Design pipe, thin wall

Shield, R, T., and D. C. Drucker, Design of Thin-Walled Torispherical and Toriconical Pressure-Vessel Heads in Pressure Vessels and Piping Design and Analysis—A Decade of Progress, American Society of Mechanical Engineers, 1972,... 

Stainless steels Thin-walled stainless steel (Fe-18Cr-8Ni) tubes are now frequently used for domestic installations in place of copper pipe . Care is required, however, in the design of stainless steel equipment for use in waters with a high chloride content, or where the concentration can increase, since pitting attack may occur. It may also be susceptible to failure by stress-corrosion cracking under certain conditions. 

A common pressure vessel application for pipe is with internal pressure. In selecting the wall thickness of the tube, it is convenient to use the usual engineered thin-wall-tube hoop-stress equation (top view of Fig. 4-1). It is useful in determining an approximate wall thickness, even when condition (t < d/10) is not met. After the thin-wall stress equation is applied, the thick-wall stress equation given in Fig. 4-1 (bottom view) can be used to verify the design (Appendix A PLASTICS DESIGN TOOLBOX). 

Sink traps of resistant plastic are now well accepted. They are easy to install and also easy to clean. Drains of glass pipe are sometimes seen in special installations. Some laboratories install regular thin-walled sink traps designed for kitchen use. The author s experience with them, even in the home, has been poor. 

The bulk density of the feedstock at ambient temperature and pressure should be measured prior to the design of a new screw, especially if it contains in-plant recycle resin. The measurement method is extremely simple and requires only a calibrated cell and a scale. A calibrated measuring cell with a volume of 500 cm can easily be constructed by welding a thin-walled metal pipe to a flat sheet of metal, as shown in Fig. 4.2. The bulk density is measured by filling the cell with feedstock, leveling the top with a steel ruler, and then weighing the cell contents. A more formal measurement technique was developed by ASTM as standard method D1895. 

The usual design procedure is to couple a specific value of design stress with a conventional stress or strain analysis of the assumed structural idealisation. The uniaxial deformation behaviour is of special importance in thin-walled pipes, circular tanks and comparable systems under simple stress. 

As noted above, externally wound tubular membrane elements are fabricated primarily of extruded ABS tubing (natural), cellu-loslc or blend membranes and dacron paper. The cartridge assembly designed to house the membrane elements and provide for the uniform dlstrlbutlon/flow of feed stock is fabricated of extruded thin walled polystyrene headers. Pressure vessels were fabricated either by using epoxy coated steel pipe or fiberglass vessels. 

Ultrasonic monitoring shows thin walls for pipes, internals or vessels faulty ultrasonic instrument/[corrosion] /faulty design. Failure of supports, internals, vessels" [corrosion] /faulty design/unexpected stress or load. 

Treating it as a pressurised thin-walled tube, determine the minimum wall thickness d for an MDPE pipe to meet the specification diameter 104 mm design pressure rating - 400... 

Figure 3-61. Variables involved in pipe-design problems. The upper-left drawing is used to analyze problems involved in spacing pipe supports the lower drawing deals with designing thin-wall tubing to contain an internal pressure the drawing at the right covers the analysis of heavy wall piping under pressure.

The reactor vessel is constructed of 2 % Cr-1% Mo steel, 2 inches thick, designed for a temperature of 1150°F and maximum pressure of 120 psi. Three 28-in.-diameter pipes carry the fluid into the reactor at the bottom and leave at the top. The entire reactor vessel is doubly contained by a relatively thin-walled containment vessel. A drain line to the fuel dump tanks is also provided. The free space above the reactor core is used as the degasser to remove volatile fission products. The reference core design has the following specifications ... 

The procedure described above is straightforward in principle. However, in practice, great care must be taken in the test fixture design to assnre that applied loads cause a uniform state of stress in the test specimen. Two types of tests that have been developed for this purpose include (1) the simple tensile test for uniaxial states of stress, (2) the thin-walled tube subjected to combined torsion and internal pressure, for biaxial states of stress. Some theoretical aspects of the simple tensile test are developed in the sample problem which follows. For a more detailed discussion on experimental procedures for characterizing the material properties of composite materials, see Caisson and Pipes and Whitney et al. ... 

The pressure tensile hoop stress in a cylinder is given by Equation 7.31 as a = PD/2t, where P = pressure, D = diameter, t = thickness, and D t. Thus, for a thin wall pipe, a S> . For the pipe, an FOM, which is related to design pressure, can be found. 

Pipe-Wall Thickness. Once the design pressure and temperature have been established and the pipe material and size selected, the wall thickness is calculated using the appropriate section of the code. In rare cases, a thin pipe must be made thicker to withstand handling. Occasionally the thickness is affected by external loads or vibrations. All codes prescribe essentially the same design formula for metallic hoUow circular cylinders under internal pressure ... 

One report stated thickness measurement a short distance away from the rupture showed the line was a nearly full design thickness. Investigators concluded the line failure was the result of the thinning of the Schedule 120 carbon steel 90-degree elbow due to long-term erosion/corrosion. [21] Another story stated the piping was originally or nominally 0.625 inches thick, but had worn down to 0.085 inches. [27] That represents an 86-percent wall loss. 

These dimensions would allow the vessel to be fabricated from a piece of available steel pipe (or tubing), and so be relatively inexpensive. Recall that piping is sized by external diameter tubing is sized by internal diameter (Chapter 2, Endnote FF). Wall thickness of each is identified by a "schedule number." Since the adsorber bed does not have to be an ASME code pressure vessel (because the design pressure and temperature are very low), the wall thickness (calculated by Equations 2.3 and 2.4) can be quite thin. Also, code welding of end caps is not required (Chapter 2, Endnotes V and W). Pipe of the appropriate diameter and any schedule number can be used. Matching the exact numerical value of LTD noted above is not required. 

Different design scenarios that were considered in this smdy are presented in Table 11.3. The erosion/defect was assumed to be circumferential with a constant circumferential depth and the wall thinning was considered in the range of 30—80% in increments of 10%. The maximum allowable internal pressure for the corroded pipe was calculated based on ASME B31.4 considering the remaining wall thickness of the pipe. In the study, the live pressure varied from 0 to 100% of the maximum allowable live pressure in steps of 25%. The minimum laminate thickness for each repair situation was calculated using Eqn (11.1) (based on ISO 24,817 and ASME PCC-2) and Eqn (11.10), as given in Table 11.3. 

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