Electrostar HVAC Replacement Compressor Testing for Alstom

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DB ESG and DB Systemtechnik put a new replacement compressor through rigorous testing to prove it can match the Electrostar fleet’s original HVAC performance and secure a reliable, future-ready retrofit.

Background

The saloon HVAC modules installed in the roof sections of Alstom’s Electrostar fleets were originally manufactured at the time the vehicles were built. The compressor units within these modules have since become obsolete and are no longer available.  Alstom identified a suitable replacement - a reciprocating type compressor and engaged DB ESG to assess its retrofit viability, leveraging its access to DB Systemtechnik’s testing laboratories in Germany.

DB ESG was tasked with conducting cooling capacity, shock and vibration testing, along with providing consulting support to determine whether the new compressors were appropriate for use in a dynamic rail environment. A key requirement was to ensure that the replacement compressors did not compromise the HVAC system’s cooling performance. To facilitate integration, the new compressors were mounted on an adaptor sub-frame for installation into the existing HVAC modules.

Scope of Work

DB ESG managed the entire test programme and schedule, providing on-site support during the cooling performance evaluations. Acting as a single source supplier, DB ESG subcontracted specialist testing elements to trusted partners, including its parent company, DB Systemtechnik who operate the Laboratory for Component Testing, Aerodynamics and Air Conditioning (LUDEK) in Munich, Germany.

The picture shows DB Systemtechnik’s LUDEK facilty

Transfers heat between two media without mixing them.

Measures the amount of air or fluid flowing through a system per unit of time

Prevents the condenser from freezing or maintains temperature in cold conditions.

Moves air across the condenser to remove heat from the refrigerant.

The following tests and activities were undertaken:

Shock and Vibration Testing

  • Conducted on a pair of compressors mounted on their sub-frame at a supplier facility in the UK.
  • Included:
    • Three 10-minute functional random vibration tests with powered motors, followed by inspection for damage or loose components.
    • Three 5-hour simulated long-life random vibration tests with unpowered motors, again followed by inspection.
    • Shock and vibration tests with unpowered motors, with post-test damage assessmen

Cooling Capacity Performance Testing

  • Performed by DB Systemtechnik at the LUDEK facility in Munich, Germany. This facility realistically simulates the air-side conditions of both the passenger compartments during operation and the surrounding environment, providing precise and actionable results.
  • A complete representative HVAC unit was tested with both the original and replacement compressors under identical conditions to ensure valid comparison.
  • Included:
    • Electrical connection of the HVAC system to enable performance measurements.
    • High accuracy airflow measurement via pressure drops using two venturi pipes.
    • Humidity and airflow variation measurements within the condenser circuit

Results

The new compressors passed the testing and were found to deliver the same performance as the previous ones. Risks were identified and recommendations were implemented through targeted adjustments to the operating strategy.

Contact DB ESG to access DB ST’s expertise

DB ST have decades of air conditioning expertise. Their portfolio includes both mobile and static measurement testing, air conditioning simulations and consultancy services.

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