Diameter.Gallons.25feet367120„234915„132114„115013„99212„84611„71010„5879„4758„3767„28761⁄2„2476„2115„14741⁄2„1194„943„5321⁄2„362„23
Supposing it was required to find the weight of the water in any cistern or tank; it can be ascertained by multiplying the number of gallons by the weight of one gallon, which is 81⁄3pounds, 8.333. For instance, taking the largest cistern in the above table containing 3671 gallons: 3671 × 8.33 = 30579.43 pounds.
The table above gives the capacities of round cisterns or tanks. If the cistern is rectangular the number of gallons and weight of water are found by multiplying the dimensions of the cistern to get the cubical contents. For instance, for a cistern or tank 96 inches long, 72 inches wide, and 48 inches deep, the formula would be: 96 × 72 × 48 = 331,776 cubic inches.
As a gallon contains 231 cubic inches; 331,776 divided by 231 gives l,436 gallons, which multiplied by 8.33 will give the weight of water in the cistern.
For round cisterns or tanks, the rule is: Area of bottom on inside multiplied by the height, equals cubical capacity. For instance, taking the last tank or cistern in the table: Area of 24 inches (diameter) is 452.39, which multiplied by 12 inches (height) gives 5427.6 cubic inches, and this divided by 231 cubic inches in a gallon gives 23 gallons.
Supposing the tank to be 24 inches deep instead of 12 inches, the result would be, of course, twice the number of gallons.
Rule for Obtaining Contents of a Barrel in Gallons.
Take diameter at bung, then square it, double it, then add square of head diameter; multiply this sum by length of cask, and that product by .2618 which will give volume in cubic inches; this, divided by 231, will give result in gallons.
Water meters, or measurers (apparatus for the measurement of water), are constructed upon two general principles: 1, an arrangement called an “inferential meter” made to divert a certain proportion of the water passing in the main pipe and by measuring accurately the small stream diverted,to infer, or estimate the larger quantity; 2,the positive meter; rotary piston meters are of the latter class and the form usually found in connection with steam plants. They are constructed on the positive displacement principle, and have only one working part—a hard rubber rolling piston—rendering it almost, if not entirely, exempt from liability to derangement. It measures equally well on all sized openings, whether the pressure be small or great; and its piston, being perfectly balanced, is almost frictionless in its operation.
Constructed of composition (gun-metal) and hard rubber, it is not liable to corrosion. An ingenious stuffing-box insures at all times a perfectly dry and legible dial, or the registeringmechanism which is made of a combination of metals especially chosen for durability and wear, and inclosed in a case of gun-metal.
Fig. 99.
Fig. 99.
Fig. 99is a perspective view of the meter, showing the index on the top. It is shown here as when placed in position. The proper threads at the inlet and outlet make it easy of attachment to the supply and discharge pipes.
The hard rubber piston (the only working part of the Meter) is made with spindle for moving the lever communicating with the intermediate gear by which the dial is moved.
The water, through the continuous movement of the piston, passes through the meter in an unbroken stream, in the same quantity as with the pipe to which it is attached when the opening in the meter equals that of the service pipe; the apparatus is noiseless and practically without essential wear.
In setting a meter in position let it be plumb, and properly secured to remain so. It should be well protected from frost.
If used in connection with a steam boiler, or under any other conditions where it is exposed to a back pressure of steam or hot water, it must be protected by a check valve, placed between the outlet of the meter and the vessel it supplies.
It is absolutely necessary to blow out the supply pipe before setting a new meter, so that if there be any accumulation of sand, gravel, etc., in it, the same may be expelled, and thus prevented from entering the meter. Avoid using red lead in making joints. It is liable to work into the meter and cause much annoyance by clogging the piston.
This engraving,Fig. 100, shows the counter of the Meter. It registers cubic feet—one cubic foot being 748⁄100U. S. gallons and is read in the same way as the counters of gas meters.
Fig. 100.
Fig. 100.
