0

I was reading the difference between a ball valve and a globe valve and https://www.linquip.com/blog/globe-valve-vs-ball-valve/ was saying that you can't control flow with a ball valve.

I'm pretty sure this is incorrect and you can control the flow with a ball valve but perhaps don't have as precise of control over it. The context is a key ball valve for a natural gas fire pit. Can anyone speak to what the proper understanding is here?

5
  • In pressurized water pipe (like home water supply plumbing), having a ball valve partially open for longer periods of time can leave a depression in the surrounding (teflon?) gasket, making the valve then leak even when fully closed.
    – Armand
    Jun 27, 2022 at 7:48
  • Flow control requires a control valve for reliable ,long life: such as a needle valve. Regular valves( globe, ball, gate, etc) are not intended to control flow but maybe adequate for limited time in homeowner applications. Jun 27, 2022 at 13:06
  • @Armand is the concern about depressions in the gasket not applicable for the natural gas use case which is at 7" WC (i.e. 0.25PSI)? Thanks
    – g491
    Jun 27, 2022 at 14:55
  • it looks like that article was written by someone who doesn't know the difference between pressure and flow. why do you want to constrict the gas supply to this appliance? does it not have its own gas controls?
    – Jasen
    Jul 1, 2022 at 6:21
  • @Jasen nope it's just an outdoor fire pit burner which doesn't have any intelligence to it and relies on the ball valve for flow control
    – g491
    Jul 1, 2022 at 14:49

2 Answers 2

1

Actually, you can probably control flow better with a ball valve since the handle gives a visual indication of it's position:

Fully closed, 1/4 open, 1/2 open, 3/4 open, fully open. (There are actually an infinite number of positions).

By looking at the valve you know what is going on. I've replaced several gate valves with ball valves and by opening them slowly I avoid a huge pressurized rush of water.

For gas, it is way different. You want it full open or full closed. It would be dangerous to have a gas valve partially open.

4
  • 5
    This isn't really correct. 1) the relationship between the handle position and flow rate is not linearly proportional, and 2) ball valves used for throttling, especially with water, can be obnoxiously noisy and have a large pressure drop and associated heating. They are meant for on/off only. Jun 27, 2022 at 5:56
  • Agreed that it is not directly proportional. Jun 27, 2022 at 14:44
  • @SteveWellens why would it be dangerous to have a gas valve partially open for a fire pit?
    – g491
    Jun 27, 2022 at 14:52
  • @g491 If the pressure regulator isn't getting a full flow of gas, it may not operate correctly. The flame could go out. There are safety mechanisms to shut off the gas when that happens...but it just seems dangerous to me. I'd rather have it working reliably. Jun 28, 2022 at 13:16
1

I'd use a needle valve:

enter image description here

With this you get good flow control.

Ball valves are excellent for on/off control, but for fine flow control they're very inaccurate because most of the useful positions are in the last few degrees before it's closed.

It's safer to put the valve before the flexible gas pipe. This way, the pipes that will be constantly under pressure are metal.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.