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SERVICES
FEM
VESSEL - FEM :
We have carried out Mechanical Design and later on developed Finite Element Analysis for
Pressure Vessel and Dome of API Tanks.
1) PRESSURE VESSEL :
SPECIFICATION :
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a. Design Code - BS : 5500
b. Design Pressure - 21.2 Kg/cm^2g at Top
c. Design Temperature - - 43 to 55°C
d. Stored Product - Propane.
e. Dia of Vessel - 3870 mm
f. T/L to T/L - 27000 mm
g. Center to Center Saddle - 17600 mm |
This vessels was a 100% Stress relieving Vessels. The vessels was fabricated in Two Half
and Stress relieved at shop leaving one field joint at 14.4 Mtr. From T/L.
The FEM was required as during the stress relieving the Shell was distorted beyond BS :
5500 Code requirement. The ovelity the shell was to the tune of 45 mm. The As-Built
distorted model of the vessel was prepared having 2100 element with each element size of
about 200 x 600 for vessel shell with saddle. The pressure was then applied and stresses
then found near field joint which were within the code allowable limit. The complete
design calculation got approved by Third Party Agency ( Bureau Veritas ) and by Client (
Indian Oil Corporation Ltd. ). The Vessel is in service for more than 10 months now.
2) DOME ROOF OF API TANK :
SPECIFICATION
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a. Design Code - API : 650 / DIN : 4119
b. Design Pressure - + 1000 / - 50 mm W.C.
c. Design Temperature - - 20 to 60°C
d. Stored Product - Liquid Oxygen.
e. Dia of Tank - 10900 mm for Internal Shell AND
- 13800 mm for External Shell
f. Type - Double Wall Tank.
g. Dome Radius - 9200 / 10654 mm |
This Tank was a Double Wall Dome Roof Tank for storage of Liquid Oxygen. The Inner Tank
was made out of S.S. Material whereas the outer tank was of Carbon Steel.
The Tank was required to be constructed in position in a limited time frame. Due to the
time constrain, it was necessary to construct Bottom and Shell portion in position ( above
foundation ) and Top Shell Course with Dome of the tank at different location ( near the
tank foundation ).
For outer tank 2263 mm height of shell + dome was
constructed at one location and for inner tank 1500 mm height of shell along with dome was
constructed at another location near the tank foundation.
Now both this dome with part of shell were required to be
lifted and kept over the main tank which was constructed on the main foundation. This
necessitate providing of lifting beam arrangement. At this point of time, we recommended
providing some 8 Nos. of lifting lug welded on the dome area which will then be connected
to a central lifting drum. Before actual lifting we have check the stresses developed on
the dome and part of shell by final element analysis. The deflection of the shell was also
quite vital because it was to be kept on already built shell. The ovelity / deflection of
the shell could lead to miss-match leading to welding problem.
The finite element model was prepared for both this shell
along with dome roof having 6060 element to observed the stresses induced and the
deflection of the shell. The stresses in the shell and the dome roof were quite low and
the deflection of the shell was 3 mm. The design calculation submitted were approved by
M/s. UHDE India Ltd. And on actual erection the behavior of the dome with shell is same as
FEM result.
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