Pump Retainer Nut Assembly Without Threads for High-Force Retention
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Solution Overview
Problem
Current hydraulic fracturing pump systems face challenges with the reliability and maintenance of retainer nuts, which often require imprecise methods like hammers for tightening and can lead to loose connections and potential ejection or damage due to high forces, concentrating stresses on threads.
Innovation Solution
A retainer nut assembly with a plug, mid-cap, and cover cap design that uses a fastener to secure the assembly within locking grooves in the fluid end block, eliminating the need for threaded connections and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded retainer nut is used to retain the suction cap, then the connection can be secured, but the threaded connection concentrates stresses on the threads which can lead to the retainer nut being forcefully ejected or causing damage to the block
Solution Approach 1:
The patent removes the threaded connection entirely from the retainer nut design. Instead of using threads that concentrate stress, the retainer nut uses a bearing surface that contacts the suction cap directly, distributing the load over a larger area and eliminating the stress concentration problem that causes ejection and damage.
Solution Approach 2:
The patent changes the fundamental parameter of connection mechanism from threaded (point/line contact) to bearing surface (area contact). This parameter change transforms how forces are transmitted, distributing stress across the bearing surface rather than concentrating it on thread roots, thereby eliminating the harmful stress concentration effect.
2Strength
If a hammer wrench and sledgehammer are used to tighten the retainer nut, then preload in the threads can be generated, but the hammer gives an imprecise result and exposes the user to harm
Solution Approach 1:
The retainer nut is designed to be self-installing using a simple tool. The bearing surface design allows the nut to be pressed or tapped into place without requiring complex threading operations, making the installation process safer and more precise while still achieving the necessary preload through direct bearing contact rather than threaded engagement.
3Reliability
If a threaded retainer nut is used, then the suction cap can be retained, but the retainer nut can work loose due to high forces generated in the fluid end block
Solution Approach 1:
The patent changes the connection parameter from threaded engagement to bearing surface contact. This fundamental parameter change creates a connection that is resistant to loosening under high forces, as the bearing surface design maintains constant contact and load distribution without the mechanical advantage that can cause threaded connections to back out under vibration and cyclic loading.
Data Source
AI summary
A retainer nut assembly for a fluid end of a pump system includes a plug with two blades separated by edge cuts, a plug exterior face and a threaded rod extending from the plug exterior face. Each of the blades includes an arcuate face. A mid-cap includes a hole for receiving the threaded rod therethrough with the mid-cap positioned adjacent the plug. The mid-cap further includes flange segments. A cover cap includes a hole for receiving the threaded rod therethrough with the cover cap positioned adjacent the mid-cap. The cover cap has extensions separated by cut outs. Each of the extensions are configured to extend axially between respective flange segments of the mid-cap when the cover cap is assembled to the mid-cap. A fastener engages the threaded rod and secures the retainer nut assembly together.