Accidents at the plant including fires, explosions or collisions with structures should also be included.
Photos can help immensely in telling the history of a facility or structure. When taking a picture of a crack, put a tape measure near it and date each picture to gauge the crack’s progress over time.
Documenting when and what type of material was being stored can also help engineers understand the history of the bin. Bins and silos are structurally designed to handle materials with different physical characteristics ranging from free-