free. Always test the glass water-gauges and the floats thoroughly the first thing in the morning before firing up. It does not follow that there is plenty of water in the boiler because there is plenty of water in the gauge-glass. The passages may be choked. Also, empty gauge-glasses are sometimes mistaken for full ones, and explosions have resulted therefrom. Her ce the importance of blowing through the test-taps frequently. Blow-out Taps and Scum Taps.-Open the blow-out tap in the morning defore the engine is started, and at dinner time when the engine. is at rest. Open the scura tap when the engine is running, before breakfast, before dinner, and after dinner. If the water be sedimentary, run down half an inch of water at each blowing. If not sedimentary, merely turn the taps round. See that the water is at the height indicated by the water-level pointer at the time of opening the scum tap. Do not neglect blowing out for a single day, even though anti-incrustation compositions are put into boiler. Water should be blown from the bottom of the boiler when steam is not being drawn off, so that the water may be at rest and the sediment have an opportunity of settling. Water should be blown from the surface when steam is being drawn off, so that the water may be in ebullition and the scum floating on the top. If the water be below the pointer, the scum tap will blow steam; if above the pointer, the scummer will miss the scum. Safety-Valves.-Lift each safety-valve by hand in the morning before setting to work, to see that it is free. If there is a low-water safety valve, test it occasionally by lowering the water level to see that the valve begins to blow at the right point. When the boiler is laid off, examine the float and lever and see that they are free, and that they give the valve the full rise. If safety-valves are allowed to go to sleep, they may get set fast. Shortness of Water.-In case the boiler should be found to be short of water, draw the fires, if practicable, and draw them quickly, beginning at the front. In some cases it may be more convenient to smother the fires with ashes or with anything else ready to hand. If the fires are not drawn, leave the furnace doors open, turn on the feed, lower the dampers, shut down the stop-valve if the boiler be one of a series, and relieve the weight on the safety-valve so as to blow off the steam. Warn passers-by from the front of the boiler. Drawing the fires must be done with discretion, and ought not to be attempted if the furnace crowns have begun to bulge out of shape. At Clay Cross, near Chesterfield, on Thursday, January 14, 1869, as the attendant was in the act of drawing the fire from a furnace overheated from shortness of water, the crown rent, when the torrent of steam and hot water that ensued blew him backwards to a distance of 25 yards, rake in hand, and killed him on the spot. Use of Anti-Incrustation Compositions.-Do not use any of these without the consent of the Manchester Steam Users' Association. If used, never introduce them in heavy charges at the manhole or safety-valve, but in small daily quantities along with the feed water. Many furnace-crowns have been overheated and bulged out of shape through the use of anti-incrustation compositions, and in some cases explosions have resulted Emptying the Boiler.-Do not empty the boiler under steam pressure, but cool it down with the water in; then open the blow-out tap and let the water pour out. To quicken the cooling the damper may be left open, and the steam blown off through the safety-valves. Do not on any account dash cold water on to the hot plates. But, in cases of emergency, pour cold water in before the hot water is let out, and mix the two together so as to cool the boiler down gradually and generally, and not suddenly and locally. If a boiler is blown off under steam pressure, the plates and brickwork are left hot. The hot plates harden the scale, and the hot brickwork hurts the boiler. Cold water dashed on to hot plates will cause severe straining by local contraction, sometimes sufficient to fracture the seams. Cleaning Out the Boiler.-Clean out the boiler at least every two months, and oftener if the water be sedimentary. Remove all the scale and sediment as well as the flue dust and soot. Show the scale and sediment to the manager. Pass through the flues, and see not only that all the soot and flue dust have been removed, but that the plates have been well brushed. Also see whether the flues are damp or dry, and, if damp, find out the cause. Further, see that the thoroughfares in the glass water-gauges and in the blow-out elbow pipe, as well as the thoroughfares and the perforations in the internal feed dispersion pipe and the scum pipe, are free. Take the feed pipe and scum troughs out of the boiler if necessary to clean them thoroughly. Take the taps and the feed valve to pieces, examine, clean, and grease them, and if necessary grind them in with a little fine sand. Examine the fusible plugs. Do not put any blocks under the pipes in the hearth pit. Putting blocks under the pipes in the hearth pit robs them of their spring, strains them, and sometimes breaks them. Preparation for Entire Examination.