Pipe Airlock Problem in University

PowerQ was invited to investigate the airlock which resulted in no space cooling in conditioned space. The airlock issue has been consistent in the past few months. It had affected the high floors while AHU was unable to provide sufficient cooling.

PowerQ investigated and analyse the problem. Root cause analysis were undertaken.

The following factors were found during site investigation and measurements:

• No significant installation issues which might be the cause of airlock were found.
• The expansion tank and raw water supply systems were functional and responded to fill in the pipe when water was drained to check the functionality.
• The degasser in system is for removing micro air bubble and may not be used for removing air packets which can only be removed from air vents at high points.
• The CHW pump is at that time manually controlled and speed is set at about 28 Hz apparently to save energy. However, this results in inadequate pressure.
• Inadequate pressure may not be able to circulate any air bubble in the system toward the air-vent creating the air lock.

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These recommendations were made:

• The pump control logic may need to re-configure to make sure the index point of the system achieve adequate pressure at the high floor AHU. Determine minimum speed to achieve requirement of the Roof AHU.
• Check working pressure for air vent. Consider re-selecting air vent considering low working pressure if it is decided that CHW pump head will be maintained at lower level.
• External Differential Pressure sensor to achieve head of roof units.
• Perform CHW system re-balancing.