OTM-7.10	Oil Tanker Manual OTM Maintenance and Inspection	Doc No.: OTM 7.10 Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD

1. INERT GAS - MAINTENANCE AND INSPECTION

The safety arrangements are an integral part of the inert gas system and it is essential for the ship's staff to give special attention to them during any inspection. All maintenance and inspections contained in this matter shall be recorded in the Inert Gas Record Book, OTM 7.11 I.G & IGG Monthly Maintenance Checklist or in the PMS System.

• Inert gas scrubber
• Inspection can be made through the man holes. Checks are to 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 internals such as trays, plates, and demister filters
• Checks are to be made to the non-metallic parts such as internal linings
• Packed beds
• Inert gas blowers
• To a limited degree, internal visual inspection will reveal damage.
• An inspection of the inert gas blowers is to 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
• 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
• This unit performs an important safety function and is to be maintained in good condition. An inspection of the deck water seal is to include:
• Opening for internal inspection to check for blockage of the venture lines in the semi-dry type
• Corrosion of inlet pipes and housing
• Corrosion of heating coil
• Corroded or sticking floats for high level/low level alarms
• Testing for function:
• Automatic filling and draining
• Presence of water carries over (open drain cocks on inert gas main line) during operation.

Tables below outline the maintenance programme:

Component	Preventive Maintenance	Maintenance Interval
Flue Gas Isolating Valves	Operate the valve	Once a week and Before start-up
	Lubricate valve	Before start-up
	Cleaning with compressed air or valve steam	Before operating
	Dismantling for inspection and cleaning	Boiler shutdown
Flue Gas Scrubber	S.W. Water Flush and FW wash	After Use
	Cleaning of demister regulators and temp probes for inspection	Three months
	Internal inspection through inspection doors	Six months
	Opening for full inspection	Dry docking
Overboard Pipes and Valve from Flue Gas Scrubber	Flushing with scrubber water pump for about 1 hour	After use
	Dismantling of the valve for overhaul / inspection of pipeline and overboard stub pipe	Dry docking
Blowers	Vibration checks	While running
	Flushing	After Use
	Internal inspection through hatches	After flushing and six months
	Dismantling for full overhaul of bearing shaft tightening and other necessary work	Dry docking
Deck Mechanical Non-return Valve	Moving and lubricating the valve	One week and before start
	Opening for internal inspection	One year
Pressure Vacuum Valves and High Velocity Valves	Operating and lubricating the valves	Six months
	Opening for full overhaul and inspection	One year
Deck Isolating Valves	Opening for overhaul	One year
Emergency Isolation valve for Inert Gas system to ballast tanks	Operating and lubricating the valves	Six months
Gas Pressure Regulating System	Removal of condensation in instrument air supply	Before start
	Opening of gas pressure regulating valves for overhaul	Dry dock
Liquid-filled pressure vacuum breaker	Check liquid level when system is at atmospheric pressure	When opportunity permits and every six months
Deck seal	Dismantling of level regulators / float valves for inspection	Six months
	Opening for total internal inspection	One year
	Overhaul of automatic valves	One year

• Also refer to Manufacturer’s Instructions.
• As far as possible, the IGS unit should be maintained and checked frequently to keep the valves in working order, this being necessary as detailed below. The valve settings and accessories may vary greatly on different ships, depending on the design of the installation.

Table 1: IGS maintenance recommendations

Equipment	Maintenance Action	Frequency
UP-TAKE VALVES	Spindle of valve should be greased	Every voyage
SCRUBBER	Scrubber should be opened, and interior and nozzles cleaned in order to prevent blockage	Every 6 months
DEMISTER	At the same time clean the PAD with fresh water	Every 6 months
FAN	Clean the IMPELLER and CASING with fresh water and inspect the drain line against sticking and clogging	Every time after water use
FAN MOTOR	Insulation test to be carried out (before operation)	Every voyage
OXYGEN ANALYSER	O2 analyser should be adjusted to "O" zero by N2 gas span	Before supplying inert gas
RECORDERS	Check operations of O2 analyser and pressure	Before supplying inert gas
SUPPLY OF AIR	Check air pressures of individual installation (before operation)	Every operation/voyage (before)
SUPPLY OF AIR	Reducing valves should be inspected, cleaned, and overhauled (before operation)	Every operation/voyage (before)
BREATHER VALVES	As far as possible, the breather valves should be inspected, overhauled, and cleaned as necessary	Every 3 months

The inspection carried out shall be recorded in OTM 7.11 -- I.G & IGG Monthly Maintenance Checklist and submit to the office when ever asked.

2 CARGO PIPELINES AND HOSES

• Cargo pipelines and associated valves shall be hydrostatically pressure tested to 100% of maximum allowable working pressure on an annual basis.
• Cargo pipelines and associated valves shall be hydrostatically pressure tested to 150% of their rated working pressure at least twice within any five-year period.
• Cargo hoses to be annually pressure tested to 150% of maximum allowable working pressure.
• All cargo pipeline reducers, U pieces, and Y pieces to be annually pressure tested to 150% of maximum allowable working pressure.
• Vessel should have ship-specific procedures for carrying out pipeline testing.

3 HYDROSTATIC TESTING OF CARGO PIPING

Testing of the cargo pipes should be preferably carried out using water in connection with a tank cleaning operation.

1. The basic steps of the procedure are the following:
• Fill up the line with water by using the cargo/stripping pump or any other portable pump like Graco pump.
• Ensure that all air that could be entrapped in the line has been removed.
• Increase gradually the pressure to MAWP.
• Increase gradually the pressure to 150% of MAWP by the portable pump or the stripping pump.
• When the pressure in the line reaches the desired pressure, the tightness of the piping system to be confirmed.
• Drain the cargo back to the cargo or slop tank.
2. A more detailed procedure is outlined below:
• Ensure that blank flanges are properly fitted in their position and fully bolted (with three threads of bolts visible after tightening).
• In case of a vessel with a conventional piping arrangement, ensure that bottom lines are isolated and not tested above 3.5kg/cm².
• Ensure that pressure gauges on either port or starboard sides of the cargo lines are fitted, and it is working properly.
• Ensure efficient communication between the positions of the cargo control room and the goose neck valves.
• Start the cargo/stripping pump with the minimum capacity taking suction from the slop tank. Ensure that the pipe is free of any air and increase the pressure slowly.
• Increase gradually the pressure to 150% of MAWP by the portable pump or the stripping pump.
• The pressure should be maintained for a period of time (at least 15min.) in order to detect any leaks which may occur. The period of time should be sufficient for inspecting all system valves and flanged connections on deck for leakages. Cargo manifolds and master valves on deck should be also tested for internal leakage during the cargo lines hydrostatic test.
• After the test, drain the cargo piping back to the relevant cargo or slop tank.