To permit partial load operation, {HEAD ~ a control arrangement} is provided to effect, in dependence upon an operating load of the boiler, {TAIL ~ control} of at least one of the flow rate of the combustion air into the boiler, and the operating pressure in the combustion chamber of the boiler 
is provided to effect
To permit partial load operation , { HEAD ~ a control arrangement } is provided to effect , in dependence upon an operating load of the boiler , { TAIL ~ control } of at least one of the flow rate of the combustion air into the boiler , and the operating pressure in the combustion chamber of the boiler
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH