N. Hawkins

The illustration, Fig. 245, on the opposite page represents the first practical steam pump ever made; on pages 67-69 will be found an interesting account of it. The water end is single acting; the steam end is, of necessity, double acting to produce the reciprocating motion. From this original design has been evolved the piston valve as well as many other designs of valve motion for pumps.

Having already taken up in some detail the construction of “the parts of the pump” and the necessary appliances connected with its use, it now remains to consider the means by which the steam power generated is made available and the mechanism by which the energy is transformed from pressure into pumping power.

It may be well to consider at some length the “Steam end” of the pump. This consists primarily of cylinders, together with their connections; these constitute the muscular system of the pump. The muscular or operating end is separate and distinct from the water end so far as construction is concerned but in operation the two are closely allied. It is therefore necessary as well as convenient to unite them in one equipment and thus enable the propelling mechanism to furnish a constant source of power.

So far as the elastic force of steam itself is concerned its history dates back to a period two hundred years B.C., when, as described by Hero, the force generated by steam was utilized for actuating certain devices constructed rather for curiosity than for any benefit which might be derived from their use. Very little advance was made in the construction of practical devices until the latter part of the eighteenth century when James Watt by his improvements placed the stationary engine on an operative basis and gave to the world what has proved to be the greatest invention of all time.

The first stationary steam engines were used for pumping water and were of the single acting type, in which the steam was admitted at one end of the cylinder, the opposite end being open to the atmosphere. The steam acting on the piston forced it to the limit of its stroke when the supply was cut off. The steam then condensed in the cylinder, forming a partial vacuum, and the force of the atmosphere upon the opposite side of the piston forced it back, causing it to complete its stroke before another supply of steam was admitted. This was a slow process, wasteful of steam and attended with many other inconveniences.

An improvement on this device was made in an engine built by Watt in 1774. This was a single acting engine but the condenser was separated from the cylinder. The valves were so arranged as to admit live steam into the upper end of the cylinder on the top of the piston and at the same time open the lower end of the cylinder to the condenser. The steam followed the piston in its downward stroke in which action it was aided by the partial vacuum formed in the condenser. At the completion of the downward stroke the valves were changed so as to close the ports to the steam supply and the condenser, and at the same time open a communication between the two ends of the cylinder equalizing the pressure above and below the piston. The weight of the pump rod on the beam or lever connection overbalanced the weight of the piston and caused it to complete the return stroke.

In 1782 the double acting steam engine was patented by Watt. This was a device in which the live steam acted on each side of the piston alternately, the opposite side of the cylinder being in communication with the condenser. The same patent covered the method of applying the principle of expansion of steam in the cylinder; a non-condensing engine was also described.

Note.—This invention was of great historical importance as it covered all the essential detail of modern practice in steam engine building and constituted the fundamental principle of all steam engines.

Improvements have been made in form and construction, necessitated by new adaptations which have been constantly developed. The requirements for higher speed, increased pressure which implies greater power, and the constant desire for greater economy in fuel have produced a variety of changes in detail but have not altered the fundamental idea.

When the steam after being utilized in the cylinder makes its exit directly to the open air, the engine is called single expansion for the reason that the action of the steam takes place in one cylinder during a single stroke, and what expansion takes place must be during one half of a revolution. When the steam from one cylinder instead of exhausting into the open air, is passed to a second cylinder, of larger area, and by expanding exerts a pressure on a second piston to aid in the completion of the revolution, the engine is called double expansion or compound, because the steam instead of completing its work in a single operation is afforded a double opportunity for expansion and an increased range of action. In the single cylinder the temperature of the walls is reduced in each revolution to correspond with that of the steam at the exhaust pressure.

This temperature must be restored by incoming steam at the beginning of a new stroke which means a reduction of power. With a double cylinder owing to the greater range of expansion, a higher temperature can be maintained in the first cylinder and a large amount of initial condensation is prevented. A still greater use of expansion may be obtained by the introduction of a condenser which allows the final exhaust to be carried below the atmospheric pressure to the extent of the vacuum formed. In stationary and marine practice triple and quadruple expansion engines are common. These are used in large units to give the greatest possible economy in fuel.

Properties of Steam.—Before taking up in detail the valve and other mechanism of the steam pump it may not be out of place to consider briefly the action of steam and its expansive properties. Heat is identical with mechanical force and the one can be converted into the other. Aside from the means used in converting or developing the action a certain quantity of heat always produces a certain quantity of work.

relative volumes of steam at 200 pounds and atmospheric pressure

Fig. 246.

The temperature of steam at atmospheric pressure (14.7 lbs. absolute) is 212° Fahr. As the pressure increases the temperature rises, but is always the same for a given pressure. The sensible heat required to raise the temperature of water from 32° to 212° is 180° and the heat absorbed by the water or latent heat at 212° is 996° making the total amount of heat expended 1176°. As the temperature rises the latent heat decreases in nearly the same proportion as the sensible heat increases. This number may therefore be taken as a constant to express the unit of heat in one pound of steam from 32° up to the temperature at which evaporation takes place. Then 1176 × 772 = 907,872 pounds raised one foot which represents the mechanical equivalent or maximum theoretical duty of the quantity of heat contained in one pound of steam.

One cubic inch of water if converted into steam at the pressure of the atmosphere (14.7 pounds) will occupy the space of 1642 cubic inches or nearly one cubic foot. As the pressure increases the volume is relatively diminished and if the same quantity of water is converted into steam say at 200 pounds pressure it will occupy a space of only 133 cubic inches. Assuming that no loss occurred by condensation, if released at this pressure it would expand and again occupy its relative volume at atmospheric pressure.

This is illustrated by the accompanying diagram, Fig. 246, showing a cylinder with an internal capacity of 1642 cubic inches provided with a movable piston. A quantity of steam representing that formed from one cubic inch of water is forced into it, supposing the weight on the piston to be 200 lbs. per square inch, this weight will be raised until the space under the piston occupied by the steam will be 133 cubic inches. If the supply is now cut off (assuming that no condensation takes place) the piston will remain at this place supporting its load. If the load on the piston is diminished the volume of steam will expand and the piston will be correspondingly raised in the cylinder. This action will be continued until all the load is removed and only the weight of the atmosphere remains. The volume of steam under the piston will then be 1642 cubic inches. It will therefore be seen that the same quantity of steam has exerted a lifting pressure upon the piston due to its relative volume commencing at 200 pounds per square inch and gradually decreasing until the pressure of the atmosphere is reached.

The English unit of heat is that which is required to raise the temperature of one pound of water one degree Fahrenheit and is known as the British Thermal Unit, or B. T. U. Dr. Joule demonstrated by an ingenious device, Fig. 247, in which a weight operated a paddle wheel agitating water in a closed vessel, that it required 772 foot pounds to raise the temperature of one cubic foot of water one degree, or, on the other hand, it was deduced that one unit of heat was capable of raising 772 pounds one foot high. The mechanical equivalent of heat is therefore accepted as 772 foot pounds for one B. T. U. based on Joule’s experiment.A

Fig. 247.

The theoretical efficiency of the use of steam by expansion can never be realized, owing to losses occasioned by condensation, caused by contact with the cooler walls of the cylinder, the unavoidable friction of the working parts, and from the fact that a certain portion of the pressure must be utilized to create a draft for the fire. All these losses must be taken into consideration in calculating the work actually done.

