Patent Application
20250188959
The present disclosure relates to hydraulic pumping systems and more particularly, relates to systems and methods that reduce wear within a reciprocating piston pump that may be caused by contamination entering a piston chamber.
Referring to
Many applications for piston pumps are in environments where a contaminant (likely a damaging solid) will enter the work chamber 5 where the contaminant, depending on its nature, causes damage, which may lead to a reduced maintenance cycle and/or leads to premature failure of the pump. For the purposes of this description, and as shown in
That is, in operation and as shown in
As is known, actuation of the drive piston 6b is controlled by a hydraulic pump system that pumps fluid into and out of the drive chamber causing the drive piston 6b to move alternately in different directions. Various hydraulic pump systems may be configured to the drive chamber to effect hydraulic fluid pumping.
When the work piston 6b is being pushed, and particularly in systems where the piston rod 5c is long (for example where the stroke length exceeds twice piston diameter), the piston rod is subjected to a compression force, which causes the piston rod to bend, known empirically as “rod buckling” as shown in
In a typical working scenario, where the pump is configured to a gas well, gas may enter the pump at about 1 atm of pressure and ultimately enter a gas pipeline at around 10 atm (150 psi). In a push pump having a 12-inch diameter cylinder/piston and a 5 foot stroke, the piston rod would be 2.5+ inch diameter to provide 150 psi and 3.5+ inches for a 10 foot stroke pump. In a push pump having a 16-inch diameter cylinder/piston and a 5 foot stroke, the piston rod would be 3+ inch diameter to provide 150 psi and 4.5+ inches for a 10 foot stroke pump.
As such, and particularly when the work piston 5b and drive piston 6b are at the end of each stroke, substantially the entire length of the piston rod 5c is unsupported within the respective work and drive cylinders. The resulting deflection of the piston rod 5c also causes a deflection of the work piston 5b which can lead to particular wear issues.
Accordingly, there has been a need for improved pumping systems that minimize issues associated with rod buckling.
Various known pumping systems include U.S. Pat. Nos. 4,946,352, 8,313,313, 4,818,191, 4,419,055, 5,137,436, 8,186,972, WO 88/01021, and JP 2018044589.
In accordance with the disclosure a reciprocating piston pump system is described, the system having: a hydraulic drive system having a first drive piston within a first drive cylinder and a second drive piston within a second drive cylinder; a work piston within a work cylinder having first and second working sides, the work piston connecting each of the first and second drive pistons via first and second piston rods; the work chamber configured to receive a fluid/gas to be pumped on the first and second working sides of the work piston and expel the fluid/gas from the first and second working sides of the work piston; a hydraulic fluid control system configured to alternately direct hydraulic fluid to respective working sides of the first and second drive pistons such that the first and second piston rods are in tension during each working stroke of the work piston.
In various embodiments:
In another aspect, a method of controlling a hydraulic pump system is described, the method having the steps of:
In various embodiments, gas on non-working sides of the drive cylinders is vented to atmosphere during each stroke and/or steps a)-c) are repeated at 0.5-9 strokes per minute.
Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.
The present disclosure describes systems and methods for reducing wear in a hydraulic pumping system. Generally, the systems described herein incorporate a central work piston running back and forth in a hydraulic cylinder under control of two drive chamber pistons, that are hydraulically pulled in both directions via piston rods and that operate in tension through a drive cycle. The systems and methods reduce or substantially eliminate buckling of work piston rods by maintaining the work pistons in tension throughout the drive cycle thus ensuring that misalignment of the central piston is substantially eliminated. The systems and methods substantially reduce or delay damage caused by contamination that may enter the work cylinder while achieving a high-volume pumping rate of more than 90%.
In a typical pump system as described above, additional details of the phenomena of rod-buckling are described. Generally, if the piston rod 5c is long enough, under compression, the rod may bend in a “C” or an “S” shape causing a misalignment of the work piston with respect to the cylinder as shown in
This deflection gap X typically happens towards the lower side of a horizontal work cylinder 5d, horizontal cylinders being the typical application of these long stroke cylinders. As the work chamber 5d is used to displace what may be contaminated fluids/gases, any contamination in the form of sand or grit 7, 7a or other debris will work its way into the shrinking gap which will abrade Z the work cylinder 5d and work piston 5b particularly during the return stroke as shown in
Furthermore, when the work piston 5b changes direction, the piston rod 5c is then put in tension and the work piston 5b centers itself in the tube which squeezes any contamination caught in the gap X between the work piston 5b and the wall also leading to wear Z. That is, when the rod goes into tension on the return stroke, the debris that is caught between the piston and cylinder is dragged back which can cause damage to both the piston and the cylinder. Examination of units that may have failed shows that the highest amount of damage typically occurs near to the end of the cylinder at the end of the piston stroke, which is the point of maximum buckling of the piston rod and where the piston may be maximally misaligned with the cylinder axis.
