Fittings, pipes

Pipe runs are normally made up from lengths of pipe, incorporating standard fittings for joints, bends and tees. Joints are usually welded but small sizes may be screwed. Flanged joints are used where this is a more convenient method of assembly, or if the joint will have to be frequently broken for maintenance. Flanged joints are normally used for the final connection to the process equipment, valves and ancillary equipment. 

Details of the standard pipe fittings, welded, screwed and flanged, can be found in manufacturer s catalogues and in the appropriate national standards. The standards for metal pipes and fittings are discussed by Masek (1968). 

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Practical applications of the presented algorithm has been done on corrosion monitoring in the pipe system of a power plant. These examples were obtained from a reducing pipe fitting after... 

Fig. 5 Erosion pit inside a reducing pipe fitting, projection technique at 160 kV, profile plot with optical densities of the digitised film. The varying background caused by the geometrical set-up prevents a wall thickness calibration as in fig. 4...

The flow resistance of pipe fittings (elbows, tees, etc) and valves is expressed in terms of either an equivalent length of straight pipe or velocity head loss (head loss = Kv /2g ). Most handbooks and manufacturers pubHcations dealing with fluid flow incorporate either tables of equivalent lengths for fittings and valves or K values for velocity head loss. Inasmuch as the velocity in the equipment is generally much lower than in the pipe, a pressure loss equal to at least one velocity head occurs when the fluid is accelerated to the pipe velocity. 

The selection and appHcation of an expansion joint is not as simple as selecting a pipe fitting or a valve and requires a sound understanding of the joint s capabihties and limitations. Improper appHcation of any type of joint can result in serious or damaging effects. However, when properly selected and integrated into the piping system, satisfactory service and safe operation can be expected. Selection and appHcation of beUows expansion joints require special attention to design and installation. 

Glass Plants Components Process Pipe Fitting HardirarefJoining and Adaption, Coming QVE Pipe, QVE Coming, New York, 1989 to 1992. 

Technical data, "Graylock Pipe Fittings and Coimectors," Gray Tool Co., 1995. 

Pipe fittings require quite high tensile and creep resistance they are thus molded from compounds that have less melt flow than for thin-waHed housings. Plasticized compounds are injection-molded into a variety of parts requiring elastomeric properties. 

Impervious graphite centrifugal pumps, pipe fittings, and valves were developed because most chemical processes require the movement of Hquids. Graphite pipe and fittings in sizes ranging from 25 to 635 mm ID are used to convey corrosive fluids. 

Many developers of software for finite-element analysis (18) provide drafting of pipelines and associated flow analysis. These companies include Algor, McAuto, MacNeal-Schwindler, and ElowDesign. In software, in-house developed pipe fittings are modularized and isometric views of the piping systems with three-dimensional detailing are now commonplace. 

For normal velocity distribution in straight circular pipes at locations preceded by runs of at least 50 diameters without pipe fittings or other obstructions, the graph in Fig. 10-7 shows the ratio of mean velocity V to velocity at the center plotted against the Reynolds number, where D = inside pipe diameter, p = flmd density, and [L = fluid viscosity, all in consistent units. Mean velocity is readily determined from this graph and a pitot reading at the center of the pipe if the quantity Du p/ I is less than 2000 or greater than 5000. The method is unreliable at intermediate values of the Reynolds number. 

TABLE 10-5 Locations of Orifices and Nozzles Relative to Pipe Fittings... 

Other Types of Piping Joints Packed-gland joints (Fig. 10-135) require no special end preparation of pipe but do reqmre careful control of the diameter of the pipe. Thus the suppher of the pipe shoiild be notified when packed-gland joints are to be used. Cast- and ductile-iron pipe, fittings, and valves are available with the bell cast on one or... 

Push -on joints (Fig. 10-137) require diametral control of the end of the pipe. They are used for brittle materials. Pipe, fittings, and valves are furnished with the bells cast on one or more ends. Considerable force is required to push the spigot through the O ring this is reduced by the extension on the O ring, which causes the friction of the pipe to elongate the cross sec tion of the main portion of the O ring. 

The coefficient of linear expansion of these alloys in the temperature range of 21 to 100°C (70 to 212°F) is 12.2 X lO C (6.8 X 10"V°F), which is slightly above that of cast iron (National Bureau of Standards). Since these loys have practically no elasticity, it is necessary to use expansion joints in relatively short pipe hnes. Connections for flanged pipe, fittings, valves, and pumps are made to 125-lb American Standarci drilling. 

Chemical-Porcelain Pipe Made of dense, nonporous material and fired at 1230°C (2250°F), chemical-porcelain pipe, fittings, and valves are inert to all acids except hydrofluoric but are not usually recommended for alkalies. Surfaces, except when ground for gasketing, are usually glazed for easy cleaning. Working pressures of 0.3 to 0.7 MPa (50 to 100 Ibftin") are recommended for valves and piping. Temperatures of 200°C (400°F) or more can be used, but sudden thermal shocks must be avoided. 

Provide operator training and administrative controls (No standing on pipes/fitting, holding of piping/tubing etc.)... 

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