_Answer._--If a boiler is placed at a long distance from the engine or
whatever the steam may be used for, there is much or little condensation
according to the distance and the weather, so that there would always be
water mixing with the steam, and that is most objectionable where a
steam engine is concerned, and by super-heating the steam it comes to
the engine as hot and dry as if the boiler were close by; but whatever
the heat of the steam may be, the pressure cannot be increased after the
steam has left the boiler. In proportion to the pressure of steam so is
the heat of it; the higher the pressure the hotter the steam.
6. _Question._--If your water gauge-glass broke while the boiler was
working, how would you proceed to rectify the mishap?
_Answer._--By immediately shutting off both cocks, the water-cock first,
then I would open the blow-out cock (at the bottom of the gauge-glass)
and keep it open to the finish, and commence unscrewing the nuts,
clearing them of any bits of india-rubber that adhered to them, also the
sockets. Get one of the half dozen glasses already cut, and my string of
rubber rings, enter two rings on the bottom end of the glass, slip the
nut over them, slip two rings on the top part of the glass after having
slipped the nut on, and enter the rings in the sockets, then screw up
both top and bottom nuts by hand alternately, and when screwed up
evenly, open the steam cock a shade to warm the glass, and when it is
hot enough, open it more and commence closing the blow-out cock, by
tapping it lightly by hand, then open the steam cock a little more and
open the water cock a little also, and shut off the blow-out cock, and
presently the water enters the glass, and both top and bottom cocks may
now be opened to their full extent, and the job is done.
7. _Question._--How would you cut a water gauge-glass to the proper
length?
_Answer._--I usually cut a piece of iron wire the length the glass
should be, in this way: I measure the length from under the top nut to
the top of the bottom nut, and cut my iron wire to that measurement;
then I cut several glasses in my spare time, instead of doing it when
the glass breaks. I mark a circle where I wish to cut the glass, and
with a three-corner file I run it round this circle to a depth of the
16th of an inch, and break it off on the edge of the vice, bench, or
other solid woodwork; of course this iron-wire gauge will perhaps only
answer for this particular boiler, but in some stoke-hold the boilers
are all alike with regard to the gauge-glasses.
8. _Question._--What is the cause of a vacuum in a boiler? And how does
it affect her injuriously?
_Answer._--The vacuum is mostly caused by letting cold water into a hot
boiler, the hotter the boiler the stronger the vacuum; when the water is
hotter than the boiler, there will be little vacuum; a strong vacuum in
the boiler will cause the air outside to press on the boiler in
proportion--the stronger the vacuum inside, the greater the pressure
outside. In this circumstance the pressure is misplaced for the boiler
was constructed to bear an internal pressure and not an external
pressure. And in getting steam up the pressure on the boiler has to be
reversed, and this tends to loosen the plates and rivets and makes her
leak, if she never leaked before. I have frequently known boilers to be
filled with water over-night to be ready for lighting up in the morning,
and have found the gauge-glass empty; this puzzled me at first, but on
opening the blow-out cock of the water-gauge the air rushed into it with
a gurgling noise, then I knew there was water in the boiler held up by
the vacuum, but I soon altered that by opening the side-cocks, and
letting air into her which soon killed the vacuum, and down came the
water into the glass again to the proper level. When getting steam up, I
always open one of the side gauge cocks and keep it open until steam
issues from it; that permits the foul air to escape and prevents a
vacuum being created; there used to be a vacuum valve in the vicinity of
the steam dome, that opened inwards and prevented a vacuum from being
created.
9. _Question._--If you had only one boiler and one engine at work, how
would you manage to clean your one fire without letting the steam go
down?
_Answer._--When pushed for steam, which usually occurs when the fire is
getting dirty, I get ready all the tools and some of the best of the
coals, and having a bright fire I take the long poker and skim all the
fire to one side and throw a couple of shovelfuls of coals evenly over
it and rake out all the clinkers on the opposite side, then with the
long poker (some people call it Kennedy) I skim all the fire over to the
opposite side and throw a couple of shovelfuls of coals evenly over the
bright fire, and rake out the clinkers on the other side, then I spread
the fire evenly over the bars and sprinkle some more coals over all, and
shut the door. This performance from first to last need not take more
than ten minutes, and the boiler was making steam all the time, and at
the finish I had a better fire than at the beginning, and the steam
hardly lost a pound; but the job must be done quickly.
10. _Question._--What is the cause of the humming noise that issues from
a steam boiler at times, and how would you prevent it?
_Answer._--It is caused chiefly through bad stoking, in having an uneven
fire, full of holes, or crooked bars, the cold air rushing through where
there is the least resistance, and into the tubes, causes the humming
noise--a locomotive nearing home after her day's work has very little
fire on the bars and will generally hum, so there is some excuse for
her, but none for a stationary boiler. Some stokers take credit to
themselves for making the boiler "Hum"; when coals are thrown into the
fire indiscriminately--small and large--the air finds the least
resistance through the small coals, which soon burst into holes, while
the lumps remain solid; then the air rushes into the holes and the
humming commences; or, if the firebars are not equally separated, the
air enters the widest space and the boiler hums; or it may be that the
bars next the side of the fireplace are out of line and lets the air
rush up against the side and the boiler hums. If the stoker would only
drop a shovelful of coals dexterously into each hole the humming would
stop immediately, or level the fire with the rake or long poker, or open
the fire door if the rake is too heavy, and the noise will cease. The
chief point is to have a good set of firebars and well placed; if they
are too long they will hump in the middle or they will bulge sideways;
if they are too close together they become red-hot because there is not
room enough for the air to pass between them to keep them moderately
cool, and if they are too short they will drop down into the ash-pit.
