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PART IX
MAINTENANCE AND TESTING
General
55. (1) As the safety arrangements are an integral part of the inert
gas system, it is important for ship’s staff to give special attention
to them during any inspection.
(2) Inspection routines for some of the main components are dealt
with in this section.
Inert Gas Scrubber
56. (1) Inspection may be made through the manholes; checks should be
made for corrosion attacks, fouling and damage to:
- scrubber shell and bottom;
- cooling water pipes and spray nozzles (fouling);
- float switches and temperature sensors;
- other internal components such as trays, plates and demister
filters.
(2) Checks should be made for damage to non-metallic parts such as:
- internal linings;
- demisters;
- packed beds.
Inert Gas Blowers
57. (1) To a limited degree, internal visual inspection will reveal
damage at an early stage; diagnostic monitoring systems greatly assist
in maintaining the effectiveness of the equipment; an acceptable level
of availability of blowers is ensured by fitting two equal blowers or,
alternatively, supplying and retaining on board a spare impeller with a
shaft for each blower; visual inspection through the available openings
in the blower casing is adequate for this purpose.
(2) An inspection of inert gas blowers should include:
- internal inspection of the blower casing for soot deposits or
signs of corrosive attack;
- examination of fixed or portable washing system;
- inspection of the functioning of the fresh water flushing
arrangements, where fitted;
- inspection of the drain lines from the blower casing to
ensure that they are clear and operative;
- observation of the blower under running conditions for signs
of excessive vibration, indicating too large an imbalance.
Deck Water Seal
58. (1) This unit must be maintained in good condition as it performs
an important function; corroded inlet pipes and damage to float
controlled valves are not uncommon; the overboard drain line and
connection are also possible sources of trouble.
(2) An inspection of the deck water seal should include:
- opening for internal inspection to check for:
- blockage of the venturi lines in semi-dry type water
seals;
- corrosion of inlet pipes and housing;
- corrosion of heating coils;
- corroded or sticking floats for water drain and supply
valves and level monitoring.
- testing for function:
- automatic filling and draining (check with a local level
gauge if possible);
- presence of water carry-over (open drain cocks on inert
gas main line) during operation.
Non-return Valve
59. The non-return valve should be opened to check for corrosion and
also the condition of the valve seat; the valve should be tested in
operation.
Scrubber Effluent Line
60. The scrubber effluent line cannot normally be inspected
internally except when the ship is in dry dock; the ship side stub
piece, referred to in paragraph 27(3)(b), and the overboard discharge
valve should be inspected at each dry-docking period.
Testing of Other Units and Alarms
61. (1) A method should be devised to test the functioning of all
units and alarms; it may be necessary to simulate certain conditions to
carry out an effective testing programme.
(2) Such a programme should include checking:
- all alarm and safety functions;
- the functioning of the flue gas isolating valves;
- the operation of all remotely or automatically controlled
valves;
- the functioning of the water seal and non-return valve (with
a backflow pressure test);
- the vibration level of the inert gas blowers;
- for leakages: deck lines in systems four years old or more
should be examined for gas leakage;
- the interlocking of the soot blowers;
- oxygen-measuring equipment, both portable and fixed, for
accuracy by means of both air and a suitable calibration gas.
Suggested Maintenance Programme
Component |
Preventive maintenance |
Maintenance interval
|
Flue gas isolating valves
|
Operating the valve
Cleaning with compressed or steam |
Before start-up and one week
Before operating valve |
|
Dismantling for inspection and cleaning |
Boiler shutdown
|
Flue gas scrubber
|
Water flushing |
After use |
|
Cleaning of demister |
Three months
|
|
Dismantling of level regulators and temperature probes for inspection
|
Six months |
|
Opening for full internal inspection |
Dry docking
|
Overboard pipes and valve from flue gas scrubber
|
Flushing with scrubber water pump for about one hour |
After use |
|
Dismantling of the valve for overhaul, inspection of pipeline and
overboard end
|
Dry-docking/regular period |
Blowers |
Vibration checking |
While running
|
|
Flushing |
After use
|
|
Internal inspection through hatches |
After flushing and six months
|
|
Dismantling for full overhaul of bearings, shaft tightenings and other
necessary work |
Two years or more frequently if required/dry-docking
|
Deck water seal |
Dismantling of level regulators/float valves for inspection
|
Six months |
|
Opening for total internal inspection |
One year
|
Component |
Preventive maintenance |
Maintenance interval
|
|
Overhaul of auto-valves |
One year
|
Deck mechanical non-return valve |
Moving and lubricating the valve if necessary |
One week and before start
|
|
Overhaul of auto-valves |
One year/18 months
|
Pressure-vacuum valves
|
Operating and lubricating the valves |
Six months |
|
Opening for full overhaul and inspection |
One year
|
Deck isolating valve
|
Opening for overhaul |
One year |
Gas pressure regulating system |
Removal of condensation instrument, air supply |
Before start
|
|
Opening of gas pressure regulating valves for overhaul.
|
As appropriate |
Liquid filled pressure-vacuum breaker |
Checking liquid level when system at atmospheric pressure |
When opportunity permits and every six months |
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