.high water level   .boiler high water  .bhwl

• Sudden increase in steam demand and feed water flow increased but not reduced proportionately when demand is reduced
• Sudden drop in steam pressure and burners firing on full-load
• ‘Forcing’ of boilers can lead to ‘swelling’ and high level alarm, example:
• When starting boilers from cold. Keep water on lower limit of normal water level [as water expands on heating]
• Feed p/p running manually
• Faulty level transmitter.

Action for High Water Level Alarm

• Immediately slow down the steam operated machinery like cargo pumps, turbo-generators etc to prevent damage
• Change to manual and stop feed pump or manually throttle feed control valve
• Check local water level gauge to ascertain the high water level alarm. Blow through at least one gauge glass.
• Operate drain valve in steam line and bottom blow down until normal water level is established
• Check controller for sluggish operation and adjust P+I+D settings, ensure control air is clean [can happen after drydock after using shipyard supplied air]

Low Water Level Alarm

.boiler low water level   .blwl   .low water level

Likely causes:

• Check if feed pump is running and if suction and discharge pressures are almost the same, ‘vapour lock’ may be taking place
• Cascade tank low
• Check if auto level controller is working and in ‘open’ position
• Check if blow down valve is leaking or left open
•  look for signs of excessive boiler tube/s leakage

action for Low Water Level Alarm

• Stop firing and investigate
• Check local water level gauge to ascertain the low water level alarm. Blow through at least one gauge glass if possible.
• Change-over to another feed pump
• Open manual/direct filling valve