CARE OF A SEPARATOR.
A good separator ought to last ten years, and many have been in use twice that time. After the season is over the machine ought to be thoroughly cleaned and stored in a dry place. Dirt on a machine holds moisture and will ruin a separator during a winter if it is left on. It also causes the wood to rot and sieves and iron work to rust.
Once in two years at least a separator ought to have a good coat of first-class coach varnish. Before varnishing, clean off all grease and oil with benzine and see that paint is bright.
At the beginning of the season give the machine a thorough overhauling, putting new teeth in cylinder if any are imperfect, and new slats in stacker web or straw rack if they are needed. Worn boxes should be taken up or rebabbitted, and conveyor and shoe eccentrics replaced if worn out. Tighten nuts, replace lost bolts, leaving the nut always turned square with the piece it rests on. Every separator ought to be covered with a canvas during the season. It will pay.
The right and left sides of a threshing machine are reckoned from the position of the feeder as he stands facing the machine.
In case of fire, the quickest way is to let the engine pull the machine out by the belt. Take blocks away from wheels, place a man at end of tongue to steer, and back engine slowly. If necessary, men should help the wheels to start out of holes or soft places.
Watch the forks of the pitchers to see that none are loose on the handles, especially if a self-feeder is used. A pitchfork in a separator is a bad thing.
[CHAPTER XV.]
QUESTIONS ASKED ENGINEERS WHEN APPLYING FOR A LICENSE.[7]
Q. If you were called on to take charge of a plant, what would be your first duty?
A. To ascertain the exact condition of the boiler and all its attachments (safety valve, steam gauge, pump, injector), and engine.
Q. How often would you blow off and clean your boilers if you had ordinary water to use?
A. Once a month.
Q. What steam pressure will be allowed on a boiler 50 inches diameter ⅜ inch thick, 60,000 T. S. 1-6 of tensile strength factor of safety?
A. One-sixth of tensile strength of plate multiplied by thickness of plate, divided by one-half of the diameter of boiler, gives safe working pressure.
Q. How much heating surface is allowed per horse power by builders of boilers?
A. Twelve to fifteen feet for tubular and flue boilers.
Q. How do you estimate the strength of a boiler?
A. By its diameter and thickness of metal.
Q. Which is the better, single or double riveting?
A. Double riveting is from sixteen to twenty per cent stronger than single.
Q. How much grate surface do boiler makers allow per horse power?
A. About two-thirds of a square foot.
Q. Of what use is a mud drum on a boiler, if any?
A. For collecting all the sediment of the boiler.
Q. How often should it be blown out?
A. Three or four times a day.
Q. Of what use is a steam dome on a boiler?
A. For storage of dry steam.
Q. What is the object of a safety valve on a boiler?
A. To relieve pressure.
Q. What is your duty with reference to it?
A. To raise it twice a day and see that it is in good order.
Q. What is the use of check valve on a boiler?
A. To prevent water from returning back into pump or injector which feeds the boiler.
Q. Do you think a man-hole in the shell on top of a boiler weakens it any?
A. Yes, to a certain extent.
Q. What effect has cold water on hot boiler plates?
A. It will fracture them.
Q. Where should the gauge cock be located?
A. The lowest gauge cock ought to be placed about an inch and a half above the top row of flues.
Q. How would you have your blow-off located?
A. In the bottom of mud-drum or boiler.
Q. How would you have your check valve arranged?
A. With a stop cock between check and boiler.
Q. How many valves are there in a common plunger force pump?
A. Two or more—a receiving and a discharge valve.
Q. How are they located?
A. One on the suction side, the other on the discharge.
Q. How do you find the proper size of safety valves for boilers?
A. Three square feet of grate surface is allowed for one inch area of spring loaded valves; or two square feet of grate surface to one inch area of common lever valves.
Q. Give the reasons why pumps do not work sometimes?
A. Leak in suction, leak around the plunger, leaky check valve, or valves out of order, or lift too long.
Q. How often ought boilers to be thoroughly examined and tested?
A. Twice a year.
Q. How would you test them?
A. With hammer and with hydrostatic test, using warm water.
Q. Describe the single acting plunger pump; how it gets and discharges its water?
A. The plunger displaces the air in the water pipe, causing a vacuum which is filled by the atmosphere forcing the water therein; the receiving valve closes and the plunger forces the water out through the discharge valve.
