PSI - Issue 45

Thi D. Le et al. / Procedia Structural Integrity 45 (2023) 109–116 "Thi D. Le" / Structural Integrity Procedia 00 (2022) 000 – 000

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like hydrogen can be beneficial for the world since it considerably reduces the greenhouse effect and the diffuse chemical pollution. The reasons for hydrogen’s positive effect are that it only releases water vapor into the atmosphere in heating application which is unpolluted and lower risks of fire in compared to fossil fuels according to Nicoletti et al. (2015). He et al. (2016) stated that even though hydrogen has advantages in environmental benefits, there are risks incorporated in the process of its storage and transport. It is due to the Hydrogen’s low volumetric energy density, meaning that a larger tank is required to store the hydrogen compared to fossil fuels. Moreover, Avas et al. (2015) pointed out because of the small molecule size and embrittlement of hydrogen, certain materials such as steel pipelines can be degraded to ruptures or leakage. To minimize these demerits of hydrogen, the research of reinforced thermoplastic pipelines RTP is needed. According to Bai et al. (2014), RTP usually consists of inner and outer high density polyethylene pipes (HDPE) and reinforced layers bonded to inner HDPE as shown in Figure 1 (a). Although the RTP can bring several benefits such as high reliability, versatility, easy installation and durability, a feasible design of RTP is not founded yet due to its limited research. Thus, the current study aims to provide a geometric design of the RTP with a typically used inner HDPE pipe at different internal pressures from 20 bars to 100 bars (2 MPa to 10 MPa).

a

b

c

Figure 1. (a) Structure of RTP (Bai et al., 2014); (b) Cross section of the cylinder; (c) Elements of the cylinder.

There are two significant factors affecting the capacity of the RTP: (i) materials of the reinforcement layers and (ii) orientation of the reinforcement layers. 1.1. Materials of reinforcement layers There are several reinforcing materials can be used for RTP such as high-strength fibers (aramid, carbon or glass). Aramid is combination of organic fibers with highly tensile strength and low density that the military industry mostly uses in anti- ballistic applications because of its’ high impact and abrasion resistance, and light weight. However, aramid fibers are now commonly used for RTP in oil and gas pipelines like Twaron - Teijin Aramid – overcoming many problems of existing steel pipelines based on Aramid (2021). Furthermore, carbon fibers are widely selected for RTP due to high strength and modulus that are produced at temperature from 1000° to 3000°C. Another advantage of carbon fibers is to enhance the HDPE characteristics of fatigue since this fiber can bear a given load reducing the strain in the PE materials as stated by Barbero (2011).

Table 1. Mechanical properties of different types of fibers applicable to the RTP concept.

Fibre

Density ( kg/m 3 )

Tensile strength ( MPa) Elastic modulus ( GPa)

Elongation to failure ( %)

Aramid-Twaron (Aramid, 2021)

420 - 3360

N/A 4590 3160 3450 3590

60-80

3.0 – 4.4

S-glass (Hyer, 2009) C-glass (Hyer, 2009) E-glass (Hyer, 2009)

2492 2492 2541 1750

85.5 68.9 72.4 235

5.7 4.8

1.8 – 3.2

Carbon-AS4 (Pilato and Michno, 1994)

N/A