The following example and directions may be of service to those unacquainted with the method:
If a pointer be between two figures, the smallest one must always be taken. When the pointer is so near a figure that it seems to indicate that figure exactly, look at the dial next below it in number, and if the pointer there has passed 0, then the count should be read for that figure. Let it be supposed that the pointers stand as in the above engraving, they then read 28,187 cubic feet. The figures are omitted from the dial marked “ONE,” because they represent but tenths of one cubic foot, and hence are unimportant. From dial marked “10,” we get 7; from the next marked “100,” we get 8; from the next marked “1,000,” we get the figure 1; from the next marked “10,000,” the figure 8; from the next marked “100,000,” the figure 2.
The Fish Trapused in connection with water meters is an apparatus (as its name denotes) for holding back fishes, etc.
For safety sake, every boiler ought to have two feeds in order to avoid accidents when one of them gets out of order, and one of these should be an injector.
This consists in its most simple form, of a steam nozzle, the end of which extends somewhat into the second nozzle, called the combining or suction nozzle; this connects with or rather terminates in a third nozzle or tube, termed the “forcer.” At the end of thecombining tube, and before entering the forcer, is an opening connecting the interior of the nozzle at this point with the surrounding area. This area is connected with the outside air by a check valve, opening outward in the automatic injectors, and by a valve termed the overflow valve.
The operation of the injector is based on the fact, first demonstrated by Gifford, that the motion imparted by a jet of steam to a surrounding column of water is sufficient to force it into the boiler from which the steam was taken, and, indeed, into a boiler working at a higher pressure. The steam escaping from under pressure has, in fact, a much higher velocity than water would have under the same pressure and condition. The rate of speed at which steam—taking it at an average boiler pressure of sixty pounds—travels when discharged into the atmosphere, is about 1,700 feet per second. When discharged with the full velocity developed by the boiler pressure through a pipe, say an inch in diameter, the steam encounters the water in the combining chamber. It is immediately condensed and its bulk will be reduced say 1,000 times, but its velocity remains practically undiminished. Uniting with the body of water in the combining tube, it imparts to it a large share of its speed, and the body of water thus set in motion, operating against a comparatively small area of boiler pressure, is able to overcome it and pass into the boiler. The weight of the water to which steam imparts its velocity gives it a momentum that is greater in the small area in which its force is exerted than the boiler pressure, although its force has actually been derived from the boiler pressure itself.
The following cut 101 represents the outline of one of the best of a large number of injectors upon the market, from which the operation of injectors may be illustrated.
S. Steam jet. V. Suction jet.R. Ring or auxiliary check.M. Steam valve and stem, handle.X. Overflow cap.C-D. Combining and delivery tube.P. Overflow valve. O. Steam plug.N. Packing nut. K. Steam valveFig. 101.
S. Steam jet. V. Suction jet.R. Ring or auxiliary check.M. Steam valve and stem, handle.X. Overflow cap.C-D. Combining and delivery tube.P. Overflow valve. O. Steam plug.N. Packing nut. K. Steam valve
Fig. 101.
The steam enters from above, the flow being regulated by the handle K. The steam passes through the tube S and expands in the tube V, where it meets the water coming from the suction pipe. The condensation takes place in the tubes V and C, and a jet of water is delivered through the forcer tube D to the boiler. Connection passages are made to the chamber surrounding the tubes C, D, and to the end of tube V. If the pressure in this surrounding chamber becomes greater than that of the atmosphere, the check valve P is lifted and the contents are discharged through the overflow.
So long as the pressure in this chamber is atmospheric, the check valve P remains closed, and all the contents must be discharged through the tube D.
There are three distinct types of live steam injectors, the “simple fixed nozzle,” the “adjustable nozzle,” and the “double.” The first has one steam and one water nozzle which are fixed in position but are so proportioned as to yield a good result. There is a steam pressure for every instrument of this type at which it will give a maximum delivery, greater than the maximum delivery for any other steam pressure either higher or lower. The second type has but one set of nozzles, but they can be so adjusted relative to each other as to produce the best results throughout a long range of action; that is to say, it so adjusts itself that its maximum delivery continually increases with the increase of steam pressure.
The double injector makes use of two sets of nozzles, the “lifter” and “forcer.” The lifter draws the water from the reservoir and delivers it to the forcer, which sends it into the boiler. All double injectors are fixed nozzle.
