Section 6 Mechanical equipment

6.1.1 Emissions abatement plant associated with engines, gas turbine and boilers is to comply with the requirements of Pt 5, Ch 2 Reciprocating Internal Combustion Engines, Pt 5, Ch 4 Gas Turbines and Pt 5, Ch 10 Steam Raising Plant and Associated Pressure Vessels respectively, as applicable.

6.1.2 The mounting arrangements for the equipment is to be capable of withstanding the forces and moments stated in Pt 5, Ch 24, 5.4 Plant support structure and Vol 2, Pt 12, Ch 1, 5.5 Loading due to wave-induced motions.

6.1.3 The design is to take account of the risk of fire or explosion hazards which may arise from deposition of chemicals, unburnt fuel, particulates or any by-products of chemical reactions which may arise during normal operation.

6.1.4 The emissions abatement plant is to be capable of being started in a hot condition without risk of failure due to thermal shock or alternatively is to be provided with a means to inhibit hot starting.

6.1.5 Safety or pressure-relief devices are to discharge to a place which will not present a hazard to the ship’s occupants or to any machinery.

6.1.6 Where bursting discs or rupture panels are used as safety and pressure-relief devices, these are to be dimensioned and designed in accordance with a recognised National or International Standard.

6.1.7 Where it can be expected that there will be deposition of materials, caking and waste, arrangements are to be provided for the safe cleaning of such systems.

6.1.8 Where there is a possibility of operating conditions in the system falling below the dew point temperature of any gases or vapours present in the system, suitable drains are to be provided to permit the discharge of any condensate formed.

6.2.1 The emissions abatement plant is to be provided with a by-pass capable of transmitting the minimum and maximum exhaust gas flows from the combustion machinery to which it is connected. Where a by-pass is considered unnecessary, the emissions abatement plant is to be capable of safely transmitting the minimum and maximum exhaust gas flows with the emissions abatement plant out of operation, such that the combustion machinery to which it is connected can continue to operate.

6.2.2 Where a by-pass is fitted, there is to be a flow path for exhaust gas at all times. The essential services shall not be impacted during the by-pass operation.

6.2.3 A means of measuring differential pressure across the emissions abatement plant is to be provided.

6.2.4 The by-pass valves are to be remotely operated from the control station. In the event of failure or loss of power to the actuator(s), by-pass valves shall fail to the open position.

6.2.5 An interlock arrangement is to be provided to ensure by-pass valves are open prior to blocking exhaust gas flow into the emissions abatement plant.

6.2.6 The activation of by-pass mode is to be automatic for conditions which activate a shutdown of the emissions abatement plant, see Table 24.9.1 Machinery emissions to air abatement plant: alarms and safeguards, to ensure that essential services are not impacted.

6.3.1 Where emissions abatement plant is connected to more than one engine or source of exhaust gas, valves or equivalent means of isolating the exhaust systems of individual engines from common manifolds are to be provided to prevent reverse flow of exhaust gas into the exhaust manifolds of engines which have been shut down.

6.3.2 Where isolating valves are fitted, a means to verify the effectiveness of the isolation is to be provided.

6.4.1 The exhaust back-pressure, after installation of emissions abatement plant, is to remain within the allowable limits stated by engine and combustion machinery manufacturers under all expected operating conditions, unless it is intended to operate the system at a negative pressure by means of an induced draught fan.

6.4.2 Where an induced draught fan is fitted to maintain the required exhaust back-pressure, a fan failure is not to prevent the combustion machinery from operating.

6.4.3 Where the emissions abatement plant is fed from multiple exhaust gas inlet streams, the back-pressure is to be maintained within the allowable limits provided by engine machinery manufacturers for all engine or combustion machinery operating configurations.

6.4.4 Emissions abatement plant in which both a scrubber and SCR are fitted together in series in an exhaust piping system will be subject to special consideration.

6.5.1 Measures are to be implemented to ensure that water from the emissions abatement plant cannot flow back into engine turbocharger(s) or other machinery.

6.5.2 Means are to be provided for protecting critical engine components from foreign object damage resulting from failure of, or damage to, the emissions abatement plant. Where such damage is considered unlikely, evidence is to be submitted accordingly.

6.5.3 Where chemicals or substances are injected into the exhaust gas stream before turbocharger(s) or emissions abatement plant are fitted, this is not to present a risk of damage, chemical attack or performance degradation to the turbocharger(s) or engine(s) or machinery with which they are associated.

6.5.4 Where fuel treatments, additives or emulsification are used as a primary means of abating exhaust emissions, machinery is to be compatible with such additives, treatments and emulsified fuel.

6.5.5 Where exhaust gas is recirculated as a means of emissions abatement, e.g. EGR, the recirculated exhaust gas is not to cause fouling and corrosion of critical engine components and scavenge air temperature is to be maintained at a level which does not adversely affect engine performance.

6.5.6 Where a wet scrubber is used to clean and cool recirculated exhaust gas, the scrubber is to satisfy the requirements of Pt 5, Ch 24, 11.1 General 11.1.8.