From the foregoing it will be readily understood that if the steam is allowed to exhaust from the cylinders at or near the pressure at which it is admitted the work which it might have accomplished by expansion will be lost. This means not only a loss of the steam but of a part of the fuel used to generate it.

It is therefore advisable to get all the work out of the steam that is possible and the nearer to atmospheric pressure the exhaust can be brought the greater will be the economy.

FOOTNOTE:

A Note.—This unit has been recently changed to 778.

USEFUL DEFINITIONS RELATING TO STEAM.

Steam is water in a gaseous state; the gas or vapor of water; it liquifies under a pressure of 14·7 and temperature of 212° F.

Steam is a joint production of the intermingling of water and heat. Water is composed of two gases which have neither color nor taste, and steam is made up of the same two gases with the addition only of that mysterious property called heat by which the water becomes greatly expanded and is rendered invisible. The French have a term for steam which seems appropriate when they call it water-dust.

This is what takes place in the formation of steam in a vessel containing water in free communication with the atmosphere. At first, a vapor is seen to rise that seems to come from the surface of the liquid, getting more and more dense as the water becomes hotter. Then a tremor of the surface is produced, accompanied by a peculiar noise which has been called the singing of the liquid; and, finally, bubbles, similar to air bubbles, form in that part of the vessel which is nearest to the fire, then rise to the surface where they burst, giving forth fresh vapor.

The curious fact must be here noted that if water be introduced into a space entirely void of air, like a vacuum, it vaporizes instantaneously, no matter how hot or cold, so that of an apparent and fluid body there only remains an invisible gas like air.

That steam is dry at high pressure is proved by an experiment which is very interesting. If a common match head is held in the invisible portion of the steam jet close to the nozzle, it at once lights, and the fact seems convincing as to complete dryness, as the faintest moisture would prevent ignition even at the highest temperature. This experiment proves dryness of the steam at the point of contact, but if throttling exists behind the jet, the steam supplied by the boiler may be in itself wet and dried by wire drawing.

Dead steam is the same as exhaust steam.

Live steam is steam which has done no work.

Dry steam is saturated steam without any admixture of mechanically suspended water.

High-pressure steam is commonly understood to be steam used in high pressure engines.

Low-pressure steam is that used at low pressure in condensing engines, heating apparatus, etc., at 15 lbs. to the inch or under.

Saturated steam is that in contact with water at the same temperature; saturated steam is always at its condensing point, which is always the boiling point of the water, with which it is in contact; in this it differs from superheated steam.

Superheated steam, also called steam-gas, is steam dried with heat applied after it has left the boiler.

Total heat of steam is the same as steam heat.

Wet steam, steam holding water mechanically suspended, the water being in the form of spray.

Specific gravity of steam is ·625 as compared to air under the same pressure.

The properties which make it so valuable are:

1. The ease with which we can condense it.

2. Its great expansive power.

3. The small space in which it shrinks when it is condensed either in a vacuum chamber or the air.

A cubic inch of water turned into steam at the pressure of the atmosphere will expand into 1,669 cubic inches.

THE DAVIDSON.

The Davidson pump is shown complete in Fig. 248; the valve motion consists principally of a valve, valve pistons, valve pin and cam. The main valve is operated by a positive mechanical connection between it and the main piston rod, also by the action of steam on the valve pistons. The engraving, Fig. 249, shows the details of valve gear and steam cylinder. The steam end consists of the cylinder, M, valve, A, and valve pistons, B and B. These pistons are connected with sufficient space between them for the valve, A, covering the steam ports, F and F₁, Fig. 250.

Fig. 248.

The valve is operated by the steel cam, C, acting on a steel pin, D, which passes through the valve into the exhaust port, N, in which the cam is located. In addition to this positive motion steam is alternately admitted to and exhausted from the ends of the valve piston through the ports, E and E₁, which moves the pistons, B and B₁.

Fig. 249.

Assumed that this pump is at rest with the valve, A, covering the main steam ports, F and F₁, in which position the cam C, holds the main valve by means of the valve pin, D, so that ports, E and E₁, admit steam to one end of the valve piston at the same time connects the other end with the exhaust port. The steam, acting on the valve pistons, moves both, opening the main ports, F and F₁, admitting steam to one end of the steam cylinder and opening the other end to the exhaust. If the valve occupies any other position than the one described, the main ports, F and F₁, will be opened for the admission and exhaust of steam; consequently it is evident that this pump will start from all points of the stroke.

Fig. 250.

On the admission of steam to the cylinder the main port, F, the main piston, cam and valve will move in the direction indicated by the arrows. The first movement of the cam oscillates the valve, preparatory to bringing it into a proper position for the opening of the auxiliary steam ports, E, to live steam, and E, to exhaust also to close the valve mechanically just before the main piston reaches the end of its stroke. This causes a slight cut-off and compression, and fully opens the auxiliary ports, E, to steam, and E₁, to exhaust. By the admission of steam to one end, the other being open to the exhaust, the valve pistons move the valve to allow the admission and exhaust of steam from the cylinder for the return stroke.

Fig. 251.

This main valve is as much under the control of the piston rod as is the valve of an ordinary steam engine worked by an eccentric which insures a positive action, the pump being capable of starting from all positions and maintaining a uniform and full stroke.

To set the valve piston, push the main pistons to the end of the stroke until the inner edge of the port and the piston coincide, then loosen the side lever, turn the cam, C, until the valve piston uncovers the auxiliary steam port, E, leading to the same end of the steam chest occupied by the main piston.

After setting, secure the cam and then connect the side lever to the connecting rod. The side lever and cam occupy correct relative positions, therefore, the lever should be secured to the cam shaft while in this position. The stroke may be regulated by raising or lowering the end of the connecting rod in the slotted end of the slide lever. Raising the connecting rod shortens the stroke and lowering it lengthens the stroke. When making the foregoing adjustments it is well to have the connecting rod at or near the bottom of the slot as shown in the engravings.

LAIDLAW-DUNN-GORDON.

The single cylinder pumps of this make are equipped with the gear illustrated in Fig. 252, in sizes varying from 4 inches in diameter by 5 inches stroke to 28 inches in diameter by 24 inches stroke.

The arrangement of valves and ports is shown in the engravings, Figs. 253 and 254.

The admission of live steam to the cylinder and of exhaust steam to the atmosphere is controlled by a valve piston, A, shown in Fig. 252.

Fig. 252.

Assume that the piston is in position shown, Fig. 253, and that both the main and auxiliary valves cover their respective steam ports. By means of a starting bar, operating through a stuffing-box in the valve chest, the piston valve, A, is moved toward the head of the steam chest, D, thus opening the ports, E and L, and admitting live steam through L, from the cavities, S, of the valve piston to the housing end of the main steam cylinder, through the port, F, Fig. 255, forcing the main piston, P, toward the opposite end of the stroke, or toward the left in the figure. The port, E, Fig. 253, being open, the exhaust steam escapes from front of the main piston through the port, F, Fig. 255, into the main exhaust port, G, through the port, E. The piston, P, travels to its extreme left position and the auxiliary slide valve has been drawn to such a position in the direction indicated by the arrow in the smaller drawing in Fig. 252, as to bring valve piston, A, toward the opposite end; the exhaust steam from the steam chest escapes from before it, through the exhaust port, K, the opening of which into the chest is at such a distance from the head as will permit sufficient exhaust steam to remain to afford a cushion to the valve piston.

