Not applicable.
The present invention relates to pump systems. More specifically, the invention relates to valves and seats used in mud pump and frac pump systems and a method for replacement of same during field operations.
Mud pump and frac pump systems utilize valves and seats similar to any normal piston pump. These pumps are generally pumping an abrasive fluid. As such, the valves and seats must be replaced (“pulled”) often to maintain proper system pressure. The replacement of the valve seats can be a safety hazard for the maintenance personnel. Most mud pump and frac pump maintenance is performed in the field utilizing hand tools. These hand tools can fail causing other system components to become projectiles and creating dangerous and even deadly environments.
There exist seat pullers in the prior art. Referring now to
The most commonly used method to replace a valve seat is a tension system that uses a seat puller head, a threaded rod (commonly known as an “allthread”), a hydraulic piston and an allthread nut. The hydraulic piston applies a force to the nut pulling the allthread. The allthread loads the seat puller head. The seat puller head then applies a force to the valve seat lifting the valve seat from its (valve seat) position inside the pump. The seat puller head is the component that most often fails. The failures often initiate at the ear area of the seat puller head. The failures can also initiate at the thread root of the seat puller head.
Such existing conventional seat pullers utilize a system that introduces clearances between system components, and more specifically, clearance between the seat puller head and the allthread. This clearance allows the two sides of the seat puller head to slide inward. This inward sliding moves the load point on the puller head ear. As the load point slides to the outside diameter of the seat puller head ear area, this increases the moment of force on one of the primary failure areas exponentially. This larger moment force greatly reduces the fatigue life of the seat puller head resulting in premature failure. Another area of failure includes the partial or complete separation of the seat puller head halves.
There is a need for a seat puller head that can increase the safety and minimize the danger surrounding the replacement of valve seats and reduces the number of mechanical components in the seat puller head. There is also a further need to eliminate or reduce the need to weld components together thereby minimizing manufacturing time, which in turn, has an economic benefit (e.g., cost savings) and additional safety advantages. There is a further need for a seat puller head that reduce clearance between system components, thereby increasing the fatigue life of a seat puller head. There is also a further need for a seat puller head to resist partial or complete separation during use, thereby further reducing or minimizing hazardous conditions encountered (or created) during operation. The present invention provides a valve seat puller head that addresses the shortcomings of the prior art.
The present invention is an improvement over the prior art. The valve seat puller head of the present invention is comprised of two (2) seat puller head halves and two (2) springs. More particularly, the present invention is comprised of a pair of seat puller head halves having threads on the interior surfaces of the halves, each facing the other. The seat puller head halves come together forming an opening. A pair of spring clips (sometimes also called “clip springs”) are clipped in place within a spring slot where the two seat puller head halves join together. The spring clips hold and secure the seat puller head halves together.
The clip springs hold the seat puller head halves of the seat valve puller head together to form such a cylindrical shape to facilitate the inserting of same into the cylindrically configured valve seat inside the mud or frac pump. The clip springs also provide the outward force required to pre-position the tool (i.e., seat valve puller head assembly) in proper area for valve seat removal and further provide a greater spring force than conventional garter springs currently used in the seat puller heads. A tapered buttress thread is used to engage the valve seat puller head with the allthread and facilitates the elimination of the thread clearance between the seat puller head and the allthread and greatly reduces the shear pressure at a root initiation area thereby reducing failure at this area.
In an alternative embodiment, the present invention may include a slot in the clip spring area. The purpose of the slot is to provide an area for the clip spring to snap into position. The clip spring is inserted from the outside diameter of the seat valve puller head. In this embodiment, the clip spring includes a portion that is bent akin to a locking tab, rendering the clip spring less likely to slide out of position. Couple with clip springs on both sides of the seat puller, the assembly of the present invention does not easily come apart.
In still another embodiment, at least one pin extends distally from the surface of the seat puller head halves to “grip” the inside diameter of the valve seat to be removed.
