Pipes material comparison

The analysis represents a way for pipeline designers and planners to view the relative value of their decisions on pipe material types and pipe sizing. The numerical values in Table 2.3 are given for example only. They have been drawn from various sources at various times and are therefore not intended for current commercial comparisons. Potential purchasers should therefore obtain up-to-date prices directly from sales organisations to conduct their own detailed cost studies. 

GFRP pipes have anisotropic properties these properties are a function of the fiber orientation and the lay-up sequence used to form the pipe. In comparison to isotropic metals, this aspect makes the design somewhat more complex, thus requiring not only a comprehensive understanding of the basic mechanics of the materials, but also an understanding of the intricacies involved in the fabrication methods and chemistry of the materials (e.g., the role of various chemicals in the curing process, etc.). 

Coetzee (1990) determined that one-third of the loss of pipeline wall thickness associ ated with pumping mine water is due to corrosion because mine water is often acidic. Since corrosion is an important contributor to wear of backfilled pipes, it became evident that lining the pipes was necessary. To compare piping materials, tests were conducted by Steward (1996) and indicated that a polyurethane rubber at a Shore hardness 55 Shore A provided the best pipeline protection in a test with slurry pumped at a speed of 3 m/s. By comparison, ASTM steel 106 grade B wore seven times faster than polyurethane 82 Shore A, or high-density polyethylene. 

The r values from Eq. (5-1) for the most important materials for pipe coatings are given in Table 5-1. Table 5-2 contains results of long-term field experiments. For comparison, the values of r°are included in Table 5-1. It can be seen that values are always smaller than r values, which is apparently due to the absorption of water when the coating is immersed in the medium. A marked reduction in the coating resistance has been observed with increasing temperature for resins [9,13,14] (see Fig. 5-2 [14]). 

In order to carry out a cost comparison of cathodic protection with the prolongation of service life of pipelines that it provides, the construction costs and the material costs of the pipeline have to be known. If there are no particular difficulties (e.g., having to lay the pipe in heavily built-up areas, river crossings, or rocky soil), the construction costs for a high-pressure DN 600 pipeline are about 10 DM km". If it is simply assumed that a pipeline has a useful life of 25 years without cathodic protection whereas with cathodic protection it has a life of at least 50 years, the... 

The gas-pipeline construction costs in 1983 showed a 1.05% increase for the composite gas pipeline cost index. Even though some of the materials (pipes, valves, and fittings, etc.) were discounted, some other costs such as labor, construction machinery and equipment increased and hence the total pipeline construction cost index showed an increase. Bigger pipelines (10—36 in.) contributed to most of the gas transportation in the United States. A comparison of costs of construction for land and offshore pipelines indicated that the offshore construction is three times as expensive as onshore projects. An annual cost index (Al) of 200 was published for the year 1983 for pipeline installation and an AI of 203 for compressor equipment and drive units in the compressor stations. The high pressure gas pipeline cost index in 1983 was the same as the previous year. 

Fig. 6.5-17 Mobile hay collection equipment with high pressure ram press [6.5.2.3]. The cylindrical compacts are transferred into an open car by pushing them through the transport pipe on top of the machine Fig. 6.5-18 Comparison of volume of compacts (left) produced with the equipment shown in Fig. 6.5-17 and a conventional bale (right) from the same material [6.5.2.3]...

The scattering of field results can be explained by the variety of situations encountered in actual plumbing systems (diameters and lengths of copper pipes, age, other materials in the plumbing system, etc.). However this comparison indicates that in this case (CRECEP tap water, copper, V2-hour stagnation samples), the pipe-rig experiments are representative of aetual contamination levels. 

Elastic PVC articles are inferior in comparison to vulcanized rubbers used for production of corrugated pipe articles regarding their tensile and tear strengths, and deterioration of their flexibility with time of use. This was improved by multilayer material. Three layered material gave the best performance. The outer layer was made out of polyester elastomer (Pelprene P-70B), the inner layer from polyester elastomer (Hytrel HTG-4275), and the intermediate layer from PVC having formulation given in the above table. 

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