All injectors are similar in their operation. They are designed to bring a jet of live steam from the boiler in contact with a jet of water so as to cause it to flow continuously in the direction followed by the steam, the velocity of which it in part assumes, back into the boiler and against its own pressure.
As a thermodynamical machine, the injector is nearly perfect, since all the heat received by it is returned to the boiler, except such a very small part as may be lost by radiation; consequently its thermal efficiency should be in every case nearly 100 per cent. On the other hand, because of the fact that its heat energy is principally used in warming up the cold water as it enters the injector, its mechanical efficiency, or work done in lifting water, compared with the heat expended, is very low.
The action of the injector is as follows: Steam being turned on, it rushes with great velocity through the steam nozzle into and through the combining tube. This action induces a flow of air from the suction pipe, which is connected to the combining tube, with the result that a more or less perfect vacuum is formed, thus inducing a flow of water. After the water commences to flow to the injector it receives motion from the jet of steam; it absorbs heat from the steam and finally condenses it,and thereafter moves on into the forcer tube simply as a stream of water, at a low velocity compared with that of the steam. At the beginning of the forcer tube it is subjected only to atmospheric pressure, but from this point the pressure increases and the water moves forward at diminished velocity.
In nine cases out of ten, where the injector fails to do good service, it will be either because of its improper treatment or location, or because too much is expected of it. The experience of thoroughly competent engineers establishes the fact that in almost every instance in which a reliable boiler feed is required, an injector can be found to do the work, provided proper care is exercised in its selection.
The exhaust steam injector is a type different from any of the above-named, in that it uses the exhaust steam from a non-condensing engine. Exhaust steam has fourteen and seven-tenths (14.7) pounds of work, and the steam entering the injector is condensed and the water forced into the boiler upon the same general principle as in all injectors.
The exhaust steam injector would be still more extensively used were it not for a practical objection which has arisen—it carries over into the boiler the waste oil of the steam cylinder.
Some injectors are called by special names by their makers, such as ejectors and inspirators, but the term injectors is the general name covering the principle upon which all the devices act.
The injector can be, and sometimes is, used as a pump to raise water from one level to another. It has been used as an air compressor, and also for receiving the exhaust from a steam engine, taking the place in that case of both condenser and air pump.
The injector nozzles are tubes, with ends rounded to receive and deliver the fluids with the least possible loss by friction and eddies.
Double injectors are those in which the delivery from one injector is made the supply of a second, and they will handle water at a somewhat higher temperature than single ones with fixed nozzles.
The motive force of the injector is found in the heat received from the steam. The steam is condensed and surrenders its latent heat and some of its sensible heat. The energy so given up by each pound of steam amounts to about 900 thermal units, each of which is equivalent to a mechanical force of 778 foot pounds. This would be sufficient to raise a great many pounds of water against a very great pressure could it be so applied, but a large portion of it is used simply to heat the water raised by the injector.
The above explanation will apply to every injector in the market, but ingenious modifications of the principles of construction have been devised in order to meet a variety of requirements.
That the condensation of the steam is necessary to complete the process will be evident, for if the steam were not condensed in the combining chamber, it would remain a light body and, though moving at high speed, would have a low degree of energy.
Certain injectors will not work well when the steam pressure is too high. In order to work at all the injector must condense the steam which flows into the combining tube. Therefore, when the steam pressure is too high, and as a consequence the heat is very great, it is difficult to secure complete condensation; so that for high pressure of steam good results can only be obtained with cold water. It would be well when the feed water is too warm to permit the injector to work well, to reduce the pressure, and consequently the temperature of the steam supplied to the injector, as low pressure steam condenses much easier, and consequently can be employed with better result. Throttling the steam supplied by means of stop valves will often answer well in this case. The steam should not be cold or it will not contain heat units enough to allow it to condense into a cross section small enough to be driven into the boiler. This is the reason why exhaust injectors fail to work when the exhaust steam is very cold. It also explains why such injectors work well when a little live steam is admitted into the exhaust sufficient to heat it above a temperature of 212°.
