Steam soot blowing

Steam soot blowing
A steam soot blower consists of a number of nozzles on a pipe that rotate and sometimes moves axially between the banks of tubes.
Designed to be used during boiler operation.

This example is an exhaust gas boiler but the same method can be used for an oil fired steam boiler.

If you don't care about your boiler then the smoke-tubes might end up like this. Many hours of work to clean up the tubes manually will be the only solution.
In this particular case the furnace pressure had increased so the combustion air fan didn't manage to blow in sufficient air for the combustion of the fuel oil and hence more soot was formed.