Page 445 - Boiler_Operators_Handbook,_Second_Edition

430 Boiler Operator’s Handbook

Figure 12-1. Chart of reasons for boiler failures in prior years

Figure 12-2. Chart of accidents, injuries and deaths, late 1990s to 2002

cause for boiler failures. Taking all the precautions and detect the water level and a lever connected to the float
conducting the regular testing should prevent them but keeps the float in position and actuates the electrical
they continue to occur. contacts that open to stop burner operation.
It doesn’t matter if it’s a hot water boiler or a steam Conductance cutoffs use probes, looking some-
boiler, it should have a low water cutoff; steam boilers thing like a spark plug, to detect water level by the dif-
should have two. In the last century the most consistent ference in conductivity of water and steam or air. Low
reason for a boiler failure, accounting for about one third water cutoffs should be installed to prevent burner op-
of the incidents, was loss of water. You should check the eration in the event the boiler water drops below a safe
cutoffs as often as possible and under different situa- level where the heating surfaces are exposed to steam.
tions to be certain they are reliable. Low water cutoffs Normally the lowest safe operating level in a boiler is
come in two basic forms, float and conductance. Float the bottom of the gauge glass so the cutoff should pre-
operated cutoffs, as their name implies, use a float to vent burner operation near it. Cutoffs are installed in