Reciprocating Pump Cross-Bore Chamber Geometry for Fatigue Resistance
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Solution Overview
Problem
Reciprocating plunger and piston-type pumps in oil well service operations face excessive stress concentrations at bore intersections due to high frequency and large magnitude pressure pulsations, leading to potential fatigue cracks despite existing smoothing techniques like quasi radii and chamfers.
Innovation Solution
The introduction of a cross-bore chamber configured as a surface of revolution, such as an ellipsoid, at the intersection of the plunger, suction, and discharge bores, creating a smooth contiguous surface that reduces stress concentrations by eliminating sharp edges and providing a single, continuous connecting surface between the bores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bore intersection geometry with sharp edges is used, then manufacturing is simpler, but stress concentrations increase leading to fatigue cracks
Solution Approach 1:
The patent applies spheroidality by replacing sharp-edged bore intersections with a cross-bore chamber having curved surfaces. The chamber is defined by a surface of revolution generated by rotating a curve around an axis, creating smooth transitions between bores that eliminate stress concentration points while maintaining structural integrity.
2Reliability
If quasi radii and chamfered features are added to smooth bore intersections, then stress concentrations are reduced to some extent, but the geometry remains susceptible to excessive stress under extreme service conditions
Solution Approach 1:
The patent segments the traditional intersecting bore geometry into distinct components: individual bores maintaining their original functions, and a separate cross-bore chamber connecting them. This segmentation allows each bore to retain its simple cylindrical shape for easy manufacturing, while the chamber provides the stress-reducing curved transitions.
Solution Approach 2:
The patent transitions from two-dimensional bore intersections to a three-dimensional cross-bore chamber volume. By adding the dimensional aspect of a volumetric chamber with curved surfaces, the design eliminates sharp edges while preserving manufacturing simplicity through standardized rotational surface generation.
3Strength
If a cross-bore chamber with surface of revolution is introduced, then stress concentrations are significantly reduced, but the fluid end housing complexity increases
Solution Approach 1:
The cross-bore chamber serves multiple functions simultaneously: it connects multiple bores, provides smooth stress-distributing curved surfaces, and acts as a structural reinforcement element. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall device complexity.
Data Source
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AI summary
A reciprocating pump comprising a fluid end housing having a number of plunger sections, each of which includes a plunger bore within which a plunger is slidably received, a suction bore within which a suction valve is positioned, a discharge bore within which a discharge valve is positioned, and a cross bore chamber which is located between said bores and is configured as a surface of revolution. Each of the bores intersects the cross-bore chamber to thereby define a respective cross curve which is spatially separated from each adjacent cross curve. In this manner, the cross-bore chamber defines a single, contiguous surface which extends around and between all of said cross curves.