Chapter 15 – Inert gas systems
Paragraph 15.2.2.2.2
The automatic shutdown of the inert gas system and its components should
involve the following:
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.1 shutdown of fans and closing of regulating valve for the following:
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.1 high water level in scrubber (not applicable
for N2);
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.2 low pressure/flow to scrubber (not applicable
for N2); or
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.3 high-high temperature of inert gas supply.
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.2 closing of regulating valve in the event of:
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.3 activation of double-block and bleed arrangement upon:
Paragraph 15.2.2.3.2.1
Where the words "forward of" are used, these words should be interpreted
to mean "downstream of".
Paragraph 15.2.2.3.2.2
"Unambiguous information" regarding the operational status of stop valves
in branch piping leading from the inert gas main to cargo tanks, means position
indicators providing open/intermediate/closed status information displayed in the
control panel, as required in paragraph 15.2.2.4. Limit switches should be used to
positively indicate both open and closed positions. Intermediate position status
should be indicated when the valve is in neither the open nor closed position.
Paragraph 15.2.2.3.2.6
Where the words "forward of" are used, these words should be interpreted
to mean "downstream of".
Paragraph 15.2.2.4.1
The operational status of the inert gas system should be based on the
indication that inert gas is being supplied downstream of the gas regulating valve
and on the pressure or flow of the inert gas mains downstream of the non-return
devices. However, the operational status of the inert gas system as required in
paragraph 15.2.2.4.1 should not be considered to require additional indicators and
alarms other than those specified in paragraphs 15.2.2.4 and 15.2.3.2 or 15.2.4.2,
as appropriate.
Paragraph 15.2.2.4.2.1
Where the words "forward of" are used, these words should be interpreted
to mean "downstream of".
Paragraph 15.2.2.4.5.3
The term "alarm system independent" means that a second pressure sensor,
independent of the sensor serving the alarms for low pressure, high pressure and
pressure indicator/recorder should be provided. Notwithstanding the above, a common
programmable logic controller (PLC) should, however, be accepted for the alarms in
the control system. The independent sensor should not be required if the system is
arranged for the shutdown of cargo pumps. If a system for shutdown of cargo pumps is
arranged, an automatic system shutting down all cargo pumps should be provided. The
shutdown should be alarmed at the control station. The shutdown should not prevent
the operation of ballast pumps or pumps used for bilge drainage of a cargo pump
room.