Leaks affect injectors the same as pumps, and in addition, the accumulation of lime and other mineral deposits in the jets stops the free flowing of the water. The heat of the steam is the usual cause of the deposits, and where this is excessive it would be well to discard the injector and feed with the pump.
The efficient working of the injector depends materially upon the size of the jet which should be left as the manufacturer makes it; hence in repairs and cleaning a scraper or file should not be used.
For cleaning injectors, where the jets have become scaled, use a solution of one part muriatic acid to from nine to twelve parts of water. Allow the tubes to remain in the acid until the scale is dissolved or is so soft as to wash out readily.
The lifting attachment, as applied to any injector, is simply a steam jet pump. It is combined with the injector proper and is operated by a portion of the steam admitted to the instrument. Nearly all the successful injectors on the market are made with these attachments, and will raise water about 25 feet, if required, from a well or tank below the boiler level.
Where an injector is required to work at different pressures it must be so constructed that the space between the receiving tube and the combining tube can be varied in size. As a rule this is accomplished by making both combining and receiving tubes conical in form and arranging the combining tube so that it can be moved to or from the receiving tube, and the water space thereby enlarged or contracted at will. The adjustment of the space between the two tubes by hand is a matter of some difficulty, however; at least it takes more time and patience than the average engineer has to devote to it, and the majority of the injectors in use are therefore made automatic in their regulation.
The injector is not an economical device, but it is simple and convenient, it occupies but a small amount of space, is not expensive and is free from severe strains on its durability; moreover, where a number of boilers are used in one establishment, it is very convenient to have the feeding arrangements separate, so that each boiler is a complete generating system in itself and independent of its neighbors.
Heat is a word freely used, yet difficult to define. The word “heat” is commonly used in two senses: (1) to express the sensation of warmth; (2) the state of things in bodies which causes that sensation. The expression herein must be taken in the latter sense.
Heat is transmitted in three ways—byconduction, as when the end of a short rod of iron is placed in a fire, and the opposite end becomes warmed—this is conducted heat; byconvection(means of currents) such as the warming of a mass of water in a boiler, furnace, or saucepan; and byradiation, as that diffused from a piece of hot metal or an open fire. Radiant heat is transmitted, like sound or light, in straight lines in every direction, and its intensity diminishes inversely as the square of the distance from its center or point of radiation. Suppose the distance from the center of radiation to be 1, 2, 3 and 4 yards, the surface covered by heat rays will increase 1, 4, 9 and 16 square feet; the intensity of heat will diminish 1,1⁄4,1⁄9, and1⁄16. and so on in like proportions, until the heat becomes absorbed, or its source of supply stopped.
Whenever a difference in temperature exists, either in solids or liquids that come in contact with or in close proximity to each other, there is a tendency for the temperature to become equalized; if water at 100° be poured into a vessel containing an equal quantity of water at 50°, the tendency will be for the whole to assume a temperature of 75°; and suppose the temperature of the surrounding air be 30°, the cooling process will continue until the water and the surrounding air become nearly equal, the temperature of the air being increased in proportion as that of the water is decreased.
The heat generated by a fire under the boiler is transmitted to the water inside the boiler, when the difference in the specific gravities, or, in other words, the cold water in the pipes being heavier than that in the boiler sinks and forces the lighter hot water upward. This heat is radiated from the pipes, which are good conductors of heat to the air in the room, and raises it to the required temperature. That which absorbs heatrapidly, and parts with it rapidly, is called a good conductor, and that which is slow to receive heat, and parts with it slowly, is termed a bad conductor.
The following tables of conductivity, and of the radiating properties of various materials, may be of service:
Conducting Power of Various Substances.—Despritz.
Material.Conductivity.Gold100Silver97Copper89Brass75Cast iron56Wrought iron37Zinc36Tin30Lead18Marble2.4Fire clay1.1Water0.9
Radiating Power of Various Substances.—Leslie
Material.Radiating Power.Lampblack100Water100Writing paper98Glass90Tissue paper88Ice85Wrought lead45Mercury20Polished lead19Polished iron15Gold, silver12Copper, tin12
From the above tables, it will be seen that water, being an excellent radiator, and of great specific heat, and iron a good conductor, these qualities, together with the small cost of the materials, combine to render them efficient, economic and convenient for the transmission and distribution of artificial heat.
