Machinery Alarms and Protection Devices
Experiments show that a large number of machinery breakdowns occur due to a mistake in operation or maintenance of the alarm systems and the protection devices.
Engines, generators, boilers, compressors do break down, sometimes fatally damaged, because the alarm systems and the protection devices, monitoring them, have been prevented from working. Sometimes deliberately disconnected, sometimes clogged up with paint and forgotten. Abandoned without checking for long periods of time.
This, of course, is asking for trouble, when only a little attention to detail by duty engineers could avoid an unforeseen incident, resulting in possible injuries of people, major machine breakdowns, upsetting the commercial operation of the vessel, leading to extra workload for ship's personnel.
Once a less than meticulous checking and maintenance regime of the alarm systems is allowed to develop on board ship, things can go wrong at any time.
The ship's systems cease to be reliable, because no one can be sure which alarm is working and which is not.
Timeline:
00:00 Machinery Alarm and Protection Devices
00:30 Negligence of alarm systems checking and maintaining
02:39 Blackout
03:43 Typical schematic view of alarm and protection systems: warning circuit and protection device
05:08 Protection circuits with shutdown circuitry
05:50 Monitoring system
06:06 Vital protection devices
06:41 Top priority alarm and protection devices: main propulsion, steering system, power generation plant and steam boilers
07:13 Critical alarm circuits: air compressors, air conditioning systems, refrigeration systems
07:32 Variable priority alarm systems: cargo pumps and bow thrusters
07:43 Warning only alarm systems: level indicators, temperature sensors in tanks and heating or cooling systems
08:03 Sensors as level indicators for fuel tank, lub. oil tank, boilers
08:45 Boiler water level: safety limits
09:26 Flame out alarm system and optical sensors
09:54 Main propulsion alarm and protection devices: temperature and pressure sensors. Monitoring of optimal temperature and effective lubrication
10:35 Main engine temperature monitoring
10:55 Main engine pressure monitoring
11:33 Regular testing of sensors
11:47 Valid certificates and assurance of calibration. Calibrated test instruments
12:01 Temperature sensors testing
12:55 Alarm settings
13:16 Pressure sensors testing
13:53 Testing level alarms (delay for bilge level alarm)
14:49 Ship's manual details
15:01 Proper function
15:14 Significance of each alarm
15:47 Conclusions
It is essential:
1. that you know your ship's alarm system and protection devices;
2. that you pay special attention to the critical alarm circuits on board ship;
3. that you always follow the alarm systems maintenance schedule and ensure that all sensors and display systems are fully functional.
When an alarm condition arises, never press the reset without noting the cause of the alarm!!!
If an adjustment must be made to temperature or pressure switches, always use calibrated instruments!!!
Always repeat the tests at different values!!!
To avoid the machine starting automatically, always switch automatic re-start circuits to manual and off before reset!!!
Equipment should never be restarted or put back into service without rectifying the cause of the alarm trip!!!
Any abnormal run indication should always be investigated, even the equipment is apparently running smoothly!!!
The engineer on watch must have confidence in the alarm system protection devices in the engine room. He must be sure all times that he will be given timely warning of any changing condition which may lead to a breakdown, so, that he can take remedial action. This confidence is an essential component of good engineering practice.
A Videotel Production for VIDEOTEL Marine International Ltd.
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