dirty steam pipes?

tom_82

Hi,

We have banging in the main pipes upon start up. A technician came out and said the water from the trap looked pretty dirty. There might be sludge in the pipe and the water might be backing up behind it and causing the water hammer. We should take the pipe apart and clean it out.

I seem to recall reading that this is untrue. That we have our pipes steam cleaned everyday with the heat on.

Any thoughts?

Thanks.

T

Jamie Hall

Oh dear...

it is very unlikely that the steam pipes are dirty, although it has been known to happen.  As you note, they are steam cleaned every time the system comes on!  Which is not to say that the wet returns might be pretty grubby, though -- but that's not where your banging is coming from, and your technician's adivce isn't going to help you much.



The banging is almost certainly water hammer, and it is coming -- almost certainly -- from water in the steam mains being propelled along by the steam, and slamming into a right angle corner somewhere.  The question is where is the water coming from, and what is to be done about it?  If it is coming from wet steam, that suggests that the near boiler piping is poorly arranged.  Always a possibility, especially if the a new boiler was installed before this started.  If not, it may well be condensate, which is completely natural, but which should be able to drain away somewhere to get back to the boiler before it runs into something hard.



To be able to say much more beyond that, though, we're going to need to know more about your system!

tom_82

thanks

Thanks,

I am going to look first to make sure all the mains upstream  are insulated and pitched  right.

Last year we had to replace some return lines. The system is pretty old, 1930. Boiler from 2000. Could it be water backing up from the return lines?

T

Jamie Hall

Quite.

You've got a good start.  First thing to do is to check all the steam mains.  They should be insulated as much as possible.  On pitch, be sure and use a very good long level or better yet a laser level.  It is not at all strange on an older system to find that there is a sag somewhere, particularly on longer horizontal takeoffs -- and it doesn't take much of a sag to hold enough water at the end of a run to make a colossal racket at the beginning of the next run.  It is not enough to just check the ends.  Nor can it be done by eyeball with any reliability.



Water could be getting trapped in the returns somewhere, too, although that will usually show up as a water level problem in the boiler.  It can also stack up in the returns sometimes, and get water into a dry return -- but that usually happens more in the middle or the end of a cycle, rather than the beginning.



However, if you had to replace some returns last year, were they replaced exactly as they had been before?  If not, it would be worthwhile to think about just exactly how the condensate which gets into them gets back into the boiler, and make sure that it works as it is supposed to.  There are way too many different steam piping systems to be able to say much more than that without knowing more about your specific systems -- except to say that there are booby traps lying in wait in return repiping jobs which aren't always obvious!

TooMuchBanging

Follow up question

I live in the same building as the original poster and am following up with some additional info.

It was recommended that our boiler needs to be skimmed and flushed -- that the boiler is surging because of dirt in the boiler that is likely causing the bangining in the pipes. Does this seem like it could be an appropriate diagnosis?

Unknown

that's part of the reason

If the boiler sight glass showing surging/boucing water lever, chance are it making wet steam and carry same into pipings. However, very common, if the near boiler pipings and return are piped incorrectly, you will have the problems. Any way you can post some pictures of the boiler and pipings?

TooMuchBanging

Follow up

I might be able to. Assuming the piping was done correctly (this is an 80 year old system and the problem has only started in the past few years), would skimming and flushing be an appropriate solution? Would this help stop the wet steam? Thanks!

Jamie Hall

Skimming and flushing

never hurt anything, assuming they are done right (read and obey your boiler's manuals.  If you don't have them, get them!).  And if the water level is bouncing badly, or you have foaming, it could certainly help.  It is possibe that oil or other contaminants from the new returns has gotten in there, and that can cause wet steam and thus problems.(it also, incidentally, does you efficiency no good at all, so it can actually save money!)



Worth a try, anyway.

Unknown

Steam Pipes

First of all, never`assume the piping is "correct". It may have been originally but since then, like people, things can sag as they get older. Also you must suspect any work done on the system over the years especially when a new boiler is installed. Replacement boilers are much smaller than the original boilers. They use their near-boiler piping to separate the water from the steam so if you want dry steam you have to make sure the near boiler piping is done properly.



 To answer your question: Would skimming and flushing help stop the wet steam ?

Yes, it would ....if it is needed. However there maybe other thing that are causing your problem and you haven't provided us with much information to go on.



Is the water in the boiler dirty? You can tell this by just looking in the sight glass.

Does the water line "bounce"?  - You can tell this by observing the water line in the sight glass during the operation of the boiler. A certain amount of movement is normal say 3/4 of an inch. However if the movement is more violent your boiler may need skimming. Also look for water droplets on the sight glass above the water. This can be a sign that the boiler needs skimming.  Other things to check are the PH of the boiler water and how high is the pressure and are there unusual changes in the water levels.



