US2290788A - Slush pump - Google Patents

Description

Patented July 21, 1942 UNITED STATES OFFICE SLUSH PUMP John Hart Wilson, Wichita-Falls, Tex.

Application July 10, 1939, Serial No. 283,652

4 Claims. (01.13826) The present invention relates to pumping mechanisms and particularly to pumps of the type employed in well drilling operations for supplying mud or slush in the quantities and at the pressures necessary to facilitate such operations.

The modern well drilling mechanism is usually known'as a portable drilling rig or rotary rig, and usually includes as one of its operatingunits a pump for withdrawing mud or slush from a slush pitor other storage reservoir and delivering itunder pressure to a conduit by means of which it is led to the drilling mechanism. It is generally preferred to use for this purpose a pump of the crank and piston type having a plurality of cylinders into each of which the mud is drawn and from which itis immediately thereafter expelled. As is wellknown, the rate of flow of fluid passing into the cylinder of a piston type pump' operated by a crank Varies throughout the suction stroke of the piston, varying closely as the sine of the crank angle. Likewise, in the case where two cylinders are employed and the cranks are disposed at right angles, the flow of fluid into-either cylinder is greatest when the crank has reached a position at right angles to the cylinder axis, and with the crank in this position the flow of fluid into the other cylinder is theoretically zero. When the cranks are somewhat further advanced, both cylinders will be drawing fluid at the same instant and when in one position the rate of flow of the fluid toward the cylinders will be approximately 41% greater than it is when one piston is pumping at its maximum rate and the other piston is pumping at its minimum rate, or zero.

In the event that there are four working cylinders and the pump is a two-cylinder duplex pump, this variation inflow to the pump, or cycle, will repeat itself every 90 of crank angle movement. Hence it follows thatthere must be a very considerable'variation in the rate of flow of the stream offluid passing through the suction inlet aperture of the pump, and a corre-' sponding variation of flow in the slush intake conduit leading to this port. Because of this, complications arise in the pumping of mud or slush, which fluid is much heavier than water, and considerably more viscous, so that it is much more difiicult to quickly accelerate streams of such slush than streams of lighter and more freely flowing fluids. As a result, a vacuum is frequently created'b'ehind the piston" of a mud pump "moving on itssuotion stroke. An'y'such vacuum made'by a receding piston of'course re duces the eficieiicyof the pump; prevents it'from being operated at'as'highaspeed as desired, and also causes" ounding; the piston on its return stroke striking the solid body of "fluid with a considerable force, the poundingbeingsufiicient if continued to actually wreck the pump.

It has heretofore been suggested that there may advantageously be employed in connection with a multi cyliiider piston and crank type'of slush pump a" device which may be designated a suction air"cha'mb'er, this'air chamber being connected toth'e'top of the suction line and'actihg as a' storage reservoir for a relatively small quantity ofslush which maybe drawn downwardly into the suction line when the pump 'demand suddenly increases and which, theoretical 1y atle'ast, is againrestored' to the'storage'chamher when the fluid flow to the pump is deceleratin rather" than" accelerating." Naturally there should exist" in' the suction air chamber, above the level of the fluid therein; a partial vacuum, and'if this partial vacuum is notmaintained, the suction air chamber becomes Wholly ineffective; In fact; unless the suctio'r'i air chamber'or auxiliary slush storage" chamber is maintained in proper operatingpondition', it'is'worse'than useless, sinceit may become simply a' reservoir for air which may be withdrawn into" the infiowing stream' of -slush inlar'ge sii'lglevolumes, causing loss of efi'iciency, pounding," and other undesirable effects. The mud or slush being pumped usually contains aif'or other gas and some muds contain substantial quantities of gases. Con"- tinual leakage-of thesegas'e'sfrorri the mud p'assirg'to the pump intake, upwardly into the'aux'il iary chamber will destroy th'ep'artial vacuum therein and thereby render the chamber useless, since the only means for evacuating"the'air'from the chamber is the' pump itself; and the pump is only effectivein accomplishing this'when it' is initially operated and the passage between pump and chamber isas yet unobstructedbyinflowing slush.