By adopting certain standards we are enabled to define, compare and calculate so as to arrive at definite results, hence the adoption of a standard unit of heat, unit of power, unit of work, etc.
The standard unit of heat is the amount necessary to raise the temperature of one pound of water at 32° Fahr. one degree,i.e., from 32° to 33°.
Specific heat is the amount of heat necessary to raise the temperature of a solid or liquid body a certain number of degrees; water is adopted as the unit or standard of comparison. The heat necessary to raise one pound of water one degree, will raise one pound of mercury about 30 degrees, and one pound of lead about 32 degrees.
Table of the Specific Heat of Equal Weights of Various Substances.
Solid bodies.SpecificHeat.Wood (fir and pine)0.650„ (oak)0.570Ice0.504Coal0.280Charcoal (animal)0.260„ (vegetable)0.241Iron (cast)0.241Coke0.201Limestone0.200Glass0.195Steel (hard)0.117„ (soft)0.116Iron (wrought)0.111Zinc0.095Copper (annealed)0.094„ (cold hammered)0.093Tin0.056Lead0.031Liquids.Water1.000Alcohol0.158Acid (pyroligneous)0.590Ether0.520Acid (acetic)0.509Oil (olive)0.309Mercury0.033Gases.Hydrogen3.409Vapor of alcohol0.547Steam0.480Carbonic oxide0.245Nitrogen0.243Oxygen0.217Atmospheric air0.237Carbonic acid0.202
It is difficult to overestimate the importance, in connection with a steam plant, of the appliance which supplies water for the boiler, not only, but a hundred other uses. Upon the steady operation of the pump depends the safety and comfort of the engineer, owner and employee, and indirectly of the success of the business with which the “plant” is connected. Hence the necessity of acquiring complete knowledge of the operation of a device so important.
Fig. 102.
Fig. 102.
Pumps now raise, convey and deliver water, beer, molasses, acids, oils, melted lead. Pumps also handle, among the gases, air, ammonia, lighting gas, and oxygen. Pumps are also used to increase or decrease the pressure of a fluid.
Pumps are made in many ways, and defined as rope, chain, diaphragm, jet, centrifugal, rotary, oscillating, cylinder.
Cylinder pumps are of two classes, single acting and double acting. In single acting—in effect issingle ended—in double acting, the motion of the cylinder in one direction causes an inflow of water and a discharge at the same time, in the other; and on the return stroke the action is renewed as the discharge end becomes the suction end. The pump is thus double acting.
Adirect pressuresteam pump is one in which the liquid is pressed out by the action of steam upon its surface, without the intervention of a piston. A direct acting steam pump is an engine and pump combined.
A cylinder or reciprocating pump is one in which the piston or plunger, in one direction, causes a partial vacuum, to fill which the water rushes in pressed by the air on its head.
Note.—Asuction valveprevents the return of this water on the return stroke of the piston, and adischarge valvepermits the outward passage of the fluid from the pump but not its return thereto or to the reservoir through the suction pipe.
The force against which the pump works is gravity or the attraction of the earth which prevents the water from being lifted. This is shown by the fact that water can be led, or trailed, an immense distance, limited only by the friction, by a pump.
Note.—It may be noted that the difference between a fluid andliquidis shown in the fact that the latter can be poured from one vessel to another, thus: air and water are both fluids, but of the two water alone is liquid: air, ammonia, etc., aregases, while they are also fluids,i.e., they flow.
The idea entertained by many that water is raised by suction, is erroneous. Water or other liquids are raised through a tube or hose by the pressure of the atmosphere on their surface. When the atmosphere is removed from the tube there will be no resistance to prevent the water from rising, as the water outside the pipe, still having the pressure of the atmosphere upon its surface, forces water up into the pipe, supplying the place of the excluded air, while the water inside the pipe will rise above the level of that outside of it proportionally to the extent to which it is relieved of the pressure of the air.
