King valves as throttles?

delcrossv

Are king valves ever used as throttles to balance multiple mains or just as isolation valves for the boiler?

EBEBRATT-Ed

just for isolation

cross_skier

King valves are never used as throttles.  Mains are often balanced by adjusting the size and number of main vents on each leg.  The usual practice is to add main vents on the slowest to heat legs.  You should see immediate improvements.  Some of us have antlers of vents on some mains.

mattmia2

they would hold condensate in the mains in the same way a partially closed radiator valve does. I suppose you could if you dripped them to carry the condensate away but I don't see why you would want to.

delcrossv

That's what I figured, but pays to ask. Thanks!
Rising stem gates for these preferred, yes?

retiredguy

If you are referencing rising stem gate valves, this must be a large heating system such as in a commercial building, school or hospital. I prefer a rising stem gate valve as an isolation valve to a non-rising stem valve. I also prefer a :non return valve" at the boilers discharge nozzle to a manually operated valve.
Since you asked the question of using king valves as throttling valves there must be a problem that someone is trying to solve. If there is ask the question.

ethicalpaul

If you attempted throttling with a king valve on a single boiler, the pressure would push the water out the back of the boiler into the wet return.

Jamie Hall

Agree with @retiredguy up there -- what is it you are trying to accomplish by throttling a main?

Throttling a steam main for saturated steam is a good deal trickier than it sounds, since saturated steam doesn't behave quite the way either air or other gasses or superheated steam does.

delcrossv

@retiredguy Yes, it's a apartment building .
Don't get the non- return valve part as those would trap condensate (???)

More of a theoretical question at this point. I'll have 3 mains: 2@ 2-1/2, 1 @ 2". Fittings and lengths differ between the two bigger mains resulting in different pressure drops ( some of which I can correct with adjusting the length of the drop down to the smaller condensate returns). Just investigating options to even up flow between them.

delcrossv

ethicalpaul said:

If you attempted throttling with a king valve on a single boiler, the pressure would push the water out the back of the boiler into the wet return.

Only with a single main, not a single boiler.

Jamie Hall

There's no need to even up the pressure drop unless it were extreme -- and if you do it right it won't be. What you want to make sure of is that your pipe sizes aren't arbitrary, but are related to the EDR which each main is serving. Assuming that is the case, you should have no concerns. It is much more important to make sure that the mains are insulated and that they are adequately vented.

Inadequate insulation is often overlooked as the cause of uneven steam arrival times at the ends of the mains, particularly from a cold start. Even a short uninsulated section -- a few feet -- can delay arrival by several minutes, regardless of the venting.

If this is a tall apartment building -- more than three stories, perhaps -- you should give consideration to insulating the main risers and venting their tops as well. Just because they are vertical doesn't mean they aren't main supplies!

delcrossv

@Jamie Hall I'm kind of stuck with what I have as I'm not re-doing the whole system . Fortunately, the EDR's for the two larger mains are similar. The risers are buried in walls for the most part so are inaccessible. The two 2-1/2" mains will be somewhat oversized for EDR.
The available variable will be the length and size of one of the larger mains after the last takeoff. I can add or reduce drag there.