The elbow behind micro-spray desuperheater of boiler no.2 in one power plant has cracked many times

seriously affecting operation of the unit.Through inspection of the pipes

analysis of coal quality

and cold-state test of the reheater

it is believed that the crack of elbow is a typical thermal fatigue crack

resulting from deviation of actual coal sort from the designed coal sort

and temperature deviation of flue gas at outlet of the furnace

thus

leading to overtemperature of the heating surface

and frequently putting desuperheating water into service.Based on these

measures and recommendations

such as retrofitting the secondary air into reverse tangential firing

enhancing the feed-water and steam quality

improving quality of furnace-incoming coal and atomizing effectiveness of the nozzles

etc.

have been put forward.