The following article is taken from the October, 1911 issue of American Thresherman column, 'Asked and Answered.'
Question of E. E. H.
I want to learn how to cut out flues and repair boilers with crude or homemade tools. Is there any substance besides lime in which flues may be annealed?
What kind of homemade tools can be made for cutting out an old set of flues or a damaged boiler plate?
Can you explain how to put a patch on a boiler and how to take out old stay bolts or put new ones in?
Answer: It is a pretty big contract to tell you all about boiler repairing in these columns. The best we can do is to give you a few ideas and leave the rest to your ingenuity and common sense. Making extensive repairs on a boiler is a boiler maker's job, and we always recommend that a competent man be engaged when such a condition arises. There is no good reason, however, why any handy man could not put in a set of flues if he understands just what the essentials are for a good job. The putting on of a patch is a more serious undertaking and one that should be turned over to a boiler maker.
If a whole set of flues is to be taken out it will prove economical to purchase a flue cutting tool. The one advertised in this journal will be found easy to use and much more rapid than any hand tool that can be made at home. After the flues are all cut off just inside the flue sheet, they may be removed through one of the hand holes. If only one flue is to be taken out there will be no trouble in getting it out if in either the top or bottom row, through one of the hand holes. If it is in the middle of the tube bank there is only one thing to do and that is to split it at both ends, pinch the ends together and take it out through the tube opening. If badly coated with scale, it is next to impossible to get it out. If copper ferrules are used in the fire box end, the difficulty is greatly lessened.
In splitting a tube, the tools shown in figure 1 can be used and in pinching in the ends figure 2 is a handy tool. An ordinary cold chisel will not do as there is danger of gouging the boiler plate around the edge of the openings. If this occurs it is, of course, next to impossible to make a tube tight enough to prevent leaking. Figure 2 is also used when taking out the ends of flues that have been cut off. The tool shown in figure 3 may also be used to split tubes but it is designed especially for cutting out a damaged piece of plate. In using this tool, it will be found advisable to lubricate the point occasionally with a little lard oil.
The ends of the tubes must be annealed, that is, softened so they can be rolled and beaded without danger of their breaking or splitting. Annealing is a simple process, but one that must be done carefully if it is to be successful. The ends of the tubes, back four or five inches from the ends, should be slowly heated to a cherry red. Be careful not to heat too hot because at the higher heats a scale forms over the surface of the iron and when it comes off the surface is left rough. When the proper temperature is reached, the tubes must be taken out and the heated ends plunged into a box containing slaked lime, dry ashes, or fine dry sand. Lime is the best. The tubes must be left to cool off slowly, after which the opposite ends may be treated in the same way.
In refluxing an old boiler measurements should be taken for each flue as the tube sheet may be somewhat warped and there may be considerable variation in the lengths of the different flues. Allow from an eighth to three-sixteenths of an inch at each end for beading. If too much is left, it is impossible to do a good job or fit the tubes so they will not burn off, especially if used in the flue box end. A small compact bead is essential to success. Another essential is to have the surface of the tube where it enters the tube sheet perfectly clean. It should have every bit of rust and scale removed with a piece of emery cloth or a file. The ends of the tube should, if it is possible, be trimmed off smooth in a lathe. Sometimes they have to be put in just as they are received from a pipe cutter but it is impossible to do as nice a job.
Either the spring expander or the roller expander may be used and it makes little difference which. Personally we prefer to use the roller on new work and the spring expander on old boilers on account of the fact that new holes are round while old ones may be slightly distorted. In expanding the tube end, it will be necessary to have a man at the free end with a heavy bar to hold it in position. After one end is expanded the other end can easily be taken care of.
Care and judgment should be exercised in expanding tubes. If they are expanded too much, the adjacent tubes will be loosened and a poor job will result. The holes will be either enlarged or distorted. The proper way to proceed is to drive the taper pin of the expander in lightly and turn it around, drive again and turn and repeat the operation until it is evident from the way the pin drives that the tube is tight. Always use oil on the expander rollers and upon the pin. It will turn much easier and the pin can be jarred loose easier.
In using the spring expander it should be turned about a fifth of a turn each time. Drive the pin in until it meets with considerable resistance, then jar it loose, turn the whole expander about a fifth of a turn and repeat the operation. In using this expander, great care must be taken to note if the bead D shown in figure 4 is inside the tube sheet. If it is not it will be impossible to do a good job. An inspection of the figure will convince the reader to do the best work there must be a special spring expander for every thickness of flue sheet. This is a point that is frequently overlooked.
It is also an argument in favor of the roller expander, which is not subject to such limitations. Not only must the spring expander be designed for the thickness of plate in which the tubes are to be expanded, but the amount the tubes project outside is limited to the width of the shoulder outside of the tube sheet. With the various points intelligently attended to there is no better tool for the purpose than the spring or Prosser expander as it is called.
Figure 5 shows the kind of work done by this tool. The depression B is formed by the bead D of figure 4.
The next operation is to bead the flues and here again care and intelligence must be exercised. First turn the ends of the tube over with the ball pene of a machinist's hammer, then use the starting tool, figure 6 and finish the job with figure 7. The finishing tool must have the right radius of curvature at E for the size of bead that is to be turned. If too deep, the point will gouge into the edge of the bead. It must be just right.
In using the beading tool, care must be taken that the direction of every blow be toward the edges of the tube sheet. There is a tendency, for beginners, to drive the tube inward, resulting in the kind of job illustrated in figure 8. A tube beaded in this way will burn off and leak in a very short time.
Many people have trouble with leaky flues and even some boiler manufacturers have trouble. They can't keep the tubes from leaking and the trouble in almost every case can be traced down to faulty workmanship in putting them in. There are some places where the water is so bad that it is next to impossible to make the tubes hold, but even there good workmanship will help wonderfully.
Figure 9 shows a calking tool. This is very necessary as a part of the equipment of the engineer. It is easy to make and may be made in a great variety of forms. There is only one thing to bear in mind and that is never to make one with a sharp edge. Such an edge will groove the plate and eventually cause a crack to develop along the seam. Another thing, under no condition calk a seam or tighten up a union or screw in a plug or attempt any repairs upon a boiler or a steam pipe under pressure.
Taking out stay bolts is a difficult job. About the only way you can do this is to drill them out from each end, then tap the hole out for the next larger size bolt. It is impossible to unscrew a stay bolt that has been riveted in on both ends. When a bolt holding a bracket gets loose, the best thing to do is to put in a new one a sixteenth of an inch larger.
We will not attempt to tell how to patch a boiler at this time as the story is too long.