What is the latest amendment to the inert gas system requirement, and what does the revised FSS Code chapter 15 require?
Short answer
| Item | Requirement |
|---|---|
| Threshold for new oil and chemical tankers built on or after 1 January 2016 | 8,000 DWT and above (was 20,000 DWT) |
| Oxygen in the gas delivered to the tanks | not exceeding 5% by volume |
| Capacity | at least 125% of the maximum discharge rate |
| Source | boiler flue gas, inert gas generator or nitrogen |
| Safeguards | deck water seal, non-return devices, pressure/vacuum breaker, oxygen and pressure alarms and shutdowns |
- Headline: SOLAS II-2/4.5.5 (MSC.365(93), in force 1 January 2016) lowered the fixed IG threshold for new oil and chemical tankers from 20,000 DWT to 8,000 DWT.
- Before: mandatory only at 20,000 DWT and above, for tankers built on or after 1 July 2002 and before 1 January 2016.
- Revised FSS Code chapter 15: source (flue gas, inert gas generator or nitrogen), oxygen not exceeding 5% by volume, capacity at least 125% of the maximum discharge rate.
- Safeguards: deck water seal and non-return devices, pressure/vacuum breaker, oxygen and pressure monitoring with alarms and shutdowns, tanks at positive pressure.
- Purpose: keep the tank atmosphere below the flammable range during discharge, ballasting, tank cleaning and gas-freeing; more tankers protected against tank explosions.
- As Chief Engineer: SOLAS II-2 and the FSS Code apply through MS Act 2025 s.147; DGMA or its RO surveys the plant I run and maintain on a tanker.
Full answer
The full answer explains each point step by step, with the regulations and figures behind it and the discussion from other candidates. It is in the MEO Class I section of the Marine One forum, open to members enrolled for the MEO Class I exam.