Page 417 - International safety guide for oil tankers and terminals

SAFETY MANAGEMENT

30. The requirements for closed operations have been agreed.
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It is a requirement of many terminals that, when the ship is ballasting into cargo
tanks, loading or discharging, it operates without recourse to opening ullage and
sighting ports. In these cases, ships will require the means to enable closed
monitoring of tank contents, either by a fixed gauging system or by using
has caused the checklift drive pin to shear and the ship’s personnel to assume,์นาวี
portable equipment passed through a vapour lock, and preferably backed up by
an independent overfill alarm system.

31. The operation of the P/V system has been verified.
The operation of the P/V valves and/or high velocity vents should be checked
using the testing facility provided by the manufacturer. Furthermore, it is
งานห้องสมุด ศูนย์ฝกพาณิชย
imperative that an adequate check is made, visually or otherwise, to ensure that
the checklift is actually operating the valve. On occasion, a seized or stiff vent

with disastrous consequences, that the vent was operational.

32. Where a vapour return line is connected, operating parameters have been
agreed.
Where required, a vapour return line will be used to return flammable vapours
from the cargo tanks to shore.
The maximum and minimum operating pressures and any other constraints
associated with the operation of the vapour return system should be discussed
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and agreed by ship and shore personnel.
33. Independent high level alarms, if fitted, are operational and have been tested.
Owing to the increasing reliance placed on gauging systems for closed cargo
operations, it is important that such systems are fully operational and that
backup is provided in the form of an independent overfill alarm arrangement.
The alarm should provide audible and visual indication and should be set at a
level that will enable operations to be shutdown prior to the tank being overfilled.
Under normal operations, the cargo tank should not be filled higher than the
level at which the overfill alarm is set.
Individual overfill alarms should be tested at the tank to ensure their proper
operation prior to commencing loading unless the system is provided with an
electronic self-testing capability which monitors the condition of the alarm
circuitry and sensor and confirms the instrument set point.

34. Adequate electrical insulating means are in place in the ship/shore
connection.

Unless measures are taken to break the continuous electrical path between ship
and shore pipework provided by the ship/shore hoses or metallic arms, stray
electric currents, mainly from corrosion prevention systems, can cause electric
sparks at the flange faces when hoses are being connected and disconnected.
The passage of these currents is usually prevented by an insulating flange
inserted at each jetty manifold outlet or incorporated in the construction of
metallic arms. Alternatively, the electrical discontinuity may be provided by the
inclusion of one length of electrically discontinuous hose in each hose string.
It should be ascertained that the means of electrical discontinuity is in place,
that it is in good condition and is not being by-passed by contact with an
electrically conductive material.

© ICS/OCIMF/IAPH 2006 383