Page 275 - International safety guide for oil tankers and terminals

SPECIAL SHIP TYPES

The ship should arrive at the loading port with all tanks inerted to less
than 8% oxygen by volume, at ambient temperature and with no traces of
---ใช้เพื่อการศึกษาเท่านั้น---
the previous cargo. If ammonia was the previous cargo, the Company
should be consulted regarding the maximum allowable ammonia vapour
content (ppm).
absorbed into the incoming liquid pentane with a consequent sudden drop์นาวี

14.2.4 Loading of Pentane Plus or Naphtha
Some terminals allow the ambient temperature loading of pentane plus or
naphtha into a tank containing propane or butane vapour at ambient
temperature and atmospheric pressure. Before conducting such an
งานห้องสมุด ศูนย์ฝกพาณิชย
operation, it must be ensured that there is no heel of liquefied gas
present in the tank. When pentane or naphtha is admitted at the bottom
of the tank, the heel of liquefied gas would almost immediately be
in vapour pressure which would give rise to a possibly dangerous
decrease in cargo tank pressure.

After the heel has been removed, loading the cargo will displace the gas
remaining as the tank fills. Some further absorption of gas will occur
during this process. When the tank is full of liquid cargo, the gas
absorbed during the loading and the small quantity of gas remaining
above the cargo will, in the absence of any other components, probably
reach an equilibrium and may have no apparent effect on the pressure.
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However, it must be kept in mind that some terminals do not allow this
practice of loading cargo into tanks containing LPG vapour.

14.2.5 Cargo Sampling
Dependent upon owner’s and charterer’s requirements, various cargo
samples and water dips will have to be taken from the tanks prior to and
during cargo operations.

Closed loading and sampling are to be carried out at all times. Ships
should ensure that vapour locks are fully functional.

14.2.6 Loading, Carriage and Discharge Procedures

During loading, carriage and discharge, a positive pressure must always
be maintained in the cargo tanks. Special vapour recovery requirements
may apply at certain terminals.

The holds or void spaces adjacent to the cargo tanks should always be
inerted during the entire carriage period.

Petroleum product vapour may, over longer voyages, condense out in the
vent lines. Regular inspections should be made of drains on these lines
so as to ensure that there is no liquid build-up. This is especially true with
lighter gasolines.

It is possible for paraffin waxes to crystallise if the cargo tank becomes
too cold. If a vessel proceeds to a very cold climate, warming the
hold/void spaces with inert gas may have some effect in preventing this
phenomenon.

© ICS/OCIMF/IAPH 2006 241