Ball Valve on Steam Main

BKJohnny

I recently moved into a building with a single-pipe steam system and have been working to make things better (insulating mains in the basement, sorting out the master venting and the radiator venting, etc.). One thing I don't quite understand: there's a full port ball valve between the header and the main. It's not fully open, though (maybe 20 degrees off open) and I can't guess why it would have been left this way. Before opening it up, though, I thought I'd ask the experts. I'm attaching a couple pictures, but they're not great. I'll try to get some better ones if needed.

pecmsg

Start using 1 1/2 - 2" wall thickness on the insulation.

I hate ball valves on steam to easy to slam open or closed. In your case id open it fully and wire the handle open!

Next get clearer pics further away!

Jamie Hall

It's called a king valve, and it's there if -- for some reason -- you ever wanted to raise the pressure in the boiler above normal. As @pecmsg said, it should be fully opened and safetied that way.

JUGHNE

If it will move.....I have seen these stuck part way for years and they are reluctant to move. If you get it open it would be good to exercise twice a year when the steam is off. IMO

Looks like welded headers and then a lot of copper in steam piping?

Hap_Hazzard

The only reason for it being there is to allow you to build up pressure to blow down the boiler, which is a pretty good thing to do now and then. That's why I have a full-port ball valve on each of my main risers. (See the picture in my signature, below.) These are known as "king valves" in the trade. But you need more than a king valve to blow down your boiler. You also need a shut-off valve on your wet return to keep the pressure from backing up condensate into your main, and you need a blow-down valve on the boiler's mud leg (or return pipe).

I'm going to have to disagree with @pecmsg about ball valves on steam systems. I love them. They're generally full-port, easy to open quickly, and you can tell if they're open or closed from across the room. I've also found them to be very reliable when rated for the application. A lot of people seem to like gate valves, but I hate gate valves for steam systems or just about anything else. They totally suck.

BKJohnny

Thanks, guys. I haven't worked on any of the insulation in the boiler room yet. Thanks for the tip on the insulation thickness.

No copper in the steam piping – just a bad picture in the boiler room where, for some reason, the domestic hot water got shoved into the same corner as the steam boiler.

I'll see if I can get it fully open.

I appreciate the quick and thorough responses!

Hap_Hazzard

I don't see the need to wire it open, except maybe as a temporary measure. Any ball valve that's capable of closing by itself should be replaced ASAP. I've never seen it happen, but a ball valve in good condition should put up a little resistance to being turned. If it doesn't, throw it out and replace it with a union, unless you plan on doing blow-downs.

coelcanth

i think it's not so much that it will close itself, it's that people unwittingly grab the valve or hang their laundry on the handle and then it ends up closed or partially closed, like what might've happened here

Hap_Hazzard

I dunno. It doesn't look that easy to get to.

BKJohnny

It's funny, because of the way the DHW systems is installed right around the boiler, it's almost impossible to get to the valve without scorching yourself on the hot water piping, so it's hard imagine someone partially closed the valve by accident. Which made me wonder if the last boiler technician had something in mind leaving it that way.

Hap_Hazzard

Let me put it this way: there is no good reason for it to ever be anything other than fully closed, when you're intentionally trying to build pressure in the boiler, or fully open, the rest of the time.

Ball valves generally aren't used for throttling. They're best thought of as on-off switches for pipes. And throttling isn't something you would ever do to a steam pipe anyway. Single-pipe steam relies on biphase flow—high-velocity steam and low-velocity water flowing through the same pipe. Anything that causes the water to pool or introduces turbulence in the steam flow can cause differential shock, a very destructive form of water hammer.

Intplm.

pecmsg said:

Start using 1 1/2 - 2" wall thickness on the insulation.

I hate ball valves on steam to easy to slam open or closed. In your case id open it fully and wire the handle open!

Next get clearer pics further away!

I agree with you @pecmsg I have had problems with ball valves. Mostly with steam. The ball valve for most everything I do is my "go to" valve. But not for steam. For the reason you mention and many others.
@BKJohnny your valve MIGHT be partially closed because the valve stem packing has loosened due to the high steam temps and the angle it is installed so the valve handle has sagged downward.
Or, quite simply, it just isn't open all the way

Hap_Hazzard

My king valves are only rated at 150 psi for steam, so, yeah, I'm sure they'll go bad any day now.

Long Beach Ed

There are easier ways to clean out a mud leg. The last time I checked, a 3" American made ball valve set us back about $500. And no, we don't buy Chinese valves or fittings...

NYC still requires a king valve on some installations, mainly to test the pressure relief valve. That sounds like it would be exciting.

Hap_Hazzard

I'm glad I didn't need 3" valves. 2" ball valves are a lot less expensive.

jumper

Industrial quality butterfly valves used to be available at relatively reasonable price?

gerry gill

JUGHNE said:

If it will move.....I have seen these stuck part way for years and they are reluctant to move. If you get it open it would be good to exercise twice a year when the steam is off. IMO

Agreed, when I was in the Navy, we had to exercise every valve on the ship at least once a quarter, in order to ensure they worked easily. Thousands of them. They would be divided up amongst work shops.

Hap_Hazzard

The PVC ball valves I use on my swimming pool are hard to turn if they sit for a week or so. I've broken more of those damn plastic handles, and those things aren't cheap. But my 2" brass/SS ball valves on my my system risers usually only get a workout in the fall. They put up resistance, but I've never had a real problem turning them. They're damn good valves!