TWO PIPE STEAM- LOUD BANGING

peterpaw

TWO PIPE STEAM- LOUD BANGING


HI THERE
we are working on a two pipe steam system. over time the banging of pipe has increased to an unacceptable level.

1. no particular work has been done to alter the system piping
2. check valve in Hartford loop replacement 5 years ago
3. all radiator steam traps replaced in the last 18 months
4. it takes 2.5 pounds pressure to heat the whole building
5. the building is 85 feet tall with a foot print of 43 x 83
6. two large air valves replaced in the basement by the boiler
7. replaced all riser steam traps in t he last two years

there were periods in the past 20-30 years where the system was almost silent


ANY HELP WOULD BE APPRECIATED

MY THOUGHTS

A. remove the check valve in the Hartford loop
B. remove all radiator steam traps and use 80% restrictors for each radiator
C. set boiler pressure to 0.8 to 1.0 pounds

So any ideas or thoughts would be appreciated

peter williams

peterpaw@aol.com

nicholas bonham-carter

Look for traps on the returns, which are called "cross-over traps", and verify that they are working. If they are, then check the main venting, which may not be adequate enough to let the air out. Temporarily removing those vents, and firing the boiler may tell you what you need to improve.
This two-pipe system may only need 4 ounces to work properly, for which you will need a vaporstat.
Post some pictures of the valves, and boiler so we can I D the system.--NBC

JUGHNE

Are there any pumps connected to this system?

Jamie Hall

Check valve in the Hartford loop has to go. Pressure has to come down -- a NBC said, it'll probably work on 4 ounces, but for starters if you have a pressurestat dial it as low as it will go. Traps are probably not a problem, provided they are working -- which is easy to check -- but if you do have crossover traps, they are critical to the working of the system and they may not be obvious.

I would leave the traps in the radiators and crossovers, and just check that they are opening and closing properly. Restrictors are very fine and very sophisticated -- but they only work if you can keep the pressure very low, and if they are calibrated to each radiator. One size does not fit all!

Now... if the changes have been somewhat gradual, go out into the system and check the pitch of every single near horizontal pipe. Every single one, for its entire length. Something may have sagged somewhere, and that will do it. You will need to be thorough.

Paul48

I wonder if you could zero in on the problem area(s) with an inexpensive decibel meter?

nicholas bonham-carter

There is a check valve low down on the return which was a necessary part of some early two-pipe systems. Look in the library here for Dunham Vapor Heating System, and you will see a check valve at underneath the air eliminator.
Are those riser traps the crossover traps, and are they on the returns?
I think we had details of a system, years ago here, with a replaced boiler that mixed up the supply and returns, with obvious consequence!--NBC

STEAM DOCTOR

Clean the boiler

nicholas bonham-carter

Cleanliness is next to godliness!
That still doesn't explain the need for 2.5 psi to heat the building.--NBC

Steamhead

Agreed. Maybe your vents aren't big enough. How big is this system? What vents did you use?

Where are you located?

peterpaw

there are two air vents one is slightly smaller than a beer can and the other is more or less a regular large valve

it is possible that the system is oversized

Located Manhattan

the confusing part is that this same system had been mostly quiet in the past. So that leads to the speculation that some part of the system has partially failed

peterpaw

hi there
i like the idea of firing it with the air vents removed. a good starting point.
i agree that the check valve should be removed.
I have referred to riser traps and here they seem to be referred to as cross over traps

pw

peterpaw

NO PUMPS

peterpaw

HI THERE

CLEANING
other than dumping the existing water, what would you suggest as a method for "cleaning" the boiler

the size of the building is five stores, high ceilings with a foot print of 43 x83 feet. concrete construction

PW

peterpaw

IMPOSSIBLE TO LOCATE SOURCE OF BANGING

PW

Paul48

I suggest you contact 72*F, LLC. He will point you at the things that need to be taken care of.
(646) 598-7230

aircooled81

Does the banging happen at the beg, mid or end of cycle boiler cycle?
Are you hearing it mostly near the boiler, or at a particular area in the building?
How would you describe the water level in the sight glass on the boiler?

peterpaw

the banging seems worse at the beginning of the day cycle but will get noise during the cycle as well

does not seem to be surging. do not get a lot of make-up water needed

Jamie Hall

Go back up (do contact one of the contractors here on the wall, too!) to nearer the top.

One, make sure those "riser" traps -- crossovers are working.

Two, dial the pressure down. Way down.

Three, check the other traps; if any of them are failed open, that can cause an interesting array of problems (failed closed just keeps that radiator from heating usually, although it can cause banging in the pipes leading to that one radiator). Fix any which are failed open.

Now, go through the building with a good level. Check every single level or near level piece of piping, both steam mains and returns. What you are looking for is a place (or places!) where something has sagged, and the pipe does not have the proper pitch to drain to a return, or where it has sagged in between supports and created a water pocket. Check all the radiators, too -- they need to be pitched at least slightly towards the outlet.

It is entirely possible that item two above will cure the problem, or at least help, and it will certainly help in a lot of other ways. But I'm going to bet that you find that somewhere there is a pitch problem...

JohnNY

Give me an hour with that 5-story steam system and I'll tell you how it'll get fixed.