The Stoker"s Catechism.
by W. J. Connor.
PREFACE.
There is no trade or calling that a working man is more handicapped in than that of a Steam Boiler Stoker; there are no books on stoking; the man leaving his situation is not anxious to communicate with the man who is taking his place anything that might help or instruct him; and the new man will be shy of asking for information for fear of being thought incapable for the post he is seeking; and the transfer takes place almost in silence, and the new man has to find out all the ways and means at his own risk, sometimes at his employer"s expense.
My object is to instruct that man in his business without his knowing it, or hurting his very sensitive opinion on stoking and other matters; for I am well aware that it is only the least experienced who are the hardest to convince, or instruct--against their will. I have therefore ventured to devise this simple method of question and answer, which I have named "The Stoker"s Catechism," which I hope may instruct and interest him.
I will not enc.u.mber this preface with my personal qualifications for this little work--the answers to the questions might suffice.
W. J. C.
THE STOKER"S CATECHISM.
1. _Question._--How would you proceed to get steam up in a boiler?
_Answer._--Having filled the boiler with water to the usual height, that is to say, about four inches over the crown of the fire-tube, I throw in several shovelfuls of coal or c.o.ke towards the bridge, left and right, keeping the centre clear; then I place the firewood in the centre, throw some coals on it, light up, and shut the door. Then I open the side-gauge c.o.c.ks to allow the heated air to escape, and keep them open till all the air has cleared out and steam taken the place of it; by this time the fire will require more fuel, and when the steam is high enough I connect her by opening the stop-valve a little at a time till it is wide open and ready for work.
2. _Question._--Supposing there are boilers working on each side of the one you got steam up in, how would you act?
_Answer._--I would light the fire by putting in a few shovelfuls of live coal from one of them instead of using firewood; that is all the difference I would make.
3. _Question._--What is the cause of the rapid motion of the water in the gauge-gla.s.s at times? Is that motion general throughout the boiler?
_Answer._--No; air enters the boiler with the feed-water, and the gauge-gla.s.s tube being in the vicinity of the incoming water, some of the air enters the gla.s.s and flies up rapidly through the top c.o.c.k and into the boiler again; in fact there is very little motion of the water in the boiler at any time while working. I have proved this to be so, and in this manner: the boiler cleaners having finished the cleaning, hurriedly scrambled out of the boiler and left several tools they had been using on the crown of the fire-box, namely, a ba.s.s hand brush, a tin can, and a tin candlestick, and a small iron pail; the manhole cover was put on and boiler filled and put to work before the things were thought of, and then it was too late and they had to remain there until the next cleaning time, which was thirteen weeks; and when the boiler was at last blown out and the manhole cover removed, the things were on the crown of the fire-box exactly as they were left three months previously. In order to satisfy myself of this, to me, extraordinary discovery, I placed several articles on the crown of the fire-box, things that could not stop up the blow-off pipe if they were swept off, and got up steam as usual, and after three months" hard steaming I blew out the water and steam, took off the manhole cover, and there were the things as I had left them thirteen weeks previously; of course they were all coated with fine mud, but no signs of having moved a hair"s breadth.
4. _Question._--But water in an open caldron with a fire under it, as in the steam boiler, will madly sweep the sides and bottom with terrific ebullition. How would you account for the great agitation in the open caldron while the steam boiler had hardly any, although both vessels had fierce fires under them?
_Answer._--In the matter of the open caldron the action of the water has no resistance but that of the atmosphere, whereas in the steam boiler the movement of the water is resisted from the moment it is heated, for then a vapour rises above it, and, as the heat increases, the resistance to the movement of the water is proportionally increased, and as the heat of the steam increases the pressure on the water increases proportionally all through, the steam being above the water. Any old stoker knows that when getting steam up in a boiler the lower parts are often only warm when there may be eight or ten lb. on the square inch in the upper portions; when the water begins to boil the steam rises in the form of minute globular particles, and remains above the water until there is an outlet for it by opening the stop-valve or through the safety-valve; and as the pressure is the same throughout every part, nook and corner, and angle, there can be no dominating force to cause any agitation within the boiler.
5. _Question._--What is superheated steam, and why is it used?
_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-gla.s.s broke while the boiler was working, how would you proceed to rectify the mishap?
_Answer._--By immediately shutting off both c.o.c.ks, the water-c.o.c.k first, then I would open the blow-out c.o.c.k (at the bottom of the gauge-gla.s.s) and keep it open to the finish, and commence uns.c.r.e.w.i.n.g the nuts, clearing them of any bits of india-rubber that adhered to them, also the sockets. Get one of the half dozen gla.s.ses already cut, and my string of rubber rings, enter two rings on the bottom end of the gla.s.s, slip the nut over them, slip two rings on the top part of the gla.s.s 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 c.o.c.k a shade to warm the gla.s.s, and when it is hot enough, open it more and commence closing the blow-out c.o.c.k, by tapping it lightly by hand, then open the steam c.o.c.k a little more and open the water c.o.c.k a little also, and shut off the blow-out c.o.c.k, and presently the water enters the gla.s.s, and both top and bottom c.o.c.ks may now be opened to their full extent, and the job is done.
7. _Question._--How would you cut a water gauge-gla.s.s to the proper length?
_Answer._--I usually cut a piece of iron wire the length the gla.s.s 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 gla.s.ses in my spare time, instead of doing it when the gla.s.s breaks. I mark a circle where I wish to cut the gla.s.s, 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-gla.s.ses.
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 circ.u.mstance 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-gla.s.s empty; this puzzled me at first, but on opening the blow-out c.o.c.k 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-c.o.c.ks, and letting air into her which soon killed the vacuum, and down came the water into the gla.s.s again to the proper level. When getting steam up, I always open one of the side gauge c.o.c.ks 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 s.p.a.ce 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 pa.s.s 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 sc.r.a.per, 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 sc.r.a.ping 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 quant.i.ty 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 pa.s.sing 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 sh.e.l.l of the fireplace; the convex bridge was built on the bottom of the sh.e.l.l 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 c.o.c.k 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 c.o.c.k at the bottom of the boiler?