4 (N. IN') shows a direct-acting steam-pump for pumping crude oil through pipe-lines. In this, as the pump-cylinder and its valve-chests are cast in one piece, there are no joints to leak. There is a removable which can be turned around when one side gets worn by sand or grit. The valve-motion is positive; a horizontal pivoted cam-lever or " rocker-bar," actuated by a projection with a fric tion-roller on the piston-rod, twists the stein of the chest-piston, which is of the rocking type, and this action uncovers ports by which the main slide-valve is thrown by steam.
exhibits a corn pound condensing pumping-engine, with an attachment which enables it to work at slow speed with as great regularity as though there were a fly-wheel. This attachment consists of two diagonally-placed "compensating" cylin ders swinging on trunnions at the end of the pumping-cylinder, each of these auxiliary compensating cylinders having a piston actuated by the reciprocation of a back-rod from the pump-piston, the back-rod having a cross-head moving in guides. The swinging cylinders are filled with the same liquid as that being pumped, and are kept under internal pressure by being connected through their trunnions with an "accumulator" whose rain moves up and down as the plungers of the compensating cylinders move in and out. The accumulator is "differential "—that is, it has below a small cylinder filled with oil or water in which its ram moves, while above it has a mucli larger cylinder filled with air. On the top of the ram of the accumulator is an enlarged piston-head which fits closely in the air-cylin der, so that the pressure per square inch on the accumulator ram is the pressure of the air in the air-cylinder per square inch, multiplied by the difference between the area of the air-piston and the accumulator rain. The pressure in the air-cylinder is controlled by that in the main delivery pipe of the pump.
As the pump begins its outward stroke the compensating cylinders are turned to point toward the outer end of the pump, with their plungers at the extreme point of their outward stroke and at an acute angle with the pinup-plunger rod, and with the full pressure of the accumulator load push ing them against the advance of the pump-plunger. As the pump-plunger begins its outward stroke each forward movement it makes changes the angle of the two compensating plungers, until at one-half stroke the latter will stand exactly opposite each other and at right angles with the pump-plunger, and then neither retard nor advance the plunger's movement. From this point on the compensating plungers point in the
direction of the pump-plunger's movement and help the latter along, so that steam cut-off may be effected at half stroke or any other point; and by proper arrangement of these parts the plunger movement may be as steady as though there was a fly-wheel.
GaskilI 4 (6/. 115) shows the high-duty pumping-engine at Saratoga Springs, New York. It is of the duplex horizontal crank-and-fly-wheel type, having compound condensing-engines with cylinders respectively 21 and 42 inches and pumping-cylinders 20 inches in diameter, the stroke being 36 inches. Its daily working duty for 1889 averaged m7,676,411 foot-pounds of work per hundred pounds of anthracite consumed in the boiler furnaces, and its capacity was 8,156,736 gallons of water in twenty-four hours. It can maintain a water-pressure of one hundred and forty pounds per square inch in the mains.
—A fire-engine is an apparatus for supplying water in great quantities for extinguishing fire. The name was originally applied to the steam-engine; the first " fire-engines " were steam-engines, and were employed in pumping water from mines. At present the name given means a pumping-engine, and, as the most important types of pumping-engines are operated by steam power, we have the term " fire engine " again meaning a steam-engine applied to pumping water.
Hand —The smaller fire-engines (pi. fig. r) consist of a tank or box on wheels or runners, bearing a pumping apparatus which draws its supply of water from the tank and forces it through hose attached to the pumps. The box may be filled by means of buckets, though sometimes the pumps draw their water through a suction inlet placed in communication with a hydrant supplying water under pressure, or with a cistern or other source. The pumps of "hand-engines," as these apparatuses are called, are worked by brakes attached to the piston-rods, each brake-rod being worked by as many men as can take hold.