Causes of High Water Level Alarms

.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]

.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

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