Wall thickness pipe schedule

The pipe wall thickness is selected to resist the internal pressure, with an allowance for corrosion. Processes pipes can normally be considered as thin cylinders only high-pressure pipes, such as high-pressure steam lines, are likely to be classified as thick cylinders and must be given special consideration (see Chapter 13). 

The British Standard 5500 gives the following formula for pipe thickness  

Pipes are often specified by a schedule number (based on the thin cylinder formula). The schedule number is defined by  

Schedule 40 pipe is commonly used for general purposes. 

Full details of the preferred dimensions for pipes can be found in the appropriate Handbook and Standards. The main United Kingdom code for pipes and piping systems is the British Standard is BS 1600. 

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MECHANICAL DESIGN OF PIPING SYSTEMS 5.5.1. Wall thickness pipe schedule... 

The most common schedule in use is 40, and it is useful for a wide range of pressures defined by ANSI Std. B 36.1 (American National Standards). Lighter wall thickness pipe would be designated Schedules 10, 20, or 30 whereas, heavier wall pipe would be Schedules 60, 80, 100, 120, 140, 160 (see Appendix Table). Not all schedules are in common use, because after Schedule 40, the Schedule 80 is usually sufficient to handle most pressure situations. The process engineer must check this schedule for both pressure and corrosion to be certain there is sufficient metal wall thickness. 

For pipe sizes NFS 8 and larger and for wall thicknesses of Schedule 140 or heavier, the minimum specification tensile strength is 483 MPa (70.0 Idp/in ). 

From the data given in App. A.3 on the diameter and wall thickness of schedule 40 pipes, show that these roughly correspond to the formula... 

Nominal pipe size, in Outside diameter, in Schedule no. Wall thickness, in Inside diameter, in Cross-sectional area Circumference, ft, or surface, fF/ft of length Capacity at 1-ft/s velocity Weight of plain-end pipe, Ih/ft... 

The wall thickness selected varies with the service and material. Carbon steel coils are often made from schedule 80 or heavier pipe to allow for corrosion. When stainless-steel or other high-aUoy coils are not subject to corrosion or excessive pressure, they mav be of schedule 5 or 10 pipe to keep costs at a minimum, altliougli high-quahty welding is required for these thin walls to assure trouble-free seiwice. 

For example, for 3-in. nominal carbon steel pipe, the Schedule 40 wall thickness is 0.216 in. If the pressure required in the system, needs 0.200 in. wall and... 

Pipe diameters are rounded up to the next standard size, and proper wall thickness (schedule) is determined consistent with the operating pressure of that portion of the system. For the rate factor, see Figure 13-15. 

It is important to note that the IDs of all pipes of the same nominal size are not equal. This is because the OD remains constant and the wall thickness increases as the schedule number increases. For example, a nominal 1-inch Schedule 40 pipe has a 1.049-inch ID. The same size Schedule 80 pipe has a 0.957-inch ID, while Schedule 160 pipe has 0.815-inch ID. In each case, the OD is 1.315-inch and the wall thickness varies. The actual wall thickness is the difference between the OD and ID divided by 2. 

Table40.7 Wall thickness schedule designation for pipe...

A pipeline constructed of carbon steel failed after 3 years operation. On examination it was found that the wall thickness had been reduced by corrosion to about half the original value. The pipeline was constructed of nominal 100 mm (4 in) schedule 40, pipe, inside diameter 102.3 mm (4.026 in), outside diameter 114.3 mm (4.5 in). Estimate the rate of corrosion in ipy and mm per year. 

The dimensionless pipe wall thickness (times 1000) is known as the Schedule number of the pipe ... 

This expression is only approximate, as it does not make any allowance for the effects of such things as pipe threads, corrosion, or wall damage. To compensate for these factors, an additional allowance is made for the wall thickness in the working definition of the schedule thickness, ts ... 

Using the actual dimensions of commercial steel pipe from Appendix F, plot the pipe wall thickness versus the pipe diameter for both Schedule 40 and Schedule 80 pipe, and fit the plot with a straight line by linear regression analysis. Rearrange your equation for the line in a form consistent with the given equation for the schedule number as a function of wall thickness and diameter ... 

Nominal pipe size (in.) Outside diameter (in.) Schedule no. Wall thickness (in.) Inside diameter (in) Metal (in.2) Flow (ft2) (ft/ft of k ngth) U.S. min lb/h water... 

A 4-in schedule 40 pipe has an outside diameter of 4.5 in, a wall thickness of 0.237 in, and an inside diameter of 4.026 in. From Table 12-3 the tensile strength SM for stainless 316 is 85,000 psi. Equation 12-4 for cylinders is used to compute the pressure necessary to rupture this pipe ... 

Standard pipe is made in a discrete number of sizes that are designated by nominal diameters in inches, as inches IPS (iron pipe size). Table A5 lists some of these sizes with dimensions in inches. Depending on the size, up to 14 different wall thicknesses are made with the same outside diameter. They are identified by schedule numbers, of which the most common is Schedule 40. Approximately,... 

The nearest commercial pipe size (Ref. T4 Table 6.6) is a nominal pipe size of 1.5, schedule number 40S (with inside diameter of 41 mm and a wall thickness of 4 mm). 

Iron and steel pipes were originally classified on the basis of wall thickness as standard, extra-strong, and double-extra-strong. Modem industrial demands for more exact specifications have made these three classifications obsolete. Pipes are now specified according to wall thickness by a standard formula for schedule number as designated by the American Standards Association. 

Pipe sizes are based on the approximate diameter and are reported as nominal pipe sizes. Although the wall thickness varies depending on the schedule number, the outside diameter of any pipe having a given nominal size is constant and independent of the schedule number. This permits the use of standard fittings and threading tools on pipes of different schedule numbers. A table showing outside diameters, inside diameters, and other dimensions for pipes of different diameters and schedule numbers is presented in the Appendix. 

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