Steam Vents Next to Chimneys in Old Photos

jjakucyk

In many historical photos of downtown areas the old buildings have a big chimney for venting the coal smoke from their boilers, but most of them also have a steam vent next to it as well. I occasionally see these on modern central heating plants or factories too, but what's the purpose of it? Is the heating system just fired continuously and the excess steam/pressure is then vented to the outside? Is it the discharge from a steam injector/ejector used to pump condensate back into the boiler? Is it used to create a vacuum for...something? These systems mostly predate reliable electricity, so I assume it's serving some function that a pump or motor would do today, but what might it be?



You can see dozens of examples in this 1906 photo of Boston (click the link in the description for the huge full size view): <a href="http://www.shorpy.com/node/10056">http://www.shorpy.com/node/10056</a>

nicholas bonham-carter

what happens to the extra steam?

many large buildings had steam engines for electric power generation, and the excess/exhaust steam was used for heating.

some early heating systems had a vent line going into the chimney for air relief, and in some cases the maintenance of a vacuum within the system. nice pics!--nbc

icesailor

Steam Vents:

I'm no steam expert but here is a thought from a Plumber. In MA, in the plumbing code, going back to the time of dirt, I understand that they had steam condensate return tanks where the hot water condensate could return to and be re-used by the boiler. These tanks had to be vented to the outside to let off the heated vapors. This hot air/steam vapor is harmful and deleterious to the plumbing system. Therefore, MA requires steam condensate receivers to be separately vented to the outside. Because the boilers were usually placed next to a venting chimney, the vent would be located very close to the chimney and the floor framing would be easy to accommodate the vent. The vents were and are usually 4" pipe.

If a plumbing license test in Massachusetts asks you to draw a sketch of something with a steam boiler, it will require a receiver tank. Your drawing better show a separate tank vent through the roof individually or you won't get credit for the question.

This may be another answer to your question.

Brad White

I agree with Icesailor

Those vent heads are rather elegant and found on so many steam heated buildings and in fact steamships near the stacks. The cast iron heads have an internal pipe and a drip pan/drip separator enclosed but heated by the nearly continuous rising steam.



The vented steam was from condensate tanks and flash tanks and with process steam, there as a lot of flash steam.



The rising steam would keep the drip separator from freezing and allow a path for the residual condensate to run back down the walls of the vent to the receiver.



Without this vent head, a block of ice would eventually form and prevent operation.



If you find one from a demolished building, they make nice relics. I wonder what my Susan would say if I brought one home? Maybe I could convince her it is an ancient form of soup pot? She loves to cook. So, yeah, that's the ticket!

jjakucyk

Flash Tank

After looking into it a little more last night I thought it might be a flash tank vent. Thanks for the confirmation on that. Are those necessary because these old buildings were most likely to be using a high-pressure steam heating system? Flash tanks aren't really needed in the low-pressure systems that started to be introduced around that time.

Brad White

It depends

Some of the older facilities, a factory for example or a large apartment complex, might have generated their own power. Certainly a factory might have engines and of course, heating boilers.



Either way, there are receivers, atmospheric (hence a vent), or flash tanks (which may have a recovery line with check valve and then a pressure relief vent. So these vents were used in any number of configurations.