Blow down piping

JoeC

is because they never piped it to the blow down tank, or any kind of tank. They simply have a nipple attached to the shutoff valve below the LWCO's. They let it dump onto the floor and it makes a terrible mess of things. The floor is covered with a layer of rusty crud from the blowdowns. The reason I asked about the acidity is because in another boiler room, the floor drain trap has totally disappeared, the only thing that ever goes down that drain is condensate from those blowdowns. In yet another boiler room, the floor drain failed the same way. After cutting concrete and such to replace the drain trap assembly, we found the horizontal runout piping was almost completely sealed shut with a rusty crystallin type formations that aare hard as rock. Anyways, my goal was to do what I could to prevent further flooding from the boiler room. Today I piped all the LWCO's together and ran the line to the floor drain. If they only blowdown one boiler at a time, maybe I wouldn't have to store a shopvac and mop there anymore. Thanks for the help Tony!

JoeC

blow down piping

When several steam boilers are in series,can the blow down piping from all the LWCO/Pump controllers(downstream of the'throttling'valve)be interconnected to share a 'common' drain type line I'm being asked to pipe to a floor drain? I don't care for the idea of discharging hot condensate and such to a sanitary sewer type drain (I'm sure the UPC disallows such practice). Is there any mechanical/safety requirements that outline that each LWCO/pump controller be individually piped to a drain?

JoeC

blow down piping

When several steam boilers are in series,can the blow down piping from all the LWCO/Pump controllers(downstream of the respective'throttling'valves)be interconnected to share a 'common' drain type line I'm being asked to pipe to a floor drain? I don't care for the idea of discharging hot condensate and such to a sanitary sewer type drain (I'm sure the UPC disallows such practice). Is there any mechanical/safety requirements that outline that each LWCO/pump controller be individually piped to a drain?

Blackoakbob

individual runouts.....

would be easier for disassembly later for cleaning and visual inspections. Although, I have manifolded the lwco blowdowns & skimmerline and use a pipe size equal to the largest pipe + 1/2 the diameter of the each of the other pipes totaled up, kinda like the rule for regulator vent lines.
Check your local plumbing code about the high temp waste requirements. You may require a flash tank with a cool down prior to dumping into the sanitary sewer. This would probably depend on the boiler pressure/temperature. Look under "special or indirect" waste connections. Best Regards,

Tony Conner

It's Very...

...common for the blowdown piping to manifold together in high pressure steam plants. A common line is run to the blow down tank, which allows the high temp water to flash to atmospheric pressure. The tank also has an internal siphon arrangement such that the incoming hot water displaces water that has sat in the tank for a while, and cooled.

You may or may not find any references to requirements like this in a plumbing code. The code that covers what I work with in Ontario is the CSA B51. But it only talks about boilers over 15 PSIG, and includes a requirement that the water heading for the sewer be no more than 150*F. It also lays out the size and dimension requirements for the blowdown tank (based on boiler capacity), minimum pipe sizes, cooling water requirements, etc.

JoeC

Blow down piping

Thank-you both for responding to my question. There is a blow down tank that serves these boilers, but it was originally specified without any tapping to allow for blowdowns of the LWCO/Pump controllers (top blowdowns), its a system Honeywell has been selling the US Military installations the past few years. Currently when blow downs are performed, they without fail flood the boiler and surrounding room floors with condensate (taking out tile and carpet). If routine daily blowdowns were being performed, then posibly such damages wouldn't occur. In addition, had Honeywell installed throttling gate valves in addition and downstream of their ball valves, maybe the LWCO's wouldn't be experiencing so many failures (imploded floats)? Which is a problem in a place where temps drop to minus degrees for weeks)

Tony Conner

Hmmmm...

...imploded floats? The only thing I know of that will collapse a float in something like a steam trap, is water hammer. Any reports of waterhammer when boilers are being blown down?

I should have been a little more clear in my previous post - the bottom blow downs usually manifolder together, as are the continuous blow downs, but the two blow down headers are not normally tied to each other. They typically run to the tank as two separate mains. This also gives you some ability to install a heat exchanger to pull the heat out of the continuous blow down, and put it into the make-up water.

Can you post a sketch or shot of the piping?

JoeC

Thanks for the explaination Tony, I appreciate your patience. I was told that that was the reason for installing both a positive shutoff valve and a throttling valve, was to ensure that a sudden blowdown could not be possible. (I guess the steam could condense and cause a hammer that could crush a float or damage the linkage). My main concern is to stop the flooding of my mech room and further damages to the surrounding rooms flooring and such. Thanks again for your help!

JoeC

I forgot to ask...

about the condensate created from the blowdowns. I under the impression that steam condensate was acidic? If this is true, should it be treated before it gets dumped down the 40 year old cast iron floor drain? These new boiler room floors are now covered with an iron powder/residue from past blowdowns (which track up floors really well)

Tony Conner_2

Why...

... is this water hitting the floor? It should drain from the blowdown tank without doing that. There's something odd going on, and I suspect it's much more mechanical in nature, than chemical.

The main reason for acidic condensate is alkalinity in the make-up water that breaks down into carbon dioxide under boiler conditions. This CO2 is carried out with the steam, (it doesn't normally have any effect on the boiler) and becomes dissolved in the condensate. It can make the condensate about the same pH as soda pop. You can tell what's going on by looking at the inside of the condensate piping. If it's rusty carbuncles, that's normally oxygen corrosion. If it's nice and clean, but thin (literally "grooved") on the bottom half of horizontal runs and full-wall on top, that's acidic condensate. If you've got boiler water that's so acidic that it's going after cast iron drains, I think that "drain problems" will be the least of your worries.

When it comes to corrosion & deposits in steam boilers and their piping systems, make-up water is pretty much the root of most problems.

Tony Conner_2

There's...

...no connection on the blowdown tank to run the low water cut-off blowdowns?