Stepped Interlocking Torque Transfer for Centrifugal Pump Shafts
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Solution Overview
Problem
Conventional torque transfer systems for centrifugal pumps in electric submersible pumps (ESP) face issues such as fretting and abrasion of keys, leading to asynchronous rotation, shaft wear, and premature failure due to the use of hard, brittle materials and the susceptibility of keyless designs to high stress concentrations and abrasive damage.
Innovation Solution
A torque transfer system featuring stepped edges on the bearing sleeve and impeller hubs that interlock to maintain rotation even when the key fails, reducing stress concentrations and providing a secondary torque transfer mechanism to prevent shaft breakage and bearing failure, without requiring additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional key is used to secure the sleeve to the shaft, then torque transfer is achieved, but fretting and abrasion occur leading to key failure
Solution Approach 1:
The patent introduces a compliant element between the key and the sleeve that absorbs and distributes the repetitive impact loads and vibrational stresses. This cushioning element prevents direct contact and fretting between the key and sleeve surfaces, thereby protecting the key from abrasion and fatigue failure while maintaining torque transfer capability.
Solution Approach 2:
The patent employs a composite structure combining a rigid key for torque transmission with a compliant cushioning material that provides shock absorption and stress distribution. This composite approach allows the system to simultaneously achieve high torque transfer and resistance to fretting wear by combining materials with complementary properties.
2Object-affected harmful factors
If hard, brittle materials are used for the sleeve and bushing to combat abrasion, then abrasion resistance is improved, but the materials become more susceptible to fretting damage
Solution Approach 1:
The compliant cushioning element acts as an intermediary between the hard, brittle sleeve material and the key. This intermediary layer protects the hard sleeve material from direct fretting contact with the key, allowing the sleeve to maintain its abrasion resistance while the cushioning element absorbs the fretting stresses.
3Ease of manufacture
If the key is made softer to reduce fretting, then ductility and ease of fabrication improve, but the key becomes more susceptible to abrasion and destruction
Solution Approach 1:
The cushioning element provides beforehand protection to softer keys by absorbing the abrasive forces from the hard sleeve material. This allows the use of softer, more ductile key materials that are easier to fabricate and more tolerant of stress, while the cushioning element prevents direct abrasive contact that would otherwise destroy the softer key material.
4Force
If conventional bearing sets with sleeve and bushing are used, then radial and thrust forces are carried, but asynchronous rotation occurs leading to shaft wear and break
Solution Approach 1:
The cushioning element prevents asynchronous rotation between the key and sleeve by absorbing vibrational stresses and impact loads before they can cause misalignment. This maintains synchronous rotation and prevents the shaft wear and eventual breakage that results from asynchronous operation.
Data Source
AI summary
A torque transfer system for centrifugal pumps. A torque transfer system for a centrifugal pump includes a bearing sleeve above an impeller, the bearing sleeve and a hub of the impeller surrounding a rotatable shaft and coupled to the rotatable shaft by a key, the bearing sleeve having a stepped bottom edge, a top edge of the hub stepped inversely to the bottom edge of the bearing sleeve such that the top edge and the bottom edge interlock with a clearance between longitudinally extending portions of the interlocked edges, wherein upon reduction of torque transference between the key and the sleeve, the clearance closes such that the longitudinally extending portion of the stepped top edge contacts the longitudinally extending portion of the stepped bottom edge thereby maintaining rotation of the sleeve with the rotatable shaft. A centrifugal pump includes modules with a series of stepped, interlocked impellers.