Mixing hot and cold water, ball valve, gate valve, or globe valve?

[barleyfreak]

I've been using two ball valves to control cold water and hot water to blend for brewhouse needs, including doughing in. PITA to get it exact with such minuscule movement, but it works, though tediously. Want to have plumber install a a couple of gates to replace them. He suggests a globe valve, but I read that they restrict flow. I can't afford to give up much flow. Anyone know how much a globe would restrict (%, for example)? Or is anyone using gates and not having probs? I could using a actual mixing valve, but he said they are meant to be set at a particular set point and not contiually moved, which would be the case here.

Thx,
dave

[gitchegumee]

Just like everything, it depends.

Different valves are made for different applications. When you talk about flow restriction, the coefficient of flow (Cv) is important. This tells you how much water can flow. Full-port ball valves are nearly a straight pipe as far as flow goes. But they are usually used for on-off control and not modulating/throttling. Gate valves are slightly better at modulating/throttling, but not recommended for it. Again, they are more of an on-off device. Globe valves are typically the best for control, albeit at the expense of more flow restriction. If you need every bit of flow due to lower pressure water, then gate valves might give you a slight advantage. But if you can use globe valves, then that's your best bet.

[ARCHON IND.]

Mixing hot and cold water, ball valve, gate valve, or globe valve?

Phillip has it right. At full flow conditions, the globe valves will cause a higher pressure drop, but it is the best way to have throttling control. If you have the hot and cold water lines pipe together for mixing, you might also consider installing check valves on each leg. Without them, you run the risk of heating your entire cold water supply with your hot water.
Our company (and others) make mixing valves for these applications. They have globe valves on the inlets, built-in check valves, and thermometers to monitor temperature. The mixing is done it a chamber so that the hot and cold water can properly blend before hitting the outlet.
Good luck,
Frank Bongiorni
ARCHON Industries

[TGTimm]

What you're looking for are called v-port ball valves: https://www.google.com/search?q=v+po...utf-8&oe=utf-8

Due to the shape of the port, these are very good at proportional flow control, and when fully open, are still full-port valves.

Frank--does your company make mixing valves appropriate to the brewing industry? I've been looking for a high-flow, high-temperature automated mixing solution for our mash tun without much luck so far.

[gitchegumee]

One more thing...

If you are mixing cold and hot water, then you should spare a few bucks for a static mixer after the valves and before the temperature probe. Cheap and easy..

[dick murton]

Or use diaphragm valves as attached

These will give excellent control. As with all valve body and valve gasket material, make sure the materials are suitable for the conditions. I have used these successfully for years - and they can be considered hygienic, though in this particular case absolute hygiene is less necessary than with say wort.

[dick murton]

I'm going to have to learn how to attach files so they don't display !!

Huge pictures again!!

[barleyfreak]

Thanks for the suggestions. Had not heard of a diaphragm valve before. In our case, I realized that the only throttling I'm doing is w/ with the cold, so my solution will be to install a globe for the cold water input, leave a ball on the hot, and run a loop/bypass on the cold/globe in case the flow drop impacts the HX. Covering the bases. Will ask about a static mixer too.

Dave