Hydraulic head

“ It becomes, therefore, necessary to balance in some way the varying displacement of the ram if economy is to be secured in the working: this is often done by the use of counter-weights attached to chains travelling over head sheaves, but this largely destroys the simplicity and safety of the direct-acting lift, and hence some form of hydraulic balancing is more satisfactory and more certain. ”

“ Water for sluicing operations is frequently brought from great distances through canals, ditches, or flumes, the proprietors of which sell the water to miners at so much the miners' inch, a miners' inch being in most localities the quantity flowing in a given time through an aperture one inch square under a head of six inches.—The celebrated hydraulic process, invented in Placer co., Cal., in 1852, consists in washing down the whole surface and underlying mass of auriferous deposits, preparatory to sluicing. ”

“ Where no other circumstance limits the loss of head to be assigned to a given length of main, a consideration of the safety of the main from fracture by hydraulic shock leads to a limitation of the velocity of flow. Generally the velocity in water mains lies between 11⁄2 and 41⁄2 ft. per second. Occasionally the velocity in pipes reaches 10 ft. per second, and in hydraulic machinery working under enormous pressures even 20 ft. ”

“ As soon as the reeking engine-funnel of an up-train is seen darting out of the tunnel at Primrose Hill, one of the Company’s servants stationed there, who deals solely in compressed air—or rather, who has an hydraulic machine for condensing it—allows a portion to rush through an inch iron pipe ”

“ In this case the head driving the hydraulic machinery is artificially created, and it is the convenience of distributing power in an easily applied form to distant points which makes the system advantageous. ”

“ A suction valve is contained within the plunger. A short arm is fitted upon a socket which enters through the side of the head or reservoir. This arm is connected by a pin to the pump inside the ram while the outer end of the socket has a tapered rectangular hole through it to receive the jack-lever. A leather collar packing makes the socket tight where it enters the side of the reservoir.
To properly use a hydraulic jack. Place the head under the weight to be raised, be careful to set the jack plumb with a good solid footing ”

“ The elevating-gear is also different, in having an arrangement for altering the height of the stationary ratchet to correspond with the different levels of the trunnions. The slide is provided with hydraulic recoil cylinders, which also act as the running in and out power. The piston-head has no holes bored in it, but when the gun recoils the oil [Pg 205] is driven out of the cylinder, the flow being regulated by a balanced valve. The pump to move the hydraulic is worked by steam, the direction of the movement being controlled by a lever in the turret. ”

“ A large finishing store, in which were working by steam fifteen turning-lathes, five slotting-machines, five planing ditto, one screwing ditto, two drilling ditto, two shaving ditto. Beneath the above we entered another workshop containing sixteen turning-lathes, two drilling-machines, one slotting ditto, one screwing ditto, one nut ditto, one cylinder-boring ditto, one shaping ditto. In the great store-yard there is an hydraulic press of a power of 200 tons for squeezing wheels on to their axles, or wrenching them off. ”

“ In these cases, an artificial source of water power is created by using a steam engine to pump water to a reservoir at a great elevation, or to pump water into a closed reservoir in which there is great pressure.
Water flowing from the reservoir through hydraulic engines gives back the energy expended, less so much as has been wasted in friction. Where a continuously acting steam engine stores up energy by pumping the water, while the work done by the hydraulic engines is done intermittently,—this arrangement is considered the most useful. ”

“ Water-pressure has sometimes been applied to operate machines which are worked continuously and not intermittently, and to continuous working rotary machines. This is unwise, for in applying hydraulic power to the continuous working of shafting or shop tools, the amount of power developed by the hydraulic engine cannot be varied to suit the work to be done, neither can the speed be regulated with sufficient nicety. ”

“ Water under pressure conveyed in pipes is a convenient and economical means of transmitting energy and distributing it to many scattered working points. Hence large and important hydraulic systems are adopted in which at a central station water is pumped at high pressure into distributing mains, which convey it to various points where it actuates hydraulic motors operating cranes, lifts, dock gates, and in some cases riveting and shearing machines. ”

“ Answer.—There are several terms common to hydraulics and steam; the steam boiler might be called an accumulator of power; there is a slide-valve in hydraulics as in the steam engine, to admit the power and to allow the exhaust to escape; there are stop-valves and intermediate valves in hydraulics, as in steam pipes, also air-vessels in each: there are suction and delivery pipes and valves in each, and relieve valves also in each; there is a cylinder in each in which the power is concentrated; there are reversing levers in a hydraulic crane, as in a steam crane. ”

“ Consequently, when the piston ascends, it no longer forces the water into M, the air of the reservoir, by the pressure it has received, reacts on the liquid, and raises it in the tube D, until the piston again descends, so that the jet is continuous.
Hydraulic Machine Tools. Probably in no department of engineering has the use of hydraulic power met with more success than in its application to certain machine tools. ”

“ In steam engines a piston is alternately pushed forward and back in its cylinder by steam; and by means of the rod to151 which the piston is secured, motion is communicated to a crank and fly-wheel, and through these to the machinery to be driven: it is the same with pressure engines when used to move other machines, except that instead of the elastic vapor of water, a column of that liquid drives the pistons to and fro.
Note.—“The hydraulic engine of Huelgoat, in Brittany, is used to drain a mine; is single-acting, and acts directly to lift the piston of the pump. ”

“ The engineer sets the pump in action, the water is rapidly forced into the cylinder, the piston is thrust inwards, and the strain upon the chain begins; the engineer then cuts off 330the water supply from the larger force-pumps, and the smaller pair go on until the strain becomes sufficient to raise the weight, and then the person in the weighing-room, by pulling a wire, opens a valve in connection with the hydraulic cylinder, which allows the water to escape, and the strain is at once taken off. ”

