Cast iron convector single pipe steam venting configuration

random12345

I have two recessed cast iron convectors made by US Radiator. This is their Capitol Fincast line from the 1930s. We have single pipe steam. Here is the catalog:

https://archive.org/details/capitolfincastra00unit/page/8/mode/2up

On page 9, there is an illustration under "Typical Piping Connections" for "One Pipe, Steam." My question is why is an angle air vent mounted in that way instead of there being a straight vent screwed directly onto the top of the convector? We have been using ours for years with straight vents directly connected. Is there some advantage to piping it the way it's drawn? Thanks.

gfrbrookline

From the picture I have two thought, strait vents were not available yet or they wanted to protect the vent from a water hammer.

random12345

I think those are strong possibilities, but I'm wondering if the convector builds up more steam piped this way before the vent closes...

gfrbrookline

How long is the pipe, 3"? It is more about allowing enough room to swing the 90 degree vent into place.

DanHolohan

I think the piping suggested is to help avoid water squirting from the vent.

random12345

DanHolohan said:

I think the piping suggested is to help avoid water squirting from the vent.

Thanks. Sounds right. In the 1939 catalog for one pipe steam the diagram changes and now they use a straight vent with something protruding below it into the convector. It's on "Page Five." Maybe this became the new way to prevent water getting into the vent...It must be built-in on mine because it says "Convectors for one pipe steam, will be regularly furnished with Fincast Vent fitting." I don't dare take it apart though to see since it's so old...I'm guessing straight vents must not have been widely available until after 1934. That old angled vent piping arrangement was more expensive and too much of a hassle probably.

DanHolohan

The convector showed up for the first time in 1923. Reuben Trane, James Trane's son, invented it. James Trane opened the business as a plumbing- and pipe-fitting shop. Reuben was the innovator.

The vent valve manufacturers were producing vents for old-style radiators at the time, hence the side connection. It must have taken a while for them to come around to making the straight-shank air vents for the convectors. In the meantime, Trane came up with the piping solutions we're looking at.

random12345

Very interesting. Thank you!