Generally speaking, operating at a large opening angle helps to extend the valve’s service life!
With the same flow coefficient, if the flow characteristics differ, the opening degree will also vary for the same flow rate.
There will be certain differences in the CV value calculated by each manufacturer, and the stroke length as well as the valve core structure also vary. When replacing a valve, it is best to provide the manufacturing conditions to the supplier.
But isn’t the control quality poor at large openings? Also, isn’t the control margin smaller?
It’s not good to keep it at a high level either; I remember it should be between 30% and 80%
Has the Fisher valve become reduced in diameter?
1. Are the CV values calculated for the two valves the same?； 2. Are the rated CV values of the two valves the same? ； 3. Are the inherent adjustable ratios RO of the two valves the same? ； 4. Are the flow characteristics of the valve cores in the two valves the same?
The CV value refers to the flow characteristic; is it affected by Fisher’s diameter reduction?