Rotary Pump Front-Loading Seals and Shaft Strength
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Solution Overview
Problem
Rotary positive displacement pumps with front loading seals face challenges in long-term reliability and manufacturing costs, while also affecting pumping efficiency.
Innovation Solution
A rotary positive displacement pump design featuring parallel shafts with gears in constant mesh, a rotor case body with a removable front cover, and torque-proof rotor drive elements mounted on rotor seats with axial abutment surfaces outside the hubs, allowing for increased shaft diameter and improved sealing with mechanical face-seal assemblies for reduced maintenance and increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If front loading seals are used, then simplified maintenance is achieved, but long term reliability and pumping efficiency are reduced
Solution Approach 1:
The rotor case body is divided into a stationary portion and a removable front cover portion, allowing the seal assemblies to be accessed and replaced by simply removing the front cover without disassembling the entire pump. This segmentation enables simplified maintenance while maintaining reliability by allowing periodic seal replacement without affecting other pump components.
2Ease of repair
If front loading seals are used, then simplified maintenance is achieved, but manufacturing cost increases
Solution Approach 1:
The rotor case body is segmented into a stationary portion and a removable front cover portion, which simplifies maintenance by allowing easy access to seal assemblies. This segmentation enables standardized, cost-effective manufacturing of modular components that can be produced independently and assembled efficiently.
3Volume of moving object
If axial abutment surface is located inside the hub, then compact design is achieved, but shaft diameter must be increased
Solution Approach 1:
The axial abutment surface for the rotor drive element is positioned on the rotor seat at the front end of the shaft, outside the hub region. This positional change in the axial dimension allows the hub to maintain a compact diameter while still providing adequate shaft strength, as the abutment surface is no longer constrained by the hub's internal geometry.
4Strength
If shaft diameter is increased, then shaft strength is improved, but pumping volume and exterior dimensions are affected
Solution Approach 1:
The axial abutment surface is repositioned from within the hub to the front end of the shaft outside the hub. This dimensional repositioning allows the shaft to have adequate diameter for strength without increasing the hub diameter, thereby preserving the pump's exterior dimensions and pumping volume while maintaining required shaft strength.
Data Source
AI summary
A rotary positive displacement pump includes a main body rotationally supporting two parallel, axially extending, shafts with gears in constant mesh condition, such that the shafts rotate in opposite directions. A rotor case body is connected to a front side of the main body and has a stationary interior pumping cavity, fluid product inlet and outlet openings, and two cylindrical rotor case hubs each receiving internally one of the shafts. A pair of rotors each have a rotor wing and a rotor drive element that is mounted torque proof on a rotor seat at an end region of one of the shafts. Each rotor seat pair has an axial abutment surface and a mounting surface. The pump also includes fasteners each engaging a mating section of one of the shafts and exerting an axial clamping force on one of the rotor drive elements against one of the axial abutment surfaces.