18" Balancing Valve 1

[glynnmack]

Hey all,

I'm in a bit of a pickle trying to find 18" Balancing Valves on the discharge of Chilled Water Pumps. Not only can I not find any above 12" from the standard valve suppliers (Crane, Velan, etc.), but I've also been told that they would be very expensive and large (space is tight). These people have recommended Butterfly Valves, which I know are limited in their ability to throttle flow. Any thoughts or recommendations to deal with this problem?

For reference, the chilled water pumps are on Variable Frequency Drives and oversized for future chilled water demand increases. The balancing valves will be used in the meantime to bring down the flow to the current levels.

Thanks,
GlynnMack

 

[btrueblood]

Visit

http://www.flowcontrol.com

<ahem> disclaimer: I may have an interest in that company.

 

[hacksaw]

characterized butterfly valves can be used in this service, but if automatic valves are used you have to make certain that the actuators are properly sized

flow balancing is quite different than flow balancing where you are correcting for minor differences in delta-p between flow paths

 

[glynnmack]

Thanks, hacksaw.

We have settled on high performance butterflies, mainly for the lack of other viable alternatives and the fact that this does not need pin point control. It won't be automated, so any added expense was mostly unjustified.

 

[gerhardl]

Recommend double or triple offset, which will have (on most cases and for quality valves) will usually have somewhat better regulating properties (accuracy, flow characteristics and regulating span). The choice of BFL will work, but as always (of course) within given flow amounts, speed and delta p's.

Laminar flow, sufficient distance from pumps?

Best, but at higher cost, would perhapsbe motorized needle valve, which could perhaps be in lower dimension. (Unsure if delta P is low). Reason: wide regulation range?

Chilled water pumps in parallell? If yes, beware of pressure and flow balancing equalizing from each single pump.