Adjustable Piston Inserts for Pump Wear Reduction
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Solution Overview
Problem
Positive-displacement pumps with close-fitting pistons and housing surfaces face issues of galling and wear, leading to potential damage and high costs due to the need for expensive non-galling materials, especially in abrasive applications.
Innovation Solution
The design incorporates replaceable and adjustable piston inserts made from anti-galling materials with low friction coefficients, allowing for a close fit with the pump housing while using less expensive materials for the piston hub, and enabling adjustment or replacement of inserts to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a relatively close fit is provided between the piston outer surfaces and the pump housing, then pump pressure and self-priming capability are improved, but galling and wear of the piston and housing surfaces occur
Solution Approach 1:
The piston is divided into two functional segments: a hub portion made of durable material and an outer surface layer made of non-galling material. This segmentation allows each part to serve its specific function - the hub provides structural integrity while the outer layer prevents galling and wear during operation with the pump housing.
Solution Approach 2:
The piston employs a composite structure combining a metal hub portion with an outer surface layer of non-galling material. This composite construction integrates the advantages of both materials - the strength and rigidity of metal with the low-friction, non-galling properties of the outer layer, resolving the contradiction between pressure capability and surface reliability.
2Reliability
If non-galling materials are used for the piston surfaces, then galling is prevented, but the material cost increases and wear resistance in abrasive applications decreases
Solution Approach 1:
The non-galling material is applied locally only to the outer surface layers of the piston that contact the pump housing, rather than using it for the entire piston structure. This localized application provides anti-galling protection exactly where needed while using more cost-effective materials for the hub and internal components, reducing overall material cost.
Solution Approach 2:
By segmenting the piston into a hub portion and outer surface layers, the invention allows the use of expensive non-galling materials only where necessary for preventing surface galling, while the bulk of the piston can be made from more economical materials, thus balancing reliability and manufacturing cost.
3Productivity
If a relatively close fit is provided between the piston outer surfaces and the pump housing, then semi-solids and solids are prevented from accumulating, but the piston and housing surfaces are subject to galling and wear
Solution Approach 1:
The composite piston structure with non-galling outer layers enables the maintenance of a close fit between piston and housing without the harmful effects of galling and wear. This close fit prevents semi-solids and solids from accumulating in the clearance space, maintaining high pump efficiency while the protective outer layers prevent surface damage.
Solution Approach 2:
The outer surface layers are designed as replaceable components that can wear and be replaced without replacing the entire piston assembly. This allows the critical anti-galling surface to be renewed periodically, maintaining pump efficiency over the long term while the expensive non-galling material is concentrated only in the wear-prone outer layers.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A piston for a pump a hub portion defining opposing outer portions, and inserts configured to provide an adjustable surface coupled to each of the opposing outer portions. The hub portion includes a first hub portion and a second hub portion configured to abut one another. Each of the inserts includes an outer shell and a base portion. The first hub portion includes a plurality of the opposing outer portions, and each of the base portions of the inserts is adjustably coupled to respective opposing outer portions of the first hub portion. A pump includes a housing having an inlet and an outlet, and at least two pistons having a hub portion and inserts. The pump may be a positive-displacement, rotary pump, and the pistons may be circumferential pistons.