SMRT Air Conditioning Improvements

Your Journey Matters – Edition 2 was published in October 2016 to update commuters on SMRT’s rail tranformation efforts to improve and renew the North-South and East-West Lines (NSEWL)- Singapore’s oldest, longest and most heavily used MRT lines.


Air conditioning is crucial in keeping commuters cool on the train. An analysis on the most frequent causes of aircon failure for NSEWL trains has shown that a key cause is fuses in the aircon motors blowing out as a result of arcing caused by build up of carbon dust inside the motor.

The source of the carbon dust is the carbon brush, a component in the aircon unit that is in contact with the aircon motor. A more effective cleaning method to remove excessive carbon dust build up has been implemented and new carbon brushes are being trialed to reduce the carbon build up.

Microcards are like the brains of the aircon unit. When there is a defective microcard, the aircon does not function properly. In some situations, the unit fails to activate when temperatures get too high. Replacing defective microcards with new ones from the manufacturer is one solution, but SMRT has been working on a more sustainable solution. The Integrated Electronics Workshop team at SMRT has studied the microcard and has been refurbishing defective microcards.

The trains’ aircon units use a gas known as freon as a refrigerant which cools the air. The freon gas cycles within the unit in a closed system of coils. If freon leaks from these coils, cooling efficiency is reduced. We are stepping up efforts to plug leaks in these tubes though a process known as “brazing”. The freon also needs to be topped up when leaks are discovered. The use of a recovery machine ensures that the precise composition of refrigerant is used to ensure cooling efficiency.

The later models of trains on the NSEWL are equipped with the Trains Information Management System, or TIMS. TIMS is a system of sensors that measures various properties of the train during operations, such as measuring the internal temperature of each car. During service, train captains can check TIMS for any aircon faults. When faults are detected, a field team is activated. The team will then verify the fault and where possible, rectify the issue immediately. Further inspections on the reported aircon system will also be carried out when the train returns to the depot.


This is part of a series on SMRT’s rail improvement efforts. Read more:
SMRT- Track Improvements
Powering SMRT Trains on the North-South and East-West Lines
SMRT- Platform Screen Door Maintenance
SMRT- Escalator Maintenance

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