2 pipe steam venting

Gimpy Greg

My son recently purchased a home with an oil fired steam boiler. Each radiator has the top steam supply pipe on the
left hand side and just an elbow at the bottom right. The
radiator in the living room has one hoffman type vent about half way down the right side that spits constantly. From
whatI can determine 2 pipe steam should have a trap or
similar device on the return side of the radiator, or should
I be looking in the basement for something other than main
line vents ? The system is working ok, I just want to understand it and put a TRV in my grandson's bedroom. I can understand hot water heat having replaced a gas convection furnace with baseboard and a coal stoker (Two zone with two
B & G circulators) (yeah coal in 1985 in present home !! )
Diagnosed with MS in 1986 so replaced stoker with a Burnham gas boiler in 1987 and went with Taco zone valves. Can
understand hot air, replaced a hand fired coal octopus with forced gas hot air in 1978 in prior home. But I digress.
Any sugesstions on the steam system would be greatly appreciated. BTW did you plumbers vs. A/C guys ever settle on ID vs. OD for copper tubing that gave me so much heartburn in my prior work life ?
Regards,
Greg

Steamhead (in transit)

That's a Vapor system

There could be a water seal or check valve in the return elbow, or not. If not, the inlet valve would have an orifice in it which would keep steam from entering the dry return if the pressure didn't get too high.

This type of system vented air from one or more central points in the basement. Vents on radiators were not used. But the average knucklehead won't learn not to add vents to Vapor radiators.

Try to find manufacturers' info on any original radiator shutoffs and any old devices in the piping around the boiler. Also take some pics and post them here. This will help us ID your son's system and tell you where to go next.

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Gimpy Greg_2

Vapor System

I will try to obtain as much info as possible. My son has
a digital camera and the means to post pictures, I may
have to provide the motivation. Can a Danfoss TRV be used on this type system, also is manual regulation of the supply valves permissible ? If some knucklehead put a Hoffman
valve on a radiator I would think it was probably not
heating as they thought it should. Maybe a cold room so vent it to get more steam in it ? Could this knucklehead remove the valve and just plug the hole? Then determine if there is a problem and fix it for real ? I don't want to monkey with a system which is working save for the one hot room. I find this system fascinating in that I don't
understand how the vacuum to move the steam is created,
one thinks of steam "pressure" even if is less than a pound. Also is the orifice in the supply valve sized so
rate of steam into radiator equals rate of condensation ?
I must also learn how live steam is not allowed down the
condensate return without a trap to control it. All good
stuff. Getting the boiler and burner cleaned and serviced
should be no problem. I would appreciate help in keeping knuckleheads away from the rest of it.
Regards,
Greg