It is the general purpose" of "the" present invention to provide means in association with a slush or mud pump of the crank and piston typewhich wil-l be'effective in smoothing'out the operation of the pump and increasing its efiiciency', par ticularly at high speeds 'of operation. This is accomplishe'd' by" providing means for rendering efficien't the' heretofore" discredited suction air chamber; Such means includes automatically operating mechanis'm for maintaining a rede termined' degreeof sub-atmospheric pressure iii the top of the chamber andto therefore control the volume of mud or slush in the chamber within close limits. Preferably I position a vacuum pump closely adjacent the auxiliary chamber, and by a float controlled valve, bring the interior of the upper end of the chamber into communication either with this pump, or with the atmosphere. Likewise, I connect the lower end of the auxiliary chamber to the pump intake line in a novel manner which eliminates the possibility of air or gas passingupwardly into the auxiliary chamber from the inflowing stream of slush. As a result of the employment of the invention a mud pump of given size may be used to deliver increased quantities of mud by being operated at higher speeds than heretofore found 7 possible.

The improved mechanism is of very simple construction and may be embodied in various forms to suit special conditions. In the accompanying drawing one form of the mechanism is illustrated by way of example but it will be appreciated by one skilled in the art that the component elements of the invention may be varied in position and design without sacrifice of any of its advantageous results.

In the drawing:

Figure 1 shows, in side elevation, a slush pump of one type employed in oil field operations and likewise a mud or slush storage chamber of the type contemplated by the present invention, this chamber being partially broken away;

Figure 2 is an axial vertical section through the lower portion of the auxiliary slush storage chamber and portion of the slush supply conduit, showing the port connecting conduit and chamber;

Figure 3 is a section on line 3,-3 of Figure 2; and

Figure 4 shows in side elevation a slush storage chamber to which has been added means for automatically operating the valve which controls communication with a vacuum pump or the atmosphere.

The details of construction of the pump, which is indicated at P, are not illustrated in the drawing since the pump may be of any suitable type of crank and piston pump having the capacity required. The pump shown may be driven from any convenient source of power, such as a gasoline engine, and has an inlet port at a low level. The actual inlet port of the pump is not shown but will be located at the end of the pipe section l0, which comprises one unit of the mud or slush conduit which extends from the pump P to the slush pit. Iube or pipe I is shown in section in Figure 2 and it will be observed that it is provided with annular rings II and I2 by means of which one end of the tube may be attached to the frame of the pump and the other end to another pipe section such as indicated at I0. Encircling pipe section H] are the annular elements l3 and I4 the inner edge of each of which is welded to the outer surface of the pipe. Encircling pipe I0 and having its ends engaging and welded to the annular elements I3 and I4, is a sleeve 15. Sleeve I5 has formed therein a relatively large aperture IS in its upper portion.

The storage chamber for mud or slush is indicated at H, this storage chamber being tubular and having its lower end attached as by welding to the sleeve IS, the opening in its lower end being in register with the aperture l6 formed in the sleeve. The undersurface of the tube I0 is cut away intermediate the annular rings I3 and M, to provide a port 3 which brings the interior of the tube I0 into communication with the interior of the sleeve l5 and hence with the interior of the mud storage chamber H. To the upper end of the storage chamber I! there is connected a short tube 20, this tube being in communication at its upper end with a horizontally extending pipe 2| one end of which, indicated at 2|, being connected to a vacuum pump or to a chamber in which a sub-atmospheric pressure obtains, the other end, indicated at 2| being open to the atmosphere. A valve 22 controls communication between pipes 2| and 2| and valve 23 controls communication between the pipe 2| and the pipe 2 I By manipulating the valves, the interior of the storage chamber may be brought into communication either with the atmosphere or with the air exhausting means and hence the operator may establish within the chamber I! the exact degree of sub-atmospheric pressure which he desires.

