Oil-Free Screw Compressor Rotor Coating for Heat Resistance

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Solution Overview

Problem

Oil-free screw compressors face challenges with high-temperature degradation and rust issues due to the lack of a suitable coating that provides both solid lubricity and heat resistance, leading to performance deterioration and maintenance concerns in industries requiring clean air.

Innovation Solution

The application of solid lubrication heat-resistance coatings on screw rotors using a resin with an imide bond, combined with Molybdenum disulfide, Titanium oxide, Aluminium oxide, and other additives, to enhance heat resistance and prevent rust, while maintaining lubricity and minimizing gap sizes between rotor surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oil is used for cooling and lubrication in screw compressors, then friction heat is effectively cooled and rotors are protected from seizure, but oil mist contaminates the compressed air making it unsuitable for clean air applications

Engineering Contradiction:

Improverotor protection from seizureVSAvoidoil mist contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention extracts the harmful oil medium from the compression system while retaining the essential lubrication and cooling functions through alternative means (solid lubricant coating and water cooling), thereby eliminating oil mist contamination while maintaining rotor protection

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention applies a composite coating on rotor surfaces consisting of solid lubricants (such as PTFE, graphite, or MoS2) combined with heat-resistant materials, creating a multi-functional layer that provides both lubrication and thermal stability without oil contamination

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If no oil is used in screw compressors, then clean air is supplied, but the rotor structure becomes more complicated requiring synchronous gears and the gaps between rotors must be minimized

Engineering Contradiction:

Improveair cleanlinessVSAvoidrotor structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention replaces the oil-based mechanical lubrication system with a solid lubricant coating system, eliminating the need for oil supply mechanisms and reducing structural complexity while maintaining clean air output

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the lubrication mechanism from fluid-based (oil) to solid-based (coating material), altering the physical state of the lubricant to eliminate contamination while maintaining functional performance

Inventive Principle:

Principle #35Parameter changes

3Reliability

If coatings are applied on rotor surfaces to provide solid lubricity and reduce gaps, then lubrication and heat resistance are improved, but the coatings degrade and separate under high temperature and pressure conditions

Engineering Contradiction:

Improvesolid lubricity and heat resistanceVSAvoidcoating integrity under high temperature

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The invention uses composite coating materials that combine solid lubricants with heat-resistant binders and additives, creating a multi-component system where each ingredient contributes specific properties (lubrication, thermal stability, adhesion) that together prevent degradation under high temperature and pressure

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes coating parameters including material composition ratios, coating thickness, and curing conditions to enhance the coating's thermal and mechanical stability, preventing separation and degradation under operational stress

Inventive Principle:

Principle #35Parameter changes

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 coatings significantly improve heat resistance and prevent rust, maintaining performance and reducing maintenance needs by extending the lifespan of the compressor and preventing air leaks, even at high temperatures.

Implementation Method 1

Molybdenum disulfide, as a solid lubricant, are dispersed in the resin

Methodology Applied

Scientific EffectSolid lubrication: Lubrication

Implementation Method 2

resin containing an imide bond is used as base resin... high heat-resistance is required for the coatings applied to the rotor surfaces

Methodology Applied

Scientific EffectHeat resistance: Thermal Insulation

Implementation Method 3

Titanium oxide, and Aluminium oxide, and Silicon nitride in resin containing an imide bond

Methodology Applied

Scientific EffectHeat resistance: Thermal Insulation

Implementation Method 4

the coatings applied on the rotor surfaces... rust prevention

Methodology Applied

Scientific EffectRust prevention: Oxidation

Data Source

PatentUS9944880B2Oil-free screw compressor coated with a base resin, a solid lubricant and a heat-resistant additive

Publication Date: 2018.04.17 HITACHI IND EQUIP SYST CO LTD

AI summary

In order to prevent deterioration in performance of an oil-free screw compressor and scuffing caused by rust, surfaces of both male and female rotors are coated with heat-resistance coatings containing a solid lubricant. A coating contains Polyimide resin to which Molybdenum disulfide, as a solid lubricant, and Aluminum oxide and Titanium oxide, as additives, are added. Accordingly, it is possible to realize a coating that is higher in heat resistance and longer in lifetime than a conventional one.