Fighting Valves
Fighting Valves
(OP)
We have the ML1400, 1762-IF4 and 1762-OF4 modules. The system consists of one pump supplying 2 water systems.
Each system has a flowmeter and a modulating valve. The flow is to be split 50/50 thru each system. There are 3 different flow rates needed.
The PID's are set up to take half the desired flow and adjust the modulating valve to achieve this.
One issue is they are butterfly valves and at the desired flows being 10-20 % open, rather than the desired mid range at desired flow. I'm not sure of the valve resolution at the low end of the valve. (I'm not a valve guy)I haven't been to the site yet, the customer reports the PID's the unit will "hunt" with a large range. Never stabilizing near the set point.
How do we make these guys quit fighting? Will a modulating valve be accurate at 10% open?
Thanks in advance!
Each system has a flowmeter and a modulating valve. The flow is to be split 50/50 thru each system. There are 3 different flow rates needed.
The PID's are set up to take half the desired flow and adjust the modulating valve to achieve this.
One issue is they are butterfly valves and at the desired flows being 10-20 % open, rather than the desired mid range at desired flow. I'm not sure of the valve resolution at the low end of the valve. (I'm not a valve guy)I haven't been to the site yet, the customer reports the PID's the unit will "hunt" with a large range. Never stabilizing near the set point.
How do we make these guys quit fighting? Will a modulating valve be accurate at 10% open?
Thanks in advance!





RE: Fighting Valves
Where is the flow measured and how are you controlling the flow?
With two systems you could have one flow meter on each of two lines after a split from the pump. Instead of two flow controllers you could have one flow controller and the other controlling a ratio against the other flow - or several other combinations of measurement and flow control.
RE: Fighting Valves
It doesn't matter how open the valve is, the sensors only measure flow and send a signal to open if flow is low, and close if flow is high. Often times undersized valves make the system stable.
RE: Fighting Valves
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RE: Fighting Valves
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