Ball Valve vs Globe Valve

[ascj]

I was discussing 3way valves with another mechanic today. I ran into a situation the other day, where the 3way globe valves were piped wrong and failed(seized). Instead of all the repiping, I was going to install some 3way ball valves. That will put my AB port on the branch of the tee and not the run. Also I stated, I have better reliability with ball valves over globe valves.

The argument was, globe valve provide better linear flow and high cv ratings. And I'll be messing up the design of the system.

I did some research and it's seems the opposite. Anyone else?

[hvac ddc]

I aggree that globe valves may often allow for a higher Cv rating, but I would disagree on the linear aspect. I would rather have a ball valve such as a Belimo CCV. If you are in the 4"+ sizes, you may have to stick to a globe valve, though Bray makes ball valves that are linear flow up until 6" under the name Delta Control Products.

[leoxxl]

Generally, a globle valve has better throtting ability than a ball valve, A lot of manufactures now provide charactrized ball valves, enhancing the throtting capablity of ball valves. It wont make a very big difference between a ball valve and globe valve with the same Kv

For heating & cooling coil control (AHU or FCU, etc), a control vavle normally has an Equal Percentage charicteristics to make a linear relationship between heating/cooling output vs valve position, so a globe valve is usually preferred than a ball valve.

[orion242]

I use balls where ever possible. I have never had a problem controlling things with a properly sized Belimo CCV ball valve. Now when you’re talking > 2" then the globes come out. >4" and depending on the application I start to look at butterflies.

Balls are far less problematic than globes in my opinion.

Higher close off
Piping is more forgiving
Cheaper
Smaller size

I would not worry at all dropping a ball valve in there to replace the globe.

>a control vavle normally has an Equal Percentage charicteristics to make a linear relationship between heating/cooling output vs valve position, so a globe valve is usually preferred than a ball valve.

Maybe I miss something here, as I hear this all the time. My thought is with a PID loop driving the control valve, it will find the happy spot regardless of linear / equal %.

[mallron]

Globe valves are better suited as triple duty valves, flow control, balancing and that sort of thing. Are the globe valves installed just as diverting/mixing valves? If so, then I would go with the ball valve.

[orion242]

Globe valves are better suited as triple duty valves, flow control, balancing and that sort of thing. Are the globe valves installed just as diverting/mixing valves? If so, then I would go with the ball valve.

How are they better suited as a triple duty valves, flow control, balancing?? They can't do any of these functions.

Globes cannot serve as flow control, ie balance valve. Balance valves are have calibrated orifices that allow flow measurement based off pressure drop. No globe I have seen even has the proper taps to measure the pressure drop, let alone the charts to calc flow.

Globes close off is no where near a ball, as far as a isolation valve, which is why I assume where your coming from in the triple duty valve.

Globe is not a check valve.

[mallron]

How are they better suited as a triple duty valves, flow control, balancing?? They can't do any of these functions.

Globes cannot serve as flow control, ie balance valve. Balance valves are have calibrated orifices that allow flow measurement based off pressure drop. No globe I have seen even has the proper taps to measure the pressure drop, let alone the charts to calc flow.

Globes close off is no where near a ball, as far as a isolation valve, which is why I assume where your coming from in the triple duty valve.

Globe is not a check valve.

I don't claim to be an expert on the subject, but this is straight from wiki-

"A globe valve is a type of valve used for regulating flow in a pipeline"

Also, I do believe that I've seen triple-duty valves that were globe valves, I could be wrong, I'll see if I can find one.

And no, globe valves don't have the close-off of a ball valve, but they will stop flow to facilitate maintenance.

[mallron]

http://www.bellgossett.com/productPages/Parts-Triple-Duty-Valves.asp

I thought these had the same type of internals as globe valves, again, I could be wrong. I see these in cond. water piping all the time.

[hvac ddc]

"A globe valve is a type of valve used for regulating flow in a pipeline"

I think this goes back to the comparing of gate valves and globe valves where gate valves were designed to be full open or full shut to prevent wire draw at the bottom of the valve gate while a manual globe valve could be throttled to regulate flow - as in a manual regulating valves on a steam radiator.



However, back to the original question, I think the asker was looking at a regular automatically controlled valve which either a globe or a ball would probably work and depending on the size, a ball would work just as well (if not better) as a globe valve.

[ascj]

These are modulating valves on hot water coils. I was trying to put the AB port on the branch(possible with a ball valve). All the globe valves that I have seen, the AB port has to be on the run. I'm just trying to avoid repiping.

I personally have better experience with ball valves, over globe valves. Ball valves don't seem to leak as often on the stems. The also seem to be more reliable to positive closure.

The question was in regards to cv and flow. After doing research, ball valve seem to have a better cv and flow then globes. So I quoted some ball valves. I couldn't get any specs off the old globe valves, but I'm going to assume the new ball valves will have a high cv rating. And with circuit setters on the bypass and the return, I should be able to set the flow.

[fxb80]

With balancing valves you will be able to set the maximum or design flow. But replacing with a bigger CV can radically affect controlability. A bigger CV valve may only have to be 20% open to achieve design flow so it has to throttle in a 0-20% range instead of 0-100% range. Maybe the correct CV is listed on a set of prints. Or if you can get the specs on the coil, pressure drop through the valve should be at least as great as pressure drop through the coil. Ideally, pressure drop through the valve should be equal to pressure drop through the entire branch, including coil, piping, strainers, and balancing valves.