Q. What is the most economical boiler-feeder?
A. The (Trix) Exhaust Injector.[8]
Q. What economy is there in the Exhaust Injector?
A. From 15 to 25 per cent saving in fuel.
Q. Where is the best place to enter the boiler with the feed water?
A. Below the water level, but so that the cold water can not strike hot plates. If injector is used this is not so material as feed water is always hot.
Q. What are the principal causes of priming in boilers?
A. To high water, not steam room enough, misconstruction, engine too large for boiler.
Q. How do you keep boilers clean or remove scale therefrom?
A. The best “scale solvent” and “feed water purifier” is an honest, intelligent engineer who will regularly open up his boilers and clean them thoroughly, soaking boilers in rain water now and then.
Q. If you found a thin plate, what would you do?
A. Put a patch on it.
Q. Would you put it on the inside or outside?
A. Inside.
Q. Why so?
A. Because the action that has weakened the plate will then set on the patch, and when this is worn it can be repeated.
Q. If you found several thin places, what would you do?
A. Patch each and reduce the pressure.
Q. If you found a blistered plate?
A. Put a patch on the fire side.
Q. If you found a plate on the bottom buckled?
A. Put a stay through the center of buckle.
Q. If you found several of the plates buckled?
A. Stay each and reduce the pressure.
Q. What is to be done with a cracked plate?
A. Drill a hole at each end of crack, caulk the crack and put a patch over it.
Q. How do you change the water in the boiler when the steam is up?
A. By putting on more feed and opening the surface blow cock.
Q. If the safety valve was stuck how would you relieve the pressure on the boiler if the steam was up and could not make its escape?
A. Work the steam off with engine after covering fires heavy with coal or ashes, and when the boiler is sufficiently cool put safety valve in working order.
Q. If water in boiler is suffered to get too low, what may be the result?
A. Burn top of combustion chamber and tubes, perhaps cause an explosion.
Q. If water is allowed to get too high, what result?
A. Cause priming, perhaps cause breaking of cylinder covers or heads.
Q. What are the principal causes of foaming in boilers?
A. Dirty and impure water.
Q. How can foaming be stopped?
A. Close throttle and keep closed long enough to show true level of water. If that level is sufficiently high, feeding and blowing off will usually suffice to correct the evil.
Q. What would you do if you should find your water gone from sight very suddenly?
A. Draw the fires and cool off as quickly as possible. Never open or close any outlets of steam when your water is out of sight.
Q. What precautions should you take to blow down a part of the water in your boiler while running with a good fire?
A. Never leave the blow-off valve, and watch the water level.
Q. How much water would you blow off at once while running?
A. Never blow off more than one gauge of water at a time while running.
Q. What general views have you in regard to boiler explosions—what is the greatest cause?
A. Ignorance and neglect are the greatest causes of boiler explosions.
Q. What precaution should the engineer take when necessary to stop with heavy fires?
A. Close dampers, put on injector or pump and if a bleeder is attached, use it.
Q. Where is the proper water level in boilers?
A. A safe water level is about two and a half inches over top row of flues.
Q. What is an engineer’s first duty on entering the boiler room?
A. To ascertain the true water level.
Q. When should a boiler be blown out?
A. After it is cooled off, never while hot.
Q. When laying up a boiler what should be done?
A. Clean thoroughly inside and out; remove all oxidation and paint places with red lead; examine all stays and braces to see if any are loose or badly worn.
Q. What is the last thing to do at night before leaving plant?
A. Look around for greasy waste, hot coals, matches, or anything which could fire the building.
Q. What would you do if you had a plant in good working order?
A. Keep it so, and let well enough alone.
Q. Of what use is the indicator?
A. The indicator is used to determine the indicated power developed by an engine, to serve as a guide in setting valves and showing the action of the steam in the cylinder.
Q. How would you increase the power of an engine?
A. To increase the power of an engine, increase the speed; or get higher pressure of steam, use less expansion.
Q. How do you find the horsepower of an engine?
A. Multiply the speed of piston in feet per minute by the total effective pressure upon the piston in pounds and divide the product by 33,000.
