1. 66” ID PRODUCT TANK-FLARE 99
Saddle and Tank stress calculations
Load Cases
The vessel and sub-frame are analyzed under the following conditions:
Load Case 1: hydro-test 975 psi internal pressure filled with water.
Load Case 2: storage vessel design pressure 750 psi with 50% filled water.
Load Case 3: empty vessel mounted on trailer running on road with 0.35g vertical
and longitudinal reactions combined with 0.2g lateral reaction
Weight of 50% filled water = 15,645 lbs
Weigh of hydro-test filled water = 31,290 lbs
Weight of vessel + attachments + saddles = 35,000 lbs
TOTAL weight of normal loaded operating = 50,645 lbs
TOTAL weight of the hydro-test condition = 66,290 lbs
FE Model weight of vessel + sub-frame = 23,599 lbs
Method of Calculation
A Finite Element Analysis is performed on the vessel with sub-frame attached (but
not shown in output) according to the following:
1. All components are modeled with plate elements.
2. Saddle is constrained at the bottom
3. Acceleration is applied according to the respective load case. The “element
load multiplier” is adjusted in order to obtain the loaded unit weight.
The FEA program employed is Algor FEMPRO Version 18.1-WIN. The geometry is
created in Superdraw.
Results and Conclusions
For load case 1, the categorized stresses should be limited to:
Pm < Sm = 34,200 x (3.5/3.0) = 39,900 psi After checking the simulated result, the
highest total stress on vessel is 39,024 psi, less than 1.5Sm and even less than Sm.
The classified Pm and Pl are definitely less than Sm and 1.5Sm, respectively.
Therefore, the vessel design under hydrostatic test is safety.
For load case 2, the categorized stresses should be limited to
1 OF 9
2. 66” ID PRODUCT TANK-FLARE 99
Pm < Sm = 23,300 psi
Pl < 1.5 Sm = 35,000 psi
Pl + Pb < 1.5 Sm = 35,000 psi
where Sm is the allowable general membrane stress, 70,000/3.0 = 23,300 psi.
After checking all the images, the maximum valve of Pm on vessel is 19,993 psi, the
maximum value of Pl + Pb on vessel is 30,017 psi. Therefore, the all above criteria is
satisfied and the vessel design is safety.
For load case 3, the code of CSA B620-03 must be satisfied. According to B620-03,
the allowable stress is based on the ultimate strength of material by using safety
factor 4. Therefore, the allowable general membrane stress Sm = 70,000/4.0 =
17,500 psi. From the simulated result, stresses on vessel are much less than the
allowable general membrane stress 17,500 psi defined in B620-03. The vessel
design to B620-03 is safety.
The saddle is made from SA-516-70, the yield strength is 38,000 psi. In all the above
load cases, the maximum value of stresses in Von Mises is 19,801 psi and safety
enough to withstand static and dynamic loads.
2 OF 9
