No matter large or small boilers, economizers are equipped to reduce heat losses, but the location of boilers are different. In general, for large utility power plant boilers, the economizer is normally an integral part of the boiler; for smaller boilers, packaged heat recovery equipment is external.
Economizers are normally bent tube exchangers. The boiler feedwater flows through the tubes on its way to the boiler. The tube bank is assembled into a section of duct work which is located in the breeching between the flue gas vent connection on the boiler and the stack or chimney. The products of combustion leaving the boiler flow through this duct, over the tube bank, giving up its heat to the boiler feedwater.
Tips on making inspection of the economizer:
Make sure all internal baffling, tube arrangements, headers, tube sheets, etc., are installed in accordance with manufacturer’s recommendations.
Tubes and headers should be checked to make sure there is no plugging nor obstructions.
Check feed piping to the economizer inlet header and piping between the economizer and the boiler.
Check and inspect shutoff and check valves, isolating valves and relief valves, test connections, thermometers and pressure gauges.