Q. Which has the most friction, a perfectly fitted, or an imperfectly fitted valve or bearing?
A. An imperfect one.
Q. How hot can you get water under atmospheric pressure with exhaust steam?
A. 212 degrees.
Q. Does pressure have any influence on the boiling point?
A. Yes.
Q. Which do you think is the best economy, to run with your throttle wide open or partly shut?
A. Always have the throttle wide open on a governor engine.
Q. At what temperature has iron the greatest tensile strength?
A. About 600 degrees.
Q. In what position on the shaft does the eccentric stand in relation to the crank?
A. The throw of the eccentric should always be in advance of the crank pin.
Q. About how many pounds of water are required to yield one horsepower with our best engines?
A. From 25 to 30.
Q. What is meant by atmospheric pressure?
A. The weight of the atmosphere.
Q. What is the weight of atmosphere at sea level?
A. 14.7 pounds.
Q. What is the coal consumption per hour per indicated horsepower?
A. Varies from one and a half to seven pounds.
Q. What is the consumption of coal per hour on a square foot of grate surface?
A. From 10 to 12 pounds.
Q. What is the water consumption in pounds per hour per indicated horsepower?
A. From 25 to 60 pounds.
Q. How many pounds of water can be evaporated with one pound of best soft coal?
A. From 7 to 10 pounds.
Q. How much steam will one cubic inch of water evaporate under atmospheric pressure?
A. One cubic foot of steam (approximately).
Q. What is the weight of a cubic foot of fresh water?
A. Sixty-two and a half pounds.
Q. What is the weight of a cubic foot of iron?
A. 486.6 pounds.
Q. What is the weight of a square foot of one-half inch boiler plate?
A. 20 pounds.
Q. How much wood equals one ton of soft coal for steam purposes?
A. About 4,000 pounds of wood.
Q. How long have you run engines?
Q. Have you ever done your own firing?
Q. What is the source of all power in the steam engine?
A. The heat stored up in the coal.
Q. How is the heat liberated from the coal?
A. By burning it; that is, by combustion.
Q. Of what does coal consist?
A. Carbon, hydrogen, nitrogen, sulphur, oxygen and ash.
Q. What are the relative proportions of these that enter into coal?
A. There are different proportions in different specimens of coal, but the following shows the average per cent: Carbon, 80; hydrogen, 5; nitrogen, 1; sulphur, 2; oxygen, 7; ash, 5.
Q. What must be mixed with coal before it will burn?
A. Atmospheric air.
Q. What is air composed of?
A. It is composed of nitrogen and oxygen in the proportion of 77 of nitrogen to 23 of oxygen.
Q. What parts of the air mix with what parts of the coal?
A. The oxygen of the air mixes with the carbon and hydrogen of the coal.
Q. How much air must mix with the coal?
A. 150 cubic feet of air for every pound of coal.
Q. How many pounds of air are required to burn one pound of carbon?
A. Twelve.
Q. How many pounds of air are required to burn one pound of hydrogen?
A. Thirty-six.
Q. Is hydrogen hotter than carbon?
A. Yes, four and one-half times hotter.
Q. What part of the coal gives out the most heat?
A. The hydrogen does part for part, but as there is so much more of carbon than hydrogen in the coal we get the greatest amount of heat from carbon.
Q. In how many different ways is heat transmitted?
A. Three; by radiation, by conduction and by convection.
Q. If the fire consisted of glowing fuel, show how the heat enters the water and forms steam?
A. The heat from the glowing fuel passes by radiation through the air space above the fuel to the furnace crown. There it passes through the iron of the crown by conduction. There it warms the water resting on the crown, which then rises and parts with its heat to the colder water by conduction till the whole mass of water is heated. Then the heated water rises to the surface and parts with its steam, so a constant circulation of water is maintained by convection.
Q. What does water consist of?
A. Oxygen and hydrogen.
Q. In what proportion?
A. Eight of oxygen to one of hydrogen by weight.
Q. What are the different kinds of heat?
A. Latent heat, sensible heat and sometimes total heat.
Q. What is meant by latent heat?
A. Heat that does not affect the thermometer and which expands itself in changing the nature of a body, such as turning ice into water or water into steam.