Fig. 253.

Fig. 254.

Fig. 255.

Fig. 256.

With the auxiliary slide valve in position to bring the hole, H, over the port, J, Fig. 256, it is plain that the exhaust through the port, K, will pass into the main exhaust through the port, L. With the main piston at its extreme travel toward the right, the ports, E and L, which correspond to F and F, respectively, in Fig. 255, are opened in such a manner as to exhaust steam to the atmosphere from the housing end of the steam cylinder through the port, F, and live steam from the chest to the head end of the main cylinder, through the port, F, thus driving the main piston, P, toward the housing end of the cylinder, or toward the right. The piston and reciprocating parts traveling in this direction move the auxiliary slide valve to its maximum point of travel in the opposite direction, thus opening the opposite auxiliary steam and exhaust ports and again driving the valve piston toward the head, D, of the steam chest, whence a new stroke begins.

Lost motion in the valve gear is taken up by adjustable links, on all sizes above 7 inches diameter by 10 inches stroke and on some smaller sizes.

Cushioning of the steam pistons in the larger sizes and upwards is accomplished by means of suitable valves called cushion valves. In the smaller sizes sufficient cushioning is done by exhaust steam passing from the clearance space next the head through a small hole drilled into the main steam port.

To set the valve of this pump it is only necessary to place the piston in its central position and adjust the lever so that the valve will occupy its central position. By this proceeding the travel of the valve is equalized.

THE FOSTER.

Fig. 257.

The Foster single cylinder pump valve motion is a compound valve piston and slide valve in one piece and performs the office of both a main and auxiliary valve. It seats over the main steam cylinder on the web or casting connecting together the valve pistons, and is provided at the bottom with vents or openings, A and B, Fig. 257, for opening and closing the main steam ports to the main steam cylinder. The sides of this valve are cut to form the recesses, C and D, which are for the purpose of opening and closing the small steam ports, which admit steam to the valve pistons; it is also provided with L shape slots for the purpose of alternately exhausting steam from the valve pistons through the steam ports.

Fig. 258.

Fig. 259.

Fig. 260.

In operation the main piston rod commences its forward stroke, motion is communicated to the vertical arm, which moves forward on the rod until it engages with one of the cams, E, Fig. 259, adjusted on the valve stem. The arm coming in contact with the inclined faces of the cam imparts a rolling or oscillating movement to the stem and valve, opens one of the recesses, C or D, cut in the side of the valve and admits steam through a port to one of the valve pistons. At the same time this oscillating movement of the valve opens the slot, F, Fig. 260, opposite the first, and exhausts steam through the alternate port from the other piston. Steam thus admitted to one of the pistons (while exhausts from the other piston), carries the valve over its seat, and by means of the vents, A and B, steam is admitted through one of the main ports and exhausts through the other. When the main piston has completed one stroke, it moves backward on its return; the arm strikes against the other cam on the valve stem and communicates a reverse motion to the valve which closes and opens the alternate ports to admit and exhaust steam to and from the pistons. It also cushions the piston at the end of each stroke which prevents the piston from striking the heads.

To set the valves. This can best be done by starting the pump slowly and adjusting the cams, E, so as to open the valve at the proper time to compel the piston to make a full stroke. A little experimenting combined with good judgment is all that is necessary, unless the piston valve be badly worn, in which case a new valve must be substituted and fitted to the valve chest.

THE CAMERON.

The plunger in the Cameron pump is reversed by means of two plain tappet valves, shown in the accompanying engraving, Fig. 261, and the entire valve mechanism consists of four pieces, all of which work in a direct line with the main piston. This pump is simple and has no delicate parts.

As here represented—A is the steam cylinder; C, the main piston; L, the steam chest; F, the valve piston, the right-hand end of which is shown in section; G, the slide valve; H, a lever, by means of which the valve piston, F, may be moved by hand when expedient; I, I are reversing valves; K, K are the reversing valve chamber bonnets, and E, E are exhaust ports leading from the ends of steam chest direct to the main exhaust. The passages, M, M, lead directly into the exhaust (although the connection is not shown, being cut away in the sectional view), and closed by the reversing valves, I, I.

The piston, C, is driven by steam admitted under the B slide valve, G, which, as it travels backward and forward, alternately supplies steam to opposite ends of the cylinder, A. The slide valve, G, is operated by the valve piston, F; F hollow at the ends, which are filled with steam, which, issuing through a hole in each end, fills the spaces between it and the heads of the steam chest in which it works.

The pressure being equal at each end, the valve piston, F, under ordinary conditions, is balanced and motionless; but when the main piston, C, has traveled far enough to the left to strike and open the reverse valve, I, the steam exhausts from behind the valve piston through the port, E. The pressure being now unequal behind the two ends, the valve piston immediately shifts accordingly and carries with it the slide valve, G, reversing the piston. No matter how fast the piston may be traveling, it must instantly reverse when it touches the valve, I.

In its movement the valve piston, F, acts as a slide valve to close the port, E, and is cushioned on the confined steam between the ports and steam chest cover. The reverse valves, I, I, as soon as the piston, C, leaves them, close by the constant pressure of steam behind supplied direct from the steam chest through the ports, N, N, shown by dotted lines.

To set the valve, it is only necessary to keep valves tight by occasional grinding. The piston as it nears the end of each stroke strikes the stem and lifts the valve off its seat; this allows the exhaust steam behind the piston valve to escape. The live steam pushes the piston towards the exhausted end carrying the main slide valve along with it.

THE MASON.

The Mason pump has a valve piston, a main valve, a preliminary valve and a yoke connected directly to the valve stem, as shown in Fig. 262. The valve piston is contained in a cylinder above the steam chest, and moves the main valve by means of a pin, which projects into a pocket in the top.

The main valve and preliminary valve travel on the same seat, and receive their motion from the yoke, E, Fig. 263, which surrounds them. This yoke fits the preliminary valve neatly, allowing an independent movement of the main valve and valve piston.

The preliminary valve is the ordinary D type and controls three ports, as shown in Fig. 263, the two steam ports are connected with either end of the auxiliary cylinder and the exhaust, with the small port, A, in the main valve seat. The duty of the preliminary valve is to alternately connect each end of the auxiliary cylinder with this port. The main valve controls four ports, and is also of the D type, having an extended cavity connecting the exhaust from the preliminary valve with the main exhaust. The main valve also controls the main steam and exhaust ports of the pump cylinder.

Steam enters the chest through the steam pipe, passes around the central portion of the valve piston and through the passages in the piston to both ends of the valve cylinder, thus balancing the valve piston.

Suppose that the yoke and preliminary valve have been carried to the back end of the chest, and have moved the main valve to bring its auxiliary cavity over the auxiliary port, A, Fig. 263, in the main valve seat, which connects the back end of the auxiliary cylinder with the main exhaust. The steam from the end of the chest passes up through port, B, down through port, C, and up through port, A, into the exhaust port, D, in the main valve. This unbalances the auxiliary piston, which is driven back by pressure on the opposite end, and carries the main valve independently of the yoke. The travel of the main valve causes it to cut off the exhaust from the auxiliary cylinder, and the remaining steam cushions the valve piston.