In yet another alternative embodiment, the present invention further comprises a “cold pull” by circulating an extremely cold glycol solution within an annular ring inside of the valve seat puller head near its outside diameter. The temperature range of the extremely cold glycol solution ranges from 0 to −10° C. (or the Fahrenheit equivalent). The preferable operating low temperature, however, is approximately −5° C. The extremely low temperature cold solution pulls and removes heat from the valve seat puller head assembly and the valve seat which is in contact therewith. Alternatively, the seat puller could act as a delivery system for a cryogenic liquid reaching extremely low temperatures of −196° C.
It is an object of the present invention to increase the safety and minimize the danger surrounding the replacement of valve seats.
It is a further object of the present invention to reduce the number of mechanical components in the seat puller head.
It is still a further object of the present invention to eliminate or reduce the need to weld components together.
It is yet a further object of the present invention to reduce clearance between system components, thereby increasing the fatigue life of a seat puller head.
It is still a further object of the present invention to include a slot in the clip spring area of the seat valve puller head, rendering the clip spring less likely to slide out of position and prevent the assembly of the present invention from separating.
It is yet a further object of the present invention to include at least one pin extending distally from the surface of the seat puller head halves to “grip” the valve seat to be removed.
The terms “valve seat puller head” and “valve seat puller” are used synonymously in this application.
Referring now to
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Clip springs 28 also provide a pivot point. Seat puller head halves 22 and 24 of seat valve puller head 20 require a pivot point so that the seat puller head jaws can squeeze together for insertion into the valve seat. The pivot point was previously provided by pins 14 that were welded to retaining ring 18 on the conventional design 10 (See,
In one embodiment of the present invention, and referring now to
The area in which machined slot 80 is located is known as the “clip spring area.” The opposite side of seat puller head halves 22 and 24 is the mirror image of and also has a clip spring area. The purpose of slot 80 is to provide an area for clip spring 28 to snap into position. Clip spring 28 includes locking tab 90, as shown in
Referring now to
The next improvement of the present invention over the prior art is that a tapered buttress thread is used to engage valve seat puller head 20 with allthread 32, as shown in
Tapered threaded buttress bottom end 36 has advantages over the typical UNC thread used in most systems. The first advantage is the elimination of the thread clearance between the seat puller head and the allthread, as described above with reference to
The next advantage of tapered threaded buttress bottom end 36 is that tapered threaded buttress bottom end 36 places more material in the load plane. This addresses the thread root initiation area failure experienced with the current technology. Conventional threads are symmetrical on both halves of the load area. A buttress thread places more material on the load area to reduce the shear pressure applied to the threads. Tapered threaded buttress bottom end 36 can only be used in load applications where the primary load is only applied in a primary direction. The tapered threaded buttress bottom end 36 will fail if loaded in the opposite direction. Valve seat puller heads 20 are only loaded in one direction. The tapered threaded buttress bottom end 36 greatly reduces the shear pressure at this root initiation area.
The tapered threaded buttress bottom end 36 of allthread 32 also allows for more “ear” material on valve seat puller head 20. Since allthread 32 will be smaller at the tip (i.e., insertion area), the inside diameter of valve seat puller head 20 at the ear will also be smaller. Since the outside diameter of valve seat puller head 20 is effectively the same at the inside of the valve seat, the thickness of the material at the ear area is increased. This further improves the fatigue life of the valve seat puller head of the present invention.
Most valve seat puller heads start with some clearance between the inside diameter of the valve seat and the outside diameter of the valve seat puller head. The valve seat puller head of the present invention reduces that clearance to zero resulting in a “fitted” puller. The fitted puller is necessary to implement the next design improvement.
Referring now to
If the user were to try and replicate the allthread, the user would need to know the angle of taper and the thread pitch. Otherwise, the equipment will not work as designed. The present invention, therefore, includes a range of tapers and thread pitches. The range of the tapers is from 2 to 10 degrees, with a preferred taper of 5.5 degrees. The range of thread pitch is from 4 to 10 threads per inch (TPI), with a preferred thread pitch of 6 TPI.