Examination of failed units having a 5-foot stroke, typically shows gouges in the cylinder that are deepest near the end of the piston stroke that taper off over about 2 feet. The remaining 3-foot section of the cylinder may have scratches but not gouges.
Moreover, depending on the type of contamination, the contamination can become embedded into the piston.
As the work piston 5b repeatedly travels back and forth, the contamination will progress the scratch into a damage causing gouge and/or several gouges, which in turn capture more and more contamination. The problem intensifies until the unit will no longer build adequate compression pressure and is deemed to have failed.
Referring to
The system works as follows using arbitrary number for the sequence of steps:
The process is controlled by the hydraulic actuation system 12 where HFs are successively passed through the directional control valves 12c to and from reservoir 12b. The cycle is repeated such that drive chamber piston rods 1 and C1 are always under tension.
Additionally, as shown in
In operation, the present system can substantially reduce wear in a hydraulic pump by reducing/eliminating buckling of piston rods and/or misalignment of the work piston C during the drive cycle. That is, by reducing/eliminating buckling and misalignment, the problems of contamination working its way between surfaces are reduced resulting in reduced wear and longer operational life of the work cylinder.
That is, contamination that enters the work cylinder 14c is processed through the work cylinder 14c without it being trapped against the wall of the work cylinder 14c. Whenever the work piston C is traveling while still being in the center of the hydraulic cylinder 14c, the contamination is simply pushed along the walls and not trapped against the walls and/or between the work cylinder 14c walls and work piston C.
In a typical pumping system, where it is desired to maximize the volume of fluid/gas being pumped, it is desired to maximize the diameter of the work piston and the length of the work cylinder. Generally, as noted above, as the length of work cylinder increases, the buckling and misalignment issue becomes greater. While larger pistons have a greater thickness, and larger diameter piston rods can be employed to help reduce misalignment problems, larger pistons and piston rods increase the mass of the system while simultaneously reducing the working volume within the work cylinder. The increase in mass then requires an increase in input power to actuate the system as a heavier mass is being accelerated/moved with each stroke. The energy efficiency of the pump is therefore decreased. In addition, and similarly, as noted the pumping volume is decreased which further decreases the operational efficiency of the pump.
Further, any buckling can affect the flow characteristics of gas/fluids entering/leaving the work chamber as the piston speed varies as buckling occurs leading to a varied pump speed. This can affect monitoring of the process as variations in speed can provide varied or inconsistent readings to equipment.
Accordingly, the subject system achieves at least the following operational advantages namely reducing the mass/thickness of work piston C and maximizing the volumetric efficiency of the pump.
A comparison of push/pull pumps and pull-only compressor pumps having a 5-foot and 10-foot stroke length is shown in Table 1. In each case the output pressure is 150 psi for the push/pull (prior art) pumps and 350 psi for the pull-only pumps. Stroke volumes are shown for a single stroke.
From the table, it can be seen that the pull-only pumps can be configured with substantially smaller piston rods which improves the volumetric efficiency (between 2-7% in typical configurations) while enabling higher pumping pressures of comparable pumps.
It should be noted that while a pull-only pump requires a second drive piston and rod within a second drive cylinder that doubles with a higher mass compared to a single drive cylinder and work cylinder, it is proportionally smaller compared to two push/pull pumps and has greater volumetric pumping equipment with an increased service life.
In various embodiments, during cylinder manufacture, the cylinders are honed to include a “rifling” pattern in the cylinder. The rifling pattern is a series of spirals within the tube that may be about 0.0002″-0.0004″ inches in depth. The rifling pattern enables a small film of oil to be retained on the bore to lubricate the piston as it moves through the bore. In addition, the spirals may cause the piston to rotate as it moves back and forth within the tube. Buckling has a tendency to prevent this rotation both due to the side forces on the piston and the effect of debris caught as described above. In addition, debris will create gouges/scratches that are deeper than the spirals which then prevent them from being effective.
Importantly, the longer a piston spirals, this can further minimize damage to the pistons and cylinders as new surfaces of pistons and cylinders are being exposed to one another over time. This spiraling motion can further minimize the likelihood of gouging or scratching between the pistons and cylinders occurring as specific contact between areas of the piston wall and cylinder wall will vary over time.
Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.
This application is a U.S. Non-Provisional application that claims priority to and the benefit of U.S. Provisional Patent Application No. 63/606,928, filed on Dec. 6, 2023, that is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63606928 | Dec 2023 | US |
