Air pump

“ This apparatus consists of a jet condenser with air pump, boiler feed pump, and engine to drive both, combined as one machine. The air pump is a single acting bucket plunger pump, driven by a crank shaft, turned by the engine, which is a single cylinder compound automatic cut-off engine, and also drives the boiler feed pump ”

“ Air under pressure increases in density and heat, and exerts an increased power in every direction. Hence compressed air is applied in locomotives; and its power is employed in many machine-plants, such as those of mines and water-works. An air-compressor or air-pump is a cylinder fitted with a piston and rod, and with valves at which the free air may enter and with others at which the compressed air may be applied, together with the needful connections of this apparatus with the driving power. ”

“ The air pump overflow valve should never be permanently fastened down. More engines have been broken down from this than from almost any other neglectful cause, because, from great leaks in the condenser tubes and engines standing for a length of time, a larger quantity of water may require to be got rid of during the first few strokes of the pump than can pass through the small air or vapor pipe, which is usually fitted from the hot well either into the bilge or else overboard. ”

“ The pump shown has a stroke of 14 ins., with an air-cylinder diameter of 28 ins. The machine is a dry air pump, and is fitted with Corliss inlet valves and special leather exhaust valves: it is fitted with ring-oiling bearings and automatic continuous lubrication, and under test it shows a mechanical efficiency of 78 per cent. from power input to air horse-power delivered. Such a pump is suitable for a plant handling 20 to 25 tons per hour and, if preferred, the pump may be driven through gearing from an electric motor on the same bed-plate. ”

“ PUMP, [1] a machine which drives a liquid from one point to another, generally at different levels, the latter being usually the higher; an air-pump is an appliance for exhausting or removing the air or other gas from a vessel, whilst a compression pump compresses the air. The simplest forms of pumps employed for forcing liquids are “plunger pumps,” consisting essentially of a piston moving in a cylinder, provided with inlet and outlet pipes, together with certain valves. The disposition of these valves divides this type of pump into suction pumps and force pumps. ”

“ By his experiments and invention, the air-pump was first brought into so useful a form that he may be called its discoverer, though the genius of others has since greatly improved that important instrument. He also demonstrated the necessity of the presence of air for the support of animal life and of combustion; showing not only that a flame is instantly extinguished beneath an exhausted receiver, but that even a fish could not live under it, though immersed in water. ”

“ A trunk air pump is necessary when the pump rod is driven direct from the crank shaft, and therefore has sufficient lateral motion to push the pump piston sideways, which would cause friction and excessive wear to the gland that keeps the trunk tight. The delivery capacity of the pump is obviously diminished to an amount equal to the displacement of that part of the plunger that passes through the gland and within the pump bore, whereas in a piston pump the delivery capacity is only diminished to an amount corresponding to the displacement of the pump piston rod. ”

“ One of the best-known makes is the Edwards air-pump. Piston air-pumps are driven either by the main engine through a suitable mechanism, or by a separate electric motor. The amount of power required to drive them varies with the size of the set, and with large engines of over 10,000 h.p. ”

“ Air-lift Pumping. The air-lift pump is a common means of conveying by pneumatic means [Pg 96] and should not be confused with the above methods of raising water by compressed air.
In the air-lift method of pumping air under pressure is admitted at the foot of a pipe already submerged in the well. The air does not merely bubble through the water, as might be supposed, but passes up the pipe as a mixture of air and water. ”

“ Sometimes instead of the foot valve a delivery valve is used, an air-pump or steam jet pump being employed to exhaust the air from the pump case.
§ 208. Design and Proportions of a Centrifugal Pump.—The design of the pump disk is very simple. Let ri, ro be the radii of the inlet and outlet surfaces of the pump disk, di, do the clear axial width at those radii. The velocity of flow through the pump may be taken 108 the same as for a turbine. ”

“ The air-lift is also very advantageous for pumping water which contains a large amount of sand or similar gritty material which would cut and score the walls of an ordinary piston pump. Air-lift pumping is frequently used, therefore, on new bore-holes until the sand, etc., has been eliminated, after which the final pump can be installed without fear of damage. ”

“ As the pressure cannot exist until the engine is running, a hand air pump is usually provided, by which a sufficient pressure may be produced in the tank to force out enough gasoline for starting. It is necessary to use as long a pressure pipe as possible, in order to prevent the possibility of flame passing through it to the supply of fuel, a long pipe, exposed to the air, cooling the gases to such an extent that they cannot ignite the gasoline. ”

“ Thus, in the case of the delivery air chamber, when the pump piston is travelling at a speed above its average for the stroke, the water accumulates in the air chamber, and the air is more compressed, while, when the pump is on the dead centre, or at the end of its stroke and the delivery valve closes, the air compressed in the air chamber continues the delivery or discharge, thus maintaining a more uniform flow. ”

“ The most severe trial to ascertain the air tightness of any system of pipes is, the trial by exhaustion, by means of an air pump, for the guage of the pump will discover the minutest leak, which the preceding method of proving pipes can not discover. ”

“ With the rotary pump there are no discharge valves to hold the atmospheric pressure from the discharge side of the impeller and the compression of the rarified air is accomplished by the atmospheric pressure admitting air through the eduction port into the chamber. ”

“ Air-Cushions.—To prevent water-hammer on the pumping main, all pumps are provided with large air-chambers. In addition, and as the special feature for absorbing the shock of pumping under high pressure through a pipe 21 miles long, a large air-chamber in the form of a closed steel cylinder, 5 ft. in diameter and 15 ft. long, is mounted on the pumping main outside of the pump-house. This cylinder is set on its side, in concrete collars, directly over the pipe beneath, to which it is connected by a 12-in. ”

