Effect of Wire Spacing on Short-Term Burst Pressure of Reinforced Thermoplastics Pipe Reinforcement Layer

Abstract Reinforced thermoplastic pipe (RTP), which consists of thermoplastic matrix and reinforced layers, has many advantages such as good flexibility, corrosion resistance, and long service life. It has been used in oil and gas transportation pipeline industry for several decades. However, for in large diameter (OD > 250 mm) and high-pressure (PN ≥ 3.5 MPa) RTP, nonuniform spacing of the wire winding is a common occurrence due to a large number of steel wires used on the composite pipe. This irregularity leads to significant variability in the burst pressure, limiting the development of the RTP for high-pressure and large-diameter applications. In this paper, the mechanical properties of a large diameter and high-pressure of RTP are studied, with emphasis on the effect of nonuniform spacing of reinforced steel wires on short-term burst pressure. A multilayer stress–strain model considering the elastic properties of steel wire and high-density polyethylene (HDPE) was established. Considering the uneven distribution of steel wire, an analytical method for predicting short-term burst pressure is proposed. Ultrasonic phased array technology is used to measure the actual position and distance of the steel wire. It is observed that nonuniform spacing may lead to uneven stress distribution, and some wires reach their load-bearing limits prematurely. In order to verify the model, short-term burst tests were carried out, and the experimental results were in good agreement with the theoretical predictions, confirming the effectiveness of the model in capturing the effect of spacing on RTP performance.