Section 18 Control and monitoring
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 2 Machinery and Engineering Systems - Part 8 Pressure Plant - Chapter 1 Steam Raising Plant and Associated Pressure Vessels - Section 18 Control and monitoring

Section 18 Control and monitoring

Parent topic: Chapter 1 Steam Raising Plant and Associated Pressure Vessels

18.1 General

18.1.1 The Control and Monitoring systems are to comply with the requirements of Vol 2, Pt 9, Ch 7 Control, Alerts and Safety Systems.

18.2 Automatic and remote controls

18.2.1 Where a boiler is fitted with automatic or remote controls so that under normal operating conditions it does not require normal intervention by the operators, it is to be provided with alarms and safety arrangements required by Vol 2, Pt 8, Ch 1, 18.2 Automatic and remote controls 18.2.2 and Table 1.18.1 Boilers: Alarms and safeguards

18.2.2 Where a first stage alarm together with a second stage alarm and automatic shutdown of machinery is required by Table 1.18.1 Boilers: Alarms and safeguards, the sensors and circuits utilised for the second stage alarm and automatic shutdown are to be independent of those required for the first stage alarm.

18.2.3 The following boiler services are to be fitted with automatic controls so as to maintain steady state conditions throughout the normal operating range of the boiler:

  1. Combustion system.

  2. Fuel oil supply temperature or viscosity, fuel oil grades requiring heating or cooling, as applicable.

  3. Boiler drum water level.

  4. De-aerator water level where applicable.

  5. Superheated steam pressure where applicable.

  6. Superheated steam temperature where applicable.

  7. De-superheated steam pressure where applicable.

  8. De-superheated steam temperature where applicable.

18.2.4 Safety systems and overrides are to comply with the requirements ofVol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.8.

18.2.5 Burner controls are to be arranged such that light off is only possible at the minimum firing rate compatible with flame establishment. If ignition is set to occur at a fuel rich condition the burner is to revert to the correct operating air/fuel ratio on establishment of a stable flame.

18.2.6 Where water level indicators are dependent upon an external power supply, the fuel oil supply to the burners is to be automatically shut off in the event of power or signal failure.

18.2.7 Burner fuel oil valve(s) are not to open:

  • prior to completion of required warm up times; or
  • when the power supply to the igniter has failed; or
  • until a pilot flame is established, as applicable; or
  • prior to the completion of furnace purging, see Vol 2, Pt 7, Ch 3, 3.1 Oil burning units 3.1.9.

18.2.8 Arrangements for flame failure detection are to be provided with self-monitoring capabilities which prove that the flame detector is not erroneously indicating the presence of a flame. In the event of failure being detected by these selfmonitoring capabilities:

  - fuel oil to the burner is to be shut-off automatically; and
  - an alarm is to be activated.

18.2.9 Where established as necessary byVol 2, Pt 7, Ch 3, 3.1 Oil burning units 3.1.10 means are to be provided to prevent starting of the ignition sequence following multiple flame failures until completion of the identified lock out period.

18.2.10 Following burner shutdown, the furnace is to be purged automatically for at least the required pre-purging time. In event of shutdown due to activation of a required safeguard this purging is to be manually initiated.

Table 1.18.1 Boilers: Alarms and safeguards

Item Alarm Note
Water level* Low Two water level sensors are to be provided each to operate independently, and automatically shut off the fuel oil to the burners and operate alarms. See Notes 1 to 3, and Note 5
  1st stage high*  
Water level 2nd stage high Where applicable; automatic closure of turbine steam inlet valves. See Vol 2, Pt 8, Ch 1, 18.2 Automatic and remote controls 18.2.2
Steam drum or superheater outlet pressure High and low —
Superheated steam temperature High —
De-superheated steam temperature* High —
Feed water forced circulation flow (if fitted) Low Fuel oil to burners to be shut off automatically, see Note 5
Feed water pH Low When automatic dosing of feed water fitted
Feed water salinity High Fitted in boiler feed system
Feed water temperature Low When automatic temperature control fitted
Combustion air pressure* Low Fuel oil to burners to be shut off automatically, see Note 5
Fuel oil pressure* Low —
Fuel oil temperature or viscosity* High and low Heavy oil only
Fuel oil atomising steam/air pressure Low —
Burner flame and ignition* Failure Each burner to be monitored. Fuel oil to burner(s) to be shut off automatically, see Vol 2, Pt 7, Ch 3, 3.1 Oil burning units 3.1.11and Vol 2, Pt 7, Ch 3, 3.1 Oil burning units 3.1.12, and Note 5
Flame monitoring device(s)* Failure See Vol 2, Pt 8, Ch 1, 18.2 Automatic and remote controls 18.2.8and Note 5
Igniter power supply* Failure Each igniter to be checked before fuel oil is supplied to burner(s), see Vol 2, Pt 8, Ch 1, 18.2 Automatic and remote controls 18.2.7 and Note 5
Forced draft fan* Power Failure Fuel oil burners to be shut off automatically, see Note 5
Air register and dampers (including those in the uptake)* Not fully open Purge sequences to be inhibited, see Vol 2, Pt 7, Ch 3, 3.1 Oil burning units 3.1.9
Control system* Power Failure Fuel oil to burners to be shut-off automatically. Control using alternative arrangements is to remain available, see Vol 2, Pt 9, Ch 7, 4.5 Control systems, general requirements 4.5.7.
Feed water or water forced circulation flow (if fitted) Low Fuel oil to burners to be shut off automatically, see Notes 5 and 6
Uptake temperature High Where economiser and/or gas air heaters are integral with the boiler and also for independent exhaust gas boilers/economisers, to monitor for soot fires. See Note 7

Note 1. For dual evaporation boilers the primary circuit is to be fitted with two independent low water level detectors which will operate alarms and shut off the fuel to the burners automatically. The secondary circuit is to be fitted with one low water level detector which will operate alarms and shut off the fuel oil to the burners automatically. Additionally one high water level alarm is to be fitted on the secondary circuit which may be operated by the same detector as that provided for low water level detection.

Note 2. Only one independent system of low water level detection, alarm and automatic fuel shut-off need be fitted in the case of small forced circulation or re-circulation coiled water tube ‘package' type boilers when evaporation is less than 2900 kg/hr or the heating surface is less than 100m2.

Note 3. Where two level sensors are provided these may be used for other functions, e.g. high level alarm, level control, trip systems, etc.

Note 4. For boilers not supplying steam for propulsion or for services essential for the safety or operation of the ship at sea, only the items marked * are required.

Note 5. These safeguards are to remain operative during automatic, manual and emergency operation.

Note 6. For exhaust gas economisers/boilers requiring feed water or forced water circulation, the low flow alarm is to be fitted with provision to override the alarm if the exhaust gas economiser/boiler is to be operated in the dry condition. See also Vol 2, Pt 7, Ch 3, 6.2 Feed and circulation pumps 6.2.4.

Note 7. Alternatively, details (including location) of an appropriate fire detection system are to be submitted for consideration.

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