PSI - Issue 2_B

O. Yasniy et al. / Procedia Structural Integrity 2 (2016) 840–846

845

6

Author name / Structural Integrity Procedia 00 (2016) 000–000

SIF was calculated by formula Yasniy et al (2014):

a





 

(3)

, T a Y T w       

,

K

yy   

I

0,295



a

a       w

  

  





/15,62

T



; Y T

(0,54 0,32 e

)

is the correction function, determined in Yasniy et

where

  



w

al. (2014), w is the thickness of header wall. The С and n parameters of Paris law for 12Cr1MoV steel at 500° С were taken from Yasniy et al (2012), according to which С = 1,96·10 -10     1 MPa m/cycle m m  , n = 2. The main parameters of operational loading of superheater header under quasi-stable mode of operation are given in Table 3 Table 3. The main parameters of operational loading of superheater header under quasi-stable mode of operation Operational parameters Quasi-stable temperature fluctuations Loading waveform Saw-tooth Stress range elastic Frequency 5∙10 -4 to 5∙10 -3 Stress ratio, R 0.3 – 0.6 Number of occurrences per year Class 1: 31755 Class 2: 365

Fig. 5. The dependency of crack depth along the hole of pipe on the number of loading cycles:  T = 10 ° C – (1); 15 ° C – (2); 20 ° C – (3); 30 ° C – 4; 40 ° C – (5); 46,2 ° C – (6); 50 ° C – (7)