“ The thick fluid of the consistency of treacle flowing from the grinding-mills is poured into round metal pots, the top and bottom of which are lined with pads of felt, and these are, when filled, put under a powerful hydraulic press, which extracts a large percentage of the natural oil or butter. ”

“ When water reached it, it forced the edges apart, one against the plunger, the other against the walls of the recess, with a degree of tightness proportionate to the pressure. On water being released from the cylinder the collar collapsed, allowing the plunger to sink without friction.
The principle of the hydraulic press is employed in lifts; in machines for bending, drilling, and riveting steel plates, or forcing wheels on or off their axles ”

“ In any large system where a number of pumping units are required they also allow a sufficient interval of time to start any additional units. Accumulators connected to the mains at a considerable distance from the central station reduce the variations of pressure, and the size of mains required for a given supply of power, and therefore have a most important influence on the economy of distribution. The mechanical efficiency of hydraulic accumulators is very high, being from 95% to 98 %, and they are practically indestructible. ”

“ They rest on a central hydraulic ram, three feet in diameter, working in two hydraulic presses underground, which can be connected at pleasure, making the troughs counterbalance one another. One trough ascends as the other descends. Hydraulic power is only required when the descending trough reaches the water in the lift-pit, the motion of the troughs being effected by removing about six inches from the lower trough. This arrangement is very economical of time, inasmuch as a 100-ton barge can be transferred from the river to the canal, and another from the canal to the river, in eight minutes. ”

“ Besides these general levels of drainage, there are subsidiary levels, called off-takes or drifts, which discharge the water of a mine, not at the mouth of the pit, but at some depth beneath the surface, where, from the form of the country, it may be run off level free. From 20 to 30 fathoms off-take is an object of considerable economy in pumping; but even less is often had recourse to; and when judiciously contrived, may serve to intercept much of the crop water, and prevent it from getting down to the dip part of the coal, where it would become a heavy load on a hydraulic engine. ”

“ Packing should fit the grooves in solid pistons moderately tight, so that the packing can be pushed into the grooves with the fingers. The depth of the packing should be such that the piston will fit the bore of the water cylinder snugly when first put in. If packing of the proper depth cannot be obtained, it is better to have the grooves turned to receive standard sizes of packing and not require special sizes. Cutting hydraulic packing is a tedious job, consuming a great deal of unnecessary time. ”

“ As soon as the pressure is relieved the check valve opens and the valve into the chamber closes automatically until a moment later the stream of water has gained sufficient velocity to repeat the performance. Thus an intermittent jet of water is forced into the air chamber and thence through a pipe to a reservoir. The height to which the water will rise depends entirely upon the velocity of the water flowing through the system. The air chamber is necessary to cushion the action of the hydraulic ram and provide a fairly steady pressure upon the water that flows up through the vent pipe. ”

“ Some of the giant nozzles spout streams from 2 to 8 inches in diameter with a pressure of from 50 to 200 pounds per square inch. The powerful streams tear into the gravel banks, washing them away into sluices in which riffle boxes are placed to catch the precious metal. The back pressure of these nozzles is very heavy and the larger ones have to be provided with strong anchorages. Water in motion resists any change of direction and long levers have to be provided to permit the miners to guide the nozzles.
The hydraulic jet is also used for general excavating wherever water power is available. ”

“ A Lifting-Jack is a contrivance for raising great weights by force from below; also called a jack-screw. From its derivation from Jack, equivalent to lad or boy, has arisen its modern use as denoting a contrivance which is subject to rough usage. It is operated by a screw, whereas—a hydraulic jack is a jack or lifting apparatus operated by some liquid, usually oil, acting against a piston or plunger, the pressure on the liquid being produced by a force pump. The hydraulic jack consists of, 1, a cylinder; 2, a ram or plunger ”

“ Thirty-four years’ practice has proved these ne plus ultra Hydraulic Machines, in their average results, to be cent per cent the most effective and durable, the best and cheapest of any in the world; they are made to discharge from half a pint to a ton weight of water, at a single clip or stroke, and are readily applied to any motive power to draw or force water, air, or any not rapidly injurious fluids, in any quantity, or to any height or distance, for any purpose, by John Shalders, Manufacturer, and Sole Proprietor. ”

“ Here it is proper to mention once for all, that the pressure for the hydraulic machines is obtained not only by natural heads of water, or by forcing-pumps worked by hand, but very frequently by forcing-pumps worked by steam power. ”

“ The hydraulic power unit HS-2 (figure 1-17) , located on silo level 6, consists of an electric motor driven pump, a reservoir, strainer, filter, valves, switches, and indicators. An accumulator is provided to store the hydraulic power. 1-60. Hydraulic power is produced by pumping fluid from the reservoir, with the electric motor driven pump, to the accumulator until pressure reaches 3500 50 psig. The accumulator is pressurized with nitrogen gas supplied by the nitrogen receiver, and retains hydraulic power until needed for operation of the retractable platforms and silo blast valve systems. ”

“ It is this principle which operates with such astonishing effect in hydrostatic presses, of which familiar examples are found in the hydraulic pumps, by the use of which boilers are tested. By the mere weight of a man’s body when leaning on the extremity of a lever, a pressure may be produced of upwards of 20 tons; it is the simplest and most easily applicable of all contrivances for increasing human power, and it is only limited by want of materials of sufficient strength to utilize it. ”

“ The shaft is the piston-plunger of a very long cylinder connected by pipes to pumping engines and hydraulic machines. It and the mass it bears up serves as a reservoir of energy. If the pumping engines were coupled up directly to the hydraulic tools, whenever a workman desired to use a press, drill, or stamp, as the case might be, he would have to send a signal to the engine-man to start the pumps, and another signal to tell him when to stop. ”