CHAPTER 3 EXHAUST GAS RECIRCULATION SYSTEM
3.1 Equipment
3.1.1 Pumps / Blowers
(a) Where provided, pumps used in EGR SOx scrubber washwater, dosing, discharge, etc., systems, essential for the continual operation of the EGR system, are to be tested and certified in accordance with relevant requirements of the Rules. This is applicable to exhaust emission abatement systems connected to diesel engines rated at 2250 kW and above or having cylinders of more than 300 mm bore.
(b) Unless alternative means of compliance in accordance with 2.3 are applicable, redundant washwater, dosing, discharge, etc., pumps, essential for the continual operation of the EGR water systems, are to be provided.
There are to be at least two of these essential pumps, and the capacity of the pumps, with any one pump out of service, is to be sufficient for continuous operation of the EGR system at full rating.
For vessels fitted with two or more identical EGR systems, the provision of a common standby pump (for each essential system) capable of serving all EGR units will suffice rather than providing individual standby pumps for each EGR unit.
(c) Unless alternative means of compliance in accordance with 2.3 are applicable and where exhaust fans or blowers form part of the EGR system and are essential for continual operation of the system at full rating, such fans or blowers are to be installed in a redundant arrangement. The number and power of the fans or blowers should be such that if one unit, or a group of units, is out of service, the capacity of the remaining unit(s) is not to be less than 100% of the total required.
3.1.2 Heat exchangers / EGR exhaust gas coolers
(a) Where provided, heat exchangers are to be designed, constructed, and certified in accordance with relevant requirements of Part V of the Rules.
(b) EGR exhaust gas coolers are not subject to 3.1.2(a). Suitability of the cooler materials for the exhaust gases is to be demonstrated.
The coolers are to be hydrostatically tested on the water side to 4 bar, but not less than 1.5 times the design pressure on the water side, either in the manufacturer's plant or in the presence of the Surveyor, after installation onboard the vessel.
3.1.3 Chemical treatment system
(a) The specific requirements for chemical treatment system components are given under 3.2.3.
3.1.4 Electrical system
The electrical system and electrical equipment are to satisfy corresponding requirements of Part VII of the Rules.
(a) Electrical load analysis
The number and capacity of generators are to be sufficient under normal seagoing conditions with one generator in reserve to carry those loads for essential services, which include the EGR system, and for minimum comfortable conditions of habitability.
CHAPTER 3 EXHAUST GAS RECIRCULATION SYSTEM fan/blower required by 3.1.1, where provided, is to be automatically started and put into service. This failure is to be alarmed at the local and remote control station(s), as applicable.
(ii) Where provided, each standby pump or fan is to be fed from separate sections of the switchboard such that in the event of failure of one section of the switchboard the standby pump or fan may be fed from the other separate section of the switchboard.
(c) Circuit protection devices and compatibility
Circuit breakers are to be installed for miscellaneous EGR system electrical loads and are to be compatible with the prospective short circuit current level calculated at the switchboards.
3.2 Piping Systems
3.2.1 Exhaust gas piping systems
(a) Exhaust gas piping materials located before the EGR SOx scrubber, where fitted, may be of the same material specification as the standard engine exhaust gas piping.
(b) The sections of the scrubber that are subjected to washwater (e.g., the interior reaction chamber or washwater piping/nozzles, etc.) are to be constructed of suitable corrosion resistant materials.
(c) Exhaust gas piping materials used after the EGR SOx scrubber unit are to be of a corrosion resistant material such as stainless steel.
(d) Hot surfaces of EGR systems or their associated equipment or systems likely to come into contact with the crew during operation are to be suitably guarded or insulated. Where the surface temperatures are likely to exceed 220℃ and where any leakage, under pressure or otherwise, of fuel oil, lubricating oil, or other flammable liquid is likely to come into contact with the EGR unit or exhaust pipes, these surfaces are to be suitably insulated with non-combustible materials that are impervious to such liquids. Insulation material not impervious to oil is to be encased in sheet metal cladding or an equivalent impervious sheath.
3.2.2 Washwater piping systems
(a) The piping material for the corrosive scrubber washwater system is to be selected based on the corrosive nature of the liquid media.
(b) Pipes and piping components made of thermoplastic or thermosetting plastic materials, with or without reinforcement, may be used in piping systems subject to compliance with the requirements of 2.8 of Part VI of the Rules. For the purpose of the Rules, “plastic” means both thermoplastic and thermosetting plastic materials, with or without reinforcement, such as polyvinyl chloride (PVC) and fiber reinforced plastics (FRP). Plastic washwater piping is to meet Level 3 fire endurance testing requirements (see 2.8.4 of Part VI of the Rules)
(c) Flexible hoses are to comply with the requirements of 2.9 of Part VI of the Rules.
