Composite pipes fittings

Whilst carbon and stainless steels are commonly used materials of construction, increasing use is being made of non-metallic and rubber lined equipment. The selection of the material of construction should take into account the cases of the worst process conditions that may occur under foreseeable conditions and should be applied to all components including valves, pipe fittings, instruments and gauges. Both composition (e.g., chlorides, moisture) and temperature deviations can have a significant direct effect on the rate of corrosion. The operator should demonstrate that procedures are in place to ensure that potential deviations in process conditions such as fluid temperature, pressure and composition are identified and assessed in relation to the selection of materials of construction for piping systems. 

Type 304 and 316 stainless steel are used in the high-pressure pipes and pipe fittings in RO plants. The 300 series SS are also sensitive to chlorides at a pH of 6.5—8 and at temperatures below 60°C. Type 316 SS tolerates chlorides up to 1000 ppm, but concentrations can reach 26,000 ppm in dry zones (for MgCl2), resulting in failure. In seawater RO desahnation plants, duplex (2205) or super-duplex (2507) steels are used instead of 316 SS. The compositions of these steels are detailed below [25] ... 

Figure 13.5 These PPSF hot water fittings, designed by Wavin for use with cross-hnked polyethylene-aluminum-cross-linked polyethylene composite pipe, are used in both household plumbing and radiator heating...

D 1939 RESIDUAL STRESS BY GLACIAL ACETIC ACID IMRSN D 2105 LONGITUDINAL TENSILE OF REINFORCED PIPE D 2115 OVEN HEAT STABILITY OF PVC COMPOSITIONS D 2122 DIMENSIONS OF THERMOPLASTIC PIPE FITTINGS D 2124 PVC ANALYSIS BY FTIR... 

More recently, attempts have been made to correlate mathematically the chemical composition of natural waters and their aggressivity to iron by direct measurements on corrosion coupons or pipe samples removed from distribution systemsThis work has been of limited success, either producing a mathematical best fit only for the particular data set examined or very general trends. The particular interest to the water supply industry of the corrosivity of natural waters to cast iron has led to the development of a simple corrosion rig for the direct measurement of corrosion ratesThe results obtained using this rig has suggested an aggressivity classification of waters by source type i.e. 

Fresh water. Aluminum and its alloys are not prone to corrosion on exposure to distilled water up to 180°C. Thus storage tanks, piping and fittings of the alloy can be used for handling distilled water. The composition of natural fresh water is variable. In spite of this restriction, the alloys are not attacked, even at 180°C in natural waters. It should be noted that pitting may occur when a small thickness of the sample is exposed. In this case Alclad 3003 is recommended for use to avoid failure due to pitting. 

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. 

Sit-and-soak tests have been earned out with BS 7766 standard test water and with laboratory tap waters (composition of waters given in Table 4.3). Pipe rig experiments have been carried out with laboratory tap waters, and four materials have been tested copper, brass (eopper with brass fittings for pipe rigs), galvanized steel, and stainless steel. 

In view of the above efforts, it is surprising that the majority of recent patents on adhesives are for solvent-based systems.The new inventions include a universal primer, an adhesive composition in which solvents have been selected based on Snyder s polarity (only solvents which belong to group III are useful in adhesive for automotive applications to avoid a deleterious effect on paint), a low VOC adhesive for pipes and fittings, a solvent-containing heat-resistant adhesive based on siloxane polyimide, a water-based polyimide adhesive,and two-component solvent-free polyurethane adhesive system for use in automotive door paneling. ... 

Experiments studying the corrosion behaviour of pipes and pipe connections made of the steel 1.4301 (SAE 304 UNS S30400) were carried out in cold drinking water in field tests lasting five years [34]. Table 20 contains data for pipes in various heat treatment states. The pipe connections were made of the same material as the pipes. Pressed fittings with a non-metallic seal and solder fittings were tested. The chemical composition of the solders used is shown in Table 21. 

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