PSI - Issue 31

J. Lukács et al. / Procedia Structural Integrity 31 (2021) 51–57 J. Lukács et al. / Structural Integrity Procedia 00 (2019) 000–000

54 4

Figure 1 shows the detailed geometry and the location of the artificial flaws on the PS-Ai-Noj (i = 1, 2; j = 1, 2, 3) and on the PS-Bi-j (i = 1, 2; j = 1, 2) pipe sections, respectively. For executing fatigue tests MTS type electro-hydraulic equipment with a maximal applicable pressure of 100 bar / 10 MPa was applied, the programmed load was a sinusoidal type. For the burst tests an own developed testing system was used, with a maximal applicable pressure of 700 bar / 70 MPa .

a)

b)

Fig. 1. Detailed geometry and the location of the artificial flaws on the a) PS-Ai-Noj and b) PS-Bi-j pipe sections.

3. Experimental results The results of the full-scale tests executed on the pipeline sections are demonstrated with a table and several figures. Table 3 summarizes the type of the investigations, the fatigue cycle and the burst pressure values, as well as the safety factor values, which are burst pressure divided by Maximum Allowable Operating Pressure.

Table 3. Full-scale investigations (fatigue and burst tests), their results and the calculated safety factors. Pipe section Full-scale investigation(s) Fatigue cycles ( cycle )

Burst pressure ( bar / MPa )

Safety factor ( – )

PS-A1-No1 PS-A1-No2 PS-A1-No3 PS-A2-No1 PS-A2-No2

fatigue

79,500 93,600

N/A N/A

N/A N/A 3.65 4.13 4.27 N/A 4.34 5.94 5.16 4.92 5.09

additional fatigue

burst, after previous fatigues

N/A

233.5 / 23.35 264.6 / 26.46 273.2 / 27.32 278.0 / 27.80 380.0 / 38.00 330.0 / 33.00 315.1 / 31.51 326.0 / 32.60 N/A

fatigue and burst

100,000

additional burst, after previous fatigue

N/A

PS-B1-1 PS-B1-2 PS-B2-1 PS-B2-2 PS-B3-1 PS-B3-2

fatigue

100,000 100,000 100,000 100,000 100,000 100,000

fatigue and burst fatigue and burst fatigue and burst fatigue and burst fatigue and burst

Figure 2 a) illustrates the internal pressure vs. time diagrams of the investigated PS-Ai-Noj (i = 1, 2; j = 1, 2, 3) pipe sections during their burst tests. The average pressure growth rate values in the first stage (between 0 MPa / bar and approximately 6 MPa / 60 bar ) of the tests were 0.36 MPa/s , 0.35 MPa/s and 0.30 MPa/s ( 3.6 bar/s , 3.5 bar/s and 3.0 bar/s ), for which can be evaluated as quasi-static values, and the another particularities of the diagrams are the same. Figures 3-4 demonstrate PS-Ai-Noj (i = 1, 2; j = 1, 2, 3) pipe sections after the fatigue and burst tests. Figure 2 b) illustrates the internal pressure vs. time diagrams of the investigated PS-Bi-j (i = 1, 2; j = 1, 2) pipe sections during