Page 377 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

CORROSION DAMAGE, DEFECTS, AND FAILURES 355

TABLE 5.8 Applications of Overlay Technology
Application Corrosives Number of Boilers Using the Overlay
Waste-to-energy boilers Municipal waste 59 (Alloy 625 overlay weld
containing chloride, metal used)
sulfur, alkali metals,
zinc, and lead
Coal-fired boilers Sulfidation attack, boiler 8 (Alloy 625 and 309 SS)
tube wastage
(50–60 mpy)
Pulp and paper digesters, Thiosulfate and 21 (Overload with 309 SS) 11
Kraft recovery boilers polysulfides, sulfate, (309 L on side walls) (625 on
chloride floor tubes)

Figure 5.37 Tube that failed in waste-to-energy boiler. (Figure originally published in Ref-
erence 29. Reproduced with permission of the Canadian Institute of Mining, Metallurgy and
Petroleum. www.cim.org.)

Crankshaft The crankshaft from an eight cylinder 2400 horsepower natural
gas-fired engine, operating at 900 rpm, was used to drive a gas compressor. The
engine operated well for 5.5 years with regular routine maintenance. The crankshaft
was removed for inspection and polishing of the bearing journal surfaces. There was
no cracking, but the critical crankshaft dimensions revealed the journal diameters to
be 0.03 mm under tolerance. The journals were lightly machined, and a chromium
layer applied by electroplating. The engine was reassembled and operated for about
2000 h when the crankshaft failed. On disassembling, the crankshaft was removed
and was found to be cracked through the web between the last rod journal and the
last main journal next to the fly wheel (Fig. 5.40).