I flush my steam system annually and skim as necessary. Skimming usually needs to be done when the boiler is new or the system has had some work done on it.

What happens is that contaminates, like oil, increase the surface tension of the boiler water.  Normally steam bubbles to the surface of the water like bubbles in a champagne glass however if the water has incresaed surface tension, the bubbles have to collect together until they are large enough to break through the water's surface. The violence of this breakthrough throws water vapor into the rising steam and this is carried along with the steam into the system and is what we call "Wet Steam". Skimming is done to remove these contaminates and may have to be done multiple times. Skim, operate the boiler for a while and then skim again until the boiler water is behaving correctly.

Skimming cures one cause of wet steam but as mentioned, there are other causes you need to consider.

- Rod

TooMuchBanging

steam pipes

I checked our boiler last night. Assuming I was looking in the right place (a 8 to 12 inch long tube that looks like it contains water from the boiler and shows the amount of water in it) -- the water color is a mid range brown color and when the boiler is on, it fluctuates at least an inch (sometimes a little more).

Unknown

Skimming

As Jamie mentioned "Skimming and flushing wouldn't hurt". It's really hard for us to diagnose your problems as there are so many variables and you haven't provided us with much information. The bounce in the waterline doesn't sound too bad though we have no idea as to what is "normal" for that boiler. The usual "normal" is about 3/4 of an inch though it sounds as though your boiler could use a good flushing anyway and a skimming certainly wouldn't hurt.



There is a very good book offered on the site called, "We Got Steam Heat" [url=http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence]http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

It's easy reading , humorous and full of information on steam heating. As you seem to be involved with your steam system, I would highly recommend getting it . It will give you enough knowledge about steam to be able to qualify if the technician working on your steam system knows what he is talking about and unfortunately there are a lot of them out there that don't.  My copy has paid for itself a hundred times over.

- Rod

tom_82

more info more questions

Hi All,

I was the original poster of this thread.

I've been away for a few days.

Our building is a one pipe steam system and has good around boiler piping. It has been looked at by some very reputable folks. We have a dropped header that was installed with a new boiler in 2000.

We have vented the system pretty well and have changed several old traps.

We have two legs branching off form the boiler feeding our courtyard building.



question.

if the water was bad in the boiler, wouldn't we have banging in both legs of the system, not just one?



What is the best way to find water in the mains? We have one those infrared hand held temp gauges. But a lot of the pipes are insulated.

Also, what would be the best way to see if the pipes are pitched right with all insulation  on the pipes? It's wrapped and taped not that hard insulation/

Unknown

Steam Pipes

This is a one pipe system with "traps"? What pressure is the operating pressure of your boiler?  Are there water droplets on the inside of the glass above the water level in the sight glass when the boiler is operating?

In answer to your question - "if the water was bad in the boiler, wouldn't we have banging in both legs of the system, not just one?"  Answer- Not necessarily- steam isn't that predictable.

If you have "reputable people" available I'd have them in to look at your system. A steam pro can spot a problem quite often immediately.

- Rod

Jamie Hall

one pipe steam?

with traps?  What does it appear that the traps do?  One pipe steam almost never has traps...

tom_82

traps

we have several steam  traps throughout the building so steam does not get down into the condensate return lines.

The boiler is cutting in around 1/2psi and cutting out around 2psi maybe a little bit higher than that, but not much.

Tom

Jamie Hall

Ah. Fair enough

I presume F&T traps?  On all of the lines which go to the condensate return?  And all of the lines have a vent/vacuum breaker downstream of the trap?  And nothing is double trapped?  And the condensate receiver is vented?  And you do have a condensate return pump or boiler feed pump and it's working properly?



Any of those could cause serious problems in the related line... anything not working or not working right!

tom_82

more

Yes, F+T's. Not sure when they were put in. Yes on all the lines that go to the returns.

Not sure what a vent/vacuum breaker is. Could you explain that?

Yes, vented condensate return tank and yes return tank pump which is working properly.

I actually just got off the phone with the tech supervisor who diagnosed this need to skim tank. He said he could hear water through the mains upon start up, so he went back to the boiler and saw the water bouncing and spilling down from the top. He felt strongly that we should do this.

THis was the first time I got to speak directly to him. He is going to dump and flush the boiler fill it  and skim it and repeat if he needs to. He is going to dump and flush the condensate return tank also.

We'll hope for the best and expect the worse! ha ha

We'll let you know the results ASAP

Thank you for all your attention.

I do have some other questions regarding the amount of venting we have. perhaps I'll take some pictures and post them.

Thanks again

Tom