D. Y. LI ET AL.

Copyright © 2013 SciRes. ENG

Figure 7. Variat ion of s tres s at point-N.

Figure 8 . Changing c urve of stress concentr ation fact or.

Impacted by the internal pressure, the mechanical

stress and the internal pressure are sharing the similar

changing tendency.The value of mechanical stress is va-

rying from 56.61MPa to 121.01MPa.

3.3. Stress Concent ration Factor

The mechanical stress concentration factor is indepen-

dent of ru nni n g co nd it ion[ 7] . T he str ess o n t he s tudy a re a

is directly proportional to the value of the internal pres-

sure. Define stress concentration factor as follow[9]:

(4)

where

= maximum stress. The changing curve of

the stress concentration factor during the process of load

pick-up at point-N is shown i n Figure 8.

Based on above computations, in the later period of

the load pick-up process, the stress concentration factor

with its value 2.51 can be considered keeping stable dur-

ing the whole process because of the tiny changes on the

amplitude o f the factor.

4. Conclusion

● Refers to the computations, the phenomenon of stress

centralization at the inside conjunction area between

the pipe and the header cylinder is obvious. Far from

the intersecting line area changes less in stress; it can

be considered as the membrane stress of the cylinder.

● The maximum stress is distributed mainly at point-N

which is focu sed o n the inters ectin g line. Accor din g to

the numerical calculation, the stress concentration

factor of point-N is 2.51.

● These analysis results, especially the stress concentra-

tion factor, can be used in life expenditure on-line

monitoring system in following research.

REFERENCES

[1] D. Q. ZHANG, S. J. YANG, G. Z. LIU and G. C. Zhang,

"Fatigue Life Assessment of Plant Drum in service,"

Shandong Electric Power, vol. 2, NO. 6, 1997, pp.

19-21+25.

[2] Y. G. PEI, Y. F. SHEN, T. L. YANG, Z. D. Cao, J. Wu, S.

X. Zhuang and H. D. Wang, "Management System of

Boiler Drum s Fatigue Life," Journal of Xi An Jiao-

tong University, vol. 5, NO. 16, 1999, pp. 64-67.

[3] L. B. HE, "Service Life Analysis of The High Tempera-

ture S uperheat er Outlet Header in a 6 00MW Su percrit ical

Boiler," Master, Thesis, North China Electric Power

University, Beijing, 2011.

[4] Q. Z. YIN, J. S. XIAO, A. L. Jiang, Y. P. Chen and Z. L.

Zhao, "Finite Element Analysis of Three Dimensional

Transient Stress in 300MW Boiler Drum," Journal of

Wuhan University of Technology(Transportation Science

& Engineering), Vol. 1, No. 17, 2007, pp.60-62+69.

[5] Vallourec & Mannesmann Tubes. "T92/P92 steel Hand-

book," In: (Ultra-) supercritical boiler steel and welding

technical symposium, 2005, pp. 285-304.

[6] Z. W. SHI, "Numerical simulation of temperature field

for T92/12Cr1MoV dissimilar steel welding," Mechanical

research and Application, Vol. 4, No. 41, 2010, pp.

99-101+104.

[7] Z. J. WANG, "Boiler structure finite element analysis,"

Chemical Industry Press, Beijing, 2005.

[8] T. Liu, "Life Estimation and On-line Monitoring for

Pressu rt e-bearing Part of Utility Bolier," Ph.D. Thesis,

North China Electric Power University, Beijing, China

2007.

[9] D. B. WANG, X. L. WEI, S. XIANG, C. X. Guo, J. X.

Wu, "Stress analysis and design for tangential opening

tubing connection on pressure vessels," China Petroleum

Machinery, Vol. 4, No. 2, 2006, pp. 5-7+85.