If the first stroke of a pump reduces the pressure of the air in the pipe from 15 pounds on the square inch to 14 pounds, the water will be forced up the pipe to the distance of 21⁄4feet, since a column of water an inch square and 21⁄4feet high is equalin weight to about 1 pound. Now if the second stroke of the pump reduces the pressure of the atmosphere in the pipe to 13 pounds per inch, the water will rise another 21⁄4feet; this rule is uniform, and shows that the rise of the column of water within the pipe is equal in weight to the pressure of the air upon the surface of the water without.
There are pumps (Centrifugal) especially designed for pumping water mingled with mud, sand, gravel, shells, stones, coal, etc., but with these the engineer has but little to do, as they are used mostly for wrecking and drainage.
The variety of pattern in which pumps are manufactured and the still greater variation in capacity forbids an attempt to fully illustrate and describe further than their general principles, and to name the following general
1st. Pumps are divided into Vertical and Horizontal.
Vertical pumps are again divided into:
1. Ordinary Suction or Bucket Pumps.2. Suction and Lift Pumps.3. Plunger or Force Pumps.4. Bucket and Plunger Pumps.5. Piston and Plunger Pumps.
Horizontal Pumps are divided into:
1. Double-acting Piston Pumps.2. Single-acting Plunger Pumps.3. Double-acting Plunger Pumps.4. Bucket and Plunger Pumps.5. Piston and Plunger Pumps.
Fig. 103.A—Air Chamber.B—Water Cylinder Cap.C—Water Cylinder with Valves and Seats in.D—Rocker Shafts, each, Long or Short.E—Removable Cylinders, each.F—Water Piston and Follower, each.„—Water Piston Followers, each.G—Rocker Stand.H—Suction Flange, threaded.I—Discharge Flange, threaded.J—Intermediate Flanges, each.K—Water Cylinder Heads, each.L—Concaves complete, with Stuffing Boxes, each.M—Steam Cylinder, without Head, Bonnet and Valve.N—Steam Cylinder Foot.O—Crosshead Links, each.P—Steam Piston complete with Rings and Follower, each.m—Steam Piston Head.n—Steam Piston Follower.Steam Piston Rings, including Spring and Breakjoint.Q—Side Water Cylinder Bonnet, each.R—Steam Chest Bonnet, each.S—Steam Chest Stuffing Box Gland, each.T—Steam Slide Valve, each.U—Piston Rods, each.V—Crossheads, each.W—Rocker Arms, each, Long or Short.X—Valve Rod Links, each, Long or Short.Y—Steam Valve Stems, each.Z—Steam Cylinder Heads, each.aa—Piston Rod Nuts, each.hh—Piston Rod Stuffing Glands, each.ii—Water Valve Seats, each.jj—Rubber Valves, each.kk—Water Valve Stems, each.ll—Water Valve Springs, each.gg—Removable Cylinder Screws, each.b—Steam Valve Stem Forks, each.c—Steam Valve Stem Fork Bolts, each.e—Valve Rod Link Bolts, each.d—Rocker Arm Pins, each.f—Crosshead Link Bolts, each.o—Collar Bolts, each.pp—Brass Steam Cylinder Drain Cocks, each.Water Packings, each.Brass Piston Rods, each.Brass Lined Removable Cylinders, extra, each.Piston Rod Stuffing Gland Bolts, each.Water Cylinder Cap Bonnets, each.Top Valve Caps, each.Valve Cap Clamps, each.
Fig. 103.
