Fluid End Assembly With Curved Closure to Prevent Thread Fatigue
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Solution Overview
Problem
Conventional fluid end assemblies in well-service pumps used for hydraulic fracturing face cyclic fatigue and failure due to high cyclic pressure, leading to costly downtime and inability to repair, as the threads between the nut and opening weaken and strip under high pressure operation.
Innovation Solution
A fluid end assembly design with a concave profiled closed inner end in the plunger bore, combined with inlet and outlet valves featuring poppets and springs, distributes cyclic pressure forces more evenly, reducing stress on the threads and enhancing the assembly's durability and operational pressure limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional fluid end assemblies are used with threaded closures, then the assembly can be disassembled for maintenance, but the threads weaken and strip under high cyclic pressure causing failure
Solution Approach 1:
The closure is divided into two separate parts: a sand cap that seals the opening and a retainer that secures the sand cap. This segmentation eliminates threaded connections that are susceptible to cyclic fatigue, as the retainer uses non-threaded fastening methods such as friction fit, interference fit, or mechanical retention features.
Solution Approach 2:
The sand cap features a domed or curved outer surface that distributes cyclic pressure forces evenly across the closure assembly. This curved geometry prevents stress concentration at thread roots, eliminating the primary failure mechanism in conventional threaded closures while maintaining structural integrity under high pressure.
2Productivity
If high cyclic pressure is applied to achieve hydraulic fracturing, then oil and gas production increases, but the threads between nut and opening fail due to cyclic fatigue
Solution Approach 1:
By separating the sealing function (sand cap) from the retention function (retainer), the design eliminates threaded connections that fail under cyclic pressure, allowing the assembly to withstand the high pressures required for hydraulic fracturing without thread failure.
Solution Approach 2:
The domed outer surface of the sand cap distributes cyclic pressure forces uniformly, preventing stress concentration and fatigue failure, thereby enabling sustained high-pressure operation for increased oil and gas production.
3Ease of operation
If threaded closures are used to seal the fluid bore, then assembly can be disassembled, but the threads strip under high pressure making repair impossible
Solution Approach 1:
The closure components are designed as separate replaceable parts (sand cap and retainer) that can be independently serviced. When wear or damage occurs, individual components can be replaced without affecting the entire assembly, significantly improving repairability compared to integrated threaded closures.
Solution Approach 2:
The domed sand cap design eliminates threaded connections that are prone to stripping, replacing them with more durable retention methods. This structural change ensures that the closure can be disassembled and reassembled multiple times without thread degradation, maintaining ease of operation throughout the service life.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly reduces the risk of cyclic fatigue and extends the operational life of the fluid end assembly by evenly distributing cyclic pressure forces, preventing thread failure and allowing for higher working pressures without premature wear.
Implementation Method 1
a spring disposed between the stop and the poppet and biasing the poppet toward the seat
Data Source
AI summary
A fluid end for a high-pressure pump with a plurality of horizontal plunger bores that have an open end and a closed end for receiving a reciprocating plunger at its open end. The fluid end is provided with a corresponding number of vertical suction bores, each of which intersect one of the horizontal plunger bores and contains a valve seat below the plunger bore and a valve seat above the plunger bore. A suction manifold is fixedly attached to the bottom of the fluid end to provide a flow of fluid into the fluid end via the vertical suction bores. A high-pressure discharge bore intersects the vertical suction bore and receives fluid pressurized by the plungers via upper valves.