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)
  DATA INPUT
                                               
    Design Conditions     Material      
    Design Pressure, Pd =  barg Housing Material Specification (1)(2)
   
                                               
    Design Temperature, Td =  °C Allowable Stress Shell, S  = MPa  
                                               
    Long. joint efficiency (circ. stress), EL =
  Dimensions      
    Circ. joint efficiency (long. stress), Ec =
  Shell Inside Diameter, Di =  mm  
See Table UW-12
Corrosion Allowance, CA =  mm Nominal wall thickness, tn =
 mm
Minimum required thickness, tr =  mm
    Undertolerance Allowance (3)(4)(5), U1 =  default value = 0                                      
Shell Outside Diameter, Do =  mm
Length, L =  mm
                    If tr ≤ tn acceptable    
    Notes:                                          
  (1) S ≤ 66.66% of σy @ temp.  
  (2) S > 66.66% but < 90% of σy @ temp.  
  (3) 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.   
  (4) 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  
  (5) 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                      
                                               
    Inside radius with corrosion & undertolerance removed, R =  mm   R = Di/2+CA+U2                      
                                               
    Longitudinal Joint                                          
    Minimum required thickness, tL =    mm   tL = P R                  
            S E - 0.6 P                
                                               
    Minimum required thickness, trL =    mm   trL = P R + CA (6)            
            S E - 0.6 P            
    Circunferential Joint                                          
    Minimum required thickness, tc =    mm   tc = P R                  
            2 S E + 0.4 P                
                                               
    Minimum required thickness, trc =    mm   trc = P R + CA (7)            
            2 S E + 0.4 P            
                                               
    Minimum required thickness [The greater between (6) and (7)], tr =  mm                                      
    Nominal wall thickness, tn =  mm                                      
                                               
    Check If tr ≤ tn                                          
                                               
    Maximum allowable working pressure  [ASME UG-27 (c)]                                          
    Longitudinal Joint                                          
    Maximum allowable working pressure, MAWPL =   barg   MAWPL = S E nt     (8)            
            R + 0.6 nt                
    Circunferential Joint                                          
    Maximum allowable working pressure, MAWPc =   barg   MAWPc = 2 S E nt     (9)            
            R - 0.4 nt                
                                               
    Max. allowable working pressure for the Body [The min. between (8) and (9)], MAWP =  barg                                      
                                               
    Check If MAWP ≥  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                                      
                                               
    Inside Volume =  m³   V = ( ( π Di² ) L ) / 10⁹                 
            4                
                                               
    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
Inside Diameter, Di =  mm
Length, L =  mm
Maximum allowable working pressure, MAWP =  barg
Inside 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: Inside 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.