Multistage Centrifugal Pump Rib Support Sealing
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Solution Overview
Problem
Multistage centrifugal pumps face inefficiencies due to fluid infiltration between stages, wear of gaskets, and misalignment issues caused by radial and axial clearances, leading to reduced pump reliability and durability, especially in submersible applications with sand and debris.
Innovation Solution
The pump design incorporates a stationary-vane diffuser and cover separated by a cylindrical spacer, with an impeller supported by a central bushing and rib, allowing for even axial load distribution and compensation for manufacturing tolerances, and featuring a ceramic ring for extended wear resistance, along with a polyamide impeller for low friction and high-temperature operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gaskets are fitted between the bottom of the chamber and the impeller to limit infiltration, then fluid infiltration is reduced, but radial clearance is limited causing sand and debris to accumulate and accelerate gasket wear
Solution Approach 1:
The invention removes the gasket component entirely from the sealing system. Instead of using a gasket between the chamber bottom and impeller, it employs a labyrinthine sealing structure formed by the diffuser housing and impeller hub geometry, which prevents fluid infiltration without requiring a gasket that would accumulate sand and debris.
Solution Approach 2:
The invention introduces a fluid barrier (a small amount of fluid maintained in the chamber) as an intermediary substance that prevents sand and debris from reaching the sealing interface between the impeller and chamber bottom, thereby protecting the sealing system without requiring a gasket.
2Force
If contact surface of gasket is limited to reduce friction, then friction between impeller and chamber bottom is reduced, but axial load becomes focused at gaskets causing misalignment and potential jamming
Solution Approach 1:
The invention removes the gasket component that would concentrate axial loads. Instead, it uses a distributed sealing structure where the seal is formed by the relative geometry of the diffuser housing and impeller hub, spreading any contact forces over a larger area and preventing localized misalignment.
Solution Approach 2:
The invention transitions from a single-point or limited-area gasket contact to a distributed sealing interface that extends radially outward, effectively adding dimensional distribution to the sealing contact area and dispersing axial loads.
3Ease of operation
If clearances are increased to prevent jamming, then friction between moving parts is reduced, but fluid infiltration between stages increases reducing pump efficiency
Solution Approach 1:
The invention converts the potentially harmful effect of clearances (which would allow fluid infiltration) into a beneficial feature by designing a labyrinthine sealing path that uses the clearance space itself to create a longer, more tortuous flow path for any leaking fluid, thereby reducing infiltration while maintaining the necessary clearances for smooth operation.
Solution Approach 2:
The sealing interface is segmented into multiple zones along the radial direction, with each zone contributing to the overall sealing effect. This segmentation creates multiple barriers to fluid flow while allowing the impeller to rotate freely within the chamber.
4Stress or pressure
If number of stages is increased to increase pressure, then pump pressure capability is improved, but number of infiltration points increases reducing overall efficiency
Solution Approach 1:
The sealing structure is designed and pre-configured during manufacturing to prevent infiltration at each stage interface before the pump operates. The labyrinthine geometry and fluid barrier are built-in features that proactively prevent fluid leakage across all stage interfaces, ensuring that adding stages does not proportionally increase infiltration losses.
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 enhances the pump's reliability and durability by evenly distributing axial loads, reducing friction, and preventing infiltration, allowing for operation without fluid lubrication and extraction of high-temperature fluids, while extending the pump's operational life by distributing wear and preventing misalignment.
Implementation Method 1
impellers shaped so as to apply on the fluid itself a centrifugal action and thanks to special diffusers... The impeller, by rotating inside the chamber, transmits a centrifugal acceleration to the fluid, from its center to the periphery
Data Source
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AI summary
A submersible centrifugal pump (1) for extracting fluids, of the multistage type, is described, each of said stages (4, 4b) comprising a stationary- vane diffuser (13b) and a cover (11) which are separated from each other by a cylindrical spacer (12), and an impeller (14) placed between said cover (11) and said diffuser (13b) and provided with a central hub (17) having a drive shaft (10) for transmitting rotary motion constrained thereto, as well as supporting and sealing means (16) to support and seal the impeller (14) to the cover (11) and/or to the diffuser (13a) of an upstream stage (4a), characterized in that said supporting and sealing means (16) comprise a central supporting element (18) for the hub (17) of said impeller (14) and a rib (15) jutting from said cover (11) and/or the diffuser (13a) of the upstream stage (13a) so that the impeller (14) is consequently supported at least in one surface region (14a) thereof far from said central hub (17) during the operation of the pump (1).