Still referring to
Referring still to
The tapered configuration of allthread provides extra material at loaded area 106 of valve seat puller head 20. This extra material is approximately 0.72″ radial thickness from the OD of nose 104 to OD of valve seat puller head 20 (as compared to 0.14″ radial thickness for conventional seat pullers). Because the allthread has a tapered configuration, the present invention provides more area at loaded area 106, i.e., thicker area, to better resist external forces (e.g., forces applied from allthread upward against internal threading, force applied from valve seat downward on ear) than are conventional seat pullers which tend to display crack initiation and propagation at this area. The thickness of loaded area 106 of the present invention further prevents deflection and fatigue failures from occurring. The tapering also has the effect of having the forces not being concentrated at one area, but rather at different areas (e.g., the force applied from allthread is concentrated on an area elevated from the force applied from the valve seat).
Thread clearance refers to the amount of clearance between the outside geometry of a stud (e.g., allthread) and the inside geometry of a nut. There are different classes of threads, as defined by the American Standard B1.1-1949. These classes reduce or increase the thread clearance according to the specifications.
Persons having ordinary skill in the art, e.g., engineers, will use a tighter clearance if the application warrants a tighter fitting nut for a certain application. Too much clearance can have a negative effect as the nut and stud slip axially with respect to one another. In the case of conventional seat pullers, the thread clearance allows radial movement at the thread interface. The seat puller halves will essentially slide inward as a hydraulic force is applied to the stud (allthread).
Now referring to
An additional advantage of the present invention is the incorporation of “cold pull” technology (in contrast to the “non-cold pull” version described with reference to
With a reduction of temperature of the valve seat, the complete geometry will reduce in size. The reduction in size is only slight, maybe only a few thousandths (0.003″ to 0.007″) in the total outside diameter. Nonetheless, this reduction in size significantly reduces the pulling force required to extract the valve seat. This is a very important point. If the pulling force is reduced, then the bending moment applied to the ear of valve seat puller head 20 is reduce. The stress applied to a thread root initiation area is also reduced. This increases the life of valve seat puller head 20 from the two main failures experienced with the current technology. This reduces maintenance cost as the present invention is anticipated to have double the life of the previous technology. In addition, less system failures minimizes exposure of maintenance personnel to the potential of projectile created by failing components.
Metal is a very good conductor of heat. While applying a cold fluid to a small component such as a valve seat can reduce the outside diameter of that valve seat, it is much more difficult to change a geometry of a much larger mass of metal. Therefore, the size of valve seat may be reduced due to the reduction in temperature, but the geometry of the much larger (300-350 times larger) mud pump case/housing is not impacted. Effectively, the present invention facilitates a small reduction in the valve seat geometry due to the reduction in temperature but does not affect the much more massive mud pump housing.
Referring now to
The present invention is comprised of steel, and more specifically of 4140 steel material. However, other robust materials or alloys may also be used and remain within the contemplation of the present invention. The present invention has application in the oil and gas industry.
The various embodiments described herein may be used singularly or in conjunction with other similar devices. The present disclosure includes preferred or illustrative embodiments of specifically described apparatuses, assemblies, and systems. Alternative embodiments of such apparatuses, assemblies, and systems can be used in carrying out the invention as described herein. Other aspects and advantages of the present invention may be obtained from a study of this disclosure and the drawings.
This original non-provisional application claims priority to and the benefit of U.S. provisional application Ser. No. 63/179,623, filed Apr. 26, 2021, and entitled “Valve Seat Puller Head Assembly,” which is incorporated by reference herein.
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6050766 | Kies et al. | Apr 2000 | A |
6227225 | Domingue | May 2001 | B1 |
10265839 | Hunter | Apr 2019 | B1 |
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Number | Date | Country |
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209579426 | Nov 2019 | CN |
Number | Date | Country | |
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20220339765 A1 | Oct 2022 | US |
Number | Date | Country | |
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63179623 | Apr 2021 | US |