US 3419041 A
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Description (OCR text may contain errors)
1968 E. R. JENNINGS 3,41
PUMP VALVE Filed Aug. 23. 1965 EARL R. JENNINGS INVENTOR BY 49M ATTORNEY United States Patent "ice 3,419,041 PUMP VALVE Earl R. Jennings, Tulsa, Okla., assiguor to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed Aug. 23, 1965, Ser. No. 481,690 Claims. (Cl. 137-533.19)
ABSTRACT OF THE DISCLOSURE This application discloses a valve for use in pumps in pumping sand-laden fluids from well bores. It includes a single-surfaced, tapered, ring-like valve seat supported by a pump cage. A special valve is adapted to freely reciprocate within the valve cage and includes a disc-like resilient seal placed about the stem of the valve. Placed adjacent to the resilient seal around the stem is a hard seal. The outer peripheral surfaces of the resilient seal and the hard seal mate with the interior tapered surface of the valve seat. The resilient seal is of a greater diameter than the hard seal. If the hard seal is prevented from sealing, differential pressure across the valve compresses the resilient seal to form a fluid-tight seal with the valve seat.
This invention relates in general to pumps and more particularly to a new and improved valve especially for use in pumps in pumping fluid from well bores.
In the production of oil, a well is first drilled to an underground reservoir. At first the pressure of the oil within the reservoir is usually sufficient to cause the oil to flow from the reservoir upwardly through the well bore to the surface. After a while, however, the pressure of the fluid in the reservoir usually declines to a point so the well will not flow. When this occurs, artificial lift of the fluid from the bottom of the well bore to the surface is initiated. A common way of lifting the oil to the surface is by the placing of a reciprocating pump in the well bore adjacent the formation. Then as oil runs into the well bore from the formation, it is forced by the pump through a string of tubing to the surface. The pump is usually reciprocated by a long rod, commonly called a sucker rod, extending from the formation at the bottom of the well to the surface where it is driven by a power source such as an electric motor. Such pumps commonly contain two valves, one called a traveling valve and the other a standing valve. These valves are commonly ball-type check valves. Such valves are usually satisfactory. However, some oil contains troublesome particles of entrained sand. When such ball-type check valves are used with oil containing sand there is a high rate of failure of the valves. When the valves fail, the pump must be pulled to the surface from the bottom of the well and the valves replaced. This is a costly and time-consuming operation. It is therefore seen that there is a need for a valve which can withstand a considerable amount of pumping of sand-laden fluids without failure. Such a valve is disclosed herein.
A complete understanding of my invention and the various objects can be had from the following description taken in conjunction with the drawings in which:
FIGURE 1 illustrates details of a conical shape valve of my invention;
FIGURE 2 illustrates the incorporation of such improved valve in a downhole well pump; and
3,419,041 Patented Dec. 31, 1968 FIGURE 3 illustrates the angle of the taper of the valve seat.
Attention is first directed toward FIGURE 1 which illustrates a preferred embodiment of the improved valve of my invention. Shown thereon is a valve cage 10 in which a valve 12 is positioned. Valve cage 10 has longitudinal slots or openings 35 at the upper end for the flow of fluid therethrough. A conical seat 28 is held in place at the lower end of cage 10 by lower tubular member 24 which connects by thread- 26 with cage 10. Valve 12 comprises a body which includes a spool having an upper head 17 and a lower head 15 and a stem 16 extending downwardly from the center of lower head 15. Upper and lower heads 17 and 15 are disc shape and are slightly smaller in diameter than the interior of cage 10. The cage guides these heads so that valve 12 is guided into seat 28.
Valve 12 has a primary or hard seal 20 and a secondary or soft seal 18 mounted on stem 16. The secondary seal 18 and primary seal 20 are held in a confined but uncompressed position about stem 16 by retaining nut 22 which is threadedly attached to stem 16 at the lower end. The peripheral surfaces of seals 18 and 20 and retaining nut 22 take the form of a conical surface and mate with the internal seating surface of seat 28.
Consideration will now be given to the preferred material for various parts of valve 12. The valve body including heads 15 and 17 and stem 16 is preferably made of stainless steel such as type 316 to provide resistance against corrosive effects of well fluids. Retaining nut 22 is also preferably made of the same material as heads 15 and 17 and stem 16.
