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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Sunday 4 November 2012

SPACER & BLIND Thickness Calculation for Internal Pressure (ASME B 31.3)


SPACER & BLIND  Thickness Calculation  for Internal Pressure (ASME B 31.3)
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Step1: Select the Spacer & Blind 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 

                                 3*P
tm   =    dg * √  (--------------)     +  c
                              16*S*E

tm= Calculated thickness including corrosion Allowance, (mm).
dg = Inside Dia. of gasket for RF/FF flanges or gasket pitch dia. for RTJ flanges, (mm).
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Step 7: Compare thickness

If      t > tm

t = Thickness as per API 590

Then selected thickness of Spacer & Blind is OK,
Else revise the thickness.
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Fluid Service Categories-ASME B31.3



ASME B31.3-Fluid Service Categories
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Fluid Service Categories
Ø  Category D Service
Ø  Category M Service
Ø  High Pressure Service (K)
Ø  Normal Fluid Services

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Category D Service
Ø  Non Flammable, Non Toxic  & Not Damaging to Human Tissue
Ø  Design Pressure does not exceed 1035 kPa(g).
Ø  Design Temperature Range -29C to 186C.
Ø  Example-Utilities Services

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Category M Service
Ø  Toxic fluid
Ø  Produce serious Irreversible harm to persons on breathing or bodily contact.(even when prompt restorative measure are taken)
Ø  Chapter VIII for piping design and construction.
Ø  Example-Lethal Fluid (Poisonous)

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High Pressure (K) Service
Ø  Pressure in excess of that allowed by ASME B 16.5 flange Class 2500 rating.
Ø  Chapter IX for piping design and construction.
Ø  Example-High Pressure Fluid

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Normal Fluid Service
Ø  A fluid service that are not
Ø  Category D
Ø  Category M
Ø  or High Pressure  (K) Fluid Service.
Ø  Piping design according to first Seven chapters of code.
Ø  Example-Process Fluid

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Severe Cyclic Conditions
Ø  Displacement Stress Range “SE” exceeds “0.8 SA” Allowable Stress Range.
Ø  And the equivalent number of cycles exceeds 7000.
Ø  Or conditions which the designer determines will produce an equivalent effect.

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Pipe Wall Thickness Calulation


Pipe Wall thickness Calculation Procedure for Internal Pressure (ASME B 31.3)
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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)
Ø  Temperature Co-efficient  = Y      (TABLE-304.1.1)


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  

                        P*D
tm   =     ----------------------     +  c
              2*[(S*E) + (P*Y)]


tm= Calculated thickness including corrosion Allowance, (mm).
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Step 7: Selection of pipe Schedule No.

                      TN
Ta =        ---------------
                [1-(e/100)]

Ta = Thickness for selected pipe
TN = Available Thickness for selected pipe @ Sch No.
e = Mill Tolerance
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Step 7: Compare thickness

If      Ta > tm

Then selected thickness of pipe is OK
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