A—Air Chamber.B—Water Cylinder Cap.C—Water Cylinder with Valves and Seats in.D—Rocker Shafts, each, Long or Short.E—Removable Cylinders, each.F—Water Piston and Follower, each.„—Water Piston Followers, each.G—Rocker Stand.H—Suction Flange, threaded.I—Discharge Flange, threaded.J—Intermediate Flanges, each.K—Water Cylinder Heads, each.L—Concaves complete, with Stuffing Boxes, each.M—Steam Cylinder, without Head, Bonnet and Valve.N—Steam Cylinder Foot.O—Crosshead Links, each.P—Steam Piston complete with Rings and Follower, each.m—Steam Piston Head.n—Steam Piston Follower.Steam Piston Rings, including Spring and Breakjoint.Q—Side Water Cylinder Bonnet, each.R—Steam Chest Bonnet, each.S—Steam Chest Stuffing Box Gland, each.T—Steam Slide Valve, each.U—Piston Rods, each.V—Crossheads, each.W—Rocker Arms, each, Long or Short.X—Valve Rod Links, each, Long or Short.Y—Steam Valve Stems, each.Z—Steam Cylinder Heads, each.aa—Piston Rod Nuts, each.hh—Piston Rod Stuffing Glands, each.ii—Water Valve Seats, each.jj—Rubber Valves, each.kk—Water Valve Stems, each.ll—Water Valve Springs, each.gg—Removable Cylinder Screws, each.b—Steam Valve Stem Forks, each.c—Steam Valve Stem Fork Bolts, each.e—Valve Rod Link Bolts, each.d—Rocker Arm Pins, each.f—Crosshead Link Bolts, each.o—Collar Bolts, each.pp—Brass Steam Cylinder Drain Cocks, each.Water Packings, each.Brass Piston Rods, each.Brass Lined Removable Cylinders, extra, each.Piston Rod Stuffing Gland Bolts, each.Water Cylinder Cap Bonnets, each.Top Valve Caps, each.Valve Cap Clamps, each.
In Figs.102and103are exhibited the outlines ofthe double acting steam pump, which is undoubtedly the pattern most thoroughly adapted for feeding steam boilers, as it is equipped for the slowest motion with less risk of stopping on a centre.
From the drawing with reference letters may be learned the terms applied generally to the parts of all steam pumps: example: “k” shows the water valve stems, “K” the water cylinder heads.
It may be remarked that nearly all pump makers furnish valuable printed matter, giving directionsas to repairs, and best method of using their particular pumps—especially valuable are their repair sheets in which are given cuts of “parts” of the pumps. It were well for the steam user and engineer to request such matter from the manufacturers for the special pump they use.
Blow out the steam pipe thoroughly with steam before connecting it to the engine; otherwise any dirt or rubbish there might be in the pipe will be carried into the steam cylinder, and cut the valves and piston.
Never change the valve movement of the engine end of the pump. If any of the working parts become loose, bent or broken, replace them or insert new ones, in precisely the same position as before.
Keep the stuffing boxes nearly full of good packing well oiled, and set just tight enough to prevent leakage without excessive friction.
Use good oil only, and oil the steam end just before stopping the pump.
It is absolutely necessary to have a full supply of water to the pump.
If possible avoid the use of valves and elbows in the suction pipe, and see that it is as straight as possible; for bends, valves and elbows materially increase the friction of the water flowing into the pump.
See that the suction pipe is not imbedded in sand or mud, but is free and unobstructed.
All the pipes leading from the source of supply to the pump must be air-tight, for a very small air-leak will destroy the vacuum, the pump will not fill properly; its motion will be jerky and unsteady, and the engine will be liable to breakage.
A suction air chamber (made of a short nipple, a tee, a piece of pipe of a diameter not less than the suction pipe and from two to three feet long, and a cap, screwed upright into the suction pipe close to the pump) is always useful; and where the suction pipe is long, in high lifts, or when the pump is running at high speed, it is a positive necessity.
Never take a pump apart before using it. If at any time subsequently the pump should act badly, always examine the pump end first. And if there is any obstruction in the valve, remove it. See that the pump is well packed, and that there are no cracks in pipes or pump, nor any air-leaks.
In selecting a pump for boiler feeding it is well to have it plenty large enough, and also these other desirable features: few parts, have no dead points or center, be quiet in operation, economical of steam and repairs, and positive under any pressure.
Granted motion to the piston or plunger, a pump fails because it leaks. There can be no other reason, and the leak should be found and repaired. Leaky valves are common and should be ground. Leaky pistons are not so common, but sometimes occur. Repairing is the remedy. Leaky plungers are common. They need re-turning. The rod must be straight as far as in contact with the packing. The packing around the plungers is sometimes neglected too long, gets filled with dirt and sediment, and hardens and scores an otherwise perfect rod, and so leaks.
