Multistage Lift Pump Shaft Float Mechanism for Thrust Wear
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Solution Overview
Problem
Compression type pumps experience significant stack deflections and wear due to cumulative downthrust loads, leading to accelerated deterioration and potential failure, especially in long pump sections with multiple stages.
Innovation Solution
The design incorporates a gap or spring at the top end of the pump shaft to allow impellers to float when deflection exceeds a certain limit, limiting thrust load transfer and using a 2-piece ring to secure impellers, allowing hybrid operation as both compression and floater pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compression type pumps are used to handle thrust load in a clean fluid environment, then reliability is improved, but cumulative stack deflection leads to accelerated deterioration and pump failure in long pump sections
Solution Approach 1:
The pump shaft is segmented into multiple sections with individual impeller stages, allowing each stage to deflect independently rather than as a single rigid unit. This segmentation reduces cumulative deflection effects and prevents stress concentration at any single location.
Solution Approach 2:
The shaft stiffness parameter is varied along its length, with the upper section having reduced stiffness to accommodate deflection while the lower section maintains higher stiffness for stability. This parameter change allows the shaft to flex where needed while maintaining structural integrity.
2Power
If the number of stacked impeller stages is increased to achieve required lift, then pump head is improved, but cumulative deflection magnitude increases leading to component deterioration
Solution Approach 1:
The pump shaft is designed with dynamic flexibility, allowing it to adapt its stiffness characteristics based on operational conditions. The shaft can deflect dynamically to accommodate varying loads while maintaining alignment through controlled flexibility rather than rigid constraints.
Solution Approach 2:
A thrust bearing is introduced as an intermediary element between the impeller stages and the pump housing, absorbing cumulative deflection forces and preventing direct transmission of stress to the impeller stack, thereby maintaining alignment stability.
3Strength
If impellers are rigidly secured to the shaft, then structural integrity is improved, but wear increases due to metal-to-metal contact during deflection
Solution Approach 1:
The impeller is extracted from rigid mechanical connection and instead secured through a floating mechanism that allows relative movement. This separation eliminates metal-to-metal contact while maintaining the functional connection needed for power transmission.
Solution Approach 2:
A floating seal or cushioning element is positioned between the impeller and shaft to prevent direct metal-to-metal contact during deflection. This beforehand cushioning absorbs wear forces before they can damage the impeller or shaft.
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
This design reduces wear and enhances reliability by localizing thrust absorption, preventing metal-to-metal contact, and extending the operational life of the pump.
Implementation Method 1
a spring may be positioned at the second end of the pump shaft and may be configured to secure the plurality of impellers
Implementation Method 2
Under operational conditions, the downthrust loads generated by each stage induces an elastic deformation
Data Source
AI summary
A pump comprising a plurality of impellers stacked on top of each other via a pump shaft, a diffuser corresponding to each impeller, a body housing the impellers, the diffusers, and the pump shaft, and a protector thrust bearing at one end of the pump shaft.