Wall Thickness Calculation of Cylindrical Shells Under Internal Pressure
 
  ASME Section VIII Div 1 - UG 27 - Thickness of Shells Under Internal Pressure
                                   
    (Enter values in yellow cells for calculations and in blue cells as information)
  DATA INPUT
                                         
    Design Conditions     Material      
    Design Pressure, Pd =  barg Housing Material Specification    
          Housing Material Type
   
    Design Temperature, Td =  °C Allowable Stress Shell, S  = MPa  
                                         
    Long. joint efficiency (circ. stress), EL =   Dimensions      
    Circ. joint efficiency (long. stress), Ec =   Shell Inner Diameter, Di =  mm  
                                         
    Corrosion Allowance, CA =  mm Nominal wall thickness, tn =
 mm  
                                         
    Undertolerance Allowance (*), U1 = default value = 0         Shell Outside Diameter, Do =  mm  
                                     
          Lengh, L =  mm  
                                         
    Notes:(*)           If tr ≤ tn acceptable    
    - As per UG-16(c) Mill Undertolerance. Plate material shall be ordered not thinner than the design thickness. Vessels made of plate furnished with an undertolerance of not more than the smaller value of 0.01 in. (0.25 mm) or 6% of the ordered thickness may be used at the full design pressure for the thickness ordered. If the specification to which the plate is ordered allows a greater undertolerance, the ordered thickness of the materials shall be sufficiently greater than the design thickness so that the thickness of the material furnished is not more than the smaller of 0.01 in. (0.25 mm) or 6% under the design thickness.   
    - As per UG-16(d) Pipe Undertolerance. If pipe or tube is ordered by its nominal wall thickness, the manufacturing undertolerance on wall thickness shall be taken into account except for nozzle wall reinforcement are a requirements in accordance with UG-37 and UG-40. The manufacturing undertolerances are given in the several pipe and tube specifications listed in the applicable Tables in Subsection C. After the minimum wall thickness is determined, it shall be increased by an amount sufficient to provide the manufacturing undertolerance allowed in the pipe or tube specification  
    - If you are ordering a head or other such fitting that is formed from plate, such as an elliptical, torispherical head, etc, you do not need to include the undertolerance. You do need to account for thinning during the forming of the head. Calculations should be done based on the minimum thickness after forming. The vendor of such heads should provide that information.  
                                         
                                       
  CALCULATIONS
                                         
    Shell Design                                    
    Minimum required thickness [ASME UG-27 (c)]                                    
                                         
    Undertolerance thickness, U2 =    mm   U2 = t*U1                    
                                         
    Nominal thickness adjusted for corrosion and undertolerance, nt =  mm   nt = t-CA-U2                    
                                         
    Inner radius with corrosion & undertolerance removed, R =  mm   R = Di/2+CA+U2                    
                                         
    Longitudinal Joint                                    
    Minimum required thickness, trL =    mm   trL = P R   + CA   (1)          
            S E - 0.6 P              
    Circunferential Joint                                    
    Minimum required thickness, trc =    mm   trc = P R   + CA   (2)          
            2 S E + 0.4 P              
                                         
    Minimum required thickness [The greater between (1) and (2)], tr =  mm                                
    Nominal wall thickness, tn =  mm                                
                                         
    Check If tr ≤ tn                                    
                                         
    Maximum working pressure  [ASME UG-27 (c)]                                    
    Longitudinal Joint                                    
    Working Pressure, PL =   barg   PL = S E nt     (1)              
            R + 0.6 nt                  
    Circunferential Joint                                    
    Working Pressure, Pc =   barg   Pc = 2 S E nt     (2)              
            R - 0.4 nt                  
                                         
    Max. working pressure for the Body [The min. between (1) and (2)], Pmax =  barg                                
                                         
    Check If Pmax ≥  P                                  
                                         
    Check Limitations                                    
    (1) Limitations: UG-27 and Appendix 1: ts < (R/2), P < 0.385 SE, trL< (R/2)                                
    If one isn’t met, review by Appendix 1-2. PL < 0.385 SEL                                
                                         
    (2) Limitations: UG-27 and Appendix 1: ts < (R/2), P < 1.25 SE, trc< (R/2)                                
    If one isn’t met, review by Appendix 1-2. Pc < 1.25 SEc                                
                                         
    Volume =  m³   V = ( ( Do -    t ) 2 π   L) / 10⁹            
            2              
                                         
    Weight =  Kg   W = ( ( ( π (Do² - Di²) ) L ) / 10⁹ ) ρm             
            4            
                                         
                                         
  RESULT
                                         
    Design Conditions      
   
    Design Pressure, Pd =  barg      
    Design Temperature, Td =  °C      
               
    Material          
Shell Material 
               
    Dimensions          
    Outside Diameter, Do =  mm      
    Nominal wall thickness, tn =  mm      
    Inner Diameter, Di =  mm      
    Lengh, L =  mm      
               
    Maximum working pressure =  barg      
    Volume =  m³      
    Weight =  Kg      
               
               
                                         
                                       
    Discussion and References  
    Information about Thickness of Shells Under Internal Pressure  
    ASME Section VIII Div 1 paragraph UG-27  
    Standards, Paragraph & Appendix  
  - ASME BPVC.VIII.1  Rules for Construction of Pressure Vessels    
  - ASME BPVC SEC II-D Material Properties    
  - ASME Section VIII Div 1 paragraph UG-27  Thickness of Shells Under Internal Pressure    
       
    Cylindrical Shell              
                                         
                                       
                                         
                                         
                                         
                                         
                                         
                                         
                                         
    Minimum required thickness [ASME VIII.1 UG-27 (c)]    
    Longitudinal Joint                      
      t = P R     (1)                
      S E - 0.6 P                    
    Circunferential Joint                      
      t = P R   (2)                
      2 S E + 0.4 P                  
    Internal design pressure [ASME VIII.1 UG-27 (c)]    
    Longitudinal Joint                          
      P = S E t         (1)                
      R + 0.6 ts                        
    Circunferential Joint                          
      P = 2 S E t         (2)                
      R - 0.4 ts                        
                                         
    Where:    
    P: Design Pressure, in bar (psig)    
    R: Inner Radius, in mm (inches)    
    S: Allowable Stress, in MPa (psi)    
    E: Welding Efficiency    
    t: Minimum required thickness, in mm [The greater between (1) and (2)]    
    (1) Limitations: UG-27 and Appendix 1: t < (R/2), P < 0.385 SE, If one isn’t met, review by Appendix 1-2. Being R the inner radius.    
    (2) Limitations: UG-27 and Appendix 1: t < (R/2), P < 1.25 SE, If one isn’t met, review by Appendix 1-2. Being R the inner radius.