Polyethylene piping

This method to be used for polyethylene pipes only by companies and persons specializing in this field. 

For polyethylene pipe, compression couplings may be used provided they comply with British Gas Specification PS/PL3. 

Figure 12.1 Creep-rupture (time to failure plotted horizontally against applied hoop stress) of polyethylene pipes under pressure at different temperatures...

ISO 7214 1998 Cellular plastics - Polyethylene - Methods of test ISO 8085-1 2001 Polyethylene fittings for use with polyethylene pipes for the supply of gaseous fuels - Metric series - Specifications - Part 1 Fittings for socket fusion using heated tools (available in English only)... 

ISO 10838-1 2000 Mechanical fittings for polyethylene piping systems for the supply of gaseous fuels - Part 1 Metal fittings for pipes of nominal outside diameter less than or equal to 63 mm... 

Patterson, S. E. and Spalding, M. A., Design Innovations of High Density Polyethylene Pipe Grade Resins, SPE ANTEC Tech. Papers, 58 (2012)... 

Model investigations undertaken using high-density polyethylene pipe dosed with particulate aluminum flaws of known size showed that resistance to stress rupture increased significantly after removal of larger stress raising particles by melt filtration [164]. 

OCEAN THERMAL ENERGY CONVERSION (OTEC). Utilization of ocean temperature differentials between solar-heated surface water and cold deep water as a source of electric power. In tropical areas such differences amount to 35-40°F. A pilot installation now operating near Hawaii utilizes a closed ammonia cycle as a working fluid, highly efficient titanium heat exchangers, and a polyethylene pipe 2000 feet long and 22 inches inside diameter to handle the huge volume of cold water required. Alternate uses for such a system, such as electrolysis of water,... 

Fig. 8 Stress versus time to failure diagram of internally pressurized HD- and MD-polyethylene pipes three failure modes are indicated. The circumferential stress a is calculated according to the standard formula o =p(d -s)/2s (with p internal pressure, d pipe diameter, s pipe wall thickness)...

As a representative example, three of the failure modes of internally pressurized polyethylene pipes are indicated in Fig. 8 in the plot of circumferential stress <7f versus time to failure ff. (Not shown is the regime of brittle fracture by unstable crack propagation, since it only occurs at much lower temperatures and frequently requires a special crack initiation procedure). 

FT-IR spectroscopy has been used in the investigation of welding crosslinked polyethylene pipes [23]. Three types of crosslinking systems were used namely, peroxide (PEXa), silane (PEXb) and electron beam (PEXc). Scholten and co-workers [23] observed that only PEXa pipes have a satisfactory electrofusion quality. The strength of electrofusion welds of PEXb and PEXc pipes is not acceptable. The most likely explanation for the differences in weld quality is related to the adhesion theory and more specifically to differences in composition. Figure 5.6 shows the infrared spectra of medium density polyethylene (MDPE), PEXa, PEXb and PEXc. 

Anselme, C., Nguyen, K., Bruchet, A., and Mallevialle, J. (1985). Can polyethylene pipes impart odors in drinking-water. Environ. Technol. Lett. 6,477-488. 

Standard specification for polyethylene pipe and fitting materials... 

Drainage Products Polyethylene Pipes Geotextiles Lubricants... 

Pinter G, Lang RW (2001) Fracture mechanics characterisation of effects of stabilisers on creep crack growth in polyethylene pipes. Plast Rubber Compos 30(2) 94-100... 

The equilibrium sorption and diffusion coefficient were determined for toluene and tetrahydrofuran in oriented linear polyethylene pipe produced by hydrostatic extrusion The results, which are summarised in Table 4, show that the sorption is about a factor of ten less than that for isotropic material, and the diffusion coefficients are a factor of a hundred less. It is clear from these results, taken in conjunction with those for gases discussed above, that the improvements in barrier properties increase with molecular size. This can be attributed to the increased difficulty of penetrating the structure as the molecular size increases. 

Fig. 2 presents the analysis based on OIT data and the linear extrapolation of these data to longer times. The time to reach depletion of the antioxidant system can thus be predicted even after relatively short testing times (see insert figure in Fig. 2). Data by Hassinen et al. (//) for the antioxidant concentration profiles taken from high-density polyethylene pipes exposed to chlorinated water (3 ppm chlorine) at different temperatures between 25 and 105°C followed the Arrhenius equation with an activation energy of 85 kJ mol (0-0.1 mm beneath inner wall surface) and 80 kJ mol (0.35-0.45 mm beneath the inner wall surface). It is thus possible to make predictions about the time for antioxidant depletion at service temperatures (20-40°C) by extrapolation of high temperature data. However, there is currently not a sufficient set of data to reveal the kinetics of polymer degradation and crack growth that would allow reliable extrapolation to room temperature.

Cross-Linking. A thermoset system is produced when a polymer is cross-linked under static conditions, as in a compression mold. This is the basis of the production of vulcanized articles or cross-linked polyethylene pipe and wire insulation. If the same polymer is lightly cross-linked while it is being sheared in the molten state, however, it will remain thermoplastic. If it is more heavily cross-linked during this process, the final product may contain significant quantities of gel particles, but the whole mass will still be tractable. 

Standard Test Method for Notch Tensile Test to Measure the Resistance to Slow Crack Growth of Polyethylene Pipes arui Resins, ASTM F1473-01. 

Rapid crack propagation, dynamic fracture toughness, crack arrest, polyethylene pipes, pressure vessels... 

Kanninen, M.F., et al., (1997). Design and Technical R erence to Mitigate Rapid Crack Propagation in Polyethylene Pipes for Gas Distribution. Southwest Research Institute Final Report (Contract 5088-271-1822) to the Gas Research Institute. 

Packed tower studies were made with a borosilicate glass column 4 inches in inside diameter packed with /4-inch ceramic Intalox saddles. The feed was metered through a rotameter from a constant-head tank, and distributed through the tower with a perforated aluminum plate. Aluminum tubing and polyethylene pipe were used to connect the ozone generator to the tower. A continuous sample was withdrawn from the tower bottom for analysis, and exit gas from the top of the tower was conducted to a wet-test meter for volume measurements. Ozone was absorbed in 5% potassium iodide solutions and titrated with thiosulfate to a starch end point. 

Aldyl [Du Pont], TM for high-strength polyethylene pipe composed principally of Ala-thon. ... 

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