The travel of the main valve also opens the main steam port to the forward end of the pump cylinder, and connects the back end of the cylinder with the main exhaust, thus reversing the motion of the piston.

This action is repeated at the end of each stroke. Whatever position of the piston, the pump will start when steam is turned on, as there is always a connection either directly from the steam inlet to one of the steam ports, or, if the main valve has covered both steam ports, it is in a position to connect the auxiliary cavity in the main valve seat with the main exhaust, which at once releases the steam from one end of the valve piston, and the pressure on the other end drives the piston, thus moving the main valve and giving direct communication between the steam inlet and one of the main steam ports.

Thus it is seen that the piston cannot get into a position where it is impossible for it to respond to the steam pressure.

To set the valve place the piston in the mid-stroke position and set the auxiliary valve with rocker arm plumb, and the preliminary valve covering all its ports equally. These positions may be secured by adjusting the position of the clamp on the valve stem and move the main piston sufficiently so that the auxiliary valve will open one of its ports.

Fig. 264.

The accompanying engraving, Fig. 264, shows a section of the slide valve chamber, which is fitted to the top of cylinder. The slide valve, B, is fitted in the valve chamber, A, the cut-off valve, C, works on top of the slide valve and is operated by the valve stem, D. The lever, F, which moves the valve, is attached to the crosshead on the piston rod. While the crosshead moves the length of the stroke, the cut-off valve, C, moves twice the width of the steam ports in the cylinder. The opening in the cut-off valve, C, is equal to the length of the dog, E, plus the throw of the slide valve, B, plus one-sixteenth inch. The length of the valve chamber on the inside is equal to the length of the cut-off valve minus the throw of the cut-off valve. The valve stem, D, is connected to the cut-off valve, C, so that it moves the latter valve a distance proportional to the movement of the steam piston. The opening through the cut-off valve is equal in width to the distance from inside to inside of the ports on top of the slide valve. As the piston moves to the right, as shown in the drawing, the cut-off valve moves to the left, so as to open the right-hand end of the valve box and admits steam, which acts upon the slide valve and moves it to the left-hand end of the valve box. This opens the port wide in the slide valve, which corresponds with the port leading to the cylinder while in the upper side of the slide valve the port is nearly closed by the cut-off valve, so that little steam is admitted to the cylinder; consequently, the piston is gradually started on its return stroke. On the return stroke the cut-off valve begins to move and opens one of the ports on top of slide valve, which stands still until the piston has made a half stroke.

By this time the valve is wide open “full port” to the cylinder. The cut-off valve, C, coming in contact with the dog, E, both the slide valve and cut-off valve move together to the end of the stroke. Notice that as soon as the cut-off valve, C, engages the slide valve and it begins to move, the port to the cylinder closes so that at the end of the stroke but little steam can get to the piston. The cut-off valve opens the valve box, A, to admit steam to complete the stroke of slide valve, and should the steam fail to throw the slide valve, the piston, by means of the cut-off valve, C, coming in contact with the dog, E, moves the slide valve, thereby opening the opposite port and preventing the piston from striking the cylinder head.

The lower corner of the slide valve, B, is removed and a slot cut to the exhaust port, the slot being of sufficient size to release the steam from the ends of the valve box and exhaust pressure of it into the pocket of the slide valve.

The movement of this valve very much resembles that produced by means of an eccentric. The movements of the valves are so timed that as the main piston nears the end of the stroke its movement is sufficiently retarded to permit the water valves to seat quietly and without jar, also on the return stroke, the steam is so gradually admitted that the piston starts with ease and gradually increases its speed to the middle of the stroke, from which point it gradually decreases toward the opposite end. A proper adjustment of the cut-off valve allows the piston to stop momentarily at the ends of the stroke without any possibility of striking the cylinder heads.

To Set the Valve. Adjust all joints so that there will be no lost motion in the valve gear. Then move the crosshead to the end of its stroke, and see that the cut-off valve opens the valve chamber one-sixteenth of an inch, and that the steam valve closes the port leading to the cylinder to within one-sixteenth of an inch. Next move the crosshead to the other end of its stroke and note that the valves are in the same relative position. If, from any cause the cut-off valve does not open correctly to admit steam to the valve chamber at the ends of the stroke of the piston, the valve can be shortened by filing off the ends. This should not be done, however, until all lost motion has been taken up in the valve gear.

In this pump (see Figs. 266, 267) the steam is admitted to the center of the valve chamber which contains the main valve, A, and the supplemental slide valve, B. The recess in the center of the valve piston, C, receives the main valve and moves it when steam is supplied to or exhausted from either end of the valve piston.

In operation live steam passes through the left-hand ports, D and E, drives the main piston to the right and the exhaust passes out of the right-hand port, F, into the cavity in the main valve, A, thence through the exhaust port, G, into the atmosphere.

As the main piston nears the right-hand port, the valve lever H, attached to and moving with piston rod brings the dog, I, on plate, J, in contact with the valve arm, K. This moves the supplemental valve, B, to the right and supplies live steam to the right of the valve piston, C, and exhausts the steam from the left-hand end through the ports, L. The main valve, being enclosed by the valve piston, moves with it to the left. As the steam enters the right hand main port and exhausts from the left hand port, the main piston commences its return stroke and the operation just described becomes practically continuous. As the main piston closes the main port, F, to the right, it cushions on compressed exhaust steam, because the main valve, A, has then closed the auxiliary port, M, leading to that end of the main cylinder. The steam in this case is supplied through the main and auxiliary ports, but exhausts through the main port only.

The slow movement of the main piston near the ends of the stroke allows the pump valves to seat quietly, and gives the pump cylinder time to fill with water, thus effectually preventing shock and noise. The valve piston, C, is cushioned by cushion valves, which are simply loose valves inserted near the ends in the valve piston. By removing the steam valve chamber, the main and supplemental valves may be readily examined or repaired. These valves are the ordinary plain flat slide with which all engineers are familiar.

To set the valve of this pump. Place the piston in the center of its travel with the valve lever, H, plumb and also valve arm, K, plumb; adjust the supplemental valve so as to cover equally all the posts, which is done by lengthening or shortening its valve stem.

Fig. 268.

The main valve in this pump is moved by steam acting upon a valve piston. The steam admitted to and released from the auxiliary cylinder is controlled by a small slide valve operated by the valve gear. This small slide valve is in every essential feature identical with the slide valve of a steam engine, admitting and releasing the steam in precisely the same manner. In this pump the usual collars and tappets on the valve stem are dispensed with, the stem receiving motion by means of a roller carried by a slide block to which the valve stem is attached.

A sectional elevation of the cylinder and main valve is also shown; the connection of the valve piston to the main valve, also the construction of the small slide valve. The valve gear is provided with roller bearings to reduce the friction.

To set the valve. The main piston must be moved to the end of the stroke, so that the face of the piston and the edge of the steam port are flush, as a preliminary step to set the small slide valve, then the set screw in the rocker arm nearest the roller on the valve stem should be adjusted so that when the roller is in contact with the set screw the small slide valve will have opened the steam port corresponding to the position of the main piston.

