OCR Text |
Show tests were performed with a 50 percent C O M . Results indicated that after a 24-hour period of full boiler load operation, the furnace ash accumulation was reduced from 184 lb without activating the furnace soot blowers to approximately two pounds when the furnace soot blowers were activated every four hours. The total steam consumption was about 70 lb per each operation of the soot blowers. Corrosion and Erosion of Boiler Tubes Prior to the 500-hour duration test, three boiler-tube test coupons were specially prepared and installed in the furnace and in the convection bank. After the test, the coupons were analyzed. The boiler tubes of 2 inches O.D. were generally covered with a thin black scale of approximately 0.001 inch thickness. Metallographic examination revealed that both the outer and inner tube surfaces exhibited a significant number of defects to a maximum depth of 0.003 inches, which apparently occurred during fabrication and processing of the tubes. Examination of the entire outer surface of each tube revealed no indication of preferential corrosion or oxidation. Only one tube in the furnace showed any difference in surface condition. The side facing the fire exhibited no surface attack, while the side covered by the refractory wall showed attack approximately 0.002 to 0.003 inches uniformly into the tube surface. There was no indication of erosion of the tube surfaces due to impingement of fly ash on any of the sections examined. Wear in Nozzles, Pumps, and Pipelines Erosive wear in the original burner nozzle was a severe problem. The high pressure-drop across the nozzle holes caused a "bugle" shape wear pattern, with most of the erosion occurring on the outer edge. The worn fuel nozzle eventually produced a poor fuel spray pattern and contributed to clinker formation on the edge of the burner 14-8 |