CN-121986218-A - Balanced pressure seal for high pressure pump

Abstract

A pump includes a cylindrical plunger chamber with an inwardly projecting radial seal. The plunger moves in a reciprocating stroke within the cylindrical plunger chamber, the plunger having a first diameter and a second diameter smaller than the first diameter, the radial seal engaging the plunger at the second diameter throughout the length of the plunger's stroke. The pressure balancing valve is in fluid communication with the pumping chamber and the hydraulic oil chamber. The fluid passage is connected to the plunger chamber at a location between the radial seal and the first diameter of the plunger and leads to a pressure balancing valve. A radial gap is between the cylinder and the second diameter, and a seal between the first portion and the cylinder having a smaller gap than the radial gap allows hydraulic fluid to leak past the seal during plunger travel.

Inventors

• Richard D. Humbury

Assignees

• 万纳工程公司

Dates

Publication Date

20260505

Application Date

20241002

Priority Date

20231005

Claims (20)

1. 1. A pump, comprising: a cylindrical plunger chamber having an inwardly projecting radial seal; A plunger moving in a reciprocating stroke within the cylindrical plunger chamber, the plunger having a first diameter and a second diameter smaller than the first diameter, the radial seal engaging the plunger at the second diameter throughout the length of the stroke of the plunger; A pressure balancing valve in fluid communication with the pumping chamber and the hydraulic oil chamber; A fluid passage providing fluid communication between the plunger chamber and the pressure balancing valve, the fluid passage being connected to the plunger chamber at a location between the radial seal and the first diameter of the plunger.
2. 2. The pump of claim 1, the plunger comprising: a first portion having a first diameter and a second portion having a second diameter smaller than the first diameter, the second portion being closer to the free end of the plunger; a first radial seal engaging the first portion of the plunger; a second radial seal engaging the second portion of the plunger; a radial volume defined between the plunger chamber and the second portion of the plunger diameter and the second seal and the first portion of the plunger.
3. 3. The pump of claim 1, wherein the radial seal comprises one or more metal piston rings.
4. 4. The pump of claim 1, wherein the pressure balancing valve comprises a spool that slides in a bore to cover and uncover the hydraulic fluid inlet port and the hydraulic fluid outlet port.
5. 5. The pump of claim 4, wherein: in a first operating condition, hydraulic fluid is drawn through a clearance space between a portion of the plunger and the cylindrical plunger chamber; In a second operating condition, the inlet port of the pressure balancing valve is open; in a third operating condition, the outlet port of the pressure balancing valve is open.
6. 6. The pump of claim 4 wherein said pressure balancing valve comprises a diaphragm having a pumping side and an oil side, said oil side having a hydraulic oil chamber partially formed by said oil side of said diaphragm.
7. 7. The pump of claim 6, further comprising a spring intermediate the valve spool and the diaphragm and exerting a biasing force on the diaphragm.
8. 8. The pump of claim 7, wherein the spring is configured to apply a force of about 5psi when the diaphragm is in a centered position.
9. 9. The pump of claim 4 wherein said pressure balancing valve comprises a piston having a pumping side and an oil side with a hydraulic oil chamber partially formed by said oil side of said piston.
10. 10. A pressure balancing system for a pump having a hydraulic fluid reservoir, the pressure balancing system comprising: a bore in fluid communication with the oil chamber; A plunger; a plunger chamber having a seal between the plunger and the plunger chamber; a fluid passage from the plunger chamber to the bore; a pressure balancing valve in fluid communication with the bore, the valve comprising: An outlet port comprising an outlet check valve; An inlet port comprising an inlet check valve; a valve spool that slides in the bore to cover and uncover the inlet port and the outlet port.
11. 11. The pressure balancing system of claim 10, further comprising a fluid displacement device having a pumping side and an oil side.
12. 12. The pressure balancing system of claim 11, further comprising a spring intermediate the valve spool and the fluid displacement device and exerting a biasing force on the fluid displacement device.
13. 13. The pressure balancing system of claim 12, wherein the spring is configured to apply a force of about 5psi when the fluid displacement device is in a centered position.
14. 14. The pressure balancing system of claim 11, wherein the fluid displacement device comprises a diaphragm.
15. 15. The pressure balancing system of claim 11, wherein the fluid displacement device comprises a piston.
16. 16. A plunger pump, comprising: A plunger having a hydraulic side and a pumping side; An oil chamber located on the hydraulic side of the plunger, the oil chamber containing hydraulic fluid; a bore in fluid communication with the oil chamber; An outlet port comprising an outlet check valve; An inlet port comprising an inlet check valve; A valve spool sliding in the bore to cover and uncover the inlet port and the outlet port; a plunger chamber having a seal between the plunger and the plunger chamber; a fluid passage from the plunger chamber to the bore.
17. 17. The plunger pump of claim 16, the plunger comprising: a first portion having a first diameter and a second portion having a second diameter smaller than the first diameter, the second portion being closer to the free end of the plunger; a first seal engaging the first portion of the plunger; a second seal engaging the second portion of the plunger; a radial volume defined between the plunger chamber and the second diameter.
18. 18. The plunger pump of claim 16, wherein: In a first operating condition, hydraulic fluid is drawn through the radial volume; In a second operating condition, the inlet port of the pressure balancing valve is open; in a third operating condition, the outlet port of the pressure balancing valve is open.
19. 19. The plunger pump of claim 16, the plunger comprising a first portion having a first diameter and a second portion having a second diameter smaller than the first diameter, the second portion being closer to a free end of the plunger; a first seal engaging the first portion of the plunger; a second seal engaging the second portion of the plunger; a radial volume between the plunger chamber and the second portion of the plunger diameter and the second seal and the first portion of the plunger.
20. 20. The plunger pump of claim 19, wherein the first seal comprises one or more metal piston rings.

