Fuel Gas Firing – Miscellaneous Instruments
The burner manifolding should include a pressure connection for setting the minimum-fire controls using a low range pressure gauge.
The operator should know the fuel flow to his firebox. Therefore, the total fuel gas flow to each firebox should be indicated or trended. Also, if the gas heating value can swing significantly, then the specific gravity of the gas from the mix drum should also be trended.
For a multiburner firebox, the operator may need to adjust the number of operating burners to keep the gas control valve in a good throttling range. For such fireboxes, alarms on the signal to the gas valve can tell the operator when it is approaching its limits. Typically, such alarms would sound at 10% and 90% of the valve’s stroke.
If, as for some boilers, the firing controls respond automatically to substantial load changes, then burner header pressure alarms are helpful. They would sound whenever the header pressure approached the maximum limit for good burner operation. This warns the operator to change the number of operating burners.