We continue our extracts from King's work on the Steam Engine, published by F. A. Brady, 24 Ann-st. The Condenser Heats. When engines are standing still, it sometimes occurs that the condenser gets so hot, that when it becomes necessary to start ngain, the pressure has become so great in it, that the injection water will not enter. Leaky steam and exhaust valves will alone cause this, but in no case should it ever be allowed to occur. When an engine begins te get hot, the cracking noise in the condenser, and about the foot valves, will always indicate what is going on, timo enough to check it, which can be done by giving a little injection, and causing the engines to make two or three revolutions back and forth. If, how ever, the engine should become too hot to take the injection water, the only plan will be to blow through, or pump water into the condenser if there be such an arrangement, or to cool the condenser by external application of cold water. If when under way it is indicated by the gage that the engine is gradually losing its vacuum, apply the hand to the condenser, in order to ascertain if it be getting hot, and if such be found to be the case give a little more injection; but if that does not help the cause, give more still. If the vacuum continues to grow less, the probability is that the injection pipe has become choked ; in which event shut off that injection and put on another. Should both the bottom and side become choked, inject from the bilge. Should the bilge injection also be out of order, the engine will have to be stopped, and the snifting valve secured down (if there be one) while the injections are blown through to clear them. Seaweed, and things of that nature, sometimes get over the strainers of injection pipes, preventing the entrance of water. Most if not all marino engines of modern construction are fitted with a thermometer to the hot well, to ascertain the temperature of the water, which is usually carried from 100 to 115 Fah, This instrument is very important, in order to maintain an even temperature (the sense of touch of the engineer's hand not being delicate enough for that purpose), for it may often occur that there may start small leaks about the condenser and exhaust pipe joints, whieh would cause a decrease in the vacuum, and, as without the thermometer, the first impulse would be to give more injection, with it we would turn our attention to finding and stopping the leak. This can be done by holding a lighted candle around the joints, and wherever there is a leak the flame will be drawn in. To stop it, mix a little putty, of white and red lead, aud apply it to the crevico ; the presence of the atmosphere will force it in. Getting Under Way. When lying in port, where the steam will not be required for at least four or five days, it is proper that the water should be blown or pumped out of the boilers, and a portion of the man and hand-hole plates removed, to allow a circulation of air. When, therefore, the order is given to get up steam, the first thing is to see that all these plates are put on, and the joints properly made, and this duty should receive the direct superintendence of the engineer having charge of the same ; for should any one of them leak badly after the steam is raised, the departure of the ship might be delayed some hours in consequence. After this duty has been properly attended to, open the blow-off cocks and run the water up in the boilers to the proper level, or, if the boilers are so situated that the water will not run up high enough, finish thesupply with the hand pumps, wood the furnaces whilo the water is entering the boiler, and when the proper height of water is attained start the fires. If it be important to raise steam quickly, start the fires as soon as water is discovered in the gages, continuing the supply while the fires are burning. As a small quantity of finely split wood, with a little shavings or oily waste placed in the mouth of the furnaces, is all that is necessary to start the fires, the back part of the furnaces, particularly in boilers with inferior draft, should be covered with a layer of coal to keep out the cold air. In raising steam it has been the custom to recommend that the valves of the engine be blocked open, so as to allow the heated air from the boilers to pass in and warm up the engine before steam begins to be generated ; but as in many cases this is attended with considerable trouble, and as the advantages to be derived from it arc very small, it hardly appears to the author's mind to "pay." Tho safety or vacuum valve should, however, be kept open until steam begins to form, in order to let the heated air escape. The strain upon boilers being from the inside, they are constructed and braced with the special view of withstanding this strain, many of the braces being entirely useless in sustaining a pressure from without ; marino boilers are therefore fitted with a small valve opening inwards, and weighted so as to open and admit air whenever the pressure from within falls toabout five pounds per square inch below the atmosphere. These valves are called differently by different parties, as follows: vacuum valve, air valve, reverse valve, &c. After steam has been raised to 3 or 4 lbs., the engine should then be blown through and warmed up, and after sufficient steam is raised to move the piston, the engine should be turned over two or three times, to see that every thing is right, before reporting ready.
This article was originally published with the title "Practical Directions to Engineers"