A glass gauge is indicated at 25 by means of which the operator is enabled to ascertain the depth of the mud or slush within the storage chamber. Ordinarily the degree of subatmospheric pressure within the chamber will be so regulated with reference to the pump suction and other factors that the level of the upper surface of the slush within this chamber will be approximately that indicated in Figure l, the slush being drawn from the conduit It through the port I8 into the chamber defined by the annular members I3 and I4 and the cylindrical member I5 and thence upwardly into tubular chamber When the pump P is in operation and its pumping capacity varies in the manner previously described, slush will be drawn from the storage chamber when needed and subsequently returned, thus smoothing out the inflow of liquid and making it unnecessary for the pump to accelerate the flow of the entire stream of slush back as far as the intake of conduit |3 at any time. The storage chamber will continue to function in this way indefinitely, although it may be necessary from time to time to manipulate the valve 22 to connect the chamber H to the vacuum pump in order to maintain the pressure within chamber H at the desired point. However, increase in pressure in the chamber I! will occur only slowly since little, if any, air escapes into this chamber from the slush passing through the pipe section ID. This is because the air bubbles in the onflowing slush tend to gather at the top of the stream of slush and hence cannot escape into chamber because the communicating port I8 is .formed in the bottom of the pipe section I0.

In the form of the invention shown in Figure 4, the pressure within the slush storage chamber is automatically maintained at approximately a predetermined value by automatic means and hence the slush level automatically maintained at approximately the desired point. In this case it is preferred that a single valve 30 be employed which valve is of such type that it may be moved to bring the vertical conduit 3|, and hence the slush storage chamber 32, either into communication with pipe or duct 33 leading to the atmosphere or pipe or duct 34 leading to a vacuum pump. The valve likewise has a third or intermediate position in which the pipe 3| is wholly closed so that the interior of the storage chamber 32 is out of communication with both the atmosphere and vacuum pump or the like.

Valve 33 is automatically actuated, the arm 35 fixed to the valve stem being connected by means of a link 36 to one arm of a two-arm lever 31, the other arm of which is pivotally attached to the float 38 supported by its own buoyancy upon the surface of the slush in a float chamber 39 disposed laterally of the storage chamber 32. Lateral conduits 40 and 4| bring the interior of the float chamber 39 into communication with the interior of the slush storage chamber 32 at vertically spaced points so that the elevation of the upper surface of the body of slush in the float chamber 39 is always the same as that of the level of the surface of the body of slush within the storage chamber 32. Change of liquid level in the float chamber, therefore, results in either rising or falling movement of the float and actution of the valve 30. The valve is thus automatically operated to bring the interior of storage chamber 32 into communication with either the duct 33 or the duct 34 so that no attendant is needed to maintain the slush storage system operating with maximum efficiency.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. The combination with a conduit through which slush or the like may be drawn by suction, of a chamber for the storage of a quantity of slush to be drawn downwardly into the conduit when the pressure in said conduit is suddenly decreased due to sudden increase in suction, said chamber being above the conduit, closed to the atmosphere, and communicating with the interior of the conduit only through an opening formed in the underside of the conduit.

2. The combination with a conduit through which slush or the like may be drawn by suction, of a chamber for the storage of a quantity of slush to be drawn downwardly into the conduit when the pressure in said conduit is suddenly decreased due to sudden increase in suction, said chamber being above the conduit and communicating therewith only through an aperture formed in the underside of the conduit, and means for maintaining an approximately constant subatmospheric pressure within said chamber above the level of the surface of the slush.

3. The combination with a conduit through which slush or the like may be drawn by suction, of a chamber for the storage of a quantity of slush to be drawn downwardly into the conduit when the pressure in said conduit is suddenly decreased due to sudden increase in suction, said chamber being above the conduit and means for maintaining an approximately constant subatmospheric pressure within said chamber above the level of the surface of the slush, said means including a duct leading from the top of said chamber, a vacuum pump to which said duct is connected, a duct leading from said chamber to the atmosphere, valve mechanism controlling both ducts, a float positioned to rise and fall with level of the surface of the body of slush within the chamber, and means operatively connecting the float to the valve mechanism.

4. The combination with a conduit through which slush or the like may be drawn by suction, of a chamber for the storage of a quantity of slush to be drawn downwardly into the conduit when the pressure in said conduit is suddenly decreased due to sudden increase in suction, said chamber being above the conduit and closed to the atmosphere, a sleeve encircling said conduit and having a port therein to bring the interior of the sleeve into communication with the interior of the chamber at the lower end thereof and closures for the ends of the sleeve, the conduit having an aperture formed in its underside intermediate said closures whereby the interior of the conduit is maintained at all times in communication with the interiors of the sleeve and chamber.

JOHN HART WILSON.

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