Corrosion Resistant Lubricant for Rotary Screw Air Compressors
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Solution Overview
Problem
Modern rotary screw air compressor lubricants based on synthetic polyalkylene glycol (PAG) face issues such as elastomer shrinkage, reduced fluid life in acidic environments, and the undesirability of barium-containing corrosion inhibitors, necessitating a formulation that balances corrosion resistance and elastomer compatibility without polyol ester co-base oil or barium-containing additives.
Innovation Solution
A lubricant comprising an alcohol-initiated propylene oxide homopolymer as the base oil, an oil-soluble polyalkylene glycol as a co-base oil, and a calcium salt of dinonylnaphthalene sulphonate as a ferrous corrosion inhibitor, which synergistically enhances corrosion resistance and prevents elastomer shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyol ester co-base oil is used to swell elastomers and boost corrosion resistance, then elastomer compatibility and corrosion resistance are improved, but fluid life is reduced in acidic environments due to hydrolysis
Solution Approach 1:
The patent removes polyol ester co-base oil from the lubricant formulation to eliminate the source of hydrolysis in acidic environments. Instead, it uses an alcohol-initiated propylene oxide homopolymer as the sole base oil, which does not undergo hydrolysis, thereby extending fluid life while maintaining corrosion resistance through alternative means (corrosion inhibitor additives and oil-soluble PAG).
Solution Approach 2:
The patent changes the chemical composition parameters of the base oil from polyol ester to alcohol-initiated propylene oxide homopolymer. This parameter change eliminates the hydrolysis vulnerability while maintaining lubrication performance and elastomer compatibility through careful selection of the homopolymer's molecular weight and viscosity grade.
2Reliability
If barium-containing corrosion inhibitors are used to protect ferrous surfaces, then corrosion resistance is improved, but environmental harm increases
Solution Approach 1:
The patent removes barium-containing corrosion inhibitors from the formulation and replaces them with calcium-based corrosion inhibitors. This extraction of the harmful barium component eliminates environmental harm while maintaining corrosion protection functionality through the alternative calcium-based additive package.
Solution Approach 2:
The patent uses calcium-based corrosion inhibitors as a more environmentally friendly, readily available alternative to barium-containing inhibitors. Calcium compounds are generally more environmentally acceptable and can be effectively used as corrosion inhibitors without the toxicological concerns associated with barium.
3Duration of action of stationary object
If PAG base oil is used to achieve long fluid life, then fluid stability is improved, but elastomeric components shrink causing lubricant leakage
Solution Approach 1:
The patent introduces oil-soluble polyalkylene glycol additives as intermediaries between the PAG base oil and elastomeric components. These additives modify the interaction between the lubricant and elastomers, preventing the shrinkage caused by pure PAG while maintaining the long fluid life characteristic of PAG-based formulations.
Solution Approach 2:
The patent modifies the physical-chemical parameters of the lubricant formulation by adding oil-soluble PAG additives with specific molecular weights and viscosities. These parameter changes alter the elastomer-lubricant interaction to prevent shrinkage while preserving the thermal and oxidative stability that gives PAG its long fluid life.
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 lubricant achieves improved corrosion resistance comparable to polyol ester formulations, extends fluid life in acidic environments, and eliminates the need for barium-containing additives, ensuring effective lubrication of rotary screw air compressors.
Implementation Method 1
oil soluble PAGs can swell elastomers similar to polyol esters
Implementation Method 2
calcium salt of dinonylnaphthalene sulphonate as a ferrous corrosion inhibitor
Implementation Method 3
Water and acidic gases can ingress from such an atmosphere into the lubricant and cause hydrolysis of the polyol ester
Data Source
AI summary
A lubricant contains alcohol initiated propylene oxide homopolymer, an oil soluble polyalkylene glycol other than the alcohol initiated propylene oxide homopolymer, and a calcium salt of dinonylnaphthalene sulphonate where the lubricant is further characterized by containing less than ten weight-percent of polyol esters based on total lubricant weight is useful as a lubricant for compressors.