Remote monitoring for ABB drives and their environment

DART H2s Case Study No 2

The DART monitoring device showing a spike in H2S in a plant room

Issue Description:


•    In November 2025, elevated Hydrogen Sulphide (H₂S) levels were detected inside a plant room, reaching concentrations high enough to adversely affect the drive which had been installed by EDC.
•    Investigation indicated inadequate air circulation and insufficient extraction of H₂S-contaminated air from the room.
•    As an immediate mitigation measure, EDC installed additional circulation fans inside the room to improve airflow and support the existing MCC extractor fans in removing accumulated H₂S gas.
•    Following the installation of the circulation fans, H₂S levels reduced and stabilized to acceptable levels.
•    Approximately 5.5 months later, DART trend data showed a gradual increase in H₂S levels within the room.
•    Upon contacting the site team, it was confirmed that the MCC extractor fans were no longer operational due to failure/breakdown.
•    The failure of the extractor fans resulted in ineffective removal of H₂S gas, allowing concentrations to build up again inside the room.

Root Cause Analysis


•    The primary root cause of the recurring H₂S accumulation was the failure of the MCC extractor fans.
•    The circulation fans installed by EDC were intended only to assist air movement within the room and depended on the extractor fans to remove contaminated air from the enclosure.
•    Once the extractor fans became non-operational, the ventilation system could no longer effectively evacuate H₂S gas, leading to gradual accumulation over time.

Contributing Factors
•    Lack of preventive maintenance or periodic inspection of the MCC extractor fans.
•    Absence of a fault monitoring/alarm system to immediately indicate extractor fan failure.
•    Dependence on existing ventilation infrastructure without redundancy.
•    Continuous or recurring generation/presence of H₂S in the surrounding environment.

Impact
•    Increased H₂S concentration inside the room created an aggressive corrosive environment.
•    Potential risk of damage or degradation to electrical drives and associated equipment.
•    Increased risk of unplanned downtime and reliability concerns for installed systems.
•    Potential health and safety risk for personnel entering the affected area.

Observations

  • The temporary mitigation implemented in November 2025 was effective only while the extractor fans remained operational.
  • DART trend monitoring successfully identified the gradual rise in H₂S levels, enabling early detection of the issue recurrence.
  • The incident highlights the critical dependency between air circulation systems and functional extraction systems in H₂S-prone environments.

Recommended Corrective Actions

  • Repair or replace defective MCC extractor fans immediately.
  • Implement routine inspection and preventive maintenance schedules for all ventilation equipment.
  • Install extractor fan health/failure alarms linked to the monitoring system.
  • Consider adding redundant extraction fans to improve reliability.
  • Continue periodic DART monitoring of H₂S levels to verify effectiveness of corrective actions.
  • Evaluate long-term ventilation improvements or H₂S mitigation measures for the room.