Wall Thickness Calculation of Straight Pipes Under Internal Pressure
 
  Calculation as per par. 304.1 Pressure Design of Components by ASME B31.3 for t < D/6
                   
  (Enter values in yellow cells for calculations and in blue cells as information)
  DATA INPUT
                   
   External Diameter,  D =  mm Material =  
                   
  Internal design pressure (gauge), P =  barg Design temperature =  ᵒC
                   
   Quality factor, E =   Allow. stress @ design temp., S  =  MPa
  See table A-1B     See table A-1M    
  Allow. for corrosion, c =  mm  Stress reduction factor, W =  
        See table 302.3.5    
  Select T̅ until T ≥ tm  mm Coefficient, Y =  
  from ASME B36.10M or B36.19M     See table 304.1.1    
                   
                   
  CALCULATIONS
                   
   Wall thickness for design pressure, t =    mm     t = PD  
          2(SEW+PY)  
                   
    Minimum wall thickness required, tm =    mm     tm = t + c eq. 2 as per par. 304.1.1
         
                   
  Especified  minimum wall thickness, T  =    mm   T = T̅(1.00 – 0.125) = T̅(0.875)  
  Considering a mill tolerance of 12.5%        
                   
  Nom. pipe wall thickness T̅ =    mm   If T ≥ tm the selection of nominal pipe wall
           thickness T̅ is accepted. 
                   
     Check for applicability  
  D/6 =       P/(S*E) =  
   t < D/6       P/(S*E) ≤ 0.385   
                   
                 
  Wall Thickness Calculation of Straight Pipes Under Internal Pressure
 
  Calculation as per par. 304.1 Pressure Design of Components by ASME B31.3 for t < D/6
     
  (Enter values in yellow cells for calculations and in blue cells as information)
  DATA INPUT
                   
   External Diameter,  D =  in. Material =  
                   
  Internal design pressure (gauge), P =   psig Design temperature =  ᵒF
                   
   Quality factor, E =   Allow. stress @ design temp., S  =   psi
  See table A-1B     See table A-1    
  Allow. for corrosion, c =  in.  Stress reduction factor, W =  
        See table 302.3.5    
  Select T̅ until T ≥ tm   in. Coefficient, Y =  
  from ASME B36.10M or B36.19M     See table 304.1.1    
                   
                   
  CALCULATIONS
                   
  Wall thickness for design pressure, t =     in.     t = PD   eq. 3a as per par. 304.1.2
          2(SEW+PY)  
                   
  Minimum wall thickness required, tm =       in.     tm = t + c eq. 2 as per par. 304.1.1
         
                   
  Especified  minimum wall thickness, T  =       in.   T = T̅(1.00 – 0.125) = T̅(0.875)  
  Considering a mill tolerance of 12.5%        
                   
  Nom. pipe wall thickness T̅ =    in.   If T ≥ tm the selection of nominal pipe wall
           thickness T̅ is accepted. 
                   
     Check for applicability  
D/6 =
P/(S*E) =
   t < D/6       P/(S*E) ≤ 0.385   
                   
       
               
    Discussion and References
      Information about Wall thickness calculation of straight pipes under internal pressure:
      ASME B31.3 Process Piping, para. 304.1
    Tables and Standards
  -  Table A-1 Basic Allowable Stresses in Tension for Metals
  -  Table A-1B Basic Quality Factors for Longitudinal Weld Joints in Pipes and Tubes
  -  Table 304.1.1 Values of Coefficient Y for t < D/6 
  -  Table 302.3.5 Weld Joint Strength Reduction Factor, W 
  -  ASME B36.10M-Welded and Seamless Wrought Steel Pipe
  -  ASME B36.19M-Stainless Steel Pipe
  -  Mill Tolerance = 12.5%
    Equations for Wall thickness calculation of straight pipes under internal pressure (304.1):
    For t < D/6, the thickness should be calculated by the equation:
      t = PD   (eq. 3a as per par. 304.1.2)  
    2(SEW+PY)    
               
  tm = t + c (eq. 2 as per par. 304.1.1))
               
    Select T̅ from ASME B36.10M or B36.19M
    Mill Tolerance = 12.5%. (See ASTM Standards & appendix S of ASME B31.3)
      T = T̅(1.00 – 0.125) = T̅(0.875)    
       
    If T ≥ tm the selection of nominal pipe wall thickness T̅ is accepted. 
    The parameters in the wall thickness calculation of straight pipes under internal pressure
    equations above are:        
     T̅  = Nominal pipe wall thickness, in. from ASME B36.10M or B36.19M
     T = Minimum thickness considering a mill tolerance of 12.5%, in. (mm)
     tm = Minimum thickness required, in. (mm)
     t = Thickness for design pressure, in. (mm)
     c = Sum of allowance for corrosion, erosion, slots and threads, in. (mm)
     P = Internal design pressure, psig (barg)
     D = External diameter, in. (mm)
     E = Quality factor (table A-1B) of ASME B31.3
     S = Allowable stress at the design temperature, psi (table A-1 or A-1M) of ASME B.31.3.
     Y = Coefficient that depends on the material and design temperature (table 304.1.1) of ASME B31.3.
     W = Stress reduction factor of welded joint, paragraph 302.3.5(e) and table 302.3.5 of ASME B31.3