Section 9 Electrical and control equipment
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 5 Main and Auxiliary Machinery - Chapter 24 Emissions Abatement Plant for Combustion Machinery - Section 9 Electrical and control equipment

Section 9 Electrical and control equipment

Parent topic: Chapter 24 Emissions Abatement Plant for Combustion Machinery

9.1 General

9.1.1 Electrical system(s) associated with emissions abatement plant are to meet the requirements of Pt 6, Ch 2 Electrical Engineering.

9.1.2 Control system(s) associated with the emissions abatement plant are to meet the requirements of Pt 6, Ch 1 Control Engineering Systems.

9.1.3 Electrical and control equipment associated with the emissions abatement plant is to be compatible with any chemicals used and meet the requirements of Chapter 10 of the Rules for Ships for Liquid Chemicals.

9.1.4 Where flammable or toxic chemicals, gases or vapours are present, as identified in Pt 5, Ch 24, 3.3 Chemical substances 3.3.1 and Pt 5, Ch 24, 3.3 Chemical substances 3.3.2, or where there is a possibility that flammable gases and vapours can be produced as a result of deviations from normal operation, the defining of hazardous zones is to be in accordance with Pt 6, Ch 2, 14 Electrical equipment for use in explosive gas atmospheres or in the presence of combustible dusts.

9.1.5 For the detection of gas and vapours, a gas detection system is to be fitted which is to activate at a concentration corresponding to the substance safe occupational level. The locations of the detectors are to be determined relative to the layouts of the individual spaces and are to be indicated on the plan submission required by Pt 5, Ch 24, 3.3 Chemical substances 3.3.9. Where gas detection equipment is not appropriate, e.g. for substances not emitting gases or vapours, alternative proposals are to be submitted to ensure the safety of persons from exposure to such substances.

9.1.6 Process tanks which form part of the operating loop of any emissions abatement equipment are to have a high level alarm, in accordance with Table 24.9.1 Machinery emissions to air abatement plant: alarms and safeguards. Effluent tanks which are not part of the normal process loop and which are used for storage of effluent or substances prior to discharge from the vessel are to be protected, in accordance with Table 24.9.1 Machinery emissions to air abatement plant: alarms and safeguards.

9.1.7 Tank alarm and shutdown sensors are to be positioned at a point which ensures a system shutdown before the tank overflows, based on the maximum design flow rates and shutdown response time. Where a low level is identified as presenting a risk to crew or machinery, tanks are to have a low level alarm and a low level shutdown. These are to be positioned so as to operate before a low level results in a hazardous condition, based on system design flow rates and a system shutdown response time.

9.1.8 An emergency stop function is to be provided, which is to:

  • Close remote shut-off valves on chemical tank(s) (where applicable, *).
  • Stop chemical feed pump(s) (where applicable*).
  • Where fitted, open exhaust gas cleaning by-pass valve.
  • Stop scrubber water pumps and close scrubber water inlet valve (where applicable).
Note * Not required for emissions abatement plant utilising urea solution, see also Pt 5, Ch 24, 7.1 General 7.1.3. Systems using other media are to be considered on a case-by-case basis.

9.1.9 The emergency stop function is to be capable of being actuated from the machinery control room, the navigating bridge and from within compartments containing exhaust gas cleaning plant. In order to mitigate the risk of chemical release, spaces containing chemical storage tanks or chemical pumping equipment are to have an emergency stop which is to shut down the chemical supply to the emissions abatement plant. Other parts of the emissions abatement plant such as wash water pumps need only be stopped by this emergency stop where loss of chemical injection could result in further risks arising from operating the plant without chemical injection. This is to form part of the submission required in Pt 5, Ch 24, 3.1 General 3.1.6.

9.1.10 Alarms and safeguards are to be provided for the critical system parameters in order to avoid danger to crew and machinery. As a minimum, the alarms and safeguards listed in Table 24.9.1 Machinery emissions to air abatement plant: alarms and safeguards are to be fitted. Where these Rules require alarms and also trip protection to be fitted, the alarm and trip are to be independent of each other.

9.1.11 Where emissions abatement plant makes use of chemical substances, a means of monitoring abnormal flows of such chemicals is to be provided.

Table 24.9.1 Machinery emissions to air abatement plant: alarms and safeguards

Item Alarm Note
Exhaust gas outlet temperature High  
Exhaust gas inlet temperature High  
Exhaust gas inlet temperature Low Only for selective catalytic reduction
Differential pressure across abatement plant unit High  
Abatement plant by-pass valve in exhaust duct Valve movement See Note 1
Machinery exhaust duct isolating valve Valve movement See Note 2
Wet emissions abatement unit overboard discharge valve Closed Emissions abatement plant is to be shut down automatically, see Note 6
Wet emissions abatement unit overflow line flow detection Flow present Emissions abatement plant is to be shut down automatically, see Note 6
Wet emissions abatement water pressure Low  
Wet emissions abatement unit water level 1st Stage high  
Wet emissions abatement unit water level 2nd Stage high Emissions abatement plant is to be shut down automatically, see Note 6
Chemical feed flow High Chemical feed pump is to be shut down automatically
Chemical feed flow 1st Stage low  
Chemical feed flow 2nd Stage low Chemical feed pump is to be shut down automatically
Process tank level 1st Stage high See Note 3
Process tank level 2nd Stage high Emissions abatement plant is to be shut down automatically, see Note 3
Chemical storage tank level 1st Stage high  
Chemical storage tank level 2nd Stage high  
Chemical storage tank level Low  
Chemical storage tank temperature High See Note 4
Chemical storage tank temperature Low See Note 4
Chemical tank containment bund level High Tank outlet remote shut-off valve is to close automatically, see Note 5
Chemical tank containment drain line flow detection Flow present Tank outlet remote shut-off valve is to close automatically, see Note 5
Exhaust gas recirculating fan failure Failure  
Recirculating exhaust gas temperature return to engine High  
Induced draught fan failure Failure Where fitted

Note 1. Only where a by-pass valve is fitted, see Pt 5, Ch 24, 3.3 Chemical substances 3.3.5. This valve shall open to the by-pass position as part of the unit shutdown logic.

Note 2. Only where fitted, see Pt 5, Ch 24, 5.1 General.

Note 3. The process tank is any tank forming part of a wet abatement system flow loop or effluent tanks which receive bleed-off from the main flow loop, or such tanks not forming part of the system flow loop but which are essential for operation of the system, including drain tanks, residue tanks, leakage tanks and those on exhaust gas recirculating installations, see Pt 5, Ch 24, 11.1 General 11.1.8. Where low level can present a hazard, process tanks are also to have low level protection.

Note 4. Where chemical substances are to be kept within a defined temperature range, alarms will be fitted, based on the allowable temperature range, see Pt 5, Ch 24, 5.1 General 5.1.2 and Pt 5, Ch 24, 7.1 General 7.1.9.

Note 5. Chemical spillage detection alarm will depend on the means of spill containment fitted, see Pt 5, Ch 24, 5.1 General 5.1.2.

Note 6. Wet emissions abatement unit shall include such systems fitted as part of the exhaust gas recirculating installations.

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