Hammer time!!!!

Onepipe

hey all so I just walked into a steam job that the customer is complaining of excessive hammering through the building. I have yet to fire up the boiler but upon walking into the basement some suspect piping jumped out. It looks like it was a Webster vapor system that was converted to a two pipe trap system.
pic 1: shows a take off with a trap at the end (I know the discharge of the trap is pitched wrong) BUT I have never seen a drip leg before a trap. I feel like that would be susceptible to steam hammer.

Pic 2,3 and 4: shows a fan coil with a trap that is below the dry return…..I am really having a hard time understanding how condinsate could ever make it to the return with out flooding the steam coil.

all advice is appreciated as I am sure this is just the tip of the iceberg

Big Ed_4

How was the water level on the boiler ?

mattmia2

Look at where those drips connect together at the ends of the mains and make sure they are below the water line and remain below the water line at whatever pressure the boiler is running. If there is not a water seal there the steam from the main will push in to the returns or the other mains.

That drip leg will fill with water and that will collide with steam but not sure if it will really cause hammer or not. The strainer will too, I believe it should be horizontal to prevent that.

Onepipe

big Ed_4 the boiler was not running and water was filled to the normal level. When you mention boiler water level are you talking dimension “A” 28”. The system has a condinsate pump and I did not measure that today. I can check when I’m back.

Onepipe

mattmia2, all of the dry returns drop into a common wet return that is sealed and then runs into a condensate pump. I did not think about the strainer but I can rotate them, good catch. As far as the drip leg before the trap do you think I could get away with removing the nipple and using a solid plug? Or should I change it to a reducing 90?

any thoughts on the crazy piping for the fan coil? That has to be flooded

EBEBRATT-Ed

A drip leg at a trap inlet is standard procedure and recommended to catch any dirt.

In the second picture the trap is discharging to the top of a return line is correct as is using a check valve. But a rise in the return line should be avoided if possible, from a steam coil or air handler (and must be avoided if the ahu or coil is subject to freezing).

Other than that the coil will work as piped but the steam pressure has to be high enough to lift the condensate to the return line. Looks like you have about 1' of rise so you need about 1/2 a psi.

Not the best way to do it but it will work.

See the story in the LAOSH about unit heaters in a factory.

Onepipe

Ebebratt-ed thanks. You mention that I only have about a 1” rise on that fan coil trap, can I ask where you are measuring to? When I think rise I’m thinking discharge of the trap outlet to the inlet on the dry return which is more like 8”. Thanks

Sylvain

I read here

https://heatinghelp.com/systems-help-center/things-you-should-know-about-steam-traps/

"Traps don’t vent air

Air moves through a trap and into the return line, but from there, it has to have a way to get out of the system or the steam won’t go where you need it to go. If the discharge of the trap goes upward, that’s going to form a water seal. Air won’t vent through a water seal (think about a sink trap). And again, where there is air, steam will not go. Think like air when you’re troubleshooting. Ask yourself, “If I were air, could I get out?” Follow the path of the air and look for the vents. If you don’t see them, that’s why the building isn’t heating well."

mattmia2

If there is enough pressure the air will push through the water. Warren Webster systems originally had a vacuum pump of some sort on the return that would help with this. It originally had traps on the emitters and the mains so the issues about water seals shouldn't be an issue.

I would look for bad traps letting steam in the returns and places where water can sit in the mains and the piping to the emitters. I would also look for modifications that don't follow these rules.

I was confused with what I was looking at with the end of the main. I thought that white pipe was the main but it is just a return.

@EBEBRATT-Ed knows way more about commercial steam systems than I ever will.

Onepipe

All, thanks for the input. I walked around today checking pitch and so far the main lines that are easy to get too are pitched well. Most every rad is incorrectly pitched and will need some work there. Supply valves at the rad are 50% original (vapor type) and the rest hodgepodge replacements. As for the rad traps they all look old and have not seen maintenance in ages. I’m guessing I’m getting a lot of steam leaking through those rad thermostat traps and reading havoc in the dry return. I got called away from the job but it’s looking like there is one failed mainline vent and no dry return vent, but as I said I was called off so it could be hiding somewhere…..need to get back and keep snooping.

mattmia2

If I'm not mistaken the returns will vent through the vent on the condensate pump.

If this was designed to have a vacuum pump on the returns then the mains would vent through the emitters in to the returns if I'm not mistaken and I think venting the mains through the emitters isn't uncommon in 2 pipe systems.

Onepipe

I think there was a vaccum pump originally but it is no longer there just a condinsate pump. I can look to see if the return use the condo vent for the system. If that’s the case the dry returns could not have a water seal prior to the pump tank correct?

As for the supply mains if they did vent through the emitters I would guess that would not be acceptable now as the vac pump is gone. So solution for that is to install/increase the main vents to keep my start up pressures low and fill my system quick.

mattmia2

I would see how it heats now once you figure out the hammer issues, it might have adequate venting through the emitters.

Forget what I said about drips and water seals, I thought I was looking at something else in that corner with the old safety switch in it. This was always a trapped system, it should never have steam in the returns and they should be arranged to not trap water so that they can vent.

EBEBRATT-Ed

@Onepipe I was just guessing from the picture that it looked like a foot of rise.

Onepipe

haha EBEBRATT-Ed I miss read your original post and I thought you said 1" ont 1'…..helps if one reads correctly.