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a welded steel plate soda pulp digester without a single riveted joint. The dimensions of this vessel, which may be likened to a cylinder boiler without flues, were as follows: Thickness of plate, 34 in.; diameter, 9 ft.; length, 43 feet. The heads were dished to the standard depth. The safe working pressure was 125 lbs. per sq. in. It appears not only possible, but probable, that the process of welding boiler joints may in time supplant the older custom of riveting.

CHAPTER II

CARE OF THE BOILER

Washing out the boiler-Duties of the boiler washer-How to pre

pare a boiler for washing—How to clean and inspect the inside of a boiler-Fusible plugs-Advantage of manholes, giving free access to top and bottom of boiler-Responsibility resting upon the boiler washer-Necessity of keeping water column clean-Scraping the flues-Fire cracks and how to deal with them-Firing up and how it should be done-Danger in too sudden heating up of a boiler-Advantages of filling a recently washed out boiler with warm water-Connecting with the main header and the safest method of proeedure. Washing Out. In order to get the best results from the burning of coal or any other fuel in a boiler furnace it is absolutely necessary to keep the boiler as clean as possible, both inside and outside. In large plants the boiler washer and his helper are detailed to look after this part of the work, and while the job is by no means a very desirable one, it is at the same time a very responsible one, and much depends upon the thoroughness with which the work is done. In small plants, consisting of one or two boilers, the engineer generally has to attend to the details of the work himself, and no matter whether the plant be large or small, the engineer in charge is the man above all others who should be most interested in seeing that thorough work is done, not only as a matter of safety, but for the sake of his reputation as an engineer. The boiler that is to be washed out should be allowed to gradually cool for ten or twelve hours. It will then be in a condition which will permit a man to go inside of it

and do effective work, and no boiler can be thoroughly cleaned and inspected unless the boiler washer does go inside.

These remarks apply, of course, to horizontal tubular or flue boilers and water tube boilers having drums large enough for a man to crawl into. Some types of internally fired boilers are provided with man-holes, but the majority of them have only hand-holes into which the hose for washing out may be inserted.

After the water has been allowed to run out, the first step in washing out a boiler is to remove all the loose mud and scale possible by means of a steel scraper fitted to a long handle and introduced through the man-hode in the bottom part of the head. This will prevent the scale from getting into the blow-off pipe and stopping the flow of the water used for washing the boiler. If there is a man-hole on top, the next thing in order is to take the hose in through it and give the sides of the shell and also the tubes a good cleaning.

Sometimes it happens that where an exhaust heater of the open type is used, oil will find its way into the boiler and, mixing with the mud, will form a thick pasty-like substance on the sides of the boiler along the water line. This should be carefully scraped off and removed, as any matter containing oil or grease is a very dangerous thing to have inside a boiler.

After cleaning the upper part of the boiler, it should be inspected for loose braces or rivets. This can best be accomplished by tapping the parts with a light hammer. A solid rivet will give a clear metallic sound, and a little practice will enable one to easily detect the sound of a loose brace or broken rivet.

Signs of corrosion or pitting of the shell along the

water line should also be carefully searched for. Fusible plugs, to be effective, must be kept clean, and the only opportunity for cleaning them is at the time of washing out the boiler. Therefore while working on the upper part of the boiler, attention should be given to the fusible plug. If it is one of the ordinary kind, screwed into the back head above the tubes, it should be taken out and cleaned and before replacing it the thread should be well coated with a mixture of cylinder oil and plumbago, which will prevent it from sticking. If the fusible plug is one of the type consisting of a brass tube extending from the top of the shell to the water level, the lower end of this tube should be cleaned of all mud cr scale.

Having thus finished above the tubes, the mud and scale hould again be scraped from the bottom, after which the hose should be inserted through the front man-hole that should be in every horizontal boiler.

Some authorities argue that a man-hole should not be cut in the bottom part of a boiler head, giving as their reason that it weakens the head, but the logic is not sound, for the reason that the man-hole can be reënforced in such a manner as to make it fully as strong as the solid sheet, and when we consider the great advantage of having a man-hole in the bottom, both as regards washing out and also for repairs, it is plain that it is really a necessity.

After washing out all the loose mud and scale that it is possible to get from the bottom, the boiler washer should next go inside and, with scrapers and tools made for the purpose, he should scrape and chip off all the scale that he can from the bottom, because there is where lies the greatest danger from burnt sheets caused by accumulations of scale preventing the

water from getting to the metal. Much good work may be accomplished in this way and no boiler washer should consider the job complete until he has gone through the boiler both top and bottom, and not only cleaned but inspected it. Any loose rivets, broken or loose braces, signs of corrosion or pitting should be at once reported to the chief engineer or superintendent.

It will thus be seen that great responsibility rests with the boiler washer, for the reason that he is the man that is in closest touch with the inside of the boiler, and it is due to the manner in which he does his work inside the boiler whether a defect is discovered and repaired in time or whether it is allowed to go until the result is often a grave disaster. The author desires to enter a plea for this hard-worked and too often underpaid craftsman, and hereby expresses the wish that his services were better appreciated.

The water column or combination should receive particular attention each time the boiler is washed out. The lower pipe leading to the boiler is liable to become clogged with scale, and if not cleaned regularly it is sure to cause trouble by preventing a free flow of the water from the boiler to the gauge glass.

If the boiler is of the horizontal tubular type, the tubes should be scraped inside, and with water tube boilers use the steam jet to blow the soot and ashes from between the tubes. Soot, in addition to choking the draft, is also a non-conductor of heat.

After the hand-hole and man-hole plates have been replaced the boiler may be filled with water to the proper level, and while this is being done it is in order to take a look into the furnace for any broken grates or accumulations of clinkers on the side walls or bridge: wall. These clinkers should be chipped off, also the

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