Q. Under what circumstances do bodies get latent heat?
A. When they are passing from a solid state to a liquid or from a liquid to a gaseous state.
Q. How can latent heat be recovered?
A. By bringing the body back from a state of gas to a liquid or from that of a liquid to that of a solid.
Q. What is meant by a thermal unit?
A. The heat necessary to raise one pound of water at 39 degrees Fn. 1 degree Fahrenheit.
Q. If the power is in coal, why should we use steam?
A. Because steam has some properties which make it an invaluable agent for applying the energy of the heat to the engine.
Q. What is steam?
A. It is an invisible elastic gas generated from water by the application of heat.
Q. What are its properties which make it so valuable to us?
A. 1.—The ease with which we can condense it. 2.—Its great expansive power. 3.—The small space it occupies when condensed.
Q. Why do you condense the steam?
A. To form a vacuum and so destroy the back pressure that would otherwise be on the piston and thus get more useful work out of the steam.
Q. What is vacuum?
A. A space void of all pressure.
Q. How do you maintain a vacuum?
A. By the steam used being constantly condensed by the cold water or cold tubes, and the air pump as constantly clearing the condenser out.
Q. Why does condensing the used steam form a vacuum?
A. Because a cubic foot of steam, at atmospheric pressure, shrinks into about a cubic inch of water.
Q. What do you understand by the term horse power?
A. A horse power is equivalent to raising 33,000 pounds one foot per minute, or 550 pounds raised one foot per second.
Q. How do you calculate the horse power of tubular or flue boilers?
A. For tubular boilers, multiply the square of the diameter by length, and divide by four. For flue boilers, multiply the diameter by the length and divide by four; or, multiply area of grate surface in square feet by 1½.
Q. What do you understand by lead on an engine’s valve?
A. Lead on a valve is the admission of steam into the cylinder before the piston completes its stroke.
Q. What is the clearance of an engine as the term is applied at the present time?
A. Clearance is the space between the cylinder head and the piston head with the ports included.
Q. What are considered the greatest improvements on the stationary engine in the last forty years?
A. The governor, the Corliss valve gear and the triple compound expansion.
Q. What is meant by triple expansion engine?
A. A triple expansion engine has three cylinders using the steam expansively in each one.
Q. What is a condenser as applied to an engine?
A. The condenser is a part of the low pressure engine and is a receptacle into which the exhaust enters and is there condensed.
Q. What are the principles which distinguish a high pressure from a low pressure engine?
A. Where no condenser is used and the exhaust steam is open to the atmosphere.
Q. About how much gain is there by using the condenser?
A. 17 to 25 per cent where cost of water is not figured.
Q. What do you understand by the use of steam expansively?
A. Where steam admitted at a certain pressure is cut off and allowed to expand to a lower pressure.
Q. How many inches of vacuum give the best results in a condensing engine?
A. Usually considered 25.
Q. What is meant by a horizontal tandem engine?
A. One cylinder being behind the other with two pistons on same rod.
Q. What is a Corliss valve gear?
A. (Describe the half moon or crab claw gear, or oval arm gear with dash pots.)
Q. From what cause do belts have the power to drive shafting?
A. By friction or cohesion.
Q. What do you understand by lap?
A. Outside lap is that portion of valve which extends beyond the ports when valve is placed on the center of travel, and inside lap is that portion of valve which projects over the ports on the inside or towards the middle of valve.
Q. What is the use of lap?
A. To give the engine compression.
Q. Where is the dead center of an engine?
A. The point where the crank and the piston rod are in the same right line.
Q. What is the tensile strength of American boiler iron?
A. 40,000 to 60,000 pounds per square inch.
Q. What is very high tensile strength in boiler iron apt to go with?
A. Lack of homogeneousness and lack of toughness.
Q. What is the advantage of toughness in boiler plate?
A. It stands irregular strains and sudden shocks better.
Q. What are the principal defects found in boiler iron?
A. Imperfect welding, brittleness, low ductility.
Q. What are the advantages of steel as a material for boiler plates?
A. Homogeneity, tensile strength, malleability, ductility and freedom from laminations and blisters.
Q. What are the disadvantages of steel as a material for boiler plates?
A. It requires greater skill in working than iron, and has, as bad qualities, brittleness, low ductility and flaws induced by the pressure of gas bubbles in the ingot.
