Re: Swing Check Valve

Steve_210

Hello Everyone. Please see photo of swing check valve. This is on the return line of a radiator of a 2- pipe air vented system. I have (3) buildings with 2 pipe air-vented systems that we are working on at the minute. They are all in the same neighborhood and i'm seeing a lot of these check valves. On all 3 jobs we have the pressure down to cutting out at about 14 ounces or slightly below 1lb. My question is: Does anybody think these check valves are original? I would think yes. As most of you here know, there are no steam traps on these radiators only hand valves with an air vent. The returns do not go to a wet return. They all join together like a ladder so you can have 6 radiators joined into a return riser before it drops into the wet return. What I'm trying to understand is the necessity for these check valves. I have a couple of areas in some of the buildings where I still have steam coming up the return before the supply and my thinking is, I should re-install some check valves. Looks like they were removed at some point, but i cant be sure. I then have to consider what type of check valve. Obviously, you want something that is going to open at low pressure or I will get water backing up in the returns. Hope this makes sense. Any Help greatly appreciated.

JUGHNE

The paint looks original.
Does every rad have one or did have?
Is it is a horizontal line?

My guess is that they were there to isolate the steam from other rads. Maybe the theory is that very low pressure steam would not swing the gate but an accumulation of water column building in height would open it and then close holding back the steam.

Or as long as they were closed no steam in that return could back up into the rad.

Both are WAG on my part.

Steve_210

Yes They're all on horizontal lines,
Not every rad has one but who knows who removed what over the years.
Wondering if there is a particular model check valve I should look for?

Big Ed_4

They where using the swing checks trying to prevent an bypass . Steam will travel the least resistant path ...Really since your venting at the radiator these are dry drip legs .. I would make them wet either straight into that old return or pipe in water traps with clean outs

Steve_210

Thanks. But not possible to do either,
Fourth and fifth floors of occupied building

JUGHNE

Have you considered orifices on the inlet valve of each rad. If you were to lower the pressure and still heat things, then you have an idea of operating pressure.

This worked for me on a 2 pipe system that had had all trap guts removed years ago. Only 80% or so of EDR is allowed into rad at a given pressure. No steam leaves the rad. In my case the returns were cool to the touch. For you as long as the existing checks would pass water, you would know of any stuck valves because of cond back-up in rad. Just an idea....econo permanent fix, no check valve replacement needed.

Steve_210

This will not work for me it's a two-pipe air vented system no steam traps. Steam will just come up the return to the air vent
I think I will proceed with some checks.
Just wondering if anybody could recommend a particular type for use on the two pipe Air vented system.

JUGHNE

If there are 6 rads on one vertical drop to the wet return and each of those rads has a controlling orifice in it's valve then there should be no steam in that branch of returns.

It would be like turning all 6 supply valves off and then just barely opening them to partially heat across the rad and keeping the outlet end of the rad cool.