Screw air compressors are vital in many industries for providing efficient compressed air solutions. However, over time, the rotors in these machines can experience wear and tear, affecting their performance. This article outlines common causes of rotor wear and various methods for repairing or restoring screw air compressor rotors.
Causes of Rotor Wear
Rotor wear in screw compressors typically occurs due to friction between the rotors, the casing, and the lubricating oil. As the rotors rotate within the cylinder, the compression gas and lubricating oil cause gradual abrasion. Over time, this results in the reduction of the rotor’s diameter and the expansion of the inner cavity of the casing. This increased gap causes the efficiency of the compressor to drop, as it leads to more leakage of air and oil, especially in the direction of the intake.
Repairing the Casing
The casing of a screw compressor is typically more durable than the rotors. However, over time, its inner diameter can increase due to wear, eventually affecting the compressor’s performance. There are a few repair methods to restore the casing to its original functionality:
- Boring and Grinding:
If the casing still has a nitrogen-hardened layer, it can be re-bored and ground to a new diameter. The new screw rotor can then be manufactured to fit this updated size. - Recasting the Casing:
When the inner diameter becomes too worn, it may be necessary to re-cast the casing. This involves adding a new alloy layer (1–2mm thick) to the casing’s interior and then machining it to the required size.
Repairing the Rotors
Rotor wear in screw compressors can be addressed in several ways, depending on the extent of the damage. Below are common methods for repairing or restoring worn rotors:
- Custom Manufacturing of New Rotors:
In cases where the rotor has broken or has significant wear, a new rotor may need to be manufactured. The new rotor will be designed based on the casing’s current inner diameter, ensuring a proper fit and optimal performance. - Thermal Spraying with Wear-Resistant Alloys:
For rotors with minor diameter reductions, the surface can be treated with a thermal spray of wear-resistant alloys. After spraying, the rotor is ground to size. This method is cost-effective and commonly used by specialized repair centers. - Welding with Wear-Resistant Alloys:
In cases of more severe wear, the worn areas of the rotor can be welded with a layer of wear-resistant alloy, typically 1–2mm thick. After welding, the rotor is ground to the correct dimensions. The alloy typically consists of materials such as Carbon (C), Chromium (Cr), Vanadium (Vi), Cobalt (Co), Tungsten (W), and Boron (B), which provide enhanced wear resistance and corrosion protection. Although this method can be more expensive, it’s highly effective for severe wear cases. - Hard Chrome Plating:
Another option for restoring the rotor’s surface is hard chrome plating. Chrome is a durable material that resists both wear and corrosion. However, the hard chrome layer can be prone to flaking, so this method is generally used in cases where the wear is not too extensive.
Preventing Rotor Wear
To extend the life of both the rotors and the casing, proper maintenance is crucial. Regular checks of lubricating oil, air filters, and other components will ensure the compressor runs efficiently. Additionally, ensuring that the machine operates within the recommended parameters (such as pressure and temperature) can help prevent unnecessary wear.
By following the appropriate repair methods and implementing effective maintenance strategies, the lifespan of screw air compressor rotors and casings can be significantly extended, leading to better overall performance and reduced downtime.
Learn More:
For more information on maintaining and repairing screw air compressors, visit Baldor Air Compressors. Our team of experts can assist with ensuring your compressors run smoothly and efficiently.
