What makes flues leak? I asked this question once, and the answer was
that the flues were not large enough to fill up the hole in flue sheet.
This struck me as being funny at first, but on second thought I
concluded it was about correct. Flues may leak from several causes, but
usually it can be traced to the carelessness of some one. You may have
noticed before this that I am inclined to blame a great many things to
carelessness. Well, by the time you have run an engine a year or two
you will conclude that I am not unjust in my suspicions. I do not blame
engineers for everything, but I do say that they are responsible for a
great many things which they endeavor to shift on to the manufacturer.
If the flues in a new boiler leak, it is evident that they were slighted
by the boiler-maker; but should they run a season or part of a season
before leaking, then it would indicate that the boiler-maker did his
duty, but the engineer did not do his. He has been building too hot a
fire to begin with, or has, been letting his fire door stand open; or he
may have overtaxed his boiler; or else he has been blowing out his
boiler when too hot; or has at some time blown out with some fire in
firebox. Now, any one of these things, repeated a few times, will make
the best of them leak. You have been advised already not to do these
things, and if you do them, or any one of them, I want to know what
better word there is to express it than "carelessness."
There are other things that will make your flues leak. Pumping cold
water into a boiler with a low gauge of water will do it, if it does
nothing more serious. Pouring cold water into a hot boiler will do it.
For instance, if for any reason you should blow out your boiler while in
the field, and as you might be in a hurry to get to work, you would not
let the iron cool, before beginning to refill. I have seen an engineer
pour water into a boiler as soon as the escaping steam would admit it.
The flues cannot stand such treatment, as they are thinner than the
shell or flue sheet, and therefore cool much quicker, and in contracting
are drawn from the flue sheet, and as a matter of course must leak. A
flue, when once started to leak, seldom stops without being set up, and
one leaky flue will start others, and what are you going to do about it?
Are you going to send to a boiler shop and get a boilermaker to come out
and fix them and pay him from forty to sixty cents an hour for doing it?
I don't know but that you must the first time, but if you are going to
make a business of making your flues leak, you had best learn how to do
it yourself. You can do it if you are not too big to get into the fire
door. You should provide yourself with a flue expander and a calking
tool, with a machinist's hammer, (not too heavy). Take into the firebox
with you a piece of clean waste with which you will wipe off the ends of
the flues and flue sheet to remove any soot or ashes that may have
collected around them. After this is done you will force the expander
into the flues driving it well up, in order to bring the shoulder of
expander up snug against the head of the flue. Then drive the tapering
pin into the expander. By driving the pin in too far you may spread the
flue sufficient to crack it or you are more liable, by expanding too
hard, to spread the hole in flue sheet and thereby loosen other flues.
You must be careful about this. When you think you have expanded
sufficient, hit the pin a side blow in order to loosen it, and turn the
expander about one-quarter of a turn, and drive it up as before; loosen
up and continue to turn as before until you have made the entire circle
of flues. Then remove the expander, and you are ready for your header
or calking tool. It is best to expand all the flues that are leaking
before beginning with the header.
The header is used by placing the gauge or guide end within the flue,
and with your light hammer the flue can be calked or beaded down against
the flue sheet. Be careful to use your hammer lightly, so as not to
bruise the flues or sheet. When you have gone over all the expanded
flues in this way, you, (if you have been careful) will not only have a
good job, but will conclude that you are somewhat of an expert at it. I
never saw a man go into a firebox and stop the leak but that he came out
well pleased with himself. The fact that a firebox is no pleasant
workshop may have had something to do with it. If your flues have been
leaking badly, and you have expanded them, it would be well to test your
boiler with cold water pressure to make sure that you have a good job.
How are you going to test your boiler? If you can attach to a hydrant,
do so, and when you have given your boiler all the pressure you want,
you can then examine your flues carefully, and should you find any
seeping of water, you can use your beader lightly untill such leaks are
stopped. If the waterworks will not afford you sufficient pressure, you
can bring it up to the required pressure, by attaching a hydraulic pump
or a good force pump.
In testing for the purpose of ascertaining if you have a good job on
your flues, it is not necessary to put on any greater cold water
pressure than you are in the habit of carrying. For instance, if your
safety valve is set at one hundred and ten pounds, this pressure of cold
water will be sufficient to test the flues.
Now, suppose you are out in the field and want to test your flues. Of
course you have no hydrant to attach to, and you happen not to have a
force pump, it would seem you were in bad shape to test your boiler with
cold water. Well, you can do it by proceeding in this way: When you
have expanded and beaded all the flues that were leaking, you will then
close the throttle tight, take off the safety valve (as this is
generally attached at the highest point) and fill the boiler full, as it
is absolutely necessary that all the space in the boiler should be
filled with cold water. Then screw the safety valve back in its place.
You will then get back in the firebox with your tools and have someone
place a small sheaf of wheat or oat straw under the firebox or under
waist of boiler if open firebox, and set fire to it. The expansive
force of the water caused by the heat from the burning straw will
produce pressure desired. You should know, however, that your safety is
in perfect order. When the water begins to escape at the safety valve,
you can readily see if you have expanded your flues sufficiently to keep
them from leaking.
This makes a very nice and steady pressure, and although the pressure is
caused by heat, it is a cold water pressure, as the water is not heated
beyond one or two degrees. This mode of testing, however, cannot be
applied in very cold weather, as water has no expansive force five
degrees above or five degrees below the freezing point.
These tests, however, are only for the purpose of trying your flues and
are not intended to ascertain the efficiency or strength of your boiler.
When this is required, I would advise you to get an expert to do it, as
the best test for this is the hammer test, and only an expert should
attempt it.