Primary seal 20 is made of a hard durable metal such as tungsten carbide. The exterior surface is tapered to match with the sealing surface of valve seat 28. Valve seat 28 is made of a hard metal, preferably tungsten carbide. Primary seal 20 effects the primary fluid seal through metal to metal contact with valve seat 28.
The secondary seal 18 is a soft seal and is a deformable or resilient seal which can be deformed and then returned to its original configuration. A preferred material for the secondary seal is urethane, a material which is an elastomer compound with a hardness of from about to durometer on the Shore scale (ASTM-D676-58T) which is the preferred hardness for the secondary seal. This particular material is resistant to the effects of most oil well fluids and is sufficiently resilient to permit embedment of said particles should they become lodged between the sealing surface of the secondary seal and seat 28. The exterior surface of the secondary seal 18 is fabricated to a continuation of the same taper as that of the primary seal 20 and both match the tapered surface of seat 28. The primary and secondary seals 20 and 18 are positioned upon stem 16. In other words, these seals are not bonded to the stem or body. To obtain this, care is taken so that the tightening of retaining nut 22 does not compress soft seal 18. It is preferred that nut 22 be tightened so that the seals 18 and 20 are held firmly between head 15 and nut 22 but not tightened to the extent that seal 18 is greatly deformed. A pin 27 is then inserted through retaining nut 22 to prevent further movement.
FIGURE 3 illustrates a cross-section of valve seat 28. The interior surface of valve seat 28 tapers upward and outwardly. This tapers outwardly at an angle a of preferably between about 14 to about 20 and especially at about 15. As stated above the outer periphery of seals 18 and 20 is ground or otherwise fabricated to match the taper of valve seat 28. When these preferred angular dimensions are followed, the matching taper on seals 18 and 20 with valve seat 28, results in a selfreleasing type fit.
Attention is next directed to FIGURE 2 which shows valve 12 and its associated seat 28 of FIGURE I inserted in a downhole reciprocating pump suitable for use in a well bore. Shown in FIGURE 2 is a traveling valve cage or barrle 30 and its associated traveling valve 12A. Traveling valve cage 30 is provided with threads 32 for connection to a string of sucker rod (not shown) which extend to the surface. The sucker rods are supported within a string of tubing (not shown) through which oil is pumped to the surface. Valve seat 28a is retained between the lower end of traveling cage 30 and lower tubular member 24a. Traveling valve 12A and seat 28A represent valve 12 and seat 28 of FIGURE 1 inserted in the traveling barrel of a downhole reciprocating pump.
Also shown in FIGURE 2 is the standing valve cage 34 of the reciprocating pump and its associated standing valve 12B, and valve seat 2813 which is held in position by tubular member 24B connected to standing valve cage 34. Valve 12B represents valve 12 placed in the standing valve cage 34- of the downhole pump. The lower end of tubular member 24B is provided with seating cups 36 which are forced into seating engagement with a tubular member (not shown) hung in the well in a conventional manner to hold the standing valve assembly in a fixed position.
By traveling valve assembly it is meant those parts which reciprocate when the well is being pumped and includes a traveling cage 30, traveling valve 12A, seat 28A, and tubular member 24A. By the standing valve assembly is meant that portion of the pump which remains essentially stationary during pumping operations and includes standing valve cage 34, valve 12B, valve seat 28B, lower member 24B and seating cups 36.
The lower end of tubular member 24A of the traveling assembly is provided with internal shoulder 38. Shoulders 38 are arranged to engage the lower surface 40 of angular shoulder 42 of the standing valve cage 34 when the traveling assembly is in its upper position with respect to the standing valve assembly. As is known, this provides a means for removing the standing valve by upward pull on the traveling assembly by the sucker rods in a conventional manner. The lower surface of interior shoulder 38 of the traveling valve assembly mates with upper angular shoulder 39 of the standing valve assembly.
