Operation of oil tankers involve many complexities and careful consideration will need to be made for all aspect of daily shipboard jobs. Our article here is about tanker procedures – tank cleaning , purging & gas free check items. These procedures are only indicative, not exhaustive in nature and one must always be guided by practices of good seamanship.
Check items before start of operation
1). Has the operational risks identified and lowered to as low as reasonably practicable (ALARP).
2). Has the working plan for tank cleaning/purging/gas freeing been notified to concerned crew (deck and engine dept.)?
3). Have various precautions and start of work been notified to crew members?
4). Is crew wearing proper PPE?
5) Have all external doors and ports in accommodation been closed and accommodation entrance been designated?
6) Positive pressure is being maintained inside the accommodation, and air conditioning intakes, which may permit the entry of cargo vapors, are closed.
7). The ships fire hoses and fire- fighting equipment are positioned and ready for immediate use.
8). Are combustible gas detector and oxygen content detector ready for use and in good working order?
9). Has reference been made to relevant recommendations in ISGOTT?
10). Is I.G. system in good working order (including PV breaker and deck seal system)?
11). Is continuity of portable tank cleaning hoses in good order (if used / applicable)?
12). Is the ships pipe lines in good condition and appropriate for the service intended?
13). Scuppers on board are effectively plugged
14). Sea and overboard discharge valves, when not in use, are closed and visibly secured.
15). Are Naked light regulations being observed and the crew been advised on the restriction to the use of portable stoves.
16). Has measures been taken to avoid funnel sparks falling on deck especially during soot blow and discussed with E/R.
17). Have gas checks been made 1m below deck and middle level of the tank(s) to confirm O2 level below 8%.
18). Is there an effective deck watch in attendance on board and adequate supervision of operations on the ship?
19). Smoking rooms have been identified and smoking requirements are being observed.
20). Hand torches (flashlights) are of an approved type.
21). Portable VHF/UHF transceiver are of an approved type.
22). Electric cables to portable electrical equipment within the hazardous area are disconnected from power.
23). Are air conditioning units put on partial recirculation. (To be kept open the Top air intake).
24). Measures have been taken to ensure sufficient mechanical ventilation in the pump room.
Check items just before start of washing
Has announcement been made prior starting of operation
1). Have tanks oxygen content been confirmed to be below 8% before start of washing?
2). Are all opening holes of tanks are to be washed closed?
3). Do tanks to be washed have positive pressure ?
4). Are tanks to be washed and water supplying/gathering tanks supplied Inert gas?
Check items during tank cleaning
1). Is oxygen content of delivered inert gas below 5%
2). Does the cleaning tanks have positive pressure?
3). Is the cleaning line pressure proper?
4). “Is the cleaning water temperature proper with respect to last cargo properties?(in case of hot water washing)”
5). Are cleaning machines working properly?
6). Are stripping systems working properly?
7). Is the level of gathering tank proper?
8). Is pump room in good order?
9). Is surrounding sea surface in good condition?
Check items for HC gas purging operation
1). Has working procedure been discussed with assigned persons?
2). Lines set for purging cargo tank?
3). Has the crew been advised to keep away from the purged gas and to carry personal gas monitor? (esp. for H2S) Are purging tanks and pipe lines related drained?
4). Is tank oxygen content below 8% by volume?
5). Has been measured primary HC gas concentration in purging tanks?
6). Has measures been taken to avoid funnel sparks falling on deck especially during soot blow and discussed with E/R?.
7). Has purge pipe cover been open for purging and the flame screen (wire mesh) is clear from choking and the gas flowing out with full flow?
8). Is oxygen content of delivered inert gas below 5% by volume?
9). Is full volume of Inert gas supplied to purging tanks? (Not releasing through Excess valve?)
Check items for gas free operation
1). Is oxygen content of tanks to be gas freed below 8% and is HC gas content below 2% by volume?
2). Is gas free equipment such as portable fans, steam hoses, portable hoses for supplying water and etc. in good condition?
3). Are inert gas delivery valves of tanks to be gas freed closed? (blanked if applicable).
4). Are cargo line suction valves(in case not applicable for gas free operation) closed?
5). Are exhaust holes suitably opened?
6). Has measures been taken to avoid funnel sparks falling on deck especially during soot blow and discussed with E/R.
7). Has tanks oxygen content reached 21 % and has combustible gas content reached below 1% LFL (for Entry into tank).
Check items for entering the tanks after gas free
1). Is tank oxygen content 21% by volume (measuring at fore and aft, high, middle and lower sections of the tank)?
2). Is tank HC gas content below 1% LFL (measuring at fore and aft, high, middle and lower sections of the tank)?
3). Are inert gas delivery valves securely closed by double valves, or shut by blinder or line segregation?
4). Are cargo main suction and stripping valves securely closed?
5). Is the tank ventilation being continued?
6). Companys Procedures for enclosed space entry complied with?
Additional check items when tank cleanings is carried out upon anchoring in harbor or vicinity of harbor limit
1). Has the Port control been notified & permission obtained (if applicable)?
2). Is it confirmed that no unauthorized persons on board?
3). Is it confirmed that no unauthorized boats alongside the vessel?
4). Any authorized boat alongside been informed about operation?
5). Are dump valves on slop tanks ready for immediate opening?
6). Are fire wires correctly positioned fore and aft?
Additional check items when tank cleaning/ de mucking is carried out by shore labor
1). Has meeting with shore personnel been conducted by Master to discuss the schedule of various operations to be performed by shore personnel and explained the on board regulations to be followed by the shore personnel for the safety of vessel and the personnel.
2). Has risk assessment is carried out?
3). Have smoking areas for workers been designated?
4). Have precautions for safety and oil leakage prevention been posted or briefed to workers?
Related article : Tanker crude oil washing procedure