Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
1999-10-13
2001-05-08
Rivell, John (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S516290, C251S337000
Reexamination Certificate
active
06227240
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention generally relates to check valves used in pumping operations. More specifically, the invention relates to a check valve for pumping applications that includes a spherically profiled valve seat, a spherically profiled valve member, a replaceable spherically or conically profiled sealing member, a secondary means for maintaining the assembly as a unit, and a fluid outlet passageway that is unrestricted about the periphery of the sealing member.
BACKGROUND OF THE INVENTION
Check valves are devices that allow fluid to flow through a passageway in one direction but block flow in the reverse direction. They are used in a variety of applications. One of the many industrial applications for check valves is in reciprocating pump assemblies. Reciprocating pumps are used by field workers in various operations to pressurize a slurry mixture of solids and liquids and transfer fluids and mixtures from one station to another.
For example, reciprocating pumps are used in drilling operations to pressurize a slurry mixture of solids and liquids known as drilling mud to the bottom of a hole drilled into the earth. The pressurized mud is used to lubricate and cool a downhole drill bit as well as to carry loosened sediment and rock cuttings back to the surface. At the surface, the cuttings and sediment are removed from the returning drilling mud for examination and the filtered drilling mud is able to be reused. In many cases, highly abrasive particles are present in the fluids that are being pumped through the system. Because of these highly abrasive components, valves and seals of reciprocating pumps must be designed to resist harsh abrasion, while maintaining positive sealing action and withstanding high operating pressures.
A schematic diagram of a check valve supported reciprocating pump is shown in FIG.
1
. In a pump of this type, a piston
21
reciprocates within a cylinder
20
in the direction shown by arrow
24
. Check valves
22
are utilized at inlets
25
and outlets
26
of the cylinder
20
to restrict the flow of fluid to one direction. At fluid inlet
25
, a check valve
22
is placed and oriented so that it only allows inward flow. At outlet
25
, another check valve
26
is located so that it that only allows outward flow. The use of check valves
22
at pump inlets
25
and outlets
26
enables the pump to function in a much simpler fashion that does not require a timing or driving means to open and close the inlet
25
and outlet
26
valves at the appropriate times. Check valves
22
are often spring loaded so that at times of low or zero flow pressure, they are automatically shut. Effective check
410
valves
22
for pumping applications are also designed so that pressure in the back-flow direction contributes to the strength of the sealing mechanism.
For pump applications that utilize multiple check valves, it is preferred that all check valves be of the same design to ensure that the inlet and outlet flow characteristics of the pump are similar. Additionally, identical check valves allow the pump operator to carry fewer replacement parts, since he or she only has to carry parts for one type of valve. In many applications, it is further preferred that the check valves be unitized, or self-contained. A damaged unitized check valve can be easily removed from the pump assembly and replaced with minimal tooling and effort. Once the unitized check valve has been removed from the pump device, it can be disassembled and repaired if possible. By replacing check valves as units, expensive delays in operations can be minimized.
FIG. 2
shows a prior art unitized check valve that is typical of those used in reciprocating pump assemblies. The prior art check valve assembly
80
includes a valve body
81
, a seal member
82
, a biasing spring
83
, and a spring retainer
84
. The seal member
82
has a conical seal face
88
and guide legs
85
that facilitate the alignment within the valve body
81
. The valve body
81
has a corresponding conical valve seat
87
, and inner diameter
89
, and rotary retaining tabs
90
for engaging the spring retainer
84
. The spring retainer
84
has rotary retaining hooks
91
and fluid flow passageways
86
. The rotary retaining hooks
91
of the spring retainer
84
correspond with the rotary retaining tabs
90
of the valve body
81
to form what is commonly referred to as a bayonet connector.
The check valve is assembled by placing seal member
82
into valve body
81
, placing biasing spring
83
on top of seal member
82
, placing the spring retainer
84
over spring
83
and compressing spring
83
until spring retainer
84
meets valve body
81
, and engaging the bayonet connectors by turning retainer
84
clockwise with respect to valve body
81
. Once assembled, seal member
82
is free to move up and down within the assembly while the guide legs
85
assure that when in the down position, the seal face
88
of the seal member
82
aligns properly with the valve seat
87
. The valve design allows flow from valve body
81
through retainer
84
but prevents the fluid from flowing from retainer
84
through the valve body
81
. The biasing spring
83
acts both to shut the valve during situations of low pressure and to maintain the tension required to keep the bayonet connection engaged.
It is preferred that all components of a reciprocating pump be designed so that the flow of the working fluid is as unrestricted as possible. Obstructions to fluid flow in the pump assembly can create fluid turbulence which increases the flow resistance of the fluid. By reducing flow resistance, a pump's efficiency, or ratio of work output to work input, can be increased. Increasing the efficiency of the pumping device reduces the costs of operation. In addition, because of the aforementioned abrasive particles existent in fluids, if prior art check valves are installed in solids laden pumping applications, they would experience a tremendous amount of erosion wear and fail prematurely. Hence, an effective check valve design for reciprocating pump applications should be able to withstand abrasive elements and maintain a tight seal.
The guide leg design of the prior art unitized check valve blocks the free flow of fluid from the valve body to the spring retainer and can cause undesirable turbulence. Also, the prior art design check valve includes a single biasing spring to compress the sealing member against the valve seat and to maintain the bayonet connection between the valve body and the spring retainer. In the event of failure or weakening of this biasing spring, the prior art valve can come apart during operation and damage the surrounding pump components. In order to prolong pump life and minimize operating costs, an alternative to the prior art design is desirable.
BRIEF SUMMARY OF THE INVENTION
The present invention is a unitized check valve that includes a spherical valve seat geometry, a free flowing design, a field replaceable valve seal, and an independent assembly maintenance device. The spherical geometry offers an improvement over traditional conical geometry by allowing the valve to function without precise alignment of its components. By eliminating the need for guidance members of traditional designs, disruptions to fluid flow within the valve and induced flow turbulence can be minimized.
The invention also incorporates a replaceable seal element about the seal disk that is able to withstand the particulate abrasion that occurs in some reciprocating pump applications. When the elastomeric seal element finally does wear to ineffectiveness, the element can be quickly replaced in the field, allowing the valve to be inexpensively repaired and returned to use.
In one preferred embodiment the assembly maintenance device is a wave spring compression element. The assembly maintenance device acts independently of the valve disc biasing device to maintain the unity of the check valve assembly in the event of failure or weakening of the main valve biasing spring.
REFERENCES:
patent: 1693355 (1928
Trammell Ronald
Wu Samuel S.
Conley & Rose & Tayon P.C.
National-Oilwell L.P.
Rivell John
LandOfFree
Unitized spherical profile check valve with replaceable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Unitized spherical profile check valve with replaceable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Unitized spherical profile check valve with replaceable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2531571