Views: 48951 Author: Site Editor Publish Time: 2025-04-13 Origin: Site
1. Introduction: The Overlooked "Blood" Crisis
Screw compressors have become key industrial equipment due to their high cost-effectiveness. However, many users still rely on a "just keep it running" maintenance mindset, ignoring the critical role of lubricant – the compressor's "blood." Once lubricant coking occurs, it directly causes efficiency loss, insufficient air delivery, and even rotor seizure, leading to expensive repairs and production shutdowns. This article moves beyond traditional technical perspectives to systematically analyze the root causes of coking from physicochemical, managerial, and operational levels, providing proven prevention solutions.
2. Physicochemical Nature of Coking: More Than Just "Getting Dirty"
Lubricant coking is essentially a complex chemical degradation process. Taking common mineral oil as an example, its hydrocarbon components undergo intense oxidation under high temperature, oxygen, and metal catalysis, leading to molecular chain scission or cross-linking. The results are:
Sharp viscosity increase
Higher acid value and insoluble matter formation
Blackening and formation of hard carbon deposits
Different lubricants show vastly different coking tendencies:
Lubricant Type | Characteristics After Deep Oxidation | Coking Tendency |
|---|---|---|
Paraffinic Mineral Oil | Viscosity keeps rising, forms hard carbon | Extremely High |
Ester Synthetic Oil | Good oxidation resistance, forms sludge, no hard carbon | Low |
PAG Synthetic Oil | Chain scission and volatilization at high temperature, no carbon or sludge | None |
Certain Polyglycols | Complete volatilization at high temperature, no residue | None |
3. Direct Triggers of Coking: Four "Invisible Killers"
Metal Ion Catalysis – Wear debris (iron, copper) acts as strong oxidation catalysts, accelerating oil aging.
High-Temperature Oxidation – Higher pressure and oxygen concentration lead to more severe oxidation. Prolonged high-temperature operation is the #1 cause.
Water Emulsification – Condensed moisture from compressed air enters the oil, forming emulsions under vigorous agitation, causing additive hydrolysis, rust, and eventual sludge formation.
Old Oil Contamination – Used oil cannot be 100% drained during changes. Residual aged oil contaminates new oil, drastically shortening its service life.
4. Root Causes: Human Factors Over Equipment Factors
Staying only at the physicochemical level will never solve coking. The real root causes are:
From Producers – Some lubricant manufacturers lack expertise; or compressor makers purchase cheap, substandard oil to cut costs, resulting in poor base oil and additive quality.
From Users:
Mixing old and new oil – Refilling without periodic changes.
Mixing different brands – Additive incompatibility leads to oil failure.
Using substitutes – Hydraulic or gear oil replacing dedicated screw compressor oil.
Ignoring accessory quality – Poor air filters, oil filters, and separators allow dust and contaminants into the oil circuit.
Cooling system failure – Fouled water coolers or blocked air-cooled radiators cause chronic high temperatures.
5. Prevention Measures: A Complete Closed-Loop from Source to Operation
Use the Correct Oil – Must be the dedicated screw compressor oil. No mixing or substitution. Prefer synthetics for longer life.
Always Clean Before Oil Change – Use specialized cleaners (carbon remover, acetone, etc.) to thoroughly flush the oil circuit, removing old oil and coking residues.
Strictly Control Accessory Quality (Especially Air Filters) – Simple field tests:
Water Test – Sprinkle water on filter paper. No penetration within 24 hours = premium quality. Penetration within 5 minutes = reject immediately.
Light Test – Hold against light. Even, good light transmission, and smooth surface indicate good quality.
Pleat Depth & Count – More pleats and deeper pleats mean larger filtration area and better airflow.
Ensure Cooling System Performance – Clean water-cooler scale every 6–12 months. Regularly clean air-cooled radiator fins to maintain airflow.
6. Conclusion
Lubricant coking is not an inevitable "terminal disease" but a direct consequence of poor management. Only by simultaneously controlling "oil procurement quality," "standardized usage practices," and "high-quality accessory supply" – while rejecting the mentality of seeking cheap shortcuts – can we truly eliminate coking and keep screw compressors healthy, efficient, and long-lasting.
