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Section 2 Automation Equipment
201. Design principles
1. All equipment for the automatic surveillance and control of submersible operating parameters is to be designed and constructed so that it works properly under the design and environmental con- ditions specified for the submersible.
2. Computer aided operating systems for the navigation and/or for the surveillance and control of the submersible are allowed. Details of the scope and redundancy requirements of these systems are to be agreed with the Society. The systems are subject to compulsory type testing. Such type testing relates both to the equipment to be used (hardware) and to the corresponding computer programs.
3. The automation equipment on board autonomous submersibles is to be constructed in accordance
Pt6 of Rules for the Classification of Steel Ships.
4. All items of surveillance and control equipment are to be clearly inscribed and identified.
5. Indicating instruments and synoptic displays are to be designed and inscribed in such a way that they can be read quickly and clearly.
6. Any fault or failure which may occur in the automation system shall not provoke a critical operat- ing condition.
7. As far as possible, automation equipment is to be safeguarded against faulty operation.
8. Automation equipment is to be capable of maintaining the submersible's assigned operating parameters.
9. Any inadmissible variations in the operating parameters are to actuate an automatic (visual and au- dible) alarm at the control platform. The same shall also occur in the event of automatic switching operations in the gas and power supply systems or faults in the control and surveillance system.
10. In addition to electronic control and surveillance equipment, independent safety devices are to be fitted which prevent a fault in one system from provoking an improper response in another system.
11. Automatic surveillance and control equipment are to be capable of being switched to manual oper- ation at all times.
12. The response values of automation equipment are to be so coordinated with each other that, when a threshold is reached, a warning is initiated, followed, after a certain warning period or if the process variable continues to change at a preset speed, by the actuation of safety devices.
13. The integral operation of automation systems are to be designed to take account of the lags and
time constants of the units and elements making up the system (e.g. by allowing for the length and cross-section of piping systems and the response time of gas analyzers).
14. The criterion for the freedom from interference of electronic systems is to be in accordance with recognized standard approved by the Society.
202 Construction
1. Electronic automation systems should comprise easily replaceable assemblies, of the plug-in type wherever possible. Standardization of units is to be encouraged and the number of assembly types is to be kept small in order to minimize the spare parts inventory.
2. Plug-in cards are to be clearly marked or coded to prevent inadvertent confusion.
3. Measures are to be taken to prevent condensation inside electronic units, even when switched off.
Shutdown heating is recommended.
4. Wherever possible, automation equipment should be capable of operation without forced ventilation.
Any cooling system used is to be monitored.
5. Components are to be effectively secured. Any mechanical loading of wires and soldered con- nections due to vibration or jolting is to be reduced to a minimum.
6. The construction of systems and units is to be simple and straightforward. Good accessibility is to be ensured to facilitate measurements and repairs.
203 Circuitry
1. Signalling equipment and control systems with a safety function are to be designed on the fail safe principle, i.e. faults due to short circuit, earthing or circuit breakers shall not be capable of provok- ing situations hazardous to personnel and/or the system. In this respect, it is to be assumed that faults occur singly. The failure of one unit, e.g. due to short circuit, shall not result in damage to other units.
2. In stored program control systems, the electrical characteristics of the signal transmitters shall con- form to the safety requirements for instruction and control devices.
3. Instruction and control units for safety functions, e.g. emergency stop buttons, shall be independent of stored-program control systems and shall act directly on the output unit, e.g. the STOP solenoid.
4. Stored program control systems are not to be reacted and, in case of fault, should cause no mal- functions in program independent safety inter-locks or stepped safety circuits for fixed subroutines.
5. Freely accessible potentiometers and other units for equipment trimming or operating point settings are to be capable of being locked in the operating position.
6. Interfaces with mechanical switchgear are to be so designed that the operation of the system is not adversely affected by contact chatter.
7. Conductive tracks forming part of circuits which extend outside the enclosure housing the circuit boards is to have qualified short circuit protection. i.e. in case of an external short circuit only the safety devices provided may respond without destroying the conductive tracks.
8. The equipment shall not be damaged by brief overvoltages in the vessel's example to switching operations. The design is to allow for over voltages
2.5 times the rated voltage and lasting 1 ms. Where systems are supplied
power supply, due for equal to approximately by static converters, it
may be necessary to make allowance for periodic voltage pulses lasting about 0.5 ms. The pulse amplitude depends on the converter type and is to be investigated in each case.
204 Power supply
1. Power supply to the said equipment is to be effected via separate circuits. Selective circuit opening of each of these in the event of short-circuit is to be ensured.
2. The reference conductor system is to be designed to preclude circuit breakers as far as possible.
This may, for example, be archived by duplicating exposed reference conductor joints and connections.
3. The automation equipment is to be capable of being safely operated in the event of voltage and frequency variations referred to in Pt 6, Ch 2 of Rules for the Classification of Steel Ships.
205 Tests
For the automation equipment of novel design, type approval test is to be carried out by the Society. The nature and scope of the type approval test will be determined by the Society in each case.