Troubleshooting Centrifugal Compressors: High Temperature and Shaft Displacement

Introduction

Plant engineers and maintenance managers frequently encounter issues with centrifugal compressors, particularly high discharge temperatures and abnormal shaft displacement readings. These conditions can indicate underlying problems that require prompt attention to avoid costly downtime and potential equipment damage.

Causes of High Discharge Temperature

High discharge temperatures in centrifugal compressors can be caused by several factors:

• Overheating due to insufficient cooling: Inadequate air or water cooling can lead to elevated temperatures. Check the cooling system for blockages, clogged filters, or malfunctioning fans.
• Compressor load: Operating the compressor at full load for extended periods can increase the temperature. Ensure the compressor is not overloaded and consider load shedding during peak demand.
• Thermal insulation: Poor thermal insulation around the compressor can cause heat to build up. Inspect and replace any damaged or missing insulation.
• Compressor efficiency: Reduced efficiency can result in higher temperatures. Regular maintenance and inspection of the compressor components are essential.

Checks for High Discharge Temperature

To diagnose high discharge temperatures, perform the following checks:

• Monitor cooling system performance: Verify that the cooling system is functioning correctly. Measure water flow rates and temperatures to ensure they meet the manufacturer's specifications.
• Inspect compressor load: Use the control system to monitor the load on the compressor. If the load is consistently high, consider reducing the load or increasing the number of compressors.
• Evaluate thermal insulation: Inspect the thermal insulation around the compressor and replace any damaged or missing sections.
• Assess compressor efficiency: Regularly inspect the compressor for signs of wear and tear. Check for any abnormal noises, vibrations, or unusual behavior that could indicate a decrease in efficiency.

Causes of Shaft Displacement

Abnormal shaft displacement readings can indicate issues such as axial or radial misalignment:

• Axial displacement: This can be caused by excessive axial thrust, which may result from improper bearing adjustment or wear. Ensure that the bearings are properly lubricated and aligned.
• Radial displacement: This can occur due to unbalanced rotating components, misaligned couplings, or excessive vibration. Regularly inspect and balance the rotating components to maintain proper alignment.

Checks for Shaft Displacement

To diagnose shaft displacement issues, perform the following checks:

• Monitor axial displacement: Use the control system to monitor axial displacement readings. If the readings are outside the normal range, inspect the bearings for wear and ensure they are properly lubricated.
• Evaluate radial displacement: Use vibration analysis to detect any abnormal radial displacement. If vibration levels are high, inspect the couplings and rotating components for misalignment.
• Perform regular maintenance: Regularly inspect and maintain the compressor to prevent wear and tear. Ensure that all components are properly aligned and lubricated.

Interlocks and Surge Protection

Interlocks and surge protection are critical for maintaining the safety and reliability of centrifugal compressors:

• Interlocks: Ensure that interlocks are properly set up to prevent operation under unsafe conditions. This includes temperature, pressure, and flow interlocks.
• Surge protection: Surge can cause significant damage to the compressor. Install surge control systems to prevent surge conditions. Regularly check and maintain these systems to ensure they are functioning correctly.

Cooling and Lubrication

Effective cooling and lubrication are essential for maintaining the performance and longevity of centrifugal compressors:

• Cooling system: Ensure that the cooling system is functioning correctly. Regularly inspect and clean the cooling system to prevent blockages and ensure proper heat dissipation.
• Lubrication system: Proper lubrication is critical for reducing wear and tear on the compressor components. Regularly inspect and maintain the lubrication system to ensure it is functioning correctly.

Key Takeaway

High discharge temperatures and abnormal shaft displacement readings in centrifugal compressors can indicate underlying issues that require prompt attention. Regular maintenance and inspection of the compressor components, cooling and lubrication systems, and interlocks are essential for maintaining the performance and reliability of the compressor.

Planning a compressed-air upgrade? Talk to SIND's engineers.