Now push the main piston to a corresponding position at the opposite end of the stroke and adjust the other set screw nearest the roller on the valve stem in the same manner as the first one.

Mark the striking points of piston on the piston rod close to the stuffing-boxes. Start the pump slowly, and if the parts work smoothly, gradually increase the speed, keeping close watch of the striking points to see that the piston has ample clearance.

If the stroke is too short, the set screws should be backed out until the stroke is found to be right. Screwing the set screws in shortens the stroke and increases the clearance at the ends of the stroke. A full stroke should always be required of every pump.

THE HILL.

This pump is for deep wells; it has a valve piston and two slide valves operated by valve stem, also supplemental port valves to regulate and control the up and down strokes of the main piston. The main and auxiliary valves are both flat slides, each covering five ports, as shown in Fig. 271. The main valve is actuated by means of a valve piston, the steam being admitted to and exhausted from the ends of the valve piston in precisely the same manner that the main valve controls the admission and release of steam in the main pump cylinder.

One of the auxiliary ports enters the end of the main steam chest, and the other enters at a point nearer the middle of the chest. The end ports are admission only and the inner ones exhaust. When the auxiliary valve reaches the upper end of its travel, as shown in the engraving, the admission port opens at the bottom of the steam chest, while the one at the top closes.

At the same time, the upper end of the main cylinder is open to the exhaust. The admission of steam drives the valve piston upward, but before reaching the end of its stroke it closes the exhaust port, thus entrapping a portion of the exhaust steam, which cushions the valve piston at the ends of the stroke.

The auxiliary slide valve is operated by means of a double-cone tappet on the piston rod, which strikes a rocker bar pivoted to the frame of the pump. The rocker bar carries an arm or lever at right angles to it and to this arm the valve rod is connected.

A short shaft runs across and through the upper part of the steam chest and is provided with a toe, as shown, by means of which the valve piston may be moved by hand when necessary and without disconnecting any part of the pump or valve gear.

The port valves provide a simple means of contracting these passages and regulating the velocity of the up and down strokes to meet the requirements of the water ends of the pump so that uniform strokes are obtained regardless of the resistance against the main piston.

When adjusting the auxiliary valve, place the rocker bar parallel to the piston rod and so that the arm to which the valve rod is connected will stand at right angles to the piston rod. The auxiliary valve must then cover all the ports equally. The upper or outer end of the arm on the rocker bar is slotted, hence moving the valve rod pin toward the end of the arm lengthens the stroke and moving it toward the piston rod shortens it.

To set the valve of this pump it is necessary only to square the levers and equalize the travel.

THE GUILD AND GARRISON.

The steam chest of this pump differs somewhat from other pumps in which valve pistons are employed to operate the main valve. See accompanying engraving, Fig. 272. This pump has a steam chest with a cover for inspection and repairs. This chest is bored at each end to form suitable cylinders to receive the valve piston, E. By the side of the valve piston, E, in the steam chest is an auxiliary slide valve, G, Figs. 273 and 274, which admits and releases the steam from the ends of the valve piston. The valve piston, E, has two slots at the center, the lower one receiving the lug on the back of the main valve and the upper one the toe on the rocker shaft, D. The rocker shaft has two toes, the larger one, F, engaging with the valve piston, and the smaller one with the auxiliary slide valve, G, as shown in Fig. 274. The auxiliary, as well as the main, valves are plain slides designed to take up the wear automatically. The pendulum lever, J, Fig. 273, is connected with the piston rod as shown and rotates the shaft, D, and by means of the toes the valves move together.

The auxiliary slide valve, G, admits and exhausts the steam to and from the ends of the valve piston. Steam being admitted, the piston moves toward one end. The two valves also move in the same direction by means of the rocker shaft and the toes. This movement continues until the piston has nearly completed its stroke, when the auxiliary valve opens one of the small ports leading to the end of the valve piston, thus admitting steam at one end and exhausting it from the other. The valve piston moving from one end of the steam chest to the other, shifts the position of the main valve and reverses the motion of the main piston. The valve piston is moved the greater part of its travel by the toe on the rocker shaft, thus reversing the steam distribution, by steam pressure, which brings the opposite end of the slot in the driver to a second engagement by the toe on the rocker shaft which begins the return stroke.

The steam acts to throw the main valve only near the ends of the valve travel, and being already in motion the valve requires but very slight help to complete its stroke quickly without shock.

The motion of the auxiliary valve is synonymous with the main piston so there can be no practical dead center. The valves are very durable under such easy motion.

With this arrangement of valves no setting is necessary because when assembling the parts the centers of the pendulum lever and the toes on the rocker shaft are adjusted parallel with one another.

The McGowan single cylinder steam pump and section is shown in Fig. 275. Its main valve is of the B form and is driven by a valve piston. Steam enters the central port in valve seat and into the cylinder through one of the cavities in the valve and exhausts through the opposite. The two tappet valves cover the auxiliary ports, shown by dotted lines, leading to the ends of the steam chest and connect with the main exhaust ports. These tappet valves are raised by means of levers, the ends of which project downward and into the cylinder so that when the piston nears the end of a stroke it comes in contact with the lever and raises it sufficiently to lift the tappet valves.

Each tappet valve lever is pivoted on a pin which fits into a recess near the main ports, as indicated by the dotted lines.

When the piston reaches the end of its stroke it lifts one of the tappet levers and with it the corresponding valve is raised from its seat, opening the port leading from the end of the steam chest to the main exhaust port. The pressure is thus relieved on one end of the valve piston and the steam pressing on the opposite end forces the valve piston to the opposite end of its stroke, thus reversing the distribution of steam to the cylinder and starting the piston on its return stroke. The valve piston thus moves back and forth, the ends of the steam chest being filled with steam at initial pressure. Steam escaping from one end of the steam chest causes a difference of pressure on the two ends of the valve piston, from which we realize the power to move the main valve. The tappet valves, having a very slight lift, operate without shock or noise. The main valve is connected with the valve piston so that all lost motion is taken up automatically.

A rocker shaft, extending through the steam chest carries a toe moving in a slot in the top of the valve piston, so that the valve can be moved by hand.

To set the valves of this pump. Simply keep the valves in order. The motion of the piston as it nears the end of the stroke opens and closes the valves.

In the Knowles pump a valve piston, G, Fig. 277, in the steam chest moves the main valve. This valve piston is driven alternately backward and forward by the pressure of steam, carrying with it the main valve, which admits steam to the main steam piston that operates the pump. The main valve is a plain slide whose section is of B form, working on a flat seat.

The valve piston is slightly rotated back and forth by the rocker bar, H; this rotative movement places the small steam ports, DEF, Fig. 276, which are located in the under side of the valve piston in proper position with reference to the corresponding ports, AB, cut in the steam chest. Steam enters through the port at one end and fills the space between the valve piston and the head, drives the valve piston to the end of its stroke and carries the main slide valve with it. When the valve piston has traveled a certain distance, a corresponding port in the opposite end is uncovered and steam enters, stopping its progress by giving it the necessary cushion. In other words, when the reciprocating rotative motion is given to the valve piston through the outside mechanism, it opens the port to steam admission on one end, and at the same time opens the port on the other end to the exhaust. There is no point in the stroke at which either the valve piston or the main piston is not open to direct steam pressure, hence the immunity from any dead position or dead center.

