Read about START-PROF pipe stress analysis software
There are three options to model the vertical pressure vessels in START-PROF software:
1. Using nozzle element at the pipe end node. In this case "global beam flexibility" is not taken into account (assumed that pressure vessel is absolutely rigid), except the situation when "FEM" option is used. Thermal expansion of pressure vessel is taken into account automatically, no need to model the pressure vessel as rigid elements or set restraint movements.
This method should be used only in the simple cases, when no horizontal loads acting on the piping and equipment like seismic, wind, etc.
2. The vessel can be modeled using cylindrical shell element ("3" on the picture below). The length between nozzle and intersection point between pipe axis and vessel axis is modeled using rigid element ("1" on the picture below). Nozzle element should be inserted into the point between pipe and rigid element (2). Both "local shell flexibility" and "global beam flexibility" will be taken into account using this method. This is a classic method, which is known by many pipe stress engineers
1 - Rigid Element, 2 - Nozzle Element, 3 - Cylindrical Shell Element
3. This method is faster and easier than method #2 gives the same analysis result. The vessel is modeled using cylindrical shell element. Nozzle element is inserted into connection point between pipe axis and cylindrical shell like a "tee" (node 1 on the picture below). In this case START-PROF will automatically add the internal hidden rigid element between nozzle and node 1. Using this method you may skip the step of creating the rigid element manually and save the time. Both local and global flexibilities will be taken into account like using method #2.
The methods 2 and 3 can be used to model the equipment of any complexity and connection of any number of nozzles into the one vessel.
Also the more realistic model of the vessel connection to the foundation can be used:
And vessels of any design can be modeled
Modelling Horizontal Vessel
Modelling Column Vessel