3. On board cargo equipment 3
Introduction to Inert Gas System
Introduction
Flammability
Flammable Range
Effect of Increasing Oxygen
Suppression of Flammability by IG
Combustion& Explosion
Inert Gas Prevents FIRE & EXPLOSION
10. On board cargo equipment 10
Inert Gas Must On Tankers
Required Under Regulation 60 of SOLAS
For All Petroleum Tankers more than 20,000 DWT –
Keel laid after 1-9-84
Exception for Existing Tankers (Keel Laid prior 84)
- i) Tank Washing Machine Capacity less than 60 Cubic
Meter/Hour &
- ii) Unreasonable & Impracticable due to design determined
by Administration
- iii) For Product Tankers between 20-40,000DWT tank
washing Machine Capacity less than 60 cubic meter/Hour
Tankers fitted with IGS to keep COT inerted at all times
19. On board cargo equipment 19
Deck Water Seal Requirement
•Regulation 62 requires that Inert Gas system is
equipped with two Non return devices one of
which shall be water seal to prevent the return of
hydrocarbon to Gas safe spaces
•In addition Regulation 62 requires that
arrangement of Deck Water Seal Shall be such
that it will prevent back flow of hydrocarbon
vapours and ensure proper Functioning of Seal
Under Operating Conditions.
23. On board cargo equipment 23
Deck seal
Deck seal prevent flow back
from deck pipe line to flame
area of boilers or scrubbers
Water column works as non
returning valve
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IGS types: Inert Gas Generator (FTU) construction -Scrubber
27. On board cargo equipment 27
Inert Gas System Non Return Devices
Reason for Non Return Devices
N/R Consist of Deck Water Seal & Deck
Mechanical N/R Valve
Deck Water Seal is a Principal Barrier
Incase of water drop, there should be
Low Water Alarm but Seal Should not
become Ineffective
Heating Arrangement For Deck Water
Seal
Sight Glass & Inspection Opening
Provided
Function of Deck Mechanical N/R V/V
Purpose of Separate Deck Isolating Valve
29. On board cargo equipment 29
Deck Water Seal Semi Dry with Heating System
30. On board cargo equipment 30
Pressure-Relief & vacuum protection Systems
Principal work of
liquid filled
pressure – vacuum
deck breakers: in
case P/V v/v fails
to operate
– Over pressure by
IG or Vapour and
blow out liquid on
deck
– Suction ambient
air in gas line and
liquid in tank
32. On board cargo equipment
The Pressure-Relief and Vacuum-Protection
System gives an automatically controlled
protection against too high or too low pressure
within the cargo-handling system
Pressure-relief piping system
Pressure-Relief & vacuum protection System for
All Cargo Tanks, as per IMO rules.
Pressure-Relief & vacuum protection Systems
34. On board cargo equipment 34
Pressure-Relief & vacuum protection Systems
P/V valves
35. On board cargo equipment 35
Pressure-Relief & vacuum protection Systems
High velocity vents valve
combines the best of modulating
valves and full-lift valves.
Valve creates "delayed" blow
down of cargo tanks. It reduces
vapor loss during low filling rates
(and due to sloshing) until venting
takes place at full rate when vapor
loss is less important.
Valve provides active protection
from fire and explosion regardless
of pipe configuration.
Valve operates in freezing
conditions without heating
arrangements.
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Pressure-Relief & vacuum protection Systems
Common liquid P/V
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Methods of Gas Replacement
DILUTION
DISPLACEMENT
Dilution is mixing process, where velocity
of incoming Gas is High
Displacement is a Layering Process,
where IG has Low Entry Velocity , to
enable stable horizontal interface
39. On board cargo equipment 39
IGS – Arrangement for Gas Replacement
40. On board cargo equipment 40
IGS – Arrangement for Gas Replacement
43. On board cargo equipment 43
Requirement for I G Main
Means for Isolating Each Tank
Breathing Possible when Tanks Isolated from IG Main
Blank Flanges for Slop Tanks & Isolation for OBOs
External IG Supply Connection
Mast Riser or High Velocity Vents Provided for
Vapour Displacement
Purge Pipes as Far as practicable from IG inlet
Effective Isolation between IG Main and Cargo piping
One or More P/V Breakers
Provision of Continuous pressure indication of IG
45. On board cargo equipment 45
Inert Gas Application to Various Shipboard Operations
46. On board cargo equipment 46
IGS types: Flue Gas System
Flue Gas Systems cool and clean flue gas from the ship's boilers, and deliver it to
deck, typically during cargo unloading and tank washing.