The operation of the pump is as follows: The piston rod with its tappet arm, J, Fig. 277, moves backward and forward with the piston. At the lower part of this tappet arm is attached a stud or bolt, K, on which is a friction roller, I. This friction roller, lowered or raised, adjusts the pump for a longer or shorter stroke. This roller coming in contact with the rocker bar at the end of each stroke, and this motion is transmitted to the valve stem, causing the valve to roll slightly. This action opens the ports, admits steam and moves the valve piston, which carries with it the main slide valve which admits steam to the main piston. The upper end of the tappet arm does not come in contact with the tappets, LM, on the valve rod, unless the steam pressure from any cause should fail to move the valve piston, in which case the tappet arm moves it mechanically.

To set the valve, loosen the set screws in the tappets on the valve stem. Then place the piston at mid-stroke, and have the rocker bar, H, in a horizontal position, as shown in the engraving. The valve piston should then occupy the position shown at C, Fig. 276. The valve piston may be rotated slightly in order to obtain this position by adjusting the length of connection between the rocker bar, H, and the valve stem. Then turn the valve piston, G, one way or the other to its extreme position, put on the chest cover, and start the pump slowly.

If the pump should make a longer stroke on one end than on the other, simply lengthen or shorten the rocker connection so that the rocker bar, H, will touch the rocker roller, I, equally distant from the center pin, J.

In case the pump hesitates in making its return stroke, it is because the rocker roller, I, is too low and does not come in contact with the rocker bar, H, soon enough. To raise it, take out the rocker roller stud, K, give the set screw in this stud a sufficient downward turn, and the stud with its roller may at once be raised to its proper height.

When the valve rod has a tendency to tremble, slightly tighten the valve rod stuffing-box nut. When the valve motion is properly adjusted, the vertical arm should not quite touch the collar, L, and the clamp, M. Rocker roller, I, coming in contact with the rocker bar, H, reverses the stroke.

The water piston is packed by means of segments that will be seen by taking off the follower. The packing may be quickly set out to insure a good vacuum and at the same time not to be so tight as to bind. All wearing parts are made adjustable.

THE MOORE.

The valve for admitting steam to and exhausting it from the cylinder of this pump is contained within the cylinder and moves simultaneously with the steam piston, having no outside mechanism. See Fig. 278.

The piston, and also the valve, are of the form of spools, each representing a hollow sleeve with a ring packed piston head at either end. The piston is secured to the piston rod and the sleeve connecting the two heads serves as the valve seat for the cylindrical valve. The sleeve of the piston contains two longitudinal ports, one port communicating with one end of the cylinder, and the other port communicating with the opposite end. Suitable holes drilled through the walls of the sleeve and communicating with the longitudinal ports, act as admission and exhaust ports, with which the holes and cavities in the sleeve coincide at proper positions in the stroke.

Referring to the accompanying engraving, Fig. 279, which represents the valve and piston in the position occupied when ready to commence a stroke from left to right, the reader will easily understand the action of these parts. When the piston reaches the end of the stroke steam enters through the steam pipe at A, between the pistons, and forces the valve to the left as shown. This movement opens the port, B, and also brings the cavity, C, in communication with port, D, steam being admitted through ports, B and D, into the longitudinal port, F, thence into the clearance, G, of the cylinder. This causes the piston to move toward the right. When the piston has moved a short distance to the right steam is admitted into the space, H, surrounding the valve, and passing into the cavity, C, and through the port, D, furnishes steam to complete the stroke.

Should the piston stop at mid-stroke it will start again as soon as steam is turned on, because the port, D, remains open until the valve is reversed at the opposite end of the stroke.

When the piston reaches the latter position, Fig. 280, the valve is reversed, due to steam entering at A, and again forcing the pistons apart, as shown. The steam, which drove the piston from left to right, now escapes through the port, I, into the cavity, J, and around the sleeve to the holes, K, Fig. 279, where it enters the hollow piston, and finally escapes through the hollow rod, L, and the port, M. The live steam for the next stroke from right to left, now enters through ports, N and O, Fig. 280, and flows through the longitudinal port, P, into the end, Q, of the cylinder.

The exhaust steam may be allowed to flow into the atmosphere or into the suction chamber as desired. A valve is located in the base of the pump, which changes the course of the steam from the atmospheric discharge to the suction chamber. The valve is operated by a lever shown by dotted lines. When the lever is turned down toward the steam end, the steam is directed into the atmospheric exhaust, and when turned in the opposite direction the steam will enter the pump suction and be condensed.

There is no valve setting to be done on this pump. Should the pump fail to work properly, due to the failure of the steam end, all that is necessary is to take out the valve and piston and clean them thoroughly and after replacing them and starting the pump to see that these parts are properly lubricated. The remainder of the pump requires the same care and attention that is, or should be, given all pumps.

The auxiliary valve of this pump is a plain flat slide operated by a valve stem, the latter being moved back and forth by means of a rocker shaft, as shown in the engraving, the upper end of which alternately comes in contact with the collars on the stem.

The outer end of the valve stem passes through a sleeve attached to a pin in the upper end of the rocker arm, as shown. A knuckle joint near the stuffing-box permits the rod to vibrate without causing any derangement in the alignment of valve stem through the stuffing-boxes.

On the valve stem at either end of the auxiliary valve is a spring, which tends to keep the valve in a central position, so that when the rocker arm engages one of the collars, the valve is drawn against the spring toward that end of the stroke. The result is that the stem and valve follow the rocker arm on the return stroke to its mid-position, and are started on the latter half of the stroke by the stem, but without shock or lost motion. This arrangement is particularly valuable in the case of condensers, and in pumps where the first part of the stroke is made quickly, and the piston is then suddenly stopped by coming in contact with a solid body of water, the latter part of the stroke being made much more slowly. The springs on either side of the auxiliary valve take up lost motion and keep the parts in absolute contact, thus preventing shocks and unnecessary wear.

To set the auxiliary valve, see that the valve is in its central position when the rocker arm is plumb, and that the collars on the valve stem are located at equal distances from each end of the sleeve. When the piston moves to one end of the stroke, the auxiliary valve will open the small port at the opposite end, provided the collars on the valve stem have been properly placed. Setting the collars closer together shortens the stroke of the piston, and moving them farther apart lengthens the stroke. The piston should always make a full stroke without danger of striking the cylinder heads.

The details of the valve gear used on the Deane single cylinder steam pumps are shown in the accompanying engraving. The main valve is operated by a small piston called the valve piston, shown in Fig. 286. The ears on the main valve fit freely but without lost motion into a slot cut in the valve piston, so that when the valve piston moves in either direction it carries the main valve with it.

The valve piston is fitted to the valve chest and is operated by steam admitted alternately to the opposite ends of the chest. The movements of this valve piston are controlled by a secondary valve, which admits and exhausts the steam to the valve piston through the small ports at the sides of the steam chest. The secondary valve derives its motion from the valve stem, tappets, links and the piston rod as shown.

