PSI - Issue 22

Lunwen Guo et al. / Procedia Structural Integrity 22 (2019) 194–200 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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reveal that the winding process takes about 30 minutes, and the weight of 3 meters straight pipe is less than 32 kg. Compared with 56kg double-layer metal pipe, it can reduce 43% of mass. 4.2. Pressure test The specimens of the full-size CFRP-steel pipes are shown in Fig. 6(a), and the pressure test is shown in Fig. 6(b). The tested pressure first increased from 0 to 12 MPa, holding for 5 minutes, then increased to 17MPa, holding for another 5 minutes. The test results show that the CFRP-steel pipes passed 17MPa water pressure test.

(a)

(b)

Fig. 6. The specimens of the full-size CFRP-steel pipes (a) and the pressure test (b)

4.3. Using assessment

The service life of the 3 meters CFRP-steel pipes and double-layer metal pipes installed on the booms of concrete pump trucks was compared and assessed. According to the results, it was found that the inner liner cracked and peeled off due to the gap between the inner and outer layers of double-layer metal pipes, leading to the early failure of the pipes, as shown in Fig. 7(a). In contrast, the metal lining of the CFRP-steel pipes was completely worn out due to the absence of this gap, as shown in Fig. 7(b). The comparison of service life between CFRP-steel pipes and double-layer metal pipes is shown in Table 2. Due to fully quenched metal lining with higher hardness, and the tightly fiber winded metal lining with the absence of gap, the service life of the CFRP-steel pipes increased by about 50%, and the worn mass of the lining per10,000 m 3 concrete was reduced by about 27%.

(a)

(b)

Fig. 7. Failure images contrasts of concrete conveying pipes: (a) double-layer steel pipe and (b) CFRP-steel pipe

Table 2. The comparison of service life

Average pumped concrete volume/10×10 3 m 3

Worn mass of lining per10,000 m 3 /kg

Main failure modes

Specimens