Thermoplastic Pipe

Extensive amount of plasdc pipe is used worldwide to move different types of liquids, gases, and solids. With the different properties of plastics (such as corrosion resistance, toughness, and strength), pipes can be fabricated to handle practically any type of material. A major and important market for plastics is in producing pipe (tube) for use such as on the ground, underground, in water, and electrical conduits. The largest use is in transporting water, gas, waste matter, industrial mining,

Pipe wall thickness determination based on internal pressure

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a etc. Use of thermoplastic, such as HDPE, PVC, and PP, provide most of the world using extruders. Plastic pipe represents about 30% of the dollar share compared to other materials (iron/steel at 45%, copper at 12%, concrete at 8%, aluminum at 4%, etc.).

Fig. 4.22 provides a method to determine pipe thickness subjected to uniform internal pressure P using the standard engineered thin-wall-tube hoop-stress equation. Top view provides an equation that is approximately accurate for t <^/10. However when the wall thickness increases the error becomes large. It is useful in determining an approximate wall thickness, even when condition (t<d/I0) is not met. Bottom view provides an equation for the maximum hoop stress that occurs on the surface of the inside wall of the pipe. After the thin-wall stress equation is applied, the thick-wall stress equation can be used to verify the design.

An important product even though it represents a small portion of the market is reinforced TS (RTS) plastic; also called reinforced thermoset resin (RTR) according to ASTM standards. Its major material construction is glass fiber with TS polyester plastic that uses fabricating methods ranging from bag molding to filament winding (Chapters 1 and 2). These RTR pipes provide high load performance both internally and externally.

There are large diameter filament-wound pipes (RTRs) used and accepted in underground burial because they provide conditions such as corrosion resistance and installation-cost savings. Pipe design equations have been used that specifically provide useful information to meet internal and/or external pressure loads. More recendy finite element analysis (FEA) has been used to design RP pipes and other structural products. These design approaches utilize performance standards based upon internal pressures and pipes' stiffness. Other requirements must be met such as longitudinal effects of internal pressure, temperature

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