The document summarizes a stress analysis of a vessel head with 3 fire tubes. A finite element analysis was performed to analyze stresses under 100 PSI pressure. The analysis found that local primary membrane stress, general primary membrane stress on the vessel and head, and total stresses including primary membrane, bending, and secondary stresses all met the stress limits defined in the ASME code. The stresses were below the material's ultimate strength of 70 ksi and satisfied the specific stress limits given in ASME VIII-2.

1. STRESS ANALYSIS REV A
HEAD WITH 3 FIRETUBES STRESS ANALYSIS TO ASME VIII-2
MaXfield Inc.
Performed by: Zhanghai (John) Wang, ASME Certificated Member
Checked By: Daryl Bast, P. Eng.
Load Case and Materials
In this revision calculation, the fire tubes are moved 2” upward. The vessel is
analyzed under pressure 100 PSI with filled water. The vessel together with the
fire tubes are made from SA 516-70. The thickness of the head welded with two
fire tube necks is 1 1/2” with corrosion allowance 1/16”. The shell connected the
head is 3/4” with corrosion allowance 1/16”. The fire tube neck nozzle is 1 1/4”
with corrosion allowance 1/16”. The geometrical dimensions could be checked
from the corresponding drawings.
Method of Calculation
A Finite Element Analysis is performed on the vessel together with fire tubes (but not
shown in output) according to the following:
1. Components are modeled with plate elements except the nozzle blind flange
modeled with brick element.
2. Vessel is partially cut and included in the mesh.
3. FEA model is constrained in cut section of the partial vessel and the end
supports of the fire tubes
The FEA program employed is Algor FEMPRO Version 19.1-WIN. The geometry is
created in Superdraw.
Results
The following output is attached:
Stress Contours:
(1) general primary membrane stress Pm and local primary membrane stress Pl
(2) local primary membrane stress plus primary bending stress (Pl+Pb)
(3) local primary membrane stress plus primary bending stress plus secondary
stress (Pl+Pb+Q)
(4) Nozzle blind flange stress in Von Mises
1 OF 8

2. STRESS ANALYSIS REV A
Conclusions
For material SA 516-70, the ultimate strength is 70 ksi. Sm = 70/3.5= 20,000 psi
According to the simulated results, local primary membrane stress Pl is 19,996 psi;
general primary membrane stress on vessel is about 14,572psi; general primary
membrane stress on head < Sm; Pl + Pb + Q is 34,709 psi. After checking the
results, we find in all stress contour area of the vessel:
Pm < Sm = 20,000 PSI
Pl < 1.5 Sm = 30,000 PSI
Pl + Pb < 1.5 Sm = 30,000 PSI
Pl + Pb + Q < 3 Sm = 60,000 PSI
Therefore, the stresses on head and fire tubes satisfy the specific stress limits given
in the Appendix 4 of ASME VIII-2.
2 OF 8

3. 3 OF 8

4. 4 OF 8

5. 5 OF 8

6. 6 OF 8

7. 7 OF 8

8. 8 OF 8