Wells – With eduction pump or plunger – With leak means
Reexamination Certificate
1999-05-04
2001-03-27
Lillis, Eileen D. (Department: 3673)
Wells
With eduction pump or plunger
With leak means
C166S105000, C166S106000, C417S423300, C417S424100
Reexamination Certificate
active
06206097
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a fluid pumping system. More particularly, the present invention relates to an improved vertical pumping system for use in pumping fluids on offshore drilling platforms.
BACKGROUND OF THE INVENTION
A variety of pumping systems are used on offshore drilling platforms to pump fluid such as oil and sea water. A conventional pumping system includes a horizontal motor coupled to a horizontal pump. The horizontal motor and pump are mounted to the deck of the drilling platform and used to pump fluids through appropriate conduits coupled to the pump. Such horizontal systems, however, require a relatively large area or “footprint” on the drilling platform. The large footprint is problematic because of the relatively severe space constraints on offshore drilling platforms.
An alternative to a horizontal system is a vertical pumping system mounted vertically on the offshore drilling platform. Vertical pumping systems employ a motor and a vertical pump connected by a motive power coupling. The internal components of a vertical pump, such as the impeller(s) and a rotatable drive shaft, are oriented vertically. Because of this vertical orientation, a vertical pumping system requires a smaller area (or “footprint”) than a comparable horizontal pumping system. Because offshore drilling platforms have very limited deck space, the smaller footprint available with vertical pumping systems makes them better suited for use in offshore drilling platforms.
Vertical pumping systems employed to transfer fluids or to pump liquids from wells or deep drilled bore holes are comprised of a motor and a vertical centrifugal pump. Vertical turbine pumps are commonly used for this application. The motor drives a rotatable shaft in the vertical pump that is, in turn, connected to the impellers of the vertical turbine pump. The pump is mounted to the deck of the drilling platform, while the motor remains above the deck. As the motor rotates, the rotatable shaft rotates the impellers. As the impellers rotate they impart motion to the fluid.
The pump suction is located at the bottom of the pump and the fluid is drawn upward through the pump and the deck, and is discharged above the deck surface at or near the top of the pump. A mechanical seal is located around the rotatable drive shaft near the motor to act as a barrier to prevent fluid from leaking out of the pump around the shaft. The mechanical seal is thus exposed to fluid at pump discharge pressure on one side and, typically, atmospheric pressure on the other. The pump discharge pressure may be several thousand pounds per square inch greater than atmospheric or pump suction pressure. The mechanical shaft seal must be designed and manufactured to withstand the considerable strain placed on it by fluid at pump discharge pressure.
The present invention overcomes the problems of the prior art and provides an apparatus which employs a vertical pump in a manner which reduces the strain on the mechanical seal by exposing the mechanical seal to the lower pressure at the pump suction rather than the much higher pressure at the pump discharge.
SUMMARY OF THE INVENTION
The present invention features an offshore pumping assembly for use on an offshore rig to pump a fluid. The system includes a deck of the offshore rig to which a vertical pump is mounted. The vertical pump includes a fluid intake, a fluid discharge, a rotatable shaft, a turbine connected to the shaft and a seal mounted about the rotatable shaft. The system further includes a power source coupled to the rotatable shaft. As the shaft and the turbine are rotated by the power source, a fluid is pumped from the fluid intake through the fluid discharge without loading of the seal with a fluid discharge pressure.
According to another aspect of the invention, a fluid pumping system is configured for mounting to a deck of an offshore platform used in pumping a production fluid. The system comprises a vertical pump and an external motive power source. The vertical pump includes a drive shaft, an impeller, and a shaft seal disposed about the drive shaft and located upstream of the impeller. The power source is coupled to the drive shaft to power the vertical pump. The orientation of the impeller, drive shaft and shaft seal are such that the shaft seal is exposed to vertical pump suction pressure, as opposed to discharge pressure, when the fluid pumping system is in operation.
According to a further aspect of the invention, a fluid pumping system is provided for use on a drilling platform. The pumping system includes a vertical pump configured for mounting to a drilling platform. The vertical pump includes a drive shaft and a shaft seal disposed about the drive shaft to prevent leakage of a pump fluid along the drive shaft. When the vertical pump is mounted to the drilling platform and operated, the shaft seal is exposed to suction pressure of the vertical pump, which allows the use of a low pressure seal.
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John L. Dicmas, Vertical Turbine, Mixed Flow, and Propeller Pumps, pp. 11, 24-25.
Camco International Inc.
Fletcher Yoder & Van Someren
Lillis Eileen D.
Mayo Tara L.
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