US3444889A - Pump valves - Google Patents

Description

May 20, 1969 o. M. KIEL ET AL 7 3,444,889

PUMP VALVES Filed Aug. 18, 19 66 OTHAR M. L INVENTORS HAROLD L. GR M ATTORNEY United States Patent 3,444,889 PUMP VALVES Othar M. Kiel and Harold L. Graham, Houston, Tex.,

assignors to Esso Production Research Company, a corporation of Delaware Filed Aug. 18, 1966, Ser. No. 573,418 Int. Cl. F16k /12, 17/196 U.S. Cl. 137547 9 Claims ABSTRACT OF THE DISCLOSURE A valve body for a reciprocating pump for handling fracturing fluids or similar liquids containing suspended particles of predetermined size including a perforated skirt that extends below the valve body into the seat as the valve closes so that suspended solids are excluded from the terminal portion of the discharged fluid and particles that might otherwise be trapped between the body and seat are swept away by fluid from which the solids have been excluded.

This invention is concerned with valves for pumps handling fluids containing suspended solids and is particularly directed toward improved valves for high pressure pumps used in hydraulic fracturing operations and similar processes.

High pressure triplex pumps are generally used for the injection of fracturing fluids into oil and gas wells. In most cases these fluids contain suspended sand grains, glass beads or similar propping agent particles. The suspended particles carried by the fluid are trapped in the pump valves as the valves close. This damages the valve bodies and seats, particularly when the solids are present in high concentration, and necessitates their replacement at frequent intervals. It is common practice to install new valves at eight hour operating intervals and to provide standby pumps for use in case valve failures occur during fracturing operations. Efforts to develop better valves and thus avoid this expense have in the past been largely unsuccessful.

In accordance with this invention, it has now been found that the difficulties outlined above can be alleviated by utilizing valves provided with slotted skirts located upstream of the valve contact surfaces. These skirts extend beyond the contact surfaces a sufficient distance to screen suspended solids from the fluid entering the valves just before they close. The skirt lengths are such that the solid-free fluid displaces particles from between the valve bodies and seats before contact is made. This reduces valve damage and makes possible the use of higher propping agent concentrations than have generally been practical heretobefore.

The nature and objects of the invention can best be understood by referring to the following detailed description and the accompanying drawing, in which:

FIGURE 1 is a cross-sectional view of a pump valve provided with a rubber skirt on the valve body;

FIGURE 2 is a bottom view of the valve body shown in FIGURE 1; and,

FIGURE 3 is a fragmentary view of an alternate embodiment of the invention.

The valve structure depicted in FIGURE 1 of the drawing includes a circular valve body 11 which is bevelled on the underside to form an annular contact surface 12. The peripheral portion of the body above the contact surface is recessed between an upper annular shoulder 13 and a lower annular shoulder 14. A seal ring 15 provided with a bevelled lower face 16 is mounted on the outer body surface above and in contact with lower shoulder 14. The seal ring may be made of neoprene,

Patented May 20, 1969 oil-resistant plastic or similar material. The bevelled lower face of the seal ring projects outwardly beyond contact surface 12 on the body. A metallic retaining ring 17 containing an internal shoulder 18 near the upper end thereof seats against the upper surface of the seal ring and is held in place below upper shoulder 13 on the body by snap rings 19 and 20. The top of the body is recessed to retain coil spring 21 which bears against the pump structure above the valve assembly and actuates the valve. The spring loading is such that the valve closes as the power piston reaches the end of the stroke. The surrounding pump structure is conventional and is therefore not shown in the drawing. The underside of the valve body 11 is provided with a stem or rod 22 by means of which the body is supported above the valve opening. This rod extends downwardly into sleeve or guide 23 of neoprene, brass or a similar low friction material. The sleeve in turn is held in place by bracket 24, attached to the pump structure 25 below the valve opening. The bracket extends across the opening as shown without substantially impeding the passage of fluid upwardly toward the opening. In lieu of the single rod depicted, two or more rods or similar members located near the outer portion of the body and extending downwardly to suitable supporting members attached to the pump structure may be provided. Still other conventional methods for supporting the valve body and permitting reciprocal movement with respect to the valve opening may be employed and will be familiar to those skilled in the art. The valve seat which extends about the opening and is held in place in the conventional manner is indicated by reference numeral 26. Contact surface 27 on the seat faces surface 12 on the underside of the body.

The valve stem or rod 22 in the apparatus of FIGURE 1 is enlarged below body 11 and provided with threads 28. The lower surface of the body is recessed between contact surface 12 and the threaded portion of the stem or rod to accommodate the perforated skirt used to prevent the entrapment of solids as the valve closes. The skirt employed in this embodiment comprises a disk 29 of neoprene rubber, oil-resistant plastic or similar resilient material which extends downwardly from the recessed portion of the body surrounding the guide. This disk is held in place by circular plate 30 and nut 31. The portion of disk 29 extending laterally beyond plate 30 contains radial slots or similar openings 32. These are shown more clearly in FIGURE 2 of the drawing. The length of the skirt or distance the disk projects below contact surface 12 of the valve body and the width of the slots are determined in part by the size of the solid particles in the fluid to be pumped. The length of the skirt should be less than the travel of the valve body between the open and closed positions and will generally be from about one and one-half to about ten times the maximum propping agent particle diameter. A travel distance of about five-eights of an inch is conventional. The slots or similar openings should be sufficiently small to exclude propping agent particles from fluid passing through the slots. The propping agents employed in hydraulic fracturing operations are generally made up of particles less than about two and one-half mesh but greater than about mesh on the U.S. Sieve Series Scale. Narrow size ranges bewteen these extremes are normally used. For a propping agent containing particles less than about eight mesh but greater than about 12 mesh in size, slots about 0.060 inch wide will be satisfactory. The skirt length should be about 0.14 inch or more where such particles are used. If a propping agent containing four to six mesh particles is employed, a slot width of about 0.125 inch and a skirt length of about 0.28 inch or more will generally be satisfactory. Since the dimensions utilized thus depend to some extent upon the size of the particles present in the fluid, it is advantageous to employ a replaceable disk or skirt as shown. This makes possible the use of fluids containing solids of various sizes without the necessity for replacing the entire valve body.

