Pipes high-density polyethylene

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]. 

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.

Permacore [Phillips], TM for high-density polyethylene pipe. 

On cooling, plastic materials tend to contract or shrink considerably more than other materials such as metals, ceramics and glass. For example, a copper pipe will shrink by 0.01% if the temperature is reduced by 10°C. Under the same conditions, a high-density polyethylene pipe would shrink by 0.07%, and polypropylene and hard PVC pipes by 0.04%. In addition, surfaces of plastic materials cool before their cores. Such a situation leads to the initial contraction of plastic materials at surfaces, before significant change in dimension occurs in the bulk. The skins of moulded plastics tend to be stiffer than the bulk, so are more prone to degradation by mechanical action, e.g. flexing. 

Some trouble was also experienced with the welds of 8-inch diameter high-density polyethylene pipe, which was later replaced by rubber-lined mild steel, or acrylonitrile-butadiene copolymers. The latter was used for all the smaller diameter piping, but was not available in the larger sizes (8-inch diameter and above), when the plant was being built. 

Figure 16.10 TGA thermal curves showing the decomposition temperatures of some common polymers PVC, polyvinylchloride PMMA, pol3miethylmethacrylate HOPE, high-density polyethylene PIPE, polytetrafluoroethylene PI, polyimide. (Courtesy of TA Instmments, New Castle, DE, www.tainst.com.)...

High-density polyethylene pipe systems meeting the challenges of the 21th century. Plastics Pipe Institutes, www.plasticpipe.org... 

The tailings from a small mine are pumped at a weight concentration of 40%. They consist of crushed rock at a specific gravity of 3.2. The c/gs of the particles is 1mm. For a flow rate of 280 m /hr, a smooth high-density polyethylene pipe with an internal diameter of 138 mm is selected. Using Newitt s method as expressed By equations 4.27 and 4.29, determine the head loss due to the presence of solids, assuming a dynamic viscosity of 1.8 cP. 

The pH of solutions from the solvent-extraction process is typically low, generally 1-2. Conventional carbon steel pipes may be inferior to high-density polyethylene pipes in resisting combined erosion and corrosion. 

For applications up to 1400 kPa (200 psi), high-density polyethylene pipes are available for a number of low to medium abrasive slurries. 

Creep failures such as those illustrated in Fig. 11.12 are often called static fatigue and are not uncommon in practical applications such as pressurized piping applications. Kinloch and Young (1983) gives data on the creep rupture of high-density polyethylene pipe (HDPE) and an excellent discussion of the mechanisms associated with static fatigue. 

High density polyethylene pipes and fittings - Chemical resistance with respect to fluids to be conveyed. ISO/TR 7471... 

U.W. Gedde, B. Tersehus and J-F Jansson, Polymer Testing 2, A Survey of Methods for the Detection of Thermal Oxidation in High-Density Polyethylene Pipes , 211-222,1981. 

High density polyethylene is widely used for pipes and drains, especially in large-diameter cormgated forms. The cormgations provide stronger walls at less thickness, which reduces the materials cost of the pipe. 

Recently, sheets of high density polyethylene extruded on to the pipe surface over an adhesive have become available and the use of polyethylene or epoxy powders sintered on to the steel surface is becoming more frequent. 

Figure 14.1 presents the main components of a typical in situ SVE system.910 Vertical extraction wells are installed inside the contaminated zone at appropriate distances from one another. The SVE wells are typically constructed of PVC pipe, with a screened interval, which is placed within the contaminated zone. The wells are connected to blowers or vacuum pumps, which induce a continuous airflow through the pores of the unsaturated zone. The soil surface is sometimes covered with an impermeable seal, made from high density polyethylene (HDPE) or bentonite clay for example, to prevent the vertical influx of air from the surface, which might cause short-circuiting problems, and promote horizontal gas flow through the contaminated area. The airstream, which contains the contaminant vapors, passes initially through an air-water separation unit to remove the entrained moisture and is then directed to the gas treatment unit, where the contaminants are thermally destroyed or removed by adsorption. 

What characteristics of high density polyethylene make it suitable for the manufacture of rigid pipe What limitations would there be in the use of this pipe ... 

The development of medium and high density polyethylene pressure pipes over the last thirty years has led to an extensive database on their stress-rupture behaviour, with associated standards for their testing and the interpretation of results [1, 2], Various forms of PVC are also used. The accelerated testing of gas and water pipes is introduced as an example of a field where there is a large database of pressure testing on which current regulations are based, the number of polymers is limited and accelerated tests are widely used (unusually, with two accelerating parameters). 

ISO 8772 1991 High-density polyethylene (PE-HD) pipes and fittings for buried drainage and sewerage systems - Specifications... 

Crystallinity. Is one of the key factors influencing properties. You can think of crystallinity in terms of how well a polymer fits in an imaginary pipe, as in Figure 22-6. Linear, straight chains are highly crystalline and fit very well. Bulky groups, coiled chains, and branched chains are not able to line up to fit in the pipe. They are amorphous, the opposite of crystalline. In a spectrum from totally amorphous, to almost totally crystalline, there is methyl methacrylate, polypropylene, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and nylon. 

Focusing collectors are usually cast acrylic Fresnel lenses, or mirrors of aluminized polyester film in frames of aluminum. These reflectors are either enclosed in a bubble of poly(vinyl fluoride) film, or under polycarbonate glazing, which may be covered with a fluorocarbon film to reduce the reflectivity. The absorbers for active systems are copper or aluminum since the temperatures are too high (325—370°C) for plastics. The frames, however, can be molded ABS, high density polyethylene or polyurethane, either solid or structural foam. Polybutylene or chlorinated PVC can be used for piping hot water, and tanks can be made of either reinforced polyester or blow- or rotational-molded, high density polyethylene (12—15). 

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