Based on the instructions for the inspection of the stability of structural facilities by the owner/authorised party of the ARGE Bau (Conference of Building Ministers of the Federal States), the VDI guideline 6200 Stability of Structures - Regular Inspection, the BetrSichV as well as the information of the BG RCI of July/ August 20201, the following inspection concept is proposed for the silo facilities:
In the course of their use, silos and their discharge devices wear out at different rates depending on the abrasive (i.e. grinding/ rubbing) properties of the stored material. This can affect the tightness of the silo walls as well as the stability of the silo structure.
The stability is also influenced by weathering influences such as wind, snow or standing moisture. External influences such as the starting up of the supports, the generation of negative pressure inside the containers during material removal or positive pressure during filling can also cause the silo to become unstable.
Further hazards can result from the functional efficiency of the attachments required for the operation of the silo. These include in particular overfill prevention devices, level indicators, explosion protection flaps, venting devices or filter elements.
To ensure the safe operation of the silo, the entire construction and its attachments must be maintained in accordance with the regulations. The building law defines stationary silo installations as constructions with a static contact to the underground, i.e. structures. The owner or the person authorized to dispose of the silos is responsible for proper maintenance, i.e. servicing, checking and, if necessary, repairing them, as well as being responsible for the traffic safety of the construction.
The regular inspection ensures that the load-bearing structure is stable throughout the entire service life of the silo facility and that it is recognised in good time when upgrading measures are required to ensure the load-bearing capacity. A possible graded procedure for checking the stability consists of an inspection by the owner or the person(s) entitled to dispose, a visual inspection by a competent person and a detailed inspection by a particularly competent person.
The inspection includes the inspection of the structure for obvious damage. In the case of load-bearing structural components such as columns, walls, roof and ceiling girders and trusses, these are mainly deformations, inclinations, cracks, moisture penetration, efflorescence and corrosion. In addition to inspecting the condition of the load-bearing construction, it is advisable to check whether there are any other damaging influences on the stability, such as moisture penetrating from outside or damaged drainage. At the same time, it is recommended that during these inspections the functional efficiency of the silo system attachments, such as full indicators, pressure switches, pinch valves, exhaust air filters as well as overpressure and vacuum safety devices, be checked.
As a rule, the walk-through inspection serves as a check between inspections by competent persons. If damage is found, it is recommended that the owner/authorised party - if he is not himself competent - consult a competent or particularly competent person.