Main Engine overheated due to faulty pump

What happened

The vessel was en route at sea; 440V low insulation alarm triggered and after a few minutes the ME Jacket CFW pump motor tripped.
The Main Engine was running at NCR RPM; Ship staff took some time to reduce speed and stop the engine. By then the Jacket CW temperature risen to 98 -100 deg C. The subject vessel does not have a standby Jacket cool FW pump, but an alternate pump ( Fire and GS pump with line to ME FW system) was provided to use in case of breakdown of ME JCFW pump.
There is no slow down or shutdown function incorporated for Jacket cooling water HT. The high JW temperature caused irreversible damage to the sealing O rings in the cooling water passage on the cylinder head and exhaust valve on 5 out of the 6 units. The vessel was drifting 12 miles off shore limits. The company managed to source spares and connect same to vessel. If the incident had happened at sea; salvage would have been required which could have cost the company a lot.
Vessel completed all the repairs and proceeded back on her voyage; there was a total off-hire of about 5 days.

Root cause

1. The vessel had to carry out the pump repair prior proceeding her voyage; as the jacket cooling water leak was excessive. Upon checking the spares inventory list, the vessel had sufficient spares and the job was taken up; but later it was noted that on actual there weren't enough spares as mentioned in the inventory list for completing the overhaul.
2. Later on testing the HT alarm with a calibrator it was found that the HT alarm was not triggering the alarm at the desired set point.

Lesson learnt

• All ME, AE alarms and trips to be tested at regular intervals with calibrator and confirmed to be in working order. The test should not to be performed by shorting / open terminal.
• Understanding of the shutdown / slow down function incorporated in the engine control system.
• Stand by pumps related to ME ( FW/ LO / FO / SW) auto start function are tested and in good order.
• All Officers must know how to take appropriate immediate action in case of an emergency.
• Good watch keeping practice to be enforced on-board. Any abnormality noticed should be immediately into CE and Ship Managers attention.