Pump (mechanical)

“ The principal feature of this pump is its valve; there is but one valve for the suction and one for the discharge, which greatly simplifies the pump end. When working against high pressures, the ordinary rubber or leather faced valves are oftentimes pounded to pieces, but in this pump, on account of the mechanical control, the valves work well under all pressures. ”

“ Suction Pumps. A pump is a device for lifting water. The pumps in common use work on the principle that water which is under the pressure of air will rise to fill a vacuum or a partial vacuum. The pump is composed of a combination of valves and a piston for forcing the air out of the pipe to allow the water from below to be forced into it. A valve catches the water as it starts to flow back. ”

“ Careful experiments on a large number of pumps of various makes at full speed, show that in a new pump with clean valves, and an air-tight suction pipe, and less than 15 feet lift, the actual delivery is only from 11⁄2 to 5 per cent. less than plunger displacement. This slip will increase with wear, and for a good average pump in practical use, probably 10 per cent. is a fair allowance to cover slip, valve leakage, slight short-stroke, etc. ”

“ The inside of the upper part of the plunger is threaded to receive the lower part with a cup leather packing and contains a valve of metal having a conical seat. Fig. 156 shows a design of a pump in common use in the 14th century.
Note.—The action of a pump is as follows: The piston or plunger by moving to one end, or out of the pump cylinder, leaves the space it occupied, or passed through, to be filled by something. As there is little or no air therein a partial vacuum is formed unless the supply to the pump is of sufficient force to follow the piston or plunger of its own accord. ”

“ In order to insure smooth and quiet running of the pump, it is necessary to keep the speed of the piston inside of the velocity with which the cylinder would fill under this pressure, reduced by the friction of the water, the pressure required to lift the valves, etc.
But this supposes that there is a perfect vacuum in A, and we cannot realize this in contact with hot water. Water at any temperature will boil unless it is under a pressure equal to or greater than that corresponding with the temperature. ”

“ In the semi-rotary pump a lifting force is obtained by means of the see-saw motion of a plunger with two valves working alternately. Another type of high-speed pump consists of two small gear wheels in mesh with one another in an enclosed space, with just sufficient space for their free revolution. ”

“ The general form of the blades is of great importance in this type of pump, because the water is driven through the fan partly by the pressure of the blades on the water and partly by centrifugal force. The ratio which each of these forces bears to the other varies in the same pump, depending upon the proportion the speed bears to the height of it. ”

“ It is due very largely to the numerous designs of steam valves, that difficulty has been encountered in managing single-cylinder pumps as successfully as those of the duplex type, the similarity of construction in the latter type, even in minor details, being much more marked.
The successful operation of a pump depends to a great extent upon the intelligence displayed in its management, and an engineer can scarcely hope to obtain quiet and smooth running pumps and freedom from breakdowns and perplexing delays except by a thorough knowledge of the details of construction and operation. ”

“ A bucket air pump is one in which there is a valve or valves in the pump piston, hence the pump is single acting, drawing on the lower side of the piston and delivering on the upper, hence the capacity of the pump per engine revolution is equal to the diameter of the bucket multiplied by the length of its stroke. ”

“ A single acting pump does its work through one end of the cylinder or barrel of the pump.
In double acting pumps the motion of the piston in one direction causes an inflow of water, and a discharge at the same time, in the other; and on the return stroke this action is renewed as the discharge end alternately becomes the suction end; the pump is thus double acting. ”

“ This engraving is plain and requires no description. Fig. 170 shows a diaphragm pump in which a sheet of rubber or its equivalent is used as a substitute for a piston in a cylinder.
Fig. 170.
Note.—When an ox or a horse plunges his mouth into a stream, he dilates his chest and the atmosphere forces the liquid up into his stomach precisely as up the pipe of a pump. It is indeed in imitation of these natural pumps that water is raised in artificial ones. The thorax is the pump; the muscular energy of the animal, the power that works it ”

“ Owing to the very high speed at which these pumps are liable to be run during a fire, all the working parts are made excessively strong, and the valve area and water passages are larger than usual. The interior of each Underwriter pump is treated with a rust-proof coating, and every precaution taken so that the pump will start instantly after an indefinite period of disuse. ”

“ European centrifugal pumps with their small impellers and consequent high speed of rotation, are especially liable to this repelling action, and very often are wholly inefficient from this cause. One maker who claims a high duty for his pumps, attaches a screw at the sides of the impeller to coax the water into the pump, and the idea is a good one if the difficulty is not otherwise provided for. In this way a pump can be made of smaller diameter for a given duty, but it is commonly inferior to a larger one for the same work.”—Industries. ”

“ The high-class turbine pumps of to-day are simply machines in which the water is given a velocity which is partially changed to pressure before discharge, and the pump is designed so that the well-known actions, outlined above, proceed along natural lines, which are, to use the common phrase, lines of least resistance. It is simply a question of careful design.
The modern pump causes the water to flow along paths naturally due to the forces acting and to guide the stream in such a way as to avoid the production of eddies and whirls within itself which so enormously cut down the efficiency. ”

“ As a sinking or station pump for mine service, the turbine pump is ideal. There are no valves, guards or springs, no reciprocating parts, and, most important of all, there is no contact surface in the machine except the shaft and its bearings. ”

“ After the pump is in condition (6) , motion of the plunger is followed by a more or less regular discharge of water through the spout, and the quantity of water which gushes [192] forth depends upon the speed with which the piston is moved. A strong man giving quick strokes can produce a large flow; a child, on the other hand, is able to produce only a thin stream. Whoever pumps must exert sufficient force to lift the water from the surface of the well to the spout exit. For this reason the pump has received the name of lifting pump. ”

“ A pump that not only pumps up an automobile tire within a few minutes, but that keeps the tire at that pressure, regardless of large punctures, is a new invention. The pump can be attached to the hub of the wheel in less than a minute. It works on the rotary-pump principle, each revolution of the wheel, while running the car, driving air into the tire. ”

“ If the pump is to work under this condition, it is better to use a pump with a vertical discharge and deliver through an elbow, or else lead the discharge pipe upward for a short distance so as to keep a slight pressure, or head on the pump, and after priming as high as possible start quickly.
Generally nothing is gained by running a pump above the proper speed required for a given elevation. ”

“ If you do understand the old town pump, I will not have much trouble with you, for while there is no old style wooden pump used on the engine, the same principles are used in the cross head pump. Do not imagine that a cross head pump means something to be dreaded. It is only a simple lift and force pump, driven from the cross head. ”

“ The volume of water which is used intermittently for the purpose of operating presses—draw-benches for brass and copper tubing and the like is replaced by a pump or pumps which are started and stopped automatically by a connection between the accumulator and the throttle or belt shifter of the pump. The accumulator is used for a double purpose of maintaining a constant pressure and to store up any surplus force of the pumps. The friction loss in the transmission of power by water through mains is very small, as for example: It has been found that water under a pressure of 700 lbs. ”

“ Where power can be had from a shaft in motion there is no pump so economical as the power or belt driven pump. This fact is shown by the rapid increase in the number of applications of this type of pump: the reduced cost of manufacture in making the teeth of the gear wheels, the use of automatic machinery, the production of interchangeable parts have tended to produce a high grade of machine at an attractive price. ”

“ The pump must be warranted so designed and with such arrangement of thickness of metal that it shall be safe to instantly turn a full head of steam on to a cold pump without cracking or breaking the same by unequal expansion. ”

“ One feature or fact in centrifugal pumping that is overlooked or not known to many makers, is that water will not enter a pump when the impeller vanes sweep over the inlet way and are driven at high speed. To illustrate this, one can not thrust a cane or lath through the spokes of a rapidly revolving wheel. ”

“ With the exception of the entrance opening, the external surface of the impeller is exposed to the delivery pressure, so that there is a resultant upward pressure on each impeller, equal to the area of its entrance multiplied by the difference between the entrance and discharge pressures of that stage. If all the impellers are alike, the total upward thrust is equal to the product of entrance area multiplied by the total head on the pump. The pumps are so proportioned that this upward thrust slightly exceeds the weight of the rotating portion, consisting of impellers and shaft. ”

“ The rotary pump is used also in places where a piston or steam pump would be objectionable either on account of floor space occupied or for the reason that steam could not be had without too much expense for lifting and forcing water and other liquids which would not nor could not find their way through the tortuous and narrow passages of the average piston and plunger pumps. ”

“ A vacuum pump is an apparatus consisting of, 1, a chamber or barrel; 2, a suction pipe with a valve to prevent return flow; 3, a discharge pipe which has a valve which is closed when the chamber is emptied and, 4, a steam induction pipe provided with a valve that is opened when the chamber is filled with water and closed when the chamber is filled with steam.
It is not right to call an air pump a vacuum pump, as the latter does not move air alone; it removes water, vapor and air from the condenser to form a vacuum. An air pump is designed to pump air alone. ”

“ Although this pump from Colonel Thacher was probably around fifty years old, it proved to be a most reliable and excellent piece of apparatus, consisting of a large, horizontal, single cylinder, “make and break” engine, driving a heavy, eighteen-inch rubber diaphragm pump. It certainly puts to shame some of the modern pump equipment of today, chugging along hour after hour like a patient old horse without much noise and clatter. ”

“ As well known, in every well-constructed injection pump, there is a system of gearing which acts upon the suction valve and stops the operation of the pump as soon as the requisite pressure is reached; but the piston, for all that, continues its motion, and, besides the resistant work of the pump has passed through different degrees of intensity, seeing that at every moment of its operation the piston has preserved the same stroke and velocity. We are speaking, be it understood, of pumps that are controlled mechanically. ”

“ The automatic action of the pump and its speed are controlled by a float in the receiver operating directly, without the use of intervening levers, cranks and stuffing boxes, to open or close a governor valve in the steam supply pipe to the pump, thus making the action of the pump conditional upon the rise and fall of the float in the receiver. ”

“ 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 main feed pump is, even in the independent type, often placed in the engine room, while the auxiliary pump, or the injector, is in the fire room. The feed pumps draw usually from the hot well, feed heater and feed tanks and discharge through main feed pipe into the boiler.
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This “doctor” pump is a substantial piece of mechanism. The bases of columns and pump chamber flanges are accurately planed, the cylinder has spring piston packing and the plain slide valve is made of gun metal. ”