Screw Compressor Rotor Abnormalities? Wear / Deformation / Seizure Troubleshooting and Solutions

The rotor of a screw compressor is the core component of the entire compression system, and its operational status directly determines the equipment's gas production efficiency and service life. This article provides a detailed explanation of common rotor malfunctions, their causes, and key prevention and control measures, helping equipment maintenance personnel quickly troubleshoot and resolve issues.

I. Rotor Component Composition

The rotor assembly centers on the drive rotor (male rotor) and driven rotor (female rotor), complemented by critical components including main bearings, thrust bearings, bearing caps, balance pistons, and balance piston sleeves.

II. Common Rotor Malfunctions

1. Normal Mechanical Wear and Aging

- Wear on outer diameters of male/female rotor tooth tracks

- Natural wear on rotor cylinders

2. Mechanical Damage Caused by Human Error

- Scratches on outer diameters of male/female rotor tooth tracks

- Scratches on inner walls of rotor cylinders

- Scratches on sides of rotor inlet/outlet end caps

- Wear on inlet/outlet end bearings and inner circles of bearing end caps

Wear on shaft diameters at rotor bearing mounting positions

Deformation of rotor shaft ends

3. High-Risk Areas for Component Scratching/Seizure

Scratching and seizure (bite) on male/female rotor meshing surfaces

Rotor outer diameter rubbing against housing inner walls

Friction between rotor exhaust end face and exhaust bearing housing

Wear and seizure between rotor intake end journal and housing shaft bore

Wear and seizure of rotor discharge end journals with discharge bearing housing bores

III. Core Causes of Rotor Failures

Improper Air Intake and Lubrication Maintenance Failure to replace air filters on schedule leads to excessive dust in intake air, causing contaminants to enter the compression chamber and severely wear rotors. Arbitrary mixing of different lubricant brands can cause carbon deposits and gumming in the oil, further accelerating rotor wear.

Non-compliant lubricant selection/replacement: Using compressor oil types that fail to meet equipment specifications or neglecting scheduled oil changes allows excessive impurities in the oil, directly causing scratches on precision components like rotors and cylinder barrels.

Abnormal Operating Parameters Trigger Cascading Failures Excessively low discharge temperatures during operation increase moisture content in the oil-gas mixture, leading to oil emulsification over time. Emulsified lubricant fails to adequately lubricate inlet/outlet bearings, causing overheating and damage under high-speed, heavy-load conditions. This ultimately results in rotor shaft misalignment, deformation, or seizure.

Drive component failures

Issues like abnormal meshing clearance in drive-end coupling gears or failed key connections can cause uneven stress distribution on the drive-end shaft end, leading to shaft end deformation.

Bearing quality defects

Using non-compliant bearing components increases the risk of abnormal bearing failure, indirectly inducing rotor eccentricity and wear.

Substandard machining and assembly precision: The suction and discharge shaft journals of the rotor are supported by bearings in the compressor housing and discharge bearing housing, respectively. If the coaxiality between the housing, bearing housing, and rotor fails to meet design standards (which must be controlled within 0.01–0.02 mm), it can easily cause rubbing or seizure between rotors, between rotors and the housing, or with other components.

Accumulation of Design and Manufacturing Errors Internal components within the compression chamber feature precision dynamic fits, with clearance measured in thousandths of an inch or millimeters. If the designed clearance is too small, combined with manufacturing tolerances, it significantly increases the probability of rotor scoring or seizure. Under normal operating conditions, the clearance between the rotor and housing is approximately 0.1mm, while the clearance between the rotor discharge end face and the discharge bearing housing ranges from 0.05 to 0.1mm.

Improper Disassembly and Assembly Procedures During disassembly, the bearing and rotor shaft have an interference fit. Excessive force during removal can cause component deformation, reducing their inherent coaxiality. After unit assembly, failure to verify overall coaxiality of assembled components may lead to part abrasion or rotor seizure if operation commences under out-of-tolerance conditions.

Summary: Most of the aforementioned rotor failures in screw compressors are closely related to human operation, maintenance, and assembly practices. During routine maintenance, strictly adhering to equipment operating and maintenance procedures while implementing regular maintenance measures can effectively prevent such failures.