nd arms and leak checks of lines:
When the cargo loading operation begins, liquid is transferred at a very slow rate thereby pre-cooling liquid lines and enabling leak checks. After confirming that the temperature of liquid lines are in the order of below -35C in the case of propane and 0 degree C in the case of butane, and no abnormal condition is observed, the cargo loading rate should be increased in sequence.
(3) Trim during loading operations:
Water ballast is discharged as the loading operation is in progress, and such operation should be carried out so that no excessive stresses may be imposed on the hull and that no excessive trim is created.
(4) Tank pressure during loading operations:
While loading, care is required to keep the tank pressure constant at a specified value.
(5) Disposal of remaining liquid and disconnection of loading arms after completion of loading:
After completion of cargo work, remaining liquid in the loading arms is disposed of in one of the following manners; and the arm disconnecting operation is carried out after checking to see that the concentration of flammable gas is 1 Vol % or less.
i) Method by which liquid and gas are pushed into the lines of the vessel by introducing nitrogen gas from the shore side. It is a method by which nitrogen gas is introduced at the roots of loading arms on the shore side to push remaining liquid and gas into cross over lines, and the following checks are made through drain valves : whether liquid still remains or not; and the concentration of remnant gas.
ii) Method by which remaining liquid is discharged into the sea With the manifold gate valve closed, a plastic hose is connected to the manifold drain valve, and is then led into the sea water overboard; through the hose remaining liquid is discharged into the sea. At this instant the end of the plastic hose should be slightly put into the sea; it should be adjusted so that it may not be placed too deep or above the sea surface.
iii) Method by which nitrogen gas or inert gas is let in from the manifold drain pipe to push liquid to the crossover line of the vessel and to purge gas via the inert gas line into the vapor line. A shore pipe line is connected with the manifold liquid drain pipe through which nitrogen gas is supplied to press remaining liquid into crossover lines of the vessel. After disposing of the remaining liquid, gas is purged on to the shore by sending remaining gas through vapor lines via inert gas lines.
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