(d) The overboard discharges of any EGR system are not to be interconnected to other systems.
CHAPTER 3 EXHAUST GAS RECIRCULATION SYSTEM 3.2 Piping Systems
(e) Due consideration is to be given to the location of overboard discharges with respect to vessel propulsion features, such as thrusters or propellers.
3.2.3 Chemical treatment piping systems
The requirements for the washwater chemical treatment system detailed in this subsection are based on the use of Caustic Soda (NaOH) in the EGR scrubber water treatment system, as applicable. If other chemicals are to be used, the requirements should be consistent with the intent of the requirements for Caustic Soda but would need to be assessed on a case-by-case basis.
The requirements detailed below are also based on an arrangement whereby the EGR residue tank is also used as an overflow tank for the NaOH storage tank. Arrangements that separate these functions into separate tanks may be applied, and in which case, the requirements for the overflow tank are detailed in 3.2.3 and the requirements for the residue tank in 3.2.4.
(a) Material for piping systems, NaOH storage tank and EGR residue/NaOH overflow tank
The material of the NaOH related piping systems, NaOH storage tank, EGR residue/NaOH overflow tank, drip trays, and any other components which may come into contact with the NaOH solution or sludge is to be of a suitable grade of stainless steel or other corrosion-resistant material established to be suitable for the application. Aluminum, zinc, brass, or galvanized steel components are not to be used.
(b) Bunkering of NaOH
(i) The bunker station(s) for NaOH is to be located on the open deck away from sources of ignition and arranged such that a spill at a bunker station would not result in NaOH contacting or mixing with other incompatible materials. Alternatively, closed or semi-enclosed bunker stations may be approved subject to the provision of effective ventilation.
(ii) Spill trays, which may be of the dry type or having means of drainage to the EGR residue/ NaOH overflow tank, are to be provided.
(c) Arrangement of the NaOH storage tank and EGR residue/NaOH overflow tank (i) General
The NaOH storage and EGR residue/NaOH overflow tank are not to be situated where spillage or leakage there from can constitute a hazard by falling onto combustibles or heated surfaces. In particular, these tanks are not to be located over boilers or in close proximity to steam piping (supply or returns).
Where necessary, the NaOH storage tank is to be provided with an appropriate heating system to prevent freezing.
(ii) Filling
The NaOH storage tank is to be provided with a fill line from the bunker station, and a shutoff valve is to be provided at the bunkering station.
Overflow and/or drains leading to the EGR residue/NaOH overflow tank are to enter at or near the top of the tank. However, if this is determined to be impracticable, these lines are to be fitted with a non-return valve at the EGR residue/NaOH overflow tank.
(iii) Vents
The NaOH storage and EGR residue/NaOH overflow tanks are to be provided with vent pipes complying with 3.2 of Part VI of the Rules, and the outlets are to terminate in a safe location in the weather.
The vents that are open to the weather should not be subject to deterioration due to the concentrations involved, and the arrangement is to be such that the potential source of moisture from the vents does not present any danger to the crew or vessel. Alternatively, the tanks are to be fitted with appropriately sized pressure/vacuum valves.
(iv) Overflow protection
Means are to be provided to prevent NaOH from spilling or accidently overflowing from the storage and EGR residue/NaOH overflow tanks. Accordingly, the NaOH storage tank is to be fitted with a high
CHAPTER 3 EXHAUST GAS RECIRCULATION SYSTEM complying with 3.2 of Part VI of the Rules that is led to the EGR residue/NaOH overflow tank. Further, in all cases, the EGR residue/NaOH overflow tank is to be fitted with a high level alarm. Other anti-spilling arrangements may be considered on a case-by-case basis.
(v) Sounding
Sounding arrangements are to be provided for the NaOH storage and EGR residue/NaOH overflow tanks, and are to comply with the sounding requirements applicable to fuel oil tanks of 3.4 of Part VI of the Rules.
A sight glass is not to be used unless the materials of construction are compatible with the concentration of caustic soda solution involved, it is well protected from mechanical damage, and the arrangements are equivalent to that of flat “glass-type” fitted with a self-closing valve at each end.
In addition to local level gauging, the NaOH storage and EGR residue/NaOH overflow tanks are to have remote level gauging indication at the manned control station.
