Page 218 - International safety guide for oil tankers and terminals

INTERNATIONAL SAFETY GUIDE FOR OIL TANKERS AND TERMINALS

The line clearing operation must be continuously supervised by
a Responsible Officer.
Clearing Ship’s Cargo Pipelinesนั้น---

11.1.15.5 Clearing Hoses and Loading Arms to the Ship
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
The clearing of hoses and loading arms to the ship using
compressed air should not be undertaken due to the risks of:
Static charge generation.

Compromising inert gas quality.

Over-pressurisation of tanks or pipelines.

---ใช้เพื่อการศึกษาเท่า

11.1.15.6 Oil mists emanating from tank vents.

When compressed air or inert gas is used to clear ship’s
pipelines, for example when evacuating the liquid column above
a submerged pump, sometimes referred to as ‘purging’, similar
hazards to those identified above may arise and similar
precautions must be observed. Line clearing operations must be
undertaken in accordance with the operating procedures
previously established for the particular ship.

ึ
11.1.15.7 Gas Release in the Bottom of Tanks
A strong electrostatic field can be generated by blowing air or
inert gas into the bottom of a tank containing a static accumulator
oil. If water or particulate matter is present in the cargo, the effect
is made worse, as the rising gas bubbles will disturb the
particulates and water droplets. The settling contaminants will
generate a static charge within the cargo. Therefore, a settling
period of 30 minutes should be observed after any blowing of
lines has taken place into a non-inerted tank or into a tank that
could possibly contain a flammable atmosphere.

Precautions should be taken to minimise the amount of air or inert
gas entering tanks containing static accumulator oils. However, it
is best to avoid the practice of blowing lines back to tanks
containing such cargo.

Whenever possible, cargo lines should be drained by gravity.

11.1.15.8 Receiving Nitrogen from Shore

Personnel should be aware of the potential hazards
associated with nitrogen and, in particular, those related to
entering enclosed spaces or areas in way of tank vents or
outlets which may be oxygen depleted. High concentrations
of nitrogen are particularly dangerous because they can
displace enough air to reduce oxygen levels to a point
where people entering the area can lose consciousness
due to asphyxiation. A problem not experienced with flue
gas is that nitrogen cannot be detected by human senses,
so smell cannot be relied upon and personnel may not be
able to recognise the physical or mental symptoms of
overexposure in time for them to take preventive measures.

184 © ICS/OCIMF/IAPH 2006