SCIENTIFIC MANAGEMENT OF A BOILER ROOM
You hear a great deal about scientific management these days, and I know of no place where the principals of scientific management diligently applied will bring greater results than in a boiler room. In thinking of scientific management one usually thinks of motion study and methods of obtaining more work per day from the employees, but scientific management means more than this; it means anything that will cause a dollar’s worth of time or material to yield a greater return. Having defined scientific management we will now see how it is possible to materially reduce one of the largest losses of the average manufacturing plant or central station through proper management. It has been stated on good authority that 25 per cent, of the coal burned in power plants is wasted unnecessarily. This is not usually the fault of the fireman nor his equipment, but the fault of the manager or superintendent ire not supplying the fireman with proper instruments and affording him sufficient supervision and moral support. The average concern operating a power plant hires an expensive man as an engineer, who is usually a good mchanic, but knows little about combustion. As a consequence he spends most of his time irr the engine room, giving but little attention to the boi’er room except to call the fireman down if he does not keep up steam to the normal pressure carried on the plant. The average fireman is trained to keep up steam without any regard to efficiency, so don’t blame him if he wastes one-quarter of the coal he feeds into the furnace either with a shovel or a mechanical stoker. The efficiency of an engine or generating unit will not vary much during its entire life, yet the engineer is given all sorts of instruments with which he can check up and keep tab on the operation of his machines. In the boiler room, however, few, if any, instruments are supplied the fireman. He has no way of knowing how much coal he burns, nor how much water he evaporates; about all he knows is that he keeps up the steam pressure, if he did not he knows he would lose his job. In the doing of any piece of work, any manager is very particular to see that no more men are put on the work than required, or can work efficiently. Why should he not take even more care to see that no more coal is burned under his boilers than is required to do the work?
Questions for the Fireman.
How many firemen have any idea what efficiency they are obtaining from their furnaces, or what draft conditions are best smted to their coal, fire thickness or load on the boiler? How many even know what draft they have over their fires? How many firemen or even the engineers in charge of the plants can answer the following questions regarding the boilers under their care:?
- How thick should your fire be for the coal vou are using?
- Ts the coal you are using the most economical for your plant?
- Should your coal be fired wet or dry?
- Are your gases completely burned before they pass to the chimney?
- What is the temperature of gases leaving your boilers?
- How many pounds of water do you evaporate per pound of coal?
- What are the causes of the black smoke your chimneys belch forth?
- Is the brick work of your furnaces tight?
- Does each of your boilers carry its share of the load? If not, why not?
- Is your boiler heating surface clean inside and out?
- Are the baffles of your boilers tight? Or are the hot gases passing to the stack without doing proper work?
If your engineer or fireman cannot answer these questions don’t blame them, but give them instruments and encouragement. If they know you are interested in the correct answers to the above questions and will show your interest to such an extent as to furnish the necessary equipment for determining the correct answers, your engineer and firemen will do the rest with a little assistance from time to time. Instruments alone are not sufficient, you must have a man of sufficient intelligence to use them, then let it be known that you expect them to be used, and see that they are used by keeping in close touch with the operation and requiring daily reports to be made. It should be possible in any boiler room for the fireman to know exactly what load is being carried on each boiler, but this is seldom the case. In the engine room you will find on each generator a voltmeter and an ammeter, and probably other instruments, especially on A. C. machines. The voltmeter tells the pressure at which the current is being generated, and the ammeter tells the amount of current. In the boiler room you seldom find more than a pressure gage on each boiler. Now* this means that in case the gages on all your boilers show 200 pounds that the pressure is the same on all boilers, but you have no way of telling how much steam each boiler is delivering. One may be operating at 200 per cent, its normal rating and another not over 50 per cent, and nothing will indicate the difference. This is just like operating two generators in parallel with only a voltmeter on each, one may carry all the load and the other none, thus reducing the capacity of the plant. The capacity of the individual boilers and the size of the plant will determine the amount which can be profitably spent for instruments, but the smallest plant can afford many more instruments than are ordinarily used. There are scarcely enough boiler room instruments on the market to make it possible to spend more than $500 per boiler for instruments. A saving of $100 per year means a return of 20 per cent, on a $500 investment, and it is possible to make this saving on a very small boiler if it is operated at 70 per cent, efficiency instead of at 60 per cent, or less, as is the usual practice in the average plant.
A 100-horsepower boiler operating at 60 per cent, efficiency eight hours per day for 250 days per year, burning coal having a heating value of 11,000 b. t. u. per pound and costing $1.50 per ton, will require $700.80 worth of coal per year. If, however, the efficiency had been 70 per cent., the cost of coal would have only been $625.15 or a saving of $108 65. It is possible to maintain an average efficiency of better than 70 per cent, with a property designed, constructed and maintained boiler and furnace, but the average boiler is operated at 60 per cent, or less. From the above illustration you can see what a wonderful saving could be made per year in all the boilers operated, if the efficiency was raised to a good standard. Suppose the above boiler had been a 1,000-horsepower boiler, operating in a central station, probably operating at an average load of 1,000 h. p. for twenty-four hours per day, 300 days per year, the saving would have been almost $4,00(i per year. It is, therefore, evident that a central station operating a number of such boilers can well afford a large outlay for instruments and high class combustion engineers to supervise their boiler room, and many large concerns are already employing college men for this work.