11. _Question._--Why is it more difficult to keep steam-tight the
manhole cover of a portable boiler than the manhole cover of a
stationary boiler?
_Answer._--The portable cover is usually on the side of the boiler, and
about half the cover is immersed in the water and half in the steam; the
portion under water is about 212° of heat, the portion of the same cover
in the steam is about 500° of heat, the hottest part expanding much more
than the cooler part, and is constantly tending to tear itself away from
the lower portion of the cover, and the joint cannot stand the unequal
strain. The manhole cover of a stationary boiler is nearly always on top
of the boiler, and the heat is equal all over it and no contraction and
expansion to cause the joint to leak as in the portable cover.
12. _Question._--How would you prepare a boiler for the inspection of a
boiler inspector?
_Answer._--I would blow her right out, take off the manhole cover, take
out the safety valve, take out all firebars and the bridge, take down
flue-port brickwork, have the boiler and flues thoroughly cleaned and
swept, have a lamp or candle ready to light, a hand hammer and chisel,
or scraper, a pailful of clean water, and a wad of cotton waste. When
the inspector arrives, he quickly dons his overalls; I hand him the
light and the tools and waste, and he is into the fireplace in a jiffy;
down the side flues, under the boiler, giving a whack with the hammer
now and then, and scraping off any suspicious scale, etc.; and when he
comes out, as black as any sweep, he slips out of the overalls, gives
them a whack against the wall, folds them up tight, and crams them into
the black bag; has a dive in the pail, and is soon ready to go off
somewhere else. But he tells me something about the boiler before he
goes--not to my discredit.
13. _Question._--How do you proceed to get her to work again, and what
materials do you use?
_Answer._--I first proceed to build the bridge and flue-ports, put in
the firebars, the thin bars at the sides; then I replace the
safety-valve, taking care not to damage it or its seat, fill the boiler
with clean water, put in the boiler the usual quantity of Naenaires
Anti-Corrosion liquid, or the powder, make the manhole joint with
plaited three-strand spun yarn and stiff putty (red lead and white lead)
and lay the fire, which is done in this way: throw a dozen shovelfuls of
coals towards the bridge, and to left and right of it till they reach
near to the dead-plate, leaving the centre clear for the firewood; then
throw in three or four shovelfuls of coals over the wood, with oily
waste or paper in front, and she is ready for lighting, and the "fire
is laid." The material for the bridge and the flue ports are firebricks
and fireclay; these are rather expensive, but I learnt a wrinkle in the
building up of bridge and flues. Through the frequent removals of these
for boiler inspection and the hitting of the end of the long poker,
several bricks were broken every three months, and I came to the
decision to try stock bricks faced with fireclay as mortar; and I was
more than satisfied with the result, and ever since then I used stock
bricks and fireclay only.
14. _Question._--How high should the top of the bridge be from the crown
of the boiler or from the fire-tube?
_Answer._--The bridge should be about nine inches from the crown of the
fire-tube, if it were eight the draught would be curtailed, if it were
ten the draught under the bars would be diminished, through much air
passing over the bridge instead of under the firebars. As I had
permission from my employers to build the bridge to the best advantage
for myself in keeping up the steam, and having tried different heights
for many years, I found that nine inches was the nearest to perfection.
And in these experiments two additional bridges were built in one
boiler; six feet behind the ordinary bridge was a concave bridge and six
feet behind that was a convex bridge. The concave bridge was built
close up to the bottom of the fire-tube, and resembled a small archway,
and extended down to within nine inches of the bottom or shell of the
fireplace; the convex bridge was built on the bottom of the shell and
reached to within nine inches of the fire-tube. When the flame from the
furnace shot over the ordinary bridge, it clashed down under the concave
bridge, then rose up and swept through the convex bridge and away to the
bottom flues; the object of these three bridges, in one tube and for one
fire, was to keep the flame and heat in the boiler as long as possible,
instead of the heat flying swiftly over the bridge and out of the
boiler. This experiment seemed to answer very well, but as there were
several other boilers connected with this one there was no opportunity
of testing it correctly, but the three bridges remained established, and
were frequently shown to engineers and others.
15. _Question._--What advantage is there in having the blow-off pipe of
a boiler entering it from the top instead of at the bottom?
_Answer._--I am not aware of any advantage in it, but I am aware of a
disadvantage in it, and it is this, that while the boiler is being blown
right out for the purpose of cleaning, or other reasons, the stoker will
often commence doing some other work, and in due course the boiler is
filled up with water, and the fire lighted, and by-and-by the stoker
comes to see what progress she is making; he looks at the water-gauge
but sees no water in it because it has syphoned out of the boiler; at
first the heated air pressed on the water and forced it through the
blow-off pipe, and then the pipe became a syphon, and the pressure
increasing as the water leaves the boiler, she is soon emptied, and if
the fire is not raked out, soon burnt. Such a mishap could not happen to
a boiler with the blow-off pipe at the bottom, for when the stoker blows
out his boiler he must shut the cock before he can fill her, and when
filled there is no chance of the water escaping out again.
16. _Question._--Is there not some disadvantage in having the blow-out
cock at the bottom of the boiler?
_Answer._--Yes; the cock and pipe are subject to corrosion on account of
water dripping down on them from the stoke-hold floor, as some stokers
quench their clinkers and ashes while they are up against the front of
the boiler, instead of drawing them forward a few inches from the front:
and as the pipe is out of sight under the plates of the floor, nobody
takes the trouble to lift them and examine--not only the pipe and the
cock, but that part of the boiler where the water streams down from the
drenched ashes so frequently. So there are disadvantages in both methods
of blowing out the boiler, and always will be, until the stoker learns
his business, and takes an interest in his work, not only for his own
sake, but his employer's also.