Gong, Z-G. Yang/ Material and Design 32(2011)671-681 (b) (c) Fig. 2. External appearances of the nozzles (a) layout of nozzles on the furnace bottom(b) perforation on the failure nozzle and (c) fractograph of the failure inlet tube (a) (b) (b) Fig. 4. External appearances of the manhole door A (a) the whole refeed valve, (b) scaling morphology and (c)magnification of scaling substance. to the practical conditions, investigation could only be carried out eral entirely different types of failure phenomena on the two man- on the refeed valve. But actually, perforation of one manhole door hole doors of the refeed valve, further characterization methods of the refeed valve was one of the prominent failures in this event. would be carried out to determine the causes and mechanisms of Fig. 4a displays the external appearance of the refeed valve, them. which owned two manhole doors respectively named A and b on its two sides. It can be learned from Fig. 4b that scaling had occurred on the surface of the refractory on the manhole door 3. Steam syster A, and the scaling substance was green and viscous liquid, seen Like conventional power plants, the Cfb boiler also possesses a in Fig. 4c. With respect to the failures on the manhole door B, be- complete steam to fully utilize the steam heat. the only dif- sides the self-detachment of the refractory on it, two perforations ference of this Fw ceb boiler was that the reheater was substituted could also be found (Fig 5a), and the diameter of the bigger one by the secondary superheater, seen in Fig. 1. Evaluation would be had reached about 10 cm, seen in Fig 5b. Moreover, it is obvious carried out on all the four steam equipments including the primary in Fig. 5c that scaling was also engendered at the edge, but the superheater, the secondary superheater, the economizer and the solid. different from that on the manhole door a. as there were sev Fig 6 shows the external appearances of the primary super heater. whose manhole do covered with brown rust. seen 1 For interpretation of color in Fig 5, the reader is referred to the web version of in Fig cted on even all the steam piping this article as well( Fig. 6b). Hence, it concluded that the only degradato the practical conditions, investigation could only be carried out on the refeed valve. But actually, perforation of one manhole door of the refeed valve was one of the prominent failures in this event. Fig. 4a displays the external appearance of the refeed valve, which owned two manhole doors respectively named A and B on its two sides. It can be learned from Fig. 4b that scaling had occurred on the surface of the refractory on the manhole door A, and the scaling substance was green and viscous liquid, seen in Fig. 4c. With respect to the failures on the manhole door B, be￾sides the self-detachment of the refractory on it, two perforations could also be found (Fig. 5a), and the diameter of the bigger one had reached about 10 cm, seen in Fig. 5b. Moreover, it is obvious in Fig. 5c that scaling was also engendered at the edge, but the scaling substance exhibited the morphology as yellow1 and grey solid, different from that on the manhole door A. As there were sev￾eral entirely different types of failure phenomena on the two man￾hole doors of the refeed valve, further characterization methods would be carried out to determine the causes and mechanisms of them. 2.3. Steam system Like conventional power plants, the CFB boiler also possesses a complete steam system to fully utilize the steam heat. The only dif￾ference of this FW CFB boiler was that the reheater was substituted by the secondary superheater, seen in Fig. 1. Evaluation would be carried out on all the four steam equipments including the primary superheater, the secondary superheater, the economizer and the air preheater in this system. Fig. 6 shows the external appearances of the primary super￾heater, whose manhole door was covered with brown rust, seen in Fig. 6a. Likewise, rust was detected on even all the steam piping as well (Fig. 6b). Hence, it can be concluded that the only degrada￾Fig. 2. External appearances of the nozzles (a) layout of nozzles on the furnace bottom (b) perforation on the failure nozzle and (c) fractograph of the failure inlet tube. Fig. 3. External appearances of the platen water wall (a) total morphology and (b) phenomenon of erosive wear. Fig. 4. External appearances of the manhole door A (a) the whole refeed valve, (b) scaling morphology and (c) magnification of scaling substance. 1 For interpretation of color in Fig. 5, the reader is referred to the web version of this article. Y. Gong, Z.-G. Yang / Materials and Design 32 (2011) 671–681 673