Amount of Air Supplied.
The greatest factor in determining the efficiency of the furnace is the amount of air supplied per pound of coal burned. A pound of any certain coal requires a definite quantity of air for complete combustion. If less is supplied, unburned fuel will be sent up the chimney, and if more is supplied, heat will be used to heat the excess air instead of to make steam. It is necessary to use some excess afr and in general this may be taken at 40 per cent., as this is about the amount which has been found togive the best results in the average plant. If less is used some of the unburned gas will escape because it did not come in contact with oxygen, while if more is used it will have to be heated uselessly. The exact amount of excess air required for any particular furnace should be determined by the analysis of the flue gas. The firemen cannot tell within several per cent, the amount of excess air he is using by only observing the color of the fire. He must have instruments to guide him. If the coal is burned efficiently in the furnace the boiler setting must be tight to prevent air leakage, since whatever air is admitted through leaks absorbs heat, which might be used to make steam. If now you have your coal burned efficiently and the gases are not cooled by air leakage, you must have your boiler tubes scrupulously clean inside and out. so the heat from the hot gases will be rapidly conducted to the water instead of allowed to pass up the chimney. Therefore, the most important things for the fireman to watch arc, is the coal burned efficiently; is air leakage a minimum; docs the boiler readily absorb heat, and does each boiler carry its share of the load? It is, of course, important to see that the blow-off valves do not leak, that the feed pumps are in good condition, and that the feed water heaters, economizers, superheaters, etc., arein proper working condition. One of the first things to do in checking the efficiency at which the coal is being burned is to know the amount being used, and automatic coal weighing devices are in use in many plants, which make it possible to keep a record, not only of the total coal being fired, but to which boilers it is fired. Tins is quite important, as oftentimes banked fires are maintained, and there is a wide variation in the coal different firemen will use for a banked fire, or even the same fireman will vary greatly from day to day. By using the weigh hopper in connection with the flow meter on a steaming boiler, it is possible to roughly check the efficiency of the boiler and furnace.
Draft is the most important thing in burning the coal, and there must be some method of telling the draft at any time. In order to tell the proper draft for any condition of load or thickness of fire, an analysis of the flue gas should be made, and there are many flue gas analyzers on the market. Some of them only show the CO, content, as the conditions are usually good if the CO, reading is high. The instrument can be made automatic and recording. In order to tell if the boiler is absorbing the heat from the gases, it is necessary to know the temperature of the gases leaving the boiler, and there are thermometers for this purpose. These thermometers must be located at the point where the gases leave the heating surface of the boiler, and not in the flue or at the base of the stack. One thermometer for a number of boilers is of no value. There are pressure gages and flow meters to tell the volume and pressure of the steam generated. There are thermometers to tell the temperature of the water entering the boilers and of the steam leaving. The temperature of steam leaving will show if the superheaters are clean. Recently an instrument has been developed to take the place ol the CO2 recorder, the flow meter, and the draft gage. I his instrument is known as a furnace indicator and boiler output gage, three records being made on one chart, one showing the thickness or condition of the fire, one the quantity of gas passing through the boiler, and the other the quantity of steam being delivered by the boiler. The output of the boiler is dependent on the quantity of any particular coal burned in the furnace, but as the quantity of the coal burned is proportional to the quantity of gas produced if burned at same efficiency, the output of the boiler is proportional to the quantity of gas passing through the boiler. The pens, therefore, indicating the output of the boiler, and the quantity of gas passing through the boiler will read the same, if the instrument is properly adjusted, as long as the efficiency is maintained the same. The pen showing the thickness of fire will show when the fire too thick, thus reducing the capacity’s efficiency, or when it is burned into holes allowing excess air to enter and cool the gases. I understand this instrument can also be fitted with recording pressure gage and thermometer. which will show the pressure and temperature of the steam delivered. By having all these different records on one chart it is easy to check up the operation of the boiler. It is, of course, necessary to have an instrument for analyzing the flue gas to check up and adjust the instrument, hut one analvzet will do for the plant where, if you had CO2 recorders, you would require one for each boiler. There are several other places around a modern boiler house where a recording instrument should be used that I will not discuss. I suppose you will say it takes an expert to operate a boiler room. This is exactly right. It is not to be inferred, however, that the subject is so complicated that the average fireman cannot use all the necessary instruments If any or all of the instruments referred to in this discussion are properly installed and adjusted, the poorest fireman can produce better results if properly instructed, than the best fireman can without the assistance of the instruments.