(vi) Temperature indication
The NaOH storage and EGR residue/NaOH overflow tanks are to be provided with local and remote temperature monitoring arrangements. The remote temperature indication is to be installed at the manned control station.
(d) Spill trays
(i) Those areas of the NaOH storage and EGR residue/NaOH overflow tanks that could result in leakage, locations where leakage from pumps and other associated equipment such as strainers, heaters, flanges, valves, etc., which may require occasional dismantling for examination or maintenance may occur, and where leakage may otherwise normally be expected are to be located within spill trays.
(ii) Either drainage arrangements for the spill tray that lead to the dedicated EGR residue/NaOH overflow tank are to be provided or arrangements to activate an alarm in the event of spillage are to be provided.
Where drainage arrangements are provided, the drain line to the EGR residue/NaOH overflow tank is to be fitted with a non-return valve.
(e) Miscellaneous piping arrangements
(i) The NaOH piping systems are to be independent of other ship service piping and/or systems.
(ii) Piping systems for NaOH systems are not to be located in accommodation, service, or control spaces.
(iii) Every pipe emanating from a tank containing NaOH, which, if damaged, would allow NaOH to escape from the tank, is to be provided with a positive closing valve located directly on the tank. The positive closing valve is to be provided with means of closure both locally and from a readily accessible and safe position outside of the space.
(iv) The pipe joints are to be kept to a minimum. The direct connections of pipe lengths are to be all welded except for necessary flanged connections to valves and other equipment for maintenance in order to minimize risk of leakage from the pipe lines.
(v) Supply, bunkering and transfer lines for NaOH systems are not to be located over boilers or in close proximity to steam piping, exhaust systems, hot surfaces required to be insulated, or other sources of ignition.
(f) Ventilation arrangements
(i) The NaOH storage and EGR residue/NaOH overflow tanks may be located within the engine room or in a separate compartment. In either location, the area is to be served by an effective mechanical exhaust ventilation system with ventilation inlets located where any vapors would be expected to accumulate. In addition, if located in a separate compartment, the ventilation system is to be capable of being controlled from outside the compartment.
(g) Personnel protection
CHAPTER 3 EXHAUST GAS RECIRCULATION SYSTEM 3.2 Piping Systems
(i) For the protection of crew members, the vessel shall have on board suitable protective equipment consisting of large aprons, rubber gloves with long sleeves, rubber boots, coveralls of chemical -resistant material, and tight-fitting chemical safety goggles or face shields or both. The protective clothing and equipment shall cover all skin so that no part of the body is left unprotected. An eyewash and safety shower should be nearby.
(h) Safety notices
(i) Safety instructions relating to precautions and corrective response actions are to be posted in the compartment containing NaOH, and beside the entrance to the compartment. Detailed guidelines given in the MSDS are to be followed.
3.2.4 Residue systems
(a) The residues generated from the exhaust gas cleaning process are to be stored in a designated residue tank, separate from the engine room sludge tank, and arranged for discharge to appropriate shore reception facilities.
The EGR residue tank is to be designed to facilitate cleaning.
Where EGR residue tanks used in closed loop chemical treatment systems are also used as the overflow tank for the NaOH storage tank, the additional requirements of 3.2.3 are to be applied.
(b) The material of the EGR residue tank is to be selected based on the corrosive nature of the EGR residue.
(c) The capacity of the EGR residue tank is to be based on the expected residue volumes applicable to the exhaust gas cleaning process and the maximum period of voyage between ports where EGR residue can be discharged. In the absence of precise data, a figure of 30 days is to be used.
(d) The EGR residue tank is to be provided with vent pipes complying with 3.2 of Part VI of the Rules.
(e) The residue tank is to be arranged with a high level alarm.
(f) Sounding arrangements are to be provided for the EGR residue tank in accordance with 3.4 of Part VI of the Rules.
(g) For those vessels that do not undertake onboard incineration and collect all engine room sludge for dis posal ashore, consideration will be given to arrangements utilizing a combined engine room sludge and EGR residue tank, provided the tank meets the requirements of 3.2.4(a) through (f), EGR residue record logs satisfy the requirements of MEPC.184(59), and residues are disposed at MARPOL reception facilities.
Combined engine room sludge and EGR residue tanks are to be sized to provide adequate capacity based on the sludge tank capacity requirements of the Rules plus the capacity requirements for EGR residue tanks of 3.2.4(c).
CHAPTER 4 CONTROL, ALARM, AND MONITORING SYSTEMS