Page 203 - International safety guide for oil tankers and terminals

SHIPBOARD OPERATIONS

when the loading rate is increased. However, if there is reason to
believe that excess water may still be present in the shore
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pipeline, then the recommended action is to:
Keep the product velocity in the shore line below 1 metre per
second throughout loading to avoid flushing the water into the
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
ship’s tank(s); or
Keep the product velocity at the tank inlet(s) below 1 metre per
second throughout loading to avoid turbulence in the tank(s).

Whichever option gives the higher loading rate consistent with
safety should be used.

11.1.7.5 Examples
Initial Loading Phase
Figure 11.2 shows the pipeline arrangements for a vessel loading
a static accumulator product at a berth. The table defines the
pipeline sizes and the volumetric flow rates at a velocity of
1 metre/second. For initial loading to two cargo tanks, the
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limitation will allow a loading rate of 366 m /hour to be requested
in the example given.
If the shore line were 510 mm diameter and water was suspected
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of being in the line, the vessel would need to load 4 tanks
simultaneously to ensure the water content could be safely
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removed and an initial loading rate of 676 m /hour should be
requested. This will allow the water to be cleared from the shore
line whilst keeping the velocity at the tank inlets below
1 metre/second.

11.1.7.6 Practical Considerations
In practice, not all terminals are equipped with flow control devices
to regulate the loading rate and therefore may not be able to
establish a loading rate to one cargo tank equivalent to a velocity
of 1 metre/second. Some terminals achieve, or try to achieve, a
low loading rate by commencing loading by gravity flow alone.

11.1.7.7 Spread Loading
Spread loading is the practice of commencing loading via a single
shore line to several of the ship’s cargo tanks simultaneously
where it is necessary to mitigate a terminal’s lack of flow control.
The aim of this practice is to achieve a loading rate that will give a
maximum velocity at each of the tank inlets of 1 metre per
second.

Spread loading presents a number of potentially significant static
generation risks that should be assessed and properly managed if
this practice is to be used safely. For example:
Uneven flow in the ship’s cargo lines can create a backflow of
vapour (gas or air) from other open tanks to the tank that is
receiving product. This eductor effect will create a two-phase
mixture of product and vapour that will result in increased
turbulence and mist formation within the tank.

© ICS/OCIMF/IAPH 2006 169