The lifting capacity of a pump depends upon proper proportion of clearance in the cylinder and valve chamber, to displacement of the piston and plunger.
An injector is a sample of ajet pump—this may either lift or force or both.
The most necessary condition to the satisfactory working of the steam pump is a full and steady supply of water. The pipe connections should in no case be smaller than the openings in the pump. The suction lift and delivery pipes should be as straight and smooth on the inside as possible.
When the lift is high, or the suction long, a foot valve should be placed on the end of the suction pipe, and the area of the foot valve should exceed the area of the pipe.
The area of the steam and exhaust pipes should in all cases be fully as large as the nipples in the pump to which they are attached.
The distance that a pump will lift or draw water, as it is termed, is about 33 feet, because water of one inch area 33 feet weighs 14.7 pounds; but pumps must be in good order to lift 33 feet, and all pipes must be air-tight. Pumps will give better satisfaction lifting from 22 to 25 feet.
In cold weather open all the cocks and drain plugs to prevent freezing when the pump is not in use.
When purchasing a steam pump to supply a steam boiler, one should be selected capable of delivering one cubic foot of water per horse-power per hour.
No pump, however good, will lift hot water, because as soon as the air is expelled from the barrel of the pump the vapor occupies the space, destroys the vacuum, and interferes with the supply of water. As a result of all this the pump knocks. When it becomes necessary to pump hot water, the pump should be placed below the supply, so that the water may flow into the valve chamber.
The air vessel on the delivery pipe of the steam pump should never be less than five times the area of the water cylinder.
There are many things to be considered in locating steam pumps, such as the source from which water is obtained, the point of delivery, and the quantity required in a given time; whether the water is to be lifted or flows to the pump; whether it is to be forced directly into the boiler, or raised into a tank 25, 50 or 100 feet above the pump.
The suction chamber is used to prevent pounding when the pump reverses and to enable the pump barrel to fill when the speed is high.
Suction is the unbalanced pressure of the air which is at sea level 147⁄10per inch, or 2096.8 per square foot.
When a valve is spoken of in connection with a pump it may be understood that there may be several valves dividing and performing the functions of one.
A simple method of obtaining tight pump-valves consists simply in grooving the valve-sheets and inserting a rubber cord in the grooves. As the valves seat themselves the cord is compressed and forms a tight joint. An additional advantage is that it prevents the shock ordinarily produced by rapid closing and prolongs the life of the valve seat. The rubber cord when worn can be easily and quickly replaced.
To find the pressure in pounds per square inchof a column of water, multiply the height of the column in feet by .434, Approximately, we say that every foot elevation is equal to1⁄2lb. pressure per square inch; this allows for ordinary friction.
To find the diameter of a pump cylinderto move a given quantity of water per minute (100 feet of piston being the standard of speed), divide the number of gallons by 4, then extract the square root, and the product will be the diameter in inches of the pump cylinder.
To find quantity of waterelevated in one minute running at 100 feet of piston speed per minute. Square the diameter of the water cylinder in inches and multiply by 4. Example: capacity of a 5 inch cylinder is desired. The square of the diameter (5 inches) is 25, which, multiplied by 4, gives 100, the number of gallons per minute (approximately).
To find the horse powernecessary to elevate water to a given height, multiply the weight of the water elevated per minute in lbs. by the height in feet, and divide the product by 33,000 (an allowance should be added for water friction, and a further allowance for loss in steam cylinder, say from 20 to 30 per cent.).
The area of the steam piston, multiplied by the steam pressure, gives the total amount of pressure that can be exerted.The area of the water piston, multiplied by the pressure of water per square inch, gives the resistance.A marginmust be made between thepowerand theresistancetomovethe piston at the required speed—say from 20 to 40 per cent., according to speed and other conditions.
To find the capacity of a cylinderin gallons. Multiplying the area in inches by the length of stroke in inches will give the total number of cubic inches; divide this amount by 231 (which is the cubical contents of a U. S. gallon in inches), and product is the capacity in gallons.
The temperature 62° F. is the temperature of water used in calculating the specific gravity of bodies, with respect to the gravity or density of water as a basis, or as unity.