A vessel had been laid up for nearly ten years. When its owner brought it back into service, the Siemens propulsion monitoring system would not talk to the alarm system on the backup server.
The vessel has two redundant servers. On the primary, the Modbus link between the two systems worked. Switching to the backup broke it.
Without working redundancy, the vessel could not pass Coast Guard inspection or Panama Canal certification.
Starting from what was there
An IKONIKA engineer went to the vessel in Louisiana. The program backups were incomplete and had no descriptions. He compared the fragments with an older version of the code to work out how the logic was meant to behave.
Matching the two servers
The primary and backup PLC configurations were different. That difference broke the data exchange whenever the crew switched servers.
The engineer rebuilt both configurations so they matched line for line. He then tested the Modbus link and switched between servers until both paths changed over cleanly.
Bringing the new temperature controllers onto the network
The crew had already replaced the temperature controllers on the transformer windings. The new controllers sent their data in a different format.
The engineer rewrote the PLC logic to read the new format over the vessel’s Modbus network. Winding temperatures then showed correctly on the control room alarm screens.
The result
There was no rewiring and no new hardware. When the engineer left, both servers held the link, and the alarm system showed correct readings on either one.
The vessel passed its Coast Guard inspection and its Panama Canal certification.
The owner said that if something went wrong now, he knew he would see it.