As pointed out above, the skirt shown in FIGURES 1 and 2 of the drawing comprises a replaceable disk of neoprene rubber or similar resilient material. Although such a resilient disk is generally more resistant to damage by the high pressure fluid and suspended particles, a slotted disk of steel or similar metal can also be used. Where a metallic member is employed, it may be made an integral part of the valve body. FIGURE 3 shows such an integral skirt. By extending the body 11 downwardly behind the annuar contact surface 12 and providing radial slots or similar perforations 40 in the edge of the extended portion, results similar to those secured with the structure shown in the drawing can be obtained. Where an integral skirt is used, the center portion of the underside of the body may be recessed so that the skirt forms a ring on the lower body surface. Slots or other perforations may extend all the way through this ring instead of being blind at their inner ends as shown. This simplifies the fabrication of valve bodies with integral skirts and may therefore be preferred. These and other modifications will be apparent to those skilled in the art.

During operation of the pump, fluid containing suspended solid particles passes upwardly around bracket 24 and between body 11 and seat 26 as shown by the arrows as long as the valve is open. Near the end of the pump piston stroke, spring 21 forces the valve body downwardly with respect to the seat and surrounding structure. Fluid containing suspended solids continues to flow between the body and seat as long as the lower edge of disk or skirt 29 is separated from the inner edge of the seat a distance greater than the diameter of the smallest particles present in the fluid. Thereafter, fluid flow is confined to the slots in the skirt and the narrow opening between the skirt and seat. Suspended particles are screened out against the surface of the disk or skirt and do not pass through the slots. The clearance between contact surface 12 on the body and opposing surface 27 on the seat at this point exceeds the diameter of the largest particles in the fluid and hence particles already present in the space between the two contact surfaces are swept out by the solids-free liquid. Complete closure of the valve can now take place without the entrapment and crushing of particles between the valve body and seat. On the next stroke of the pump, the particles accumulated adjacent the skirt are swept through the space between the body and seat as the valve opens. This screening out of the particles from the fluid as the valve closes substantially reduces valve damage and makes possible longer continued pump operation than has generally been feasible in the past. Although the valve structure of the invention has been discussed in terms of hydraulic fracturing fluids, it will be apparent that pumps containing the improved valves may be used with fluids containing other granular solids of comparable size.

What is claimed is:

1. A circular valve body for a reciprocating pump for handling fluids containing suspended solid particles of predetermined size, said body including an upper surface provided with means for retaining a spring used to actuate the valve, a lower surface tapered at the outer edge to form an annular contact face, means on said lower surface for supporting said body above a valve seat in the body of said pump, and a circular skirt on said lower surface extending downwardly adjacent the inner edge of said contact face, the length of said skirt being less than the travel of said valve body between the open and closed positions, said skirt containing a plurality of elongated fluid passageways extending inwardly in the lower surface of the skirt beneath the portion of the valve body surrounded by said annular contact face and each of said passageways being sufliciently small to exclude suspended particles of said predetermined size from fluid passing through said passageway.

2. A valve body as defined by claim 1 wherein said skirt comprises a disk attached to said lower surface of said body and wherein said passageways are elongated slots in said disk, the width of each slot being less than the diameter of said particles of predetermined size.

6. A valve body as defined by claim 2 wherein said disk is made of a resilient rubber-like material.

4. A valve body as defined by claim 3 wherein said means for supporting said body comprises a valve stem extending downwardly from said lower surface.

5. A valve body as defined by claim 4 wherein said disk is held in place by a plate connected to said valve stem.

6. A valve body as defined by claim 1 wherein said skirt is an integral part of the valve body.

7. A circular valve body for a positive displacement pump used to handle fluids containing suspended solid particles of predetermined size, said body including a tapered annular contact face near the outer edge thereof, a circular skirt of rubber-like material surrounded by said contact face and extending downwardly below said face adjacent the inner edge thereof a distance less than the travel distance of said valve body between the open and closed positions, said skirt containing a plurality of elongated slots extending inwardly beneath said body from the skirt periphery, said slots being open for the entry of fluid from beneath said body and the width of each slot being less than the diameter of said solid particles of predetermined size, and at least one elongated supporting member extending below said skirt.

8. A valve body as defined by claim 7 wherein said skirt comprises a disk of said rubber-like material aflixed to the lower surface of said valve body.

9. A valve body as defined by claim 8 wherein said disk is partially recessed with respect to said contact face.

References Cited UNITED STATES PATENTS Re. 20,246 1/1937 Binnall 251-40 XR 896,939 8/1908 Roberts 137547 XR 2,002,672 5/ 1935 Melott 137-516.29 2,024,270 12/ 1935 Binnall 25140 XR 2,706,490 4/ 1955 Grieshaber et al. 137-51627 HENRY T. KLINKSIEK, Primary Examiner.

US. Cl. X.R. 137516.29

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