Fluid End Bore Retention Without Internal Threads
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Solution Overview
Problem
Existing fluid end assemblies in oil and gas operations experience issues with retaining nuts backing off due to high fluid pressures, leading to plug displacement and leakage, as well as erosion and cracking of internal threads in the bores.
Innovation Solution
The fluid end assemblies are designed without internal threads in the bores, using retainer elements and fastening systems to secure components within the bores, ensuring no external or internal threads are formed, thereby preventing unthreading and erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal threads are formed in the bores to secure retaining nuts, then components can be held in place, but the internal threads erode and crack under high fluid pressure, leading to failure
Solution Approach 1:
The patent removes the internal threads from the bore structure entirely, extracting the problematic threaded connection system that was susceptible to erosion and cracking. Instead, a smooth-bore design is implemented with components secured through alternative means such as set plugs or external fastening mechanisms, eliminating the source of thread failure while maintaining component retention capability
Solution Approach 2:
Rather than securing components through internal threading within the bore, the invention inverts the approach by using external fastening systems or set plugs that engage with the component from the outside or through separate mounting mechanisms, avoiding the creation of internal threads that would be exposed to erosive fluid flow
2Reliability
If retaining nuts are used to secure plugs in high-pressure bores, then plugs are held in place, but the retaining nuts back off due to high fluid pressures, causing plug displacement and leakage
Solution Approach 1:
The patent eliminates the retaining nut mechanism entirely from the bore assembly, removing the component that was prone to backing off under pressure. The plug retention is achieved through alternative designs such as threaded plugs that integrate directly into the bore without separate retaining nuts, or through mechanical set plugs that use deformation or friction-based retention rather than threaded connections
Solution Approach 2:
The invention merges the plug and retention function into a single integrated component design, where the plug itself incorporates the retention mechanism (such as integrated threads in the plug rather than the bore, or a set plug design where the retention feature is part of the plug body), eliminating the separate retaining nut that was susceptible to backing off
3Reliability
If no internal threads are formed in the bores, then thread erosion and cracking are prevented, but alternative fastening mechanisms are required to secure components
Solution Approach 1:
The patent employs self-service retention mechanisms where the plug or component itself provides the retention function through its design (such as a threaded plug that screws directly into the smooth bore, or a set plug that uses its own deformation or expansion to secure itself), eliminating the need for separate complex fastening systems while maintaining secure component retention
Solution Approach 2:
The invention changes the retention mechanism from threaded mechanical engagement to alternative parameters such as friction-based retention, deformation-based locking, or pressure-activated sealing, where the retention force is derived from fluid pressure or mechanical deformation rather than thread engagement, simplifying the overall fastening system while maintaining reliability
Data Source
AI summary
A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.