Description

Balanced pressure seal for high pressure pump Cross Reference to Related Applications The present application claims the benefit of U.S. provisional patent application No. 63/588,226 filed on month 05 of 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field The present invention relates to a sealing system for a high pressure pump that balances the pressure on the seals and avoids wear problems. Background Conventional positive displacement pumps for pumping high pressure liquids typically use a reciprocating plunger with packing to seal the pumped fluid. At high pressures (sometimes above 10,000 psi), these fillers are pressurized and press with extremely high force against the moving plunger. Such forces create high friction, leading to heat generation and rapid wear, which may lead to failure. This situation becomes worse when the fluid contains abrasive solid particles. In these high pressure, abrasive fluid applications, the plungers, packing, and stuffing boxes experience wear and may wash away, resulting in the need for expensive, frequent maintenance. To minimize this problem, pressurized lubricant is fed into the stuffing box to cool and lubricate the stuffing. While lubrication is helpful, lubrication alone does not eliminate the above-described problems. One way to try and avoid this problem is to use a plunger pump whose plunger displaces only the oil, which displaces a diaphragm or piston, which in turn displaces the abrasive slurry. The plunger may seal against high pressure through a tight clearance with the cylinder so that the viscosity of the oil is sufficient to maintain pressure without seals. Us patent 7,425,120 describes a pump in which a valve system holds oil that displaces a diaphragm so that there is only a small pressure differential across the diaphragm. However, this type of pump becomes less viable in very high pressure applications of large pumps due to the size of the diaphragm and the large chamber diameter that must accommodate the high pressure. Balancing the pressure across the seal is challenging for this arrangement because the pressure varies dramatically between the pressure stroke and the suction. Furthermore, such a sealing arrangement must prevent abrasive fluids from wearing the seal. Accordingly, it should be appreciated that a new and improved sealing system for a high pressure positive displacement pump is needed. Such a system should balance the pressure on the seal or packing both on the pressure and on the suction stroke so that the seal is never pressurized and therefore does not exert a high force on the plunger. In addition, the seals of such systems should always have a small oil biasing force to prevent abrasive fluids from wearing the seals. The present invention addresses these problems, as well as other problems associated with seals for high pressure pumps. Disclosure of Invention The present invention relates to a positive displacement pump, such as a plunger pump. For a multi-cylinder pump, the pump is driven by being connected to a rotating crankshaft mounted in the crankcase. The pump may include a plurality of plunger assemblies and associated components connected to a crankshaft. The manifold houses one or more check valves and inlet/outlet valves associated with each plunger assembly. The plunger has a first portion having a first diameter (D1) that is made to fit to the sleeve with a tight clearance (C). The gap (C) is dimensioned small enough so that high-pressure oil can only pass through the gap (C) very slowly. Typically, the gap is about 0.001 inches measured radially. The plunger has a second portion with a second diameter (D2) that is slightly smaller than the first diameter. The low pressure seal is positioned such that the low pressure seal contacts the second diameter (D2) throughout the stroke of the plunger. The fluid passage is connected to an annular space (a) between a first diameter (D1) of the plunger and the seal. As the plunger reciprocates, the length of the annular space (a) changes during the stroke, resulting in a small discharge of oil in this space. The volume displaced is defined by the area formed by the difference between diameter (D1) and diameter (D2) multiplied by the stroke of the plunger: V=πL((Dl/2)2-(D2/2)2) Wherein V is the volume D1 is the outer diameter D2 is the inner diameter L is the length of plunger travel The diameters (D1, D2) are configured such that the oil displacement is slightly greater than a maximum expected volume of oil leaking through the clearance (C) during a pressure stroke of the pump. In one embodiment, the plunger extends into the main pumping chamber. During the intake stroke, the plunger draws pumped fluid (such as water) into the chamber through the inlet check valve. During the pressure stroke, the plunger moves forward and fluid is moved out of the chamber through the discharge check valve. The pressure balancing valve is connected