water hammer on start up

SRC

My steam main goes downhill at some point.  Thus I assume there is a way they get whatever steam condenses on shut down out. What should I look for? The water hammer is on second floor radiators which are the farthest from the boiler and after the main takes a 6 in drop down. Two pipe system. The worst hammer is on the very last radiator in the loop upstairs, I assume because that is where all the water has to finally come to a stop. Thanks for any suggestions on getting rid of the condensate in the main between cycles.

jpf321

can you sketch a diagram?

can you sketch a diagram?

when you say "main" you mean a pipe in the basement correct?

please describe what you mean by "upstairs loop"

water should never "come to a stop" except in the boiler .. but if you have a specific thing in mind that the water is doing ... please explain a bit more.

SRC

more details

As main steam pipe weaves its way in the basement it sends off risers to the upstairs radiators. Steam hits the first riser and thus the first radiator upstairs  a bit sooner than the second riser and its radiator. Thus water hammer on the first, followed by the second, third, fourth, fifth and last riser/radiator. This happens on start up. Steam left over in the main from previous cycle condenses leaving water in the main. On next cycle start up  the steam picks up the condensed water that is now in the main and slams it into the radiators causing the water hammer.

Should there be some device on the main steam line that would drain off water that has condensed in main line? Wouldn't be a problem if mains drained back to the boiler but that is not my case obviously or I wouldn't have water hammer on start up.

This wasn't two much of a problem due to short cycling and little time for steam to condense in the line. Since changing out thermostat which limits the boiler to two cycles an hour there is more water hammer because it gives time for main to cool and thus leftover steam to condense in the lines.

SRC

more details

As main steam pipe weaves its way in the basement it sends off risers to the upstairs radiators. Steam hits the first riser and thus the first radiator upstairs  a bit sooner than the second riser and its radiator. Thus water hammer on the first, followed by the second, third, fourth, fifth and last riser/radiator. This happens on start up. Steam left over in the main from previous cycle condenses leaving water in the main. On next cycle start up  the steam picks up the condensed water that is now in the main and slams it into the radiators causing the water hammer.

Should there be some device on the main steam line that would drain off water that has condensed in main line? Wouldn't be a problem if mains drained back to the boiler but that is not my case obviously or I wouldn't have water hammer on start up.

This wasn't two much of a problem due to short cycling and little time for steam to condense in the line. Since changing out thermostat which limits the boiler to two cycles an hour there is more water hammer because it gives time for main to cool and thus leftover steam to condense in the lines.

jpf321

i think pipe expansion

i think that you are experiencing pipe-expansion not H2O hammer .. the way you describe it .. and b/c of your last comment .. before changing the t-stat your pipes were warmer .. but be sure that all the steam had condensed .. but b/c they were warmer, you didn't have as much pipe expansion .. please realize that the steam condensed in the mains very quickly and became water very quickly within 60-90secs after the boiler shut down assuming normal operating temps of 1.5psi or below.



so i think the sounds you are hearing are pipe expansion .. i'm happy to have others chime in.

SRC

expansion?

Expansion on just the 5 second floor radiators that are serviced at the end of the steam main? The other 10 radiators upstairs/downstairs, no problemo.

Note: No expansion noise/water hammer  on first start up of the heating season or if boiler is not fired for a long period of time which allows condensed water in mains to evaporate and go out of system through air vents that are open when steam is not present.

nicholas bonham-carter

2-pipe hammer

first, get a copy of "the lost art of steam heating" at the shop here. it will give you an excellent background of information on steam heating.

in any steam system the steam is constantly condensing as it gives up its heat to the radiators and pipes. i would check the following:

1. is your pressure set below 1.5 psi [some 2-pipe systems require only ounces of pressure].

2.are your main steam supply pipes insulated? the lack of insulation can cause rapid early condensation, which can lead to water-hammer.

3.are your supplies/returns adequately vented? the air must be let out, before the steam can arrive at the radiators.

4. are there any steam traps which are allowing steam into the returns?

5.is your boiler water clean and steady during firing?

check out these items, and tell us the results.--nbc

SRC

insulated main steam pipe

Insulation - where do you start insulating the steam pipes. The pipes coming off the boiler aren't insulated for about 10-12 ft as they rise up to the ceiling. Then they got insulation from there. If they need insulation to start from boiler what is the best type of insulation to use. I got the 1930's brand on mine now.

Also I have one boiler return trap. Also from 1930. Do these last forever. Any kind of maintenance for them? Mine is a Wiley Size 1, I believe.

jpf321

at least 1" thick insulation

the insulation I got recently from Allstate Insulation (a local supplier near me) was:

Johns Manville Micro-Lok HP (2x1) which means 1" thick for 2" pipe. It was about $1.50/linear ft.