-Have the boiler cooled and carefully cleaned out as explained above. Show both scale and sediment to the inspector, as well as the old cap of the fusible plug, and tell him of any defects that may have manifested themselves in working, and of any repairs or alterations that may have been made since the last examination. Unless a boiler be suitably prepared, a satisfactory entire examination cannot be made. Inspectors are sent at considerable expense to make entire examinations, and it is a great disappointment when their visits are wasted from want of preparation. The Association is always happy to afford information to boiler attendants by means of its printed monthly reports, and to help them in the discharge of their duties, and expects them in return to do all they can to promote a thoroughly sound inspection of the boilers under their charge. Fusible Plugs.-Keep these free from soot on the fire side, and from incrustation on the water side. Change the fusible metal once every year, at the time of preparing for the Manchester Steam Users' Association annual entire examination. If fusible plugs are allowed to become incrusted, or if the metal be worked too long, they become useless, and many furnace crowns have rent from shortness of water, even though fitted with fusible plugs. General Keeping of Boiler.-Polish up the brass and other bright work in the fittings. Sweep up the flooring plate frequently. Keep ashes and water out of the hearth-pit below the flooring plates. Keep the space on the top of the boiler free, and brush it down once or twice a week. Take a pleasure in keeping the boiler and the boiler-house clean and bright, and in preventing smoke. Remarks.-Shortness of water generally arises from neglect of the boiler attendant, and ought not to occur. It is by no means easy to give precise instructions as to what should be done to put things right when shortness of water has occurred, so as to meet every case. Drawing the fires when the water is out of sight must always be a matter of more or less risk, as there is a difficulty in determining how far and for how long a time the furnace crowns have been laid bare. If it is known that the water has only just passed out of sight, say from the sticking fast of the blow-out tap when attempting to shut it, the fires may be drawn with safety. But if an empty gauge glass has been mistaken for a full one, and the boiler has been worked on in this state for some time, the case will be different. Again, there would be more risk in drawing the fires from a plain furnace tube, or from one made of ordinary plates, than from one strengthened with encircling rings and made of ductile steel, or of iron equal to Lowmoor or Bowling. In the Manchester Steam Users' Association Museum there is a photograph of a pair of steel furnaces, strengthened with flanged seams, which have bulged down to the firebars through overheating from shortness of water, without rending. Also there is a pair of furnaces made of Lowmoor iron and strengthened with flanged seams, which, though seriously overheated through shortness of water, have rent for a limited extent only in the neighbourhood of the flanged joint, the opening formed measuring about 7 inches in length by 1 inch at the widest part. On the other hand, there are in the museum two furnaces from different boilers, neither of which is strengthened with encircling hoops, nor made of ductile steel or of Lowmoor or Bowling iron, both of which have rent right across, forming an opening 12 inches wide in one case and 6 inches in the other. Thus it will be seen it is difficult to give precise instructions to suit all cir cumstances. A fire may be safely drawn in one case and not in another. Discretion must be exercised. It should be borne in mind that the rupture of a furnace crown is not only dangerous to the fireman, but in many cases to those outside the works, as the torrent of steam and hot water that ensues frequently carries away the furnace mountings along with any brickwork lying in its course, and scattering the debris like so much grape shot, severely injures, and sometimes kills persons on their own premises. Thus boiler attendants must remember that shortness of water endangers other persons' lives as well as their own. The best advice the Manchester Steam Users' Association can give to boiler attendants with regard to shortness of water is-Do not let it occur. Keep a sharp look-out on the water-gauge. Wood Fuel for steam boilers requires one-third more grate-surface, and two-thirds more cubical space in the furnace, than is required for coal, for equal generation of steam. Two cords of wood will evaporate about the same quantity of water as one ton of coal. A cord of dry pine-wood, 4 feet X 4 feet x 8 feet 128 cubic feet, weighs 17 cwt. = Expansion of Water by Heat.-Water attains its maximum density at 39°1 Fahr.-or say 40° Fahr.-from which point, any rise or fall of temperature is accompanied by expansion. Sea Water requires more heat to boil it, than is required to boil fresh water. No salt passes away with the steam. Its average boiling point is 213.2° F. The proportion of salt held in solution is part of its weight, or about 4 ounces of salt per gallon of sea water. The point of saturation is, when the water is full of salt, and will hold no more. Salt water varies in density, and in the nature of its ingredients in different seas. The composition of average sea water is-water, 96.6 parts: chloride of sodium 26; chloride of magnesia, 4; sulphate of soda, 37; carbonate of lime, 02; sulphate of lime, 'or. The ice of sea water contains no salt. For further information on Steam-Boilers, see the Author's work "Steam-Boiler Construction," published by Crosby Lockwood & Son, London. |