Section 7 Instrumentation, control, alarm, safety and monitoring systems

7.1.1 All compressors are to be provided with the following instrumentation and automatic shutdowns:

• Indication of suction pressure (saturated temperature), including intermediate stage, when applicable.
• Indication of discharge pressure (saturated temperature), including intermediate stage when applicable.
• Indication of lubricating oil pressure.
• Indication of cumulative running hours (screw compressors).
• Automatic shutdown in the event of low lubricating oil pressure.
• Automatic shutdown in the event of high discharge pressure, see also Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.7.
• Automatic shutdown in the event of low suction pressure.

7.1.2 The automatic safety equipment is to be designed to fail safe and the arrangements are to be such that the compressors can be operated manually with the equipment out of action, in accordance with the relevant requirements of Pt 6, Ch 1 Control Engineering Systems.

7.1.3 For installations greater than 25 kW the following instrumentation, additional to that required by Pt 6, Ch 3, 7.1 Instrumentation 7.1.1, is to be provided:

• Indication of lubricating oil temperature.
• Indication of cooling water outlet temperature.
• Indication of cumulative running hours (reciprocating compressors).
• Indication of suction and discharge temperatures.

7.2.1 Where the refrigerating system is fitted with automatic or remote controls, so that under normal operating conditions no manual intervention by the operators is required, it is to be provided with the alarms required by Pt 6, Ch 3, 7.2 Control, alarm and safety systems 7.2.2 and Pt 6, Ch 3, 7.2 Control, alarm and safety systems 7.2.3 in accordance with the relevant requirements of Pt 6, Ch 1 Control Engineering Systems.

7.2.2 Alarms are to be initiated in the event of the following compressor fault conditions:

• High discharge pressure.
• Low suction pressure.
• Low oil pressure.
• High discharge temperature.
• High oil temperature.
• Motor shutdown.

7.2.3 Alarms are also to be initiated in the event of the following fault conditions:

• Failure of condenser cooling water pumps.
• High condenser cooling water outlet temperature.
• Failure of air cooler fans.
• High and low refrigerated air delivery temperatures.
• High secondary refrigerant temperatures.
• Failure of secondary refrigerant pump.
• Failure of air refreshing fans.
• Low level in secondary refrigerant header tank.

7.3.1 Temperature sensors are to be of a type which has been approved by LR. The number of sensors and their locations are to be such as to give a true measurement of the temperatures within the refrigerated spaces and of the cooler delivery and return air temperatures.

7.3.2 At least one automatic recorder is to be provided for the remote monitoring and continuous recording of air temperatures within the refrigerated spaces, and delivery and return air temperatures of individual air coolers. Where only one recorder is installed, at least one sensor in each refrigerated space or in its air distribution system is to be connected to a separate remote temperature indicating instrument.

7.3.3 Where the equipment controlling the temperature of the air delivered from the air coolers is equipped with a temperature indicator, this indicator will be given consideration as a standby instrument.

7.3.4 In the case of freezer fishing vessels, where the catch is frozen on board and stored in a refrigerated space, thermometer(s) hung within each space(s) will be accepted as the standby temperature indicator, provided the space is accessible at all times.

7.3.5 Automatic temperature recorders and temperature indicators are to be of a type which has been approved by LR and, where appropriate, are to be in accordance with the requirements of Pt 6, Ch 1 Control Engineering Systems. Approval will be granted on the basis of compliance with Pt 6, Ch 3, 7.3 Temperature monitoring and recording 7.3.6 and Pt 6, Ch 3, 7.3 Temperature monitoring and recording 7.3.7, together with satisfactory environmental testing in accordance with the requirements of LR's Type Approval System. This is to include low temperature testing at the class notation minimum temperatures for any components which may be installed in environments subject to temperatures below ambient.

7.3.6 All temperature instrumentation is to be accurate to within ±0,15°C of the true temperature in the range minus 3°C to plus 15°C , and to ±0,3°C in other parts of the range and is to register to 0,1 of a degree Celsius.

7.3.7 Where the installation is intended for the carriage of frozen cargo only, the readings need only be accurate to within ±0,5°C of the true temperature, throughout the range.

7.3.8 A spirit-in-glass thermometer is to be carried on board for checking purposes, which is to be calibrated to a recognised National Standard.

7.3.9 Thermometer tubes with their flanges and covers are to be insulated from the deck plating, and on weather decks they are to be so arranged that water will not run down the tubes when temperatures are being taken.

7.3.10 The inside diameter of thermometer tubes is to be not less than 50 mm, and the tubes are not to be in contact with cold decks.

7.3.11 Where thermometer tubes pass through compartments other than those which they serve, they are to be efficiently insulated.