Steam Boilers need to monitor the feedwater in the main steam drum for a number of reasons. Most boilers have some kind of level control which compensates for level changes due to changes in load, "shrink and swell", blow down from skimmer lines, etc. It is not really important to know the reason.

Generally there will be some technique for sensing level already on the boiler. The level gauge is employed to give a visual indication to the operators and serve as a redundant or back up level alarm.

Actually boilers generally have sight glasses and the level gauges replace them because these sight glasses are very hard to read and very dangerous.

Boilers are rated as to the pressure of the steam they generate, i.e., 150#, 300#, 600# etc. Level gauges have been used on boilers up to 2500#. Power generating plants typically run in the 1200# range. This is no problem for the chamber, but does require a very special float.

Also, associated with the boiler is a condensate make up tank. Feedwater to the boiler comes from this tank and it is desirable to know the level here which may run in the 300 psig range. Saturated steam at 650# is almost 500 degrees Fahrenheit. The feedwater temperature will be the same and have a gravity of about 0.8 thus requiring a high pressure float about 10 in. long. Please Email suggestions, comments or requests for information to ISE-Magtech.