1. Field of the Invention
This invention relates to the design of fluid pumps used for pumping fluid at a relatively high pressure into a well. One example of such a process is the hydraulic fracturing process for oil and/or gas well applications. These pumps are commonly referred to as frac pumps. Other uses may include pumping cement or other fluids into the well.
In the case of frac pumps, the pumps are typically mounted on a truck/trailer and several may be used in series or in parallel to pump the fracturing fluid under high pressure into the well. As fracturing techniques become more popular and productive there is a continuing need to increase the horsepower capability of the pumps and the flow rate. However, as horsepower and operating pressures increase, so does the size of the pump and the failure rate.
The present invention addresses techniques to balance and/or modify stress loads within the pump housing which permits larger capacity pumps to be fabricated using lighter housings than previously thought possible with less failure.
2. Description of Related Art
Known frac pumps comprise generally two sections, the power end and the fluid end. The power end includes a housing for the drive shafts for the reciprocating pistons that extend into the fluid end. The fluid end includes the inlet ports, outlet ports and the cylinders for the reciprocating pistons. The two ends are normally bolted together. The fluid end may include up to five or more separate fluid pump chambers. Examples of this type of pump can be found in U.S. Pat. Nos. 6,419,459 B1 and 7,341,435 B2. Currently the fluid end of the pump tends to be damaged due to pressure imbalances, fatigue, and higher pressures and horsepower. The current invention overcomes these difficulties by a technique referred to as sculpturing the normally flat end surface of the front side of the fluid end. This technique can be used to balance the forces within the fluid portion of the pump. This technique also allows for higher pressure with no increase in mass. These and other advantages of the invention will be more fully explained in the detailed description of the invention which follows.
The essence of the invention is the discovery that by varying the shape, that is, sculpturing the front side of the fluid end of a high pressure pump, the internal stresses within the fluid housing can be controlled. This allows the pump to be designed in such a manner so as to minimize the mass of the pump end to minimize the possibility of structural failure. For example a frac pump can be designed so that the tendency of the fluid end of the pump to be pumped off the power end is minimized as well as lowering the occurrence of structural failure within the housing due to internal pressure.
a is a perspective view of a conventional fluid end having one pump chamber.
b is a cross section of the fluid end of
a is a perspective view of a fluid end of a pump according to one embodiment of the invention.
b is a cross section of the fluid end of
a is a perspective view of a fluid end of a pump according to a second embodiment of the invention.
b is a cross sectional view of the fluid end of
a is a perspective view of a fluid end of a pump according to a third embodiment of the invention.
b is a cross sectional view of the fluid end of
a is a perspective view of a fluid end of a pump according to a fourth embodiment of the invention.
b is a cross sectional view of the fluid end of FIG. 6Aa
a is a perspective view of a fluid end of a frac pump according to a further embodiment of the invention.
b is a cross sectional view of the embodiment of
a is a perspective view of a further embodiment of the invention.
b is a cross sectional view of the embodiment of
a is a perspective view of a further embodiment of the invention.
b is a cross sectional view of the embodiment of
The differences in stress at points 30 and 33 is believed to contribute to the tendency of the fluid end to separate from the power end.
An embodiment of the principles of the present invention is shown in
In the embodiment of
The effects of the various designs of the front surface 11 of the various embodiments on the stress measured at points 30-37 are summarized in the following table:
The above table illustrates that the stress levels within the pump chamber and the forces working on the upper and lower portions of the inside face 13 of the fluid end of the pump can be dramatically changed by altering the shape of the front face 11 of the fluid end.
Based on this discovery, it is possible to select an appropriate design that will improve the reliability of the pump and increase its power handling capability with no increase in mass.
For example in the case of the embodiment of
Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims. For example, the inlet valves could be arranged in the top portion 20 of the fluid end and the outlet valves could be arranged in the bottom portion 19 of the fluid end. Outlet passageway 16 would then be relocated to the lower portion.