What is this radiator valve?

mligneau

Hi everyone,

I found surprising radiator valves in a multifamily building in NYC; attached are pictures of the valve and of its inside.
It's a 2-pipe steam heating system with Arco radiators and no steam traps nor TRVs. The building is 14-story and was built in 1905.

Have you ever seen this kind of valve ? If so, do you know who's the manufacturer and in what kind of system they were?

I'd like to understand if they have some kind of variable orifice in it like orifice plates and how they work.

Please let me know if I can add anything that could help understand the system.

Thanks in advance for your help !

Steamhead

That's a classic- the ARCO Model K Vapor Orifice System!

Basically, the adjustment you see there is set so that when the system pressure is at its highest point, the radiator fills with steam to about 80-85% of its volume. This way, no steam can get into the dry returns as long as the system pressure stays within limits. I believe this was one of many systems that was designed to run at a half-pound or so- that means the boiler should have a Vaporstat instead of a Pressuretrol.

Dan has written about this system here:

https://heatinghelp.com/blog/adjustable-orifices-on-steam-system-radiator-valves/

and here's one we encountered:

http://forum.heatinghelp.com/discussion/131004/arco-model-k-system-in-the-jersey-skylands

There is a diagram of this system on page 269 of "The Lost Art of Steam Heating".