Flue gas already contains less than 5% oxygen, which is the IMO higher limit for
inert gas, no further treatment is therefore necessary.
The main components are the scrubber unit, inert gas blowers, the deck water seal,
main non-return valve, the pressure/vacuum breaker, valves, instrumentation and
the control system.
Surplus gas is automatically re-circulated back to the scrubber unit, and gas
production hence follows gas demand.
The system can also, like the other variants dealt with in this presentation, be
preset to deliver fresh air for gas-freeing purposes.
47. On board cargo equipment 47
IGS types: Inert Gas Generator
Inert Gas Generator Systems is used when no existing supply of
flue gas is available.
The scrubber unit of the flue gas system is here integrated into a
generator unit consisting of a combined burner part and scrubber
part, both sea water cooled. MDO or HFO fuel is burning in the
horizontal combustion chamber to produce flue gas with an
oxygen content of typically 2-4%.
The gas then enters the scrubber part, where it is cooled and
cleaned by sprayed sea water before being piped to the deck area.
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Tank Pressure & Oxygen Concentration
54. On board cargo equipment 54
Inert Gas systems
Carbon dioxide (IG) generation system
– Burning fuel for generation carbon dioxide gas is
common procedure on gas tankers
– Take off carbon dioxide gas form boilers
Inert Gas (IG) is sent via drier / non returning valves
and used for replacing air to prevent explosion
concentrations :
– in Cargo Tanks and
– in Ballast tanks (some times).
IG can be supplied from the shore facilities in
emergency condition
56. On board cargo equipment 56
IGS types: Flue Gas System with Topping Up Generator
This alternative consists of a flue gas system supplemented
by a separate small (500Nm3/h) inert gas generator, and is
often preferred to aboard OBO and VLCCs
The flue gas system covers the bulk of the inerting during
cargo unloading etc., and the topping up generator tops up
tank pressures during the sea voyage.
57. On board cargo equipment 57
IGS types: Inert Gas Generator (FTU) construction
- Panel
- Generator
- Fan
- Scrubber
58. On board cargo equipment 58
IGS types: Inert Gas Generator (IGG)
Moss Inert Gas Generators for Oil/
Chemical/ Products
Moss Inert Gas Generators for
LPG/LNG
59. On board cargo equipment 59
IGS types: Flexinert
Flexinert is a fuel-saving combination of a flue gas system and an
inert gas generator.
As long as sufficient boiler flue gas is available, Flexinert works as
a flue gas system. When no basis gas is available, it works as an
inert gas generator, and when high-oxygen exhaust gas from the
main engines or diesel generators is available, it afterburns this
gas to produce inert gas with the acceptable oxygen content.
Afterburning saves fuel since the combustion "air" already has a
reduced oxygen content.
60. On board cargo equipment 60
Inert Gas Generator (IGG) – output
Oxygen: 0.5% - 1%
Carbon Dioxide: ~ 14 %
Nitrogen: ~ 85%
Carbon Monoxide, oxides of
Nitrogen and Sulphur
Dioxide: ~ 0,5%
– Carbon Monoxide: Max 100
ppm
– Oxides of Nitrogen: Max 100
ppm
– Sulphur Dioxide: Max 1 ppm
Moisture: Dew Point of -45C
Modes: Inerting
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Ballast tank inerting
Ballast tanks are inerted in
emergency conditions
Flexible Hose used for inerted
operation
Pressure 250 mmWC,
64. On board cargo equipment 64
Pressure-Relief & vacuum protection Systems
Vent riser