As mentioned above, one of the main causes of valve failure in downhole oil pumps is sand erosion and fluid cutting. When a sand particle is caught between a hard valve element such as a steel ball and a hard seat, the valve does not seal. Thus fluid leaks by the valve and in some cases obtains a rather high velocity. This high velocity of a fluid between the valve and valve seat causes severe damage and is commonly known as fluid cutting. The exact theory of how my valve works may not be completely understood; however, a consideration of the valve shown in my invention will indicate how damage is minimized or practically eliminated. If a sand particle is caught between the valve and the valve seat it will be between hard valve seat 28 and either the soft seal 18 or the hard seal 20. If a sand particle is caught between soft seal 18 and hard seat 28, the sand grain is embedded in the soft seal, and the primary seal is between the two hard metals. Thus there is no leakage of fluid by the valve. If the sand particle is caught between the two hard metals there is a pressure differential across the soft seal 18 caused by the fluid load in the tubing above the valve which deforms the soft seal and effects a positive fluid seal between the soft seal and the valve seat. Thus, again no leakage of fluid by the valve. Should a sand particle also be caught at the same time between the soft seal and the valve seat and the head seal and the valve seat (which is believed to be highly unlikely), then this same pressure differential would occur and the soft valve is deformed to cause a positive seal, even around the sand particle embedded therein, thus once again preventing any fluid cutting damage. If no sand is caught when the valve starts to seat the hard metal valve 20 seats against the hard seat 28.
Several valves of the type described above have been built. Before putting them in field use a testing program was effected. The testing was carried out in one embodiment of the valve of this invention under greatly accelerated conditions in order to include as many cycles (opening and closing) of such test valve in as short and reasonable a period of time as possible. In this test oil containing approximately 5 to 10% formation sand of about -60 +325 U.S. sieve size, was pumped through the valve. In this test, the valve cycled at the rate of 360 cycles per minute at 100 p.s.i. differential pressure across the seals while circulating sand-laden oil. At the time the test was terminated, a total of 30,500,000 cycles had accumulated without failure. Converting this total to a representative rate of operation of 12 strokes per minute, the time is equivalent to 4.85 years of continuous pumping. At the conclusion of this test the valve was still performing satisfactorily although it did show uniform wear on the primary seal disc and valve seat. The primary seal showed a reduction of .118 inch from its original diameter of 1.200 inches, while the valve seat showed a .030 inch increase in diameter from its original diameter of 1.365 inches. The urethane secondary seal 18 showed considerably less wear. The distribution of wear and erosion on the sealing surface was uniform, therefore compensation of such wear was made through deeper setting of the tapered surfaces. Seat 28 and primary valve seal 20 of this test valve were made of A151 4130 carbon steel. By making the seat and primary valve of a harder metal such as tungsten carbide, the wear will be much less. This test clearly indicates the effectiveness of the valve of my invention for minimizing valve damage in pumping sand-laden oil.
While I have described but a limited number of embodiments of my invention, it is possible to produce many other embodiments without departing from the scope or spirit of my invention. It is therefore desired that the invention be defined by the following claims.
1. A valve for use in a downhole pump which includes: a valve body having a stern and a head including disclike element;
a resilient, compressible, disc-shaped seal surrounding said stem adjacent said disc-like element, said resilient seal surrounding a portion of said stem;
a hard seal surrounding a portion of said stem in contact with said resilient sea-l, said resilient seal being between said hard seal and said disc-like element of said head;
means holding said hard seal about said stem;
the outer peripheral surfaces of said resilient seal and said hard seal forming a frusto-conical shape;
a valve seat having a frusto-conical shape to mateingly receive said hard seal and said resilient seal simultaneously;
whereby when said valve is seated in said seat said hard seal is in intimate contact with and sealing to said seat, and the pressure of fluid on top of said valve compresses said resilient seal vertically by movement of said hard seal against said resilient seal and expands it radially, creating a high radial pressure sealing contact with said seat.
2. An apparatus as defined in claim 1 in which said resilient seal has a hardness of about to about durometer.
3. An apparatus as defined in claim 2 in which said resilient seal is urethane.
5 6 4. An apparatus as defined in claim 2 in which said 2,962,039 11/1960 Shand et a1 251-333 X seat and said hard seal are tungsten carbide. 3 059 7 10 9 2 Coceano 251 3 3 X haf'aiolifiikii fiii biwi i iblu?13 1213213383 3,297,298 1/1967 Sachnik P368 X 5 2,985,424 5/1961 Anderson et a1. 251357 X References Cited 3,188,302 6/1965 Lorenz 25l368 X UNITED STATES PATENTS WILLIAM F. ODEA, Primary Examiner. 33233 31322 %$;g; X DENNIS H. LAMBERT, Assistant Examiner. 2,272,351 2/1942 Polcari 251 333 X 10 U.S. c1. X.R. 2,590,244 3/1952 Harbison 137-515.7 251 332 3 2,930,401 3/1960 Cowan 251368 X