Tank bulging-radial growth occurs on the shell due to product static head for large diameter tanks. Bulge formations appear because a static head may cause circumferential and longitudinal strains.
For large-diameter storage tanks( above 36” dia ) with heavy liquid, tank bulging occurs since there is a slight growth of the tank shell in radial direction. When this radial-shell growth occurs at the nozzle location, the nozzle is rotated slightly. Even the smallest nozzle rotation will cause the associated piping to either lift-off from the first support from the tank foundation or excessively compress the pipe at the first support from the tank foundation. This happens even if the vertical displacement of the tank nozzle is in a downward direction. This condition is assumed when the first support is a rigid support from the tank foundation extension.
For large-diameter storage tanks( above 36” dia ) with heavy liquid, tank bulging occurs since there is a slight growth of the tank shell in radial direction. When this radial-shell growth occurs at the nozzle location, the nozzle is rotated slightly. Even the smallest nozzle rotation will cause the associated piping to either lift-off from the first support from the tank foundation or excessively compress the pipe at the first support from the tank foundation. This happens even if the vertical displacement of the tank nozzle is in a downward direction. This condition is assumed when the first support is a rigid support from the tank foundation extension.
Modeling the storage considering settlement and Bulging effect:-
1-Input the design and operating Temp & Pressure
2-Model the nozzle flange 10-20.
3-Model the projection as pipe element 20-30 with same pipe diameter & schedule given in the drawing for the nozzle up to nozzle pipe and Tank intersection.
4-Define API 650 Nozzle at element 20-30 i.e. Check mark the Nozzle option and select the type as API 650.
5-Fill up the details of the tank in API Nozzle spreadsheet from the Data Sheet provided by the vendor.
6-Fill up the details as nozzle node as 30 (intersection of tank and nozzle) and tank node as 40.
7-Start the next element 40-50 length equal to the radius of the tank with dia & schedule of the tank.
8-Model 40-50 as weightless rigid element with diameter & schedule of the tank.
9-Model 50-60 vertically length equal to the elevation of the nozzle up to bottom of the tank as rigid with no weight and diameter and schedule that of the tank.
10-Define the Anchor at 60 with C Node 61.
11-Define the displacement at node 61 DY equal to the Tank settlement in mm and input 0 in all other fields DX, DZ, RX, RY, RZ.
12-For the Tank Bulging effect and radial expansion of tank, define the displacement at node 40 along the Nozzle axis DZ in mm and rotations RX in degrees and input 0 in all other fields DX, DY, RY, RZ IN VECTOR 2.
13-Check the Nozzle loads at node 30 against the allowable given by the vendor from the datasheet.
1-Input the design and operating Temp & Pressure
2-Model the nozzle flange 10-20.
3-Model the projection as pipe element 20-30 with same pipe diameter & schedule given in the drawing for the nozzle up to nozzle pipe and Tank intersection.
4-Define API 650 Nozzle at element 20-30 i.e. Check mark the Nozzle option and select the type as API 650.
5-Fill up the details of the tank in API Nozzle spreadsheet from the Data Sheet provided by the vendor.
6-Fill up the details as nozzle node as 30 (intersection of tank and nozzle) and tank node as 40.
7-Start the next element 40-50 length equal to the radius of the tank with dia & schedule of the tank.
8-Model 40-50 as weightless rigid element with diameter & schedule of the tank.
9-Model 50-60 vertically length equal to the elevation of the nozzle up to bottom of the tank as rigid with no weight and diameter and schedule that of the tank.
10-Define the Anchor at 60 with C Node 61.
11-Define the displacement at node 61 DY equal to the Tank settlement in mm and input 0 in all other fields DX, DZ, RX, RY, RZ.
12-For the Tank Bulging effect and radial expansion of tank, define the displacement at node 40 along the Nozzle axis DZ in mm and rotations RX in degrees and input 0 in all other fields DX, DY, RY, RZ IN VECTOR 2.
13-Check the Nozzle loads at node 30 against the allowable given by the vendor from the datasheet.
API 650 CALCULATIONS DATA FOR ANALYSIS:
* Input data
* Tank Diameter
* Nozzle Height above bottom Plate
* Nozzle Outer Diameter
* Shell Course Thickness
* Max Fluid Height above bottom plate
* delta Temperature
* Modulus of Elasticity
* Expansion Coefficient
* Fluid Specific Gravity
* Reinforcement on Shell or Nozzle
* Input data
* Tank Diameter
* Nozzle Height above bottom Plate
* Nozzle Outer Diameter
* Shell Course Thickness
* Max Fluid Height above bottom plate
* delta Temperature
* Modulus of Elasticity
* Expansion Coefficient
* Fluid Specific Gravity
* Reinforcement on Shell or Nozzle
Displacement for Settlement of Tank (vector1)
Displacement for Bulging & expansion tank (vector 2)
Displacement for Bulging & expansion tank (vector 2)
WHERE:
D1= DISPLACEMENT DUE TO SETTLEMENT
D2= DISPLACEMENT DUE TO BULGING EFFECT
D1= DISPLACEMENT DUE TO SETTLEMENT
D2= DISPLACEMENT DUE TO BULGING EFFECT