Trunnion Stress Validation

TRUNNION STRESS VALIDATION

I)

Evaluation using Kellog’s formulae.

Inputs : Header Dia of Pipe (mm) Radius of Pipe (mm) Thickness of pipe (mm)

Trunnion

D p R  p

DT R T

t p

tT

Corrosion allowance  C (mm) Reinforcement thickness tr (mm) Total wall thickness, t = [t p(1-milltol/100)- C ]+ tr (mm) t1=[t p(1-milltol/100)- C ] Design temperature = TDes (º C) Design pressure = PDes ( N/mm²) Hot allowable stress = SH (MPa) Load Inputs: Longitudinal load Circumferential load Axial load Moment arm (from skin of header pipe)

: : : :

Fl ( N) Fc (N) Fa (N) L (mm)

Calculations: Longitudinal Longitudinal bending bending moment moment = ML =

Fl X L (N-mm)

Circumferential bending moment = MC =

Fc X L (N-mm)

Longitudinal pressure stress = SLP =

PDes X R  p (N/mm²) (2 * t1)

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TRUNNION STRESS VALIDATION

PDes X R  p (N/mm²) t1

Circumferential pressure stress = SCP = Kellog’s formulae:

Trunnion loading: f L =

ML X R T2

f A =

Fa 2X

f C =

MC X R T2

X R T

{Note: These are distributed loads on header pipe} Stress in the pipe wall due to trunnion load: Longitudinal stress = SL =

1.17 X f L X √ R  p 3/2 √t

Circumferential stress = SC =

2.34 X f C X √ R  p 3/2 √t 1.5 X1.17 X f A X √ R  p 3/2 √t

Axial stress = SA =

------------------------------------------------------------------------------------------------------------------------------------------------------------------

√ (ML2 + MC2) DT4- (DT - 2t) 4 32 X DT

Bending stress in trunnion = ST =

Combined Allowable Stress Check: The trunnion is said to be qualified for the given loads iff the following conditions are satisfied. 1) SL + SA + SLP

1.5 X SH

2) SC + SA + SCP

1.5 X SH

3) Stress in Trunnion, ST

SH

4) Shear stress in fillet weld, SW

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0.8 SH

TRUNNION STRESS VALIDATION

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