Dan H says dont throttle pump with gate valve.. but?

oil-2-4-6-gas

Dave, your way does work Until it wears the ball so much that you have to readjust --or it develops a leak on the side of the valve --

sreja

Dan H says dont throttle pump with gate valve.. but?

Dan Holohan (as well as my peerles manual) talks about the importance of throttling down the speed of the water coming from a condensate pump into the boiler.

Here's what dan says to use (p. 172; lost art of steam heating):

"install a lubricated plug cock or other suitable balancing valve after the service valve.. You can't throttle with a gate valve because when closed part way, the gate hangs perpendicular to the flow of water. It will rattle back and forth and eventually shake itself off its stem."

the hvac installer is using a "ball valve" is seems to do the throttling. (the kind with the handle that makes a quarter turn between opening and closing).

so my question is -- is this ok?

I know it's not ideal because someone can come and turn it by accident or turn it off or on and leave it in that position during servicing.

But short of that issue -- which i think i can solve by putting a sign on that valve -- is there any other reason why using such a valve to throttle speed is bad?

Brad White_203

Throttling

The least valve you should use for balancing is a bona-fide balancing valve (I like Macon but there are others).

Traditionally, a globe valve is used in your application, if not a lubricated plug cock as Dan suggests.

The issue is not just the velocity but how the valve responds to the velocity and to entrained solids in the flow...

A ball valve is better than a gate valve but a ball valve also can wear over time more than other valves. See, ball valves have a PTFE (Teflon) seal which encapsulates the ball. The channel of higher velocity flow and entrained rust particulates will abrade that softer material and you will have a valve that no longer seats, after a time. All valves wear, these moreso in this application.


Used for throttling in general, a ball valve's response is "minimal", meaning you have to turn the valve halfway or more closed before you have effective throttling. Your 90 degrees of turn is really 45 degrees and the last ten degrees is shut-off, essentially.

Kind of a paradox with these kinds of pumps. You want it both ways, sufficient pressure generated but then have second thoughts when it leaves the pumps!

Unknown

Brad has a great explanation,

but I have used ball valves to throttle the condensate line.
Who wants it to seat?, I just want to slow the inrush of water to the boiler.
Once I get it set, just remove the handle.

Dave

Brad White_203

I'll buy that!

There is really nothing wrong with using a ball valve "in a pinch" for throttling, just that it can wear to one side and is not very accurate but for that, who cares? But a bona-fide balancing valve or globe valve is the right thing to do.

If you do want a seating (shut off) valve, then a full-port ball valve downstream of the "balancing ball valve" (which should be "reduced port" meaning "standard port"), would allow you to isolate that other line.

Better yet, this is what I do, starting from the pump outlet:

Nipple/Increaser to Running Size/Nipple/Check Valve/Nipple/Balancing Valve/Nipple/Isolation Ball Valve. Running pipe size to boiler. Done!

Pressure gauges we specify for our commercial and institutional work but these are optional. If your boiler feed rate is right, you are fine. If it is not, you will know that too.

Unknown

Gottem like that

some 15 Yrs, still no probs!
Besides service work can net a little money too(if it happens).

Dave

Unknown

The ball will wear away over time,,,

so the flow will increase over time. But you guys knew that.

Unknown

Typical you MPF,

always take "Brad`s side",, no one can ever disagree with the King!

Dave

I`m sure he`ll have a Canadian "shot" for that-one LOL!

Brad White_191

King??

Dave, you flatter yourself. I am a regular goy. I mean, guy. Besides, I was agreeing with you!

Mark Custis

Brad: LOL, keep up your participation.

I hope I can get past the entry log-in.

Mad Dog_2

goyim............vodka all around

ARe you coming down? FOR THE EVENT??? MD

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Gee,,,

I thought I was ever so gently going against what Brad said.

If I found myself in the position of needing a valve to balance I would never use a ball valve and definitely not a gate valve, I'd use a balancing valve. Right tool and all that. A globe valve would be my second choice but I'd feel like I ws doing something wrong. That's good old Navy MM/A school still ingrained in my psyche. That school started with why you should use the right size screwdriver and what the difference between a 6 point and a 12 point box end wrench is. They were pretty thorough.

Once I got out of there and made it to the "fleet" I learned how to double wrench and picked up a few other bad habits besides! LOL...