Q. When would you oil an engine?
A. Before starting it and as often while running as necessary.
Q. How do you find proper size of any stay bolts for a well made boiler?
A. First, multiply the given steam pressure per square inch by the square of the distance between centers of stay bolts, and divide the product by 6,000, and call the answer “the quotient.” Second, divide “the quotient” by .7854, and extract the square root of the last quotient; the answer will give the required diameter of stay bolts at the bottom of thread.
Q. In what position would you place an engine, to take up any slack motion of the reciprocating parts?
A. Place engine in the position where the least wear takes place on the journals. That is, in taking up the wear of the crank-pin brasses, place the engine on either dead center, as, when running, there is but little wear upon the crank-pin at these points. If taking up the cross-head pin brasses—without disconnecting and swinging the rod—place the engine at half stroke, which is the extreme point of swing of the rod, there being the least wear on the brasses and cross-head pin in this position.
Q. What benefits are derived by using flywheels on steam engines?
A. The energy developed in the cylinder while the steam is doing its work is stored up in the flywheel, and given out by it while there is no work being done in the cylinder—that is, when the engine is passing the dead centers. This tends to keep the speed of the engine shaft steady.
Q. Name several kinds of reducing motions, as used in indicator practice?
A. The pantograph, the pendulum, the brumbo pulley, the reducing wheel.
Q. How can an engineer tell from an indicator diagram whether the piston or valves are leaking?
A. Leaky steam valves will cause the expansion curve to become convex; that is, it will not follow hyperbolic expansion, and will also show increased back pressure. But if the exhaust valves leak also, one may offset the other, and the indicator diagram would show no leak.
A leaky piston can be detected by a rapid falling in the pressure on the expansion curve immediately after the point of cut-off. It will also show increased back pressure.
A falling in pressure in the upper portion of the compression curve shows a leak in the exhaust valve.
Q. What would be the best method of treating a badly scaled boiler, that was to be cleaned by a liberal use of compound?
A. First open the boiler up and note where the loose scale, if any, has lodged. Wash out thoroughly and put in the required amount of compound. While the boiler is in service, open the blow-off valve for a few seconds, two or three times a day, to be assured that it does not become stopped up with scale.
After running the boiler for a week, shut it down, and, when the pressure is down and the boiler cooled off, run the water out and take off the hand-hole plates. Note what effect the compound has had on the scale, and where the disengaged scale has lodged. Wash out thoroughly and use judgment as to whether it is advisable to use a less or greater quantity of compound, or to add a small quantity daily.
Continue the washing out at short intervals, as many boilers have been burned by large quantities of scale dropping on the crown sheets and not being removed.
Q. If a condenser was attached to a side-valve engine, that had been set to run non-condensing, what changes, if any, would be necessary?
A. More lap would have to be added to the valve to cut off the steam at an earlier point of the stroke; if not, the initial pressure into the cylinder would be throttled down and the economy, to be gained from running condensing, lessened.
Q. If you are carrying a vacuum equal to 27½ inches of mercury, what should the temperature of the water in the hot well be?
A. 108 degrees Fahrenheit.
Q. Define specific gravity.
A. The specific gravity of a substance is the number which expresses the relation between the weights of equal volume of that substance, and distilled water of 60 degrees Fahrenheit.
Q. Find the specific gravity of a body whose volume is 12 cubic inches, and which floats in water with 7 cubic inches immersed.
A. When a body floats in water, it displaces a quantity of water equal to the weight of the floating body. Thus, if a body of 12 cubic inches in volume floats with 7 cubic inches immersed, 7 cubic inches of water must be equal in weight to 12 cubic inches of the substance and one cubic inch of water to twelve-sevenths cubic inches of the substance.
As specific gravity equals weight of one volume of substance divided by weight of equal volume of water, then specific gravity of the substance in this case equals 1 divided by twelve-sevenths.