“ Now, if the piston, instead of being loaded by weights, be connected to the piston rod of a steam engine, or by means of a connecting rod to a crank (which is rotated by a belt or some other driving mechanism, and the valves be operated automatically, as the valves on a water pump) , the simple apparatus is converted into a perfect air compressor, which really is nothing else than an air pump, and the air can be pumped into the receiver against a high pressure the same as water is forced into an elevated reservoir by a pump. ”

“ Most of you, no doubt, know that the plunger in a pump is made air-tight by one or a set of leather washers, which, owing to their pliable structure, can expand or contract so as to always fit air-tightly the pipe in the pump. ”

“ A pump or exhauster to create a partial vacuum in the pipe line and so induce a high velocity air current in which the material will be conveyed. (2) An air filter in which any light dust carried over beyond the receiver is trapped, to prevent its entering the exhauster where it would quickly damage the piston rings and cylinder walls of reciprocating pumps. (3) A main receiver or discharger, and occasionally one or more subsidiary receivers, in which the conveyed material is extracted from the system and discharged into the receptacle or on to a dump as required. ”

“ An air-pump consists of numerous moving parts, which should operate with the least possible amount of friction: consequently, it is important that the machine should be properly lubricated,—not deluged with grease for ten minutes, and then run on the interest of the excess for two hours, but sparingly furnished with clean oil, which will keep the moving parts moist all the time. ”

“ The use of compressed air has become very general through the use of small hand pumps; the cylinder of these must be smooth, and the plunger is usually packed with a cup leather packing.
Fig. 340.—Gas Fitter’s Proving Pump.
Fig. 340 shows a gas fitter’s air proving pump. The gauge is attached to any opening into the system of pipes to be tested, with a rubber hose leading to the pump. By working the pump the air is forced into the pipes; upon stopping the pump if the hand upon the gauge remains stationary there are no leaks in the system. ”

“ Meanwhile the various parts of the pump can be heated with a moving Bunsen burner to detach air and moisture, the cement being protected by wet lamp-wicking. In one experiment I measured the amount of air that was detached from the walls of the pump by heating them for ten minutes somewhat above l00° C., and found that it was 1/1,000,000 of the air originally present. I have also noticed that a still larger amount of air is detached by electric discharges. ”

“ When it becomes necessary to pump water, there are numerous machines from which to choose; only the more important ones will be considered. We may use pumps operated by manual labor, those run by ani [Pg 40] mal power, pumping machinery using the power of the wind or that of falling or running water; then there are hot-air, steam, and electric pumps, besides several forms of internal-combustion engines, such as gas, gasoline, and oil engines. Each has advantages in certain locations and under certain conditions. ”

“ The exhaust valve now opens and the piston starts to return. The low pressure steam instead of passing direct to the atmosphere, as is the case of a high pressure engine, flows into a chamber “C,” and is brought in contact with a spray of cold water. The heat being absorbed by the water, the steam is condensed and reduced in volume, thus forming a vacuum. It is, however, necessary to remove the water formed by the condensed steam together with the water admitted to condense the steam, also a small amount of air and vapor. For this purpose, a pump is required, which is called the air pump. ”

“ In using a fuel engine it is desirable, because of the attendance required, to take a machine of such capacity and size that the water supply required for two or three days may be pumped to the storage tank in a few hours.
Expansive Force of Heated Air Utilized
A favorite and extensively used type of domestic pump is the hot-air engine, in which the expansive force of heated air is used to do useful work. Among the types are simple and safe machines which do not easily get out of order. They are started by hand by giving the fly wheel one or more revolutions. ”

“ The suction nozzle through which the material enters the system, together with the “free air” which is to act as the conveying medium.
Pumps and Exhausters. The type of apparatus used for creating the flow of air varies according to the ideas of the numerous makers of the plants. It must be remembered that for a pump working under the conditions required for pneumatic plants it is not a high vacuum that is required; the most [Pg 11] important function is to handle very large quantities of air at a comparatively low vacuum. ”

“ It is clear then, that however high the pump may be above the level of the water, the water cannot rise more than 34 feet up the suction pipe, even though all the air be excluded from it and a perfect vacuum formed, because the propelling force, that is, the atmospheric pressure, can only raise a column of water equal in weight to itself, and it is found in practice to be an unusually good pump that will lift water thirty feet. ”

“ SUCTION OF VACUUM PUMP AND BLOWER.--John Doyle and Timothy A. Martin, New York City.--This invention consists in arranging valves and air passages with a hollow cylinder or drum having an oscillating movement, and provided with a chamber or chambers to receive water, mercury or other fluid, whereby an exceedingly simple and compact pump or blower is obtained, one not liable to get out of repair or become deranged by use. ”

“ To this, however, may be added, at little cost, an opening for admitting, and channels behind the skirting for distributing, the fresh air; and to make the thing really complete, there must be also the means, by a stove or by hot water pipes, of warming the air before its distribution; and there must be the ventilating pump to inject and measure air when such action may be required. During the winter, in many cases the chimney draught would be sufficient to produce the desired currents of air without the pump. ”

“ Iron ignition tubes may be used, and one heating lamp serves a double purpose in keeping the tube and vapouriser hot at the same time. This lamp is fed by means of a pump actuated from the side shaft. The plunger of the pump is loaded with a spiral spring, which may be adjusted to give any desired pressure, and is kept constant and steady by means of an air vessel. This pump is shown in fig. 48. It is actuated by means of a rod and lever from the side shaft of engine. ”