Case study
Citect SCADA audit and redundancy rebuild on an effluent treatment plant
A redundant SCADA pair that had never actually failed over, found during a first AMC visit and rebuilt without taking the plant out of service.
The problem
What we found
The plant believed it had a redundant SCADA pair. It had two servers, configured as a pair, that had never been failover-tested since commissioning six years earlier.
A routine first-visit audit under a new maintenance contract found the standby server would not take over: its project version was eleven months behind the primary, and the alarm server configuration pointed at a decommissioned IP address.
There was also no restorable backup. The most recent copy sat on a laptop that had been reimaged.
The constraint
An effluent treatment plant under a discharge consent cannot be taken out of service for a SCADA rebuild, and losing historical data would have broken the compliance reporting record.
The approach
How it was done
- 01
Audit and written report first
Tag count, project version drift, redundancy configuration, licence position and backup state, written up and handed over before any remedial work was quoted.
- 02
Standby rebuilt in parallel
The standby was rebuilt off-line against the current project, then reintroduced and failover-tested by deliberately stopping the primary during a low-load period.
- 03
History preserved
Trend and alarm history was migrated rather than restarted, keeping the compliance reporting record continuous.
- 04
Backups made routine and proved
Scheduled off-site backups for both nodes and the controllers, with a restore proved on a test machine — then re-proved at each subsequent contract visit.
The result
What changed
Failover now works and is tested at every scheduled visit rather than assumed.
Six years of trend history retained, keeping the discharge compliance record intact.
Next step
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