The inert gas system referred to in paragraph (a) of Regulation 60 of this Chapter shall be capable of providing on demand a gas or mixture of gases to the cargo tanks so deficient in oxygen that the atmosphere within a tank may be rendered inert, i.e. incapable of propagating flame. Such a system shall satisfy the following conditions:
| (a) | The need for fresh air to enter a tank during normal operations shall be eliminated, except when preparing a tank for entry by personnel. |
| (b) | Empty tanks shall be capable of being purged with inert gas to reduce the hydrocarbon content of a tank after discharge of cargo. |
| (c) | The washing of tanks shall be capable of being carried out in an inert atmosphere. |
| (d) | During cargo discharge, the system shall be such as to ensure that the volume of gas referred to in paragraph (f) of this Regulation is available. At other times sufficient gas to ensure compliance with paragraph (g) of this Regulation shall be continuously available. |
| (e) | Suitable means for purging the tanks with fresh air as well as with inert gas shall be provided. |
| (f) | The system shall be capable of supplying inert gas at a rate of at least 125 per cent of the maximum rated capacity of the cargo pumps. |
| (g) | Under normal running conditions, when tanks are being filled or have been filled with inert gas, a positive pressure shall be capable of being maintained at the tank. |
| (h) | Exhaust gas outlets for purging shall be suitably located in the open air and shall be to the same general requirements as prescribed for ventilating outlets of tanks, referred to in paragraph (a) of Regulation 58 of this Chapter. |
| (i) | A scrubber shall be provided which will effectively cool the gas and remove solids and sulphur combustion products. |
| (j) | At least two fans (blowers) shall be provided which together shall be capable of delivering at least the amount of gas stipulated in paragraph (f) of this Regulation. |
| (k) | The oxygen content in the inert gas supply shall not normally exceed 5 per cent by volume. |
| (l) | Means shall be provided to prevent the return of hydrocarbon gases or vapours from the tanks to the machinery spaces and uptakes and prevent the development of excessive pressure or vacuum. In addition, an effective water lock shall be installed at the scrubber or on deck. Branch piping for inert gas shall be fitted with stop valves or equivalent means of control at every tank. The system shall be so designed as to minimize the risk of ignition from the generation of static electricity. |
| (m) | Instrumentation shall be fitted for continuously indicating and permanently recording at all times when inert gas is being supplied the pressure and oxygen content of the gas in the inert gas supply main on the discharge side of the fan. Such instrumentation should preferably be placed in the cargo control room if fitted but in any case shall be easily accessible to the officer in charge of cargo operations. Portable instruments suitable for measuring oxygen and hydrocarbon gases or vapour and the necessary tank fittings shall be provided for monitoring the tank contents. |
| (n) | Means for indicating the temperature and pressure of the inert gas main shall be provided. |
| (o) | Alarms shall be provided to indicate— |
| (i) | high oxygen content of gas in the inert gas main; |
| (ii) | low gas pressure in the inert gas main; |
| (iii) | low pressure in the supply to the deck water seal, if such equipment is installed; |
| (iv) | high temperature of gas in the inert gas main; and |
| (v) | low water pressure to the scrubber; |
and automatic shutdown of the system shall be arranged on predetermined limits being reached in respect of subparagraphs (iii), (iv) and (v) of this paragraph.
| (p) | The master of any ship equipped with an inert gas system shall be provided with an instruction manual covering operational, safety and occupational health requirements relevant to the system. |
