Wear-Resistant Pump Barrel and Plunger Coating for Cryogenic Service
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Solution Overview
Problem
Conventional high-pressure pumps face issues with friction and wear due to tight tolerances and thermal expansion differences between ceramic plungers and housings, particularly when handling low-temperature cryogenic fluids like LNG, leading to reduced efficiency and lifespan.
Innovation Solution
A pumping mechanism with a stainless steel barrel and plunger, coated with tribological materials such as nickel plating and diamond-like carbon (DLC) to reduce friction and wear, and nitride-hardened to specific depths for enhanced durability and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tight tolerances are used between plunger and barrel, then fuel leakage is reduced, but friction and wear increase
Solution Approach 1:
The patent applies a chromium oxide coating to the plunger surface, changing the surface properties to provide both low friction and high wear resistance. This allows the maintenance of tight tolerances for leakage prevention while the coated surface reduces friction and wear through its specialized tribological properties
Solution Approach 2:
The plunger is constructed as a composite structure with a metal substrate and a chromium oxide surface coating. This composite approach combines the mechanical strength of the metal base with the low-friction, wear-resistant properties of the ceramic-like oxide layer, resolving the contradiction between tight clearance requirements and friction reduction
2Object-generated harmful factors
If ceramic material is used for plunger and plunger housing, then wear is reduced, but thermal expansion differences cause fuel leakage
Solution Approach 1:
The patent uses the same metal material (e.g., stainless steel) for both the plunger and plunger housing, ensuring homogeneous thermal expansion characteristics. This eliminates the thermal expansion mismatch problem that occurs with ceramic components, preventing fuel leakage while the chromium oxide coating provides the necessary wear protection
3Reliability
If stainless steel with nickel plating is used, then corrosion resistance is improved, but friction and wear at cryogenic temperatures increase
Solution Approach 1:
The patent applies a chromium oxide coating specifically to the plunger surface where friction and wear occur, while the nickel plating provides general corrosion resistance. This local quality enhancement addresses the cryogenic temperature friction issue at the critical contact surface without compromising the overall corrosion resistance provided by the nickel layer
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
The solution significantly reduces friction and wear, maintaining efficiency and extending the lifespan of the pump by matching thermal expansion properties and providing effective lubrication at cryogenic temperatures.
Implementation Method 1
The plunger substrate may be nitride-hardened to a depth of between 20 and 150 microns below an outer surface of the plunger
Implementation Method 2
A coating may be disposed on the outer surface of the plunger, the coating comprising a tribological material
Data Source
AI summary
A pumping mechanism is disclosed. The pumping mechanism may include a barrel formed of a barrel substrate and including a first end surface, a second end surface opposite the first end surface, and a bore between the first and second end surfaces. Each of the first and second end surfaces and the bore is coated with a metal plating. The pumping mechanism may further include a plunger formed of a plunger substrate and configured to be slidably disposed in the bore in barrel, the plunger substrate having a tribological coating.