TRUNNION STRESS VALIDATION
I)
Evaluation using Kellog’s formulae.
Inputs :
Header
Dia of Pipe
(mm)
Radius of Pipe
(mm)
Thickness of pipe
(mm)
Trunnion
Dp
DT
Rp
RT
tp
tT
Corrosion allowance → C (mm)
Reinforcement thickness→ tr (mm)
Total wall thickness, t = [tp(1-milltol/100)- C ]+ tr (mm)
t1=[tp(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 bending moment = ML =
Fl X L (N-mm)
Circumferential bending moment = MC =
Fc X L (N-mm)
Longitudinal pressure stress = SLP =
PDes X Rp (N/mm²)
(2 * t1)
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TRUNNION STRESS VALIDATION
PDes X Rp (N/mm²)
t1
Circumferential pressure stress = SCP =
Kellog’s formulae:
Trunnion loading:
fL =
ML
X RT2
fC =
MC
X RT2
Fa
fA =
2X
X RT
{Note: These are distributed loads on header pipe}
Stress in the pipe wall due to trunnion load:
Longitudinal stress = SL =
1.17 X fL X √ Rp
3/2
√t
Circumferential stress = SC =
2.34 X fC X √ Rp
3/2
√t
1.5 X1.17 X fA X √ Rp
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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