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Q: What to do when boiler is over-pressurised?
Two worst dangers: explosion and meltdown.
If my hot water kettle at home is boiling over, obviously first thing is switch off power (or cut off the gas if I’m boiling using stove). Same principle apply to onboard. Assuming this is an Auxiliary Boiler (not talking about composite boiler getting M/E exhaust gas) overpressurised scenario, immediately raise alarm and activate boiler emergency stop button either in ECR or boiler area, which will stop the boiler burner from firing, which obviously is the source of heat to create steam in an aux boiler.
If this is composite boiler scenario where ship at sea, M/E providing continuous supply of hot exhaust gas to the composite boiler (and boiler burner not running) but for some strange reason it’s overpressurised, there’s several ways to handle. I’ll apply the hot water kettle scenario. First response is raise alarm, and CE can consider slow down M/E to reduce the temperature of exhaust gas supplying to composite boiler while engine team figure out why overpressurised (pressure build up in boiler cos some where the pipeline is blocked? The steam cannot flow properly?) and take action.
At the same time, check if the boiler safety valve has lifted? It’s okay for safety valve to open, as much more dangerous if safety valve stuck closed then boiler damage. As needed, use the Easing Gear.
Q: Boiler gauge glass – Blow down is carried out if water level rises, but suddenly drops when steam is introduced, where is the water level and what’s the next action taken.
I would consider carrying out blow down both gauge glass + cross check visible water level with the reading from the remote water level transmitter which sends signal to the boiler panel, which has setting how much is low water level. The low low water level safety device is quite direct, inside that black cylinder is a float, if the float falls to the low low water level, triggers alarm and boiler burner shut down (if was running). The boiler water level transmitter also forwards the reading to a gauge in ECR to monitor boiler water level.
If both gauge glasses and remote water level transmitter indicates boiler water level is abnormally low, take actions to ensure boiler does not overheat. Introduce warm (70~80 degrees celcius) boiler water into the boiler, to reduce possibility of thermal shock if cold boiler water was pumped into an extremely hot boiler.
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