The valve piston is steam jacketed which insures equal expansion of the parts in starting the pump and prevents the seats from pinching the valve piston before these parts have acquired a uniform temperature.

The action of this pump is as follows: Suppose the piston moving in the direction of the arrow nears the end of the stroke; the tappet block comes in contact with the left-hand tappet and throws the secondary valve to the left until it’s edge, A, Fig. 284, uncovers the small port, S, Fig. 283, admitting steam to the valve piston.

The port, E, and chamber, F, in the secondary valve provide for the exhaust of steam from the left-hand end of valve piston in the same manner and at the same time that steam is admitted behind the right-hand end. The exhaust ports in the chest allow for properly cushioning the valve piston. The small ports on the other side of the steam cylinder, Fig. 283, control the motion of the valve in the other direction and act in exactly the same manner as those just described. In case the steam pressure should for any reason fail to start the valve piston in time there is a lug, B, Fig. 286, which forms a part of the valve stem and comes in contact with the valve piston and the entire power of the steam cylinder starts it. The correct timing of the valve movements is controlled by the position of the tappets. If they are too near together, the valve will be thrown too soon and thus the stroke of the pump will be shortened, while on the other hand if too far apart, the pump will complete its stroke without moving the valves. The tappets are set and keyed securely before leaving the factory.

The exhaust from the cylinder is cut off when the piston covers the inner port, and forms a steam cushion for the piston to prevent it striking the heads.

To set the valve. Place the steam piston at the end of stroke nearest stuffing-box and the secondary valve so that it will uncover the steam port, S, Fig. 283. Set the tappet next to the steam cylinder on the valve stem against the tappet block and secure it in this position.

Slide the secondary valve forward until the opposite steam port is uncovered and place the steam piston in its extreme outward position, then set the other tappet against the tappet block. Now set the valve so that the inside main steam port is open and the valve piston in position to engage the main steam valve, put the valve chest on the cylinder and secure it in place. The pump will then be ready to start on the admission of steam to the steam chest.

If when steam is turned on the pump refuses to start, simply move the valve rod by hand to the end of its stroke and the pump will move without trouble.

In renewing the packing between the steam chest and cylinder extreme caution should be observed to cut out openings for the small ports.

The engravings, Figs. 287, 288, show the valve gear, also section of steam cylinder and steam chest. The piston and valves are in their central position, which condition never occurs in the operation of this pump; if it did the pump would stop. The valves and pistons being at one end or the other of the stroke uncovers the ports, and the moment steam is admitted the pump will start. Referring to the engravings, A, is the main steam pipe, and B, the auxiliary steam pipe. These pipes are one, inside the casting, so that one pipe supplies both. Assume the valve, C, moved to the left so that the port, D, is uncovered.

Live steam then flows through the port, D, and pushes the balanced piston valve, E, to the left, carrying the slide valve, F, with it to the left, so that the port, G, is opened to the steam cylinder. The steam enters through the port, G, pushes the main piston, H, to the left, completing one stroke of the piston. As the piston travels to the left the lever, J, pushes the crosshead, I, to the right, which opens corresponding ports in the left-hand end of the cylinder, and the piston valve, E, is pushed to the right, which admits steam on the left-hand side of the main piston through the port, K, pushing the piston to the right, completing the second stroke of the piston. The auxiliary slide valve, C, is operated by the crosshead, I, coming in contact with the tappets, L L.

The auxiliary tappets and stem, M M, theoretically could be dispensed with, but they are put in place for the reason that occasionally the valve, E, might stick, due to the pump standing for some time unused or from some other cause. In such a contingency the crosshead, I, is pushed to the right by the action of the main piston and comes in contact with the tappets, M M, which causes the piston valve to start, after which steam will complete the work. When the pump is running, the crosshead, I, never quite touches the tappets, M M, because it engages the tappets, L L, admitting steam to the piston valve and shifts it before the tappets, M M, are touched.

The reason of the double ports in the auxiliary steam chest is to have one port, D, for steam, and one port, N, for the exhaust. Steam being imprisoned between these two ports forms a cushion, preventing the piston valve from striking the heads of the chest. The tappets, L L, set closer together or farther apart control the stroke of the main piston, H. When the pump is running very fast the momentum of the moving parts increases and the tappets will have to be set closer together for high speed than for slow. The tappets, M M, are adjustable to their right relation with the tappets, L L. The general design and easy means of adjustment make a reliable single cylinder valve motion.

To set the valves. There are no complicated internal parts requiring adjustment, and almost all parts requiring manipulation can be handled while the pump is running.

THE WEINMAN.

The accompanying engraving, Fig. 289, represents the Weinman pump and the sectional engraving, Fig. 291, the valve motion.

The motion of the main piston is controlled by steam valve, A, which is a hollow cylinder combining a valve piston and slide valve in one and the same casting and sliding horizontally in steam chest, D. This valve is prevented from revolving by a cap screw, B. Small drilled openings, C, C, permit the steam to pass from the steam valve to each end of the steam chest, D. This valve, A, is moved horizontally in either direction by steam pressure, and the movement is controlled by an auxiliary valve, E. The openings, F, F (Fig. 290), conduct the steam from the ends of the steam chest to the auxiliary valve, which is connected to the piston rod by a tappet rod and the side arm, X.

Steam being admitted to steam chest, it passes through steam valve, A, to ports, H, H. As the construction permits but one of the ports, H, H, to be in communication at a time with one of the passages, I, I, leading to the opposite ends of the steam cylinder a dead center becomes an impossibility. While one of the ports, H, H, is in communication with one of the passages, I, I, the opposite passage, I, is in communication with the exhaust, J.

Suppose that the steam piston has moved to the end of its stroke, the auxiliary valve, which, as stated above, is connected to the piston rod, is shifted. This releases the steam from one end of the steam chest, D, through port, K, to exhaust, L. The steam pressure at the opposite end of the steam chest causes the steam valve to slide to opposite end of the steam chest, thus reversing the motion of the main steam piston.

To set the auxiliary valve, remove the pendulum or tappet lever, X, and the cap or bonnet, O, and take out the auxiliary valve, E. With a straight edge and scriber indicate the working edges on the end of the valve, and mark the edge of the port on the valve seat so that it can be seen when the auxiliary valve is in its proper place. Replace the valve, and the pendulum lever, omitting the bonnet.

Push the steam piston to one end of the stroke, then swing the pendulum lever toward the end of the cylinder corresponding to the piston, and until the auxiliary valve uncovers the port leading to the end of the valve chest farthest from the piston. Connect the horizontal rod to the bottom of the pendulum lever. Then remove the lever from the auxiliary valve stem and replace the bonnet and pendulum lever, shown by dotted lines. The length of the stroke may be regulated by raising or lowering the end of the horizontal rod in the slotted lower end of the pendulum lever. Lowering the rod produces a longer stroke, and raising it shortens the stroke.

Fig. 292.

The accompanying engravings illustrate the cylinder valves and valve motion of the Burnham single cylinder pump. Fig. 294 is a plan of the main cylinder valve face, having the same arrangement of ports as the cylinder shown in Fig. 293.

A longitudinal section of the steam cylinder is shown in Fig. 292. Motion is imparted to the slotted arm and cam, A, by means of a crosshead and a roller on the piston rod.

