Industrial Filter Device, Germany

This project for designing a filter/dryer device, including agitator, required a complete stress and deformation analysis in RFEM.

The complex modeling of the structure, which had 1,424 surfaces, 158 solids, and 425 members, represented a special design challenge.

Model Input

The filter was modeled with a linear elastic shell and solid elements. It consists of the following main structural components:

  • Floor slab
  • Filter bottom
  • Container wall with torispherical head and ring flange applied at bottom
  • Brackets on container wall
  • Support plate for agitator
  • Pipe connection and lifting eyes on torispherical head
  • Circulating serpentine pipes

The connection of the container and floor slab was especially interesting for the modeling process. The ring flange was applied in the form of a solid element to the bottom of the tank plate. It was fixed to the floor slab with 53 clamping bolts (M 27).

They were uniformly distributed around the circumference to ensure a constant prestressing force. In order to anchor the ring flange against the floor slab with defined prestress forces, a circulating counter element was modeled as a solid element on the tank wall. Thus, it was possible to clamp the container flange against the conical floor slab.

To reproduce this conical fastening in RFEM, it was necessary to define the contact property between these structural components in the analysis model. Contact solid elements defining an elastic spring were distributed uniformly around the circumference.


The following loads were applied to the structure:

  • Design pressure for container -0.01 psi, heating for flat bottom -0.006 psi, heating coil -0.006 psi
  • Vertical loads due to self-weight and equipment
  • Design temperature -4/392°F
  • Internal positive and negative pressure with design of pressure fluctuations from 0.0 to 43.5 psi for 28,000 cycles of load according to AD‑S1 and S2
  • Agitator loads for 2 million Stress cycles

Calculation in RFEM

Five load groups were created from the single load cases and the FE mesh was generated. Then the internal forces, stresses, and deformations were determined in RFEM.

In addition to the general stress analysis, fatigue designs due to pressure fluctuations and agitator loading were performed.

Structural Engineering Peter & Partner
Engineering and Expert Company for Structural Mechanics, Much

Project Specifications

Model data

Number of Nodes 3612
Number of Lines 3351
Number of Members 425
Number of Surfaces 1424
Number of Solids 158
Number of Load Cases 10
Number of Load Combinations 5
Total Weight 9.559 tons
Dimensions 15.55 x 15.5 x 10.97 feet
Program Version 5.01.44

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