PSI - Issue 40

N.A. Makhutov et al. / Procedia Structural Integrity 40 (2022) 283–295

290

8

N.A. Makhutov at al. / Structural Integrity Procedia 00 (2022) 000 – 000

Substantiation of strength and durability based on technical diagnostics results

Identification of critical conditions according to Tables 1 and 2

Preparation of design diagrams and design scenarios

Design diagrams

Design scenarios

Calculation using diagram Fig. 2, a)

Calculation using nominal stresses from pressure

Calculation using diagram from Fig. 2, b)

Calculation using nominal stresses from all pressure effects

Calculation using diagram from Fig. 3, a); 3, b)

Calculation using local criteria

Decision making

Extension of operation

Performance of repairs

Termination of operation

Fig. 5. Flow diagram of analysis and substantiation of strength and durability

 1            3 ( ) S ( ) S ( ), S 1 ( ) S III e IV

(6)

  2 

  2 



2

1 ( ) S      2

( ) S

2 ( ) S      3

( ) S

3 ( ) S      1

( ) S

2

Maximum reduced stresses σ e ( τ S ) according to expression (6) shall not exceed the strength of pipe steel   ( ) ( ), ( ) e S y S u S        (7) If condition (7) is met, operation of the critical pipeline section being analyzed can be continued. Calculated strength assessment using local deformation criteria is used in cases when condition (7) is not met or when diagnostics show local defects in pipeline wall and near welds according to Fig. 3, b) in the form of expressed pitting corrosion that forms concentration of stresses with theoretical factor ( ) . Implementation of such approach for elastic and elastic-plastic deformations requires determination by Lisin et al. and Mahutov (2008) of the maximum equivalent deformation к in the concentration zone max ( ) ( ) ( ) ( ) / , e S en S S y S e e E           (8)

(9)

( ) S 

( ) ( ) with  

( ) S

( ) / , E

e

en S e S e K

e



y S    

max

max

e

e