Butterfly valves for flow balancing through parallel chiller circuits 1

[95chris]

Hi Everyone,
I'm looking for advice how butterfly valves will perform as good as DRVs ( double regulating valves) in flow balancing through parallel chiller(er) water circuits.The butterfly valve I had is 10 diameter, and propose to replace Oventhop Double regulating valve, as the later is more expensive.

 

[dcasto]

We use Bf valves to balance split flow all the time. One valve would be reverse acting, the other direct. You can even keep one a manual valve and the other in control. Or you can have one fail open the other fail closed and use only one action. Your Risk Management review will lead you to the best set up.

Most valves will also allow you to put a mechanical stop, so that it will not go 100% open or shut, if required in your Risk Management.

 

[95chris]

Thanks, dcasto.
I just have 4 butterfly valves, that is one per circuit in a 4 chillers parallelcircuit configuration.Any comment/comparison of actual experience between the two types of valves ( cheaper against the expensive. The butterfly valves adjustment is manual and a mechanical stop will be placed to prevent further opening during subsequent normal operation once balancing is achieved for the 4 parallel circuits.
I hope to be able to balance the water flow during commissioning using these butterfly valves as good as but not using the more expensive DRVs, and orifice plates to measure flow during the commissioning stages for balancing.

 

[JimCasey]

Butterfly valves are commonly used in such an application and frequently they are the most utilitarian, rubber-lined valves such as the Keystone AR2. A double-offset valve WOULD be more suited particularly for modulating because of less torque and less friction, but a bit more pricey. Google does not find any mention of "Oventhop Double regulating valve", which is kind of remarkable even if it is mis-spelled.

 

[dcasto]

For water, there are so many brands. I'd just get a whole bunch of quotes.

If you need positive seal off for maintenace, then go fo the better seals. Jim is correct on the offset part, but if you are not moving them much, it's not mandatory.

Here will be your problem when balancing the system. This is not always true, but from experience of such systems. Everyone in the plant will want to adjust the valves and water flow. Pretty soon you'l see a slow decline in performance of the cooling system. What you will find is all the valve will be at some partial closed state. You need to find the loop with the least resistance (shortest line or smallest exchanger, whatever.) and make sure that vale is 100% open, then adjust the other three, do not ever close the that valve.

 

[95chris]

Thanks,dcasto and Jim. Sorry wrong spelling, should be oventrop!! One site is

http://www.oventrop.co.uk/en/index.htm.

AS the 4 circuits are parallel connected to headrs on both suction and discharge sides, I would not expect the resistance thr' the chillers appreciably different; and even if there are different resistance, should I not start with manually opening 100% the valve in the circuit with the highest resistance, so that the other 3 circuits ( of lesser resistance) can have the valves manually adjusted to less than 100% open to balance the flows thr' all 4 chilers during commissioning and a stop placed on their opening at position where balance were found.
Wellcome any comment and advice.