The cam works between and in contact with two blocks on the valve stem, and by adjusting these two blocks the stroke may be shortened or lengthened, as the case may require. The valve stem of the auxiliary valve, H, Fig. 293, always moves in a direction opposite to that of the piston.

The action of this valve alternately admits steam through the double ports, J J, and K K, to each end of the valve cylinder, causing the valve piston, I, to move the main slide valve, D, which, in turn, admits steam to the main cylinder through the double ports, E E, and L L. As the travel of the cam is only one-fifth that of the piston travel, the valve moves slowly, and without jar or noise which is often caused by long travel and rapid motion.

Steam enters the steam chest at B, and fills the space, F, between the valve piston heads and the auxiliary valve chest, G, shown in Fig. 292. With the auxiliary valve, H, in the position shown, Fig. 293, steam passes into both ports, J and K, but as the port, J₁, is closed by the valve piston, I, no steam can enter the valve cylinder through it, but the other port, K (extending to the extreme end of the valve cylinder), never being covered by the piston, is open, and admits steam into the space, M.

As this port is quite small the space fills slowly and the piston moves gradually until it uncovers the last port, J₁, when the full volume of steam is admitted, which quickly moves the piston to the opposite end of the valve cylinder. During this movement of the valve piston, the large port, J, remains open to the exhaust until it is covered by the valve piston. When the port, J, is covered by the valve as at J₁, it has no connection with the exhaust, consequently, there being no outlet for the exhaust vapor, it is compressed and forms a cushion for the valve piston, I. The valve piston carries with it the main valve, D, which admits steam to the main steam cylinder through the double ports, E, E₁, and L, L₁, Fig. 294. The same cushioning and slow starting of the piston occurs in the main as in the valve cylinder, each having double ports.

This arrangement insures a uniform travel of piston under varying degrees of load. A momentary pause of the piston at each end of the stroke permits the water valves to seat quietly, without shock or jar, and the slow initial movement of the piston (whereby the water columns are started gradually) relieves the pump and piping of excessive strains.

To set the valve. Set the lever, A, plumb and the valve to cover all the ports equally.

The Dean Bros. pump is shown in Figs. 295, 296 and 297.

The auxiliary valve, A, Fig. 297, has in its face two diagonal exhaust cavities, B B₁. The ports, C C₁, and the exhaust port, D, are placed in a triangular position with one another, the diagonal cavities diverging so that the cavity B, when the valve is in place, connects the ports, C₁ and D. Cavity B₁ connects the ports C and D, when the valve, A, is at the end of the stroke. The three small cuts show relation of auxiliary valve to ports.

The piston starts from left to right when the valve, A, moves in an opposite direction, opens the port, C, admitting steam to the auxiliary cylinder at the moment the main piston has reached the end of its stroke. The auxiliary piston, E, is forced to the left, opening the main port and admitting steam to the main cylinder, reversing the movement of the main piston the return stroke of the main piston reverses the movement of the auxiliary valve, whereby the port, C, is closed, at the moment the main piston reaches the end of its outer stroke. The port, C₁, is opened by the valve, A, and reverses the valve piston, E, opens the main port and reverses the motion of the main piston.

This port arrangement admits of a short valve with a long travel. The stroke of the pump can be regulated by moving the stud up or down in the segmental slot, Fig. 296, which varies the travel of the auxiliary valve and reverses the stroke of the main piston as desired. By raising the stud the pump will make shorter strokes, and by lowering it will make longer strokes.

The motion of the auxiliary steam slide valve is like that derived from an eccentric. The ports leading to the valve piston, E, Fig. 297, remain closed, except at the moment the main piston is reversed; hence, there can be no waste of steam from leaks when the valve piston becomes worn.

Having a long stroke and a rapid motion, the auxiliary valve insures a certain reversal of the piston at the proper time.

To set the valve, turn the steam chest upside down. Put valve stem through the stuffing-box and secure in place the clamp for small slide valve. The diameter of valve stem is smaller where the clamp is attached.

Now screw up the stuffing-box nut (having previously removed the packing), then move the valve and stem so that the small port at right of valve will be open ¹/₁₆ inch and make a scratch upon the stem close to stuffing-box nut. The valve should then be moved in the opposite direction to open the other small port ¹/₁₆ inch and make a second scratch upon the valve stem next to stuffing-box nut. Prepare joint and replace steam chest on cylinder. To square the valve, slacken the screw in crosshead and move the latter to the end of stroke with edge of crosshead flush with the end of guide, then set the valve stem so that the first scratch is flush with the face of nut, same as when the scratch was made. Tighten screw in set screw under valve rod dog and move the crosshead to the opposite end of stroke, and note the position of second scratch. If it does not come to the position in which it was made, split the difference by slackening the set screw under valve rod dog and move the valve rod to equalize the travel of valve.

In replacing steam chest on cylinder, cover the opening with a thin board, or piece of sheet iron, before turning it over to prevent the valve from dropping out of place.

This slide valve has a fixed travel and the process of setting is precisely the same as for that upon a steam engine with a plain slide valve.

Figs. 298, 299.

The accompanying sectional view of steam end of the “Smith-Vaile” exhibits some very novel features. So far as the piston and cylinder in this pump are concerned they are not unlike the average first class pump, but with this difference. It has only one set of cored ports, B, B. The supplemental ports, C, C, are drilled.

The main valve, A, is a slide and is moved by a valve piston, D. Almost all the valve pistons as now made are simply plugs turned accurately to fit the holes in the chest and without any means of adjustment to compensate for wear. After these valve pistons become worn they have to be replaced with new ones, but there is a period between the time when the valve piston becomes so leaky as to render the action of the pump uncertain and the time when the worn valve is replaced by a new one that the pump is very wasteful of steam.

The valve piston in this pump is provided with packing rings, E, E, which compensate for wear of these parts so that this valve is expected to do efficient service long after a slow valve. The supplemental valve, F, has a reciprocating rotary motion which is communicated to it by the rock arm, G, and pitman, H, connecting with the crosshead, I, secured to the piston rod. It will be observed that the piston rod, J, and the rod, K, of the water end are separated so that should either one give out through wear or accident it can be replaced without sacrificing both, as would be the case if they were solid in one piece. This supplemental valve, F, in general appearance very closely resembles the “Corliss” valve, and its action is somewhat similar, in controlling the action of the valve piston, which will be understood from the engraving without further description. These pumps all have removable water ends and can be rebored or otherwise manipulated without disturbing the steam end of pump. The cylinder can be separated from the foot by removing the bolt, M.

The duplex pump is also shown in the accompanying engraving, where, A, A, represents the steam cylinders, secured to the foot, B, by bolts, as previously described.

The usual slide valves have been replaced by piston valves, C, in this instance and are provided with removable seats, D, D.

These piston valves have packing rings, E, E, also to compensate for wear and the valves are cast hollow to reduce their weight as much as possible consistent with good workmanship, also to serve as ports for steam admission. When these valve seats become worn they may be easily removed and rebored or replaced by new ones, as desired. It will be observed that these ports are very short to reduce the clearance as much as possible, and to secure a more satisfactory cushion. Each valve is operated by the rock arm connected with the opposite engine in the usual way.