Chapter 19 - Line Sizing

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19.2    CODE FORMULA FOR WALL THICKNESS
Codes B31.1 and B31.3 have a different approach to calculation of pipe wall thickness as shown below.

B31.1 Power Piping Code
104.1.2  MINIMUM WALL THICKNESS
(Refs: 104.1.2 (A)
Straight Pipe Under Internal Pressure – Seamless, Longitudinal Welded or Spiral Welded and Operating Below the Creep Range.   
(A)     Minimum Wall Thickness.
The minimum thickness of pipe wall required for design pressures and for temperatures `not exceeding those for the various materials listed in the Allowable Stress Tables, including allowances for mechanical strength, shall not be less than that determined by eq. (3) or (4), as follows:


Where
tm=     minimum wall thickness - in. (mm.)
P =     internal design pressure - psig. (kPa.)   
Do=    outside diameter of pipe as given in tables of standards and specifications - in. (mm.)
d =     inside diameter of pipe. - in. (mm.). For pressure design calculation, the inside diameter of the pipe is the maximum value allowable under the purchase specification.
SE =    maximum allowable stress for material and joint efficiency at the design temperature – psi. (kPa.)
A=    additional thickness to provide for threading, grooving, corrosion, erosion, mechanical strength, etc. – in. (mm.)
y =     coefficient given in Table 104.1.2(A)

19.4    FRICTION LOSS CALCULATIONS FOR WATER
PIPE SIZING (Calculating Pipe Diameter)
The criteria in determining the bore of a pipe is the ‘amount of fluid’ required to flow through it in a specified period of ‘time’.  i.e. volumetric flow or mass flow
The units are as follows:
Water or Liquids        LPM (litres per minute) or GPM (gallons per minute)
Steam                         kg /hr (kilogram per hour) or lb/hr (pounds per hour)
Gases                          m3/hr (cubic meters per hour) or ft 3/hr (cubic feet/hr)
Velocity                       m/s (meters per second) or ft/sec (feet per second)

 

Above is an excerpt from the chapters of the book: Detail Engineering and Layout of Piping Systems 5th Edition.
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