Pumps and Pumping Machin Ery

The term °duty') represents the work done by a steam pumping engine expressed in mil lions of pounds of water lifted to the height of one foot by the consumption of 100 pounds of coal, 1,000 pounds of dry steam, or by posing its advance with the full pressure of the accumulator load. As the plunger-rod ad vances outward, the angle between itself and the ram is increased gradually to 90 degrees. The rams recede into their cylinders, and their pressure against the rod is decreased until the pump plunger-rod has reached the halfway point of its stroke, when the rams will be at right angles to it —a position in which they neither retard nor advance its movement. As the pump plunger-rod continues on its outward stroke, the angle between itself and the rams is again decreased, but now the rams, pointing in the opposite direction, emerge from their cylinders, and exert their power to push the plunger onward to the termination of its out ward stroke. It is obvious that similar con ditions obtain during the return stroke of the plunger, the effect of the action being to store up power during the early part of the stroke, either forward or backward, when the steam is under its greatest pressure, and to release it at the end of the stroke, when the pressure in the steam cylinder has fallen away to its lowest point, that is, below the amount neces sary to move the plunger against the pressure of the water column.

The Worthington pumps with this attach ment and the use of multiple expansion steam engines operate with absolute freedom from the noise and shock so characteristic of the crank and fly-wheel machines.

1,000,000 British thermal units (B. T. U.). On account of the variable quality of coal, the two last-named constants give the more correct re sults, and are the values now employed in de termining the comparative efficiencies of pump ing engines, which range from 20.6 per cent for the high-duty engines, to about 0.13 per cent for Jet pumps. During the last 100 years, the development of pumping engines has increased their duty from about 5,000,000 foot-pounds for the Newcomen atmospheric engines, to over 170,000,000 foot-pounds for the crank and fly-wheel, or duplex triple expansion pump mg engines of the latest construction.

Somewhat of an idea of the difference be tween the first duplex Worthington pumping engines and those of their latest construction may be obtained by comparing that of the Charlestown, Mass., waterworks, with its ca pacity of 5,000,000 gallons per day, with the installation at the Baltimore, Md., waterworks high service pumping station, which delivers 18,000,000 gallons per day. The former gave a duty of 70,000,000 foot-pounds, while the duty of the latter exceeded 140,000,000 foot-pounds per 1,000 pounds of dry steam.

Hydraulic pressure pumps are designed as a rule for driving water into an accumulator, whence it may be drawn for power service in mains, or for use in hydraulic presses (q.v.), hydraulic cranes (q.v.), and similar machines.

The pumps which do this exceptionally heavy work are of the plunger type of direct-acting pumps, the plungers being very small — about one and one-quarter inches in diameter and of six-inch stroke, while the steam cylinders are of the usual size. The high and low pressure cylinders are commonly placed side by side and work upon a crank-shaft which carries a heavy fly-wheel. These pumps work up to 4,000 or 5,000 pounds per square inch.

In all reciprocating pumps, valves play an essential part. In the simplest forms the valves are made of leather or rubber, and are fixed in position by a hinge on the edge, gen erally, for the larger sizes, having a metal form which prevents too great relaxing. They are made in a great variety of forms and operate in response to certain pressure, or, as in the case of the Reidler valve, by mechanical means. They consist essentially of a °valve seat?' to which the or valve proper is attached, the which controls the lift of the disc and prevents its displacement from the seat, the "cover plate," and the "valve spring," intro duced in some forms to take up slacks. When a valve is required only to prevent the back pressure or a reverse flow, a single flap or check valve is used. In large pumps a number of small valves are employed, equal in aggre gate area to a single large valve of sufficient size to allow the passage of the whole flow, thus preventing injurious shocks when the valves are opened and closed suddenly, as all of the smaller valves do not close simultaneously hut each as its critical pressure supervenes. Excepting the discs, all the other parts of a valve arc made of bronze, while metallic ball and cone valves are extensively used in deep well pumps. A detailed description of the more commonly used valves will be found in the special article under the title VALVE.

History.— The raising of water for eco nomical purposes dates hack to the remotest periods. It is not easy to determine just when mechanical appliances worthy to he classed as pumps first made their appearance, and it has been the custom of some writers to dignify the common water-pail by the name of pump if only it were lifted by mechanical means — as, for example, with the old-time well-sweep. In this connection mention has been made of the of Egypt, authentically recorded as having been in use over 1,500 years B.c., in the time of the Pharaohs, a period antedating the Exodus. It is still used extensively in that region, myriads of them lining the banks of the Nile, where they are worked unceasingly by relays of men, without intermission, day and night. It is also used extensively all over

Hindustan, where it is called the "picotah." In fact, the in some form is used exten sively in all of the Oriental countries from Asia Minor to China and Japan and also in Mexico and South America, for domestic pur poses and for the irrigation of land. For the latter purpose, however, it was superseded in India by the ') arrangements operated by cranks or by tread-wheels, the latter worked by men .or animals, appear to have followed the /sweep, first among the Chinese, and later among the earliest Greeks and Romans. About the beginning of the Christian Era, Vitruvima, a Roman engineer, described a number of pumping machines involving a rotary principle — the of buckets or pots,') the "screw)" and the "pump?. The tympanum consisted of a series of gutters with their open ends joined to a shaft hollow at one end and placed above the surface of the water at the height to which the water was to be ele vated. The gutters thus arranged radially ex tended to a short distance below the surface of the water which they scooped up successively when the shaft was rotated. Each gutter as it passed above the horizontal position delivered its water to the shaft to be subsequently dis charged through a trough at the desired point. This primitive device continued in use from the remote ages of antiquity up to the 18th cen tury without any change of construction; when La Faye, a member of the Royal Academy of Sciences of France, improved it by substituting a series of curved canals for the original straight gutters, thus developing the progenitor of the "scoop wheel," which, propelled by streams, are extensively used for draining pur poses. La Faye's improvement and the geo metrical reasoning which developed it are ex haustively described by Belidor (Tom. ii, 385, 387). While the tympanum consisted of a series of revolving gutters, the noria may be described as a number of "sweeps" arranged around a central shaft like the spokes of a wheel, each carrying on its outer end a vessel which fills as the rotary motion of the shaft plunges it beneath the surface of the water, and subsequently discharges its liquid freight into a reservoir placed at the upper part of the circle. It is commonly known as the Persian wheel. The "chain of buckets or pots" was an elaboration of the simple bucket and cord arrangement, by the introduction of a pulley operating an endless rope or chain, to which several buckets or pots were attached. It was employed by all the foremost nations of an tiquity, and is yet used in many parts of Eu rope and Asia. Among half-civilized nations it was the highest type of hydraulic machines. Sometimes, when the source of supply was a river, as in the case of the Persian wheels on the Orontes, the driving wheels of the arrange ment were placed in the river and propelled by its current. About the middle of the 17th cen tury, European mechanics recognized that when the water was admitted into the receiving ves sels of a noria or a chain of pots at the upper part of the circumference, it was converted into an overshot wheel, thus affording a means of power transmission to other machines, and in cases where the water supply was limited, but descended from a considerable elevation, it was substituted for the overshot wheel as a prime mover in operating mining pumps, dredg ing, threshing and other machines of a similar character; while as a conveyor, originally used i exclusively as a water elevator, it has also been employed to raise mortar in the construction of buildings, city walls and fortifications, and for carrying grain and flour to the different floors of a mill. In its original form, that of the "salciali of Egypt, it was unquestionably the pump introduced into Greece by Danaus when he dug the wells of Argos, 1485 B.C., about a thousand years before the building of Baby lon by the Persians. Danaus was a brother of the Pharaoh Rameses, who resigned during the period the Israelites were in ypt. He was compelled to leave that country on account of domestic troubles, and accompanied by his fam ily and friends sailed for Greece. They landed on the coast of Peloponessus,.. and settled at Argos. According to Pliny (vii, 56), previous to the arrival of these Egyptians, the Greeks were unacquainted with wells and pumps; there fore, it is natural to conclude that the wells of Argos dug by Danaus were equipped with the Egyptian pumping devices most adaptable to wells, which was the chain of pots, and not a form of atmospheric or force pump, the pioneer of which is described in Hero's as invented by Ctesibius of Alexandria, one of the most eminent mathematicians and mechani cians of that period, In the year 224 B.c. The most modern refinement of the chain of pots is the *chain pump,* while Vera's *rope pump* and the hydraulic belt are applications of the same idea, and consist of endless double bands of rope or woolen cloth passing over two roll ers, one placed below the surface of the water, the other at thepoiro of delivery. The rollers are driven at a velocity ranging from one to two thousand feet per minute, and as the bands pass over the upper roller, die water held be tween them by capillarity is forced out pressure and discharged into a receiving ber connected with the delivery spout.