Monday, 5 November 2012

MITRE BEND Calculation


MITRE BEND Calculation Work Procedure for Internal Pressure (ASME B 31.3)


Step1: Select the Pipe Material
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Step2: List Down

Ø  Pipe Outside Diameter, (mm) = D
   Ø  Internal Design Pressure,(Kg/cm²) = P
   Ø  Design Temperature, (C°) = T°

For the material under consideration.
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Step 3: List down

Ø  Allowable Stress, (Kg/cm²)  = S

ASME B 31.3 @ Design Temperature.  (TABLE A-1)
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Step 4: Select

Ø  Joint Efficiency factor = E             (TABLE A-1A)


ASME B 31.3  (TABLE-1A)
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Step 5: Select

Ø  Corrosion Allowance, (mm) = c
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Step 6: Formula @ ASME B 31.3 

                  S*E*(T-c)                        (T-c)
Pm1   =    -------------- [---------------------------------------------]    + c    ……….Eq.-I
                     r2                 (T-c) + 0.643*TAN θ * √r2*(T-c)




                  S*E*(T-c)         (R1-r2)
Pm2   =    -------------- [---------------------]    + c                                  ……….Eq.-II
                     r2                (R1-0.5*r2)


Pm1 = Max. Allowable Internal Pressure for Mitre Bend, (Kg/cm²)        @ Eq.-I
Pm2 = Max. Allowable Internal Pressure for Mitre Bend, (Kg/cm²)         @ Eq.-II
    P = Internal Design Pressure, (Kg/cm²)
     θ = Angle of mitre cut
    r2 = Mean Radius of pipe, mm       (D-T)/2
   R1 = Effective radius of mitre bend, mm
     T = Available thickness,(mm) ( after deducting Mill Tol. & Corrosion Allowance)

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Step 7: Compare values of Pm1 & Pm2

Min (Pm1, Pm2) = Pm
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Step 8: Compare values of Pm & P

If (Pm < P)

Pipe Thickness (T) is OK.

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2 comments:

  1. Pm should be greater than P write.

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  2. as far as i concern, Pm should be greater than P so it would not derate the pipe system. If Pm lower than P, then miter bend angle should decrease or increase the thickness.

    ReplyDelete