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Analyzes structural members (legs), support lugs and lifting lugs. The following information is required for each of these analysis types:
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Vessel design internal pressure
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Design temperature for the attachment
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Vessel outside diameter
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Weight of vessel operating and dry
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Vessel dimensions
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Additional horizontal force on vessel
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Location of horizontal force above grade
The design temperature for the attachment is used to compute the material properties for attachment being analyzed. In most cases the actual attachment temperature will be different from the vessel design temperature. The controlling stress for support lug and vessel leg calculations is the yield stress. The material yield stress can be looked up in the tables in ASME Section II Part D.
The weight of the vessel should be the weight of the vessel while it is operating. This should include operating fluid, trays, insulation etc. Support lug calculations should use the same loading conditions. However since vessels are typically lifted "dry" the empty weight of the vessel should be used when performing lifting lug calculations. There is a separate field for lifting weight of the vessel.
Support Legs
The number of vessel legs must be between 3 and 16. The program computes the number of legs for bending and shear of the vessel.
CodeCalc must have a valid material from which to determine material properties. You can select the material from the Material Database by selecting the material database lookup button. If a material is not contained in the database, you can enter its specification and properties manually by selecting Tools/ Edit/Add Materials, from the Main Menu.
Currently there are 929 structural shapes in the AISC database. CodeCalc is intended to perform unity checks on I-beam and angle type sections. AISC's method for computing unity checks for angle type sections are rather complicated when compared to the corresponding method used for "I" type sections.
Each beam section has a strong and weak orientation. If the beam is attached such that the tangent to the vessel is parallel to the beam's strong axis this designation is considered strong, otherwise it is weak.
If the legs are cross braced, bending stresses are significantly reduced.
Support Lugs
If the number of support lugs to be analyzed is between 2 and 16, CodeCalc assumes that each support lug has two gussets equally spaced about a bolt hole. The distance between gussets is used to determine the bending stress in the lug bottom plate. The lug bottom plate is analyzed as a beam on simple supports, where the support spacing is the gusset spacing. The allowable stress in bending is 66 percent of the yield stress, per the AISC manual. In addition, the stress in the gusset is one half of the lug force divided by the gusset area. This compression is compared to the AISC compression allowable.
Usually when analyzing stresses in the lug plate the stresses in the wall of the vessel at the attachment location should be checked. This can be accomplished by checking the box to perform WRC 107 analysis from within the support lug dialog.
Lifting Lugs
There are two types of lifting lug orientations; flat and perpendicular. Flat lugs are generally welded below the top head seam and extend far enough above the seam for the lifting cables to clear the head and its nozzles. Perpendicular lugs (ears) are used to clear some obstruction at or near the top head (such as a body flange) by moving the support point away from the vessel shell. They are also used as tailing lugs.
The width of the lug is its dimension in the direction of orientation described above. The length is in the vertical direction relative to the vessel.
The length of the welds will also need to be entered. For flat lugs the weld at the bottom will usually be the same as the lug width. For perpendicular lugs the weld length will be the same as the thickness of the lug.
CodeCalc will take the square root of the sum of the squares (W, N, and T) to determine the total shearing load. The forces W and N cause bending loads on flat lugs, while W and T cause bending loads on perpendicular lugs. The corner of the weld group is where the stress will be checked.
Baseplates
Baseplate thickness calculation is included in the vessel leg analysis for I-beam, pipe, and angle leg only, and can be activated by clicking the Analyze Baseplate check box.
The design is based on the method for I-beam leg described in the Pressure Design Manual by D. Moss and is applied to the other leg shapes. CodeCalc will assume the following for all Baseplate Thickness calculations:
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Strong axis leg orientation.
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Bolts are installed along the length sides only (B dimension).
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The leg is attached symmetrically on the baseplate.
It is advisable to check the baseplate dimensions using the graphic feature of CodeCalc.
Trunnions
A hollow or solid circular trunnion with or without pad reinforcement can be analyzed using the Trunnion Design module. The main considerations regarding the trunnion design are stresses at the vessel/trunnion junction and on the trunnion itself. Bending stress, shear stress, bearing stress and unity check are calculated and compared with the appropriate allowables. Local stresses at the junction can be analyzed using the WRC 107 Analysis Selection check box. The lifting orientation, vertical and horizontal positions, and the orthogonal input forces are needed for WRC 107 Analysis.
CodeCalc assumes that the loads entered act on one trunnion. Typically vessels are lifted with two trunnions thus the load is divided between them. An option is to analyze the trunnion with the maximum load acting on that trunnion during the lift. The program multiplies this lifting load by the importance factor specified by the user.
Before the analysis it is advisable to check the trunnion dimensions and the forces' magnitude and direction using the graphic feature in CodeCalc.
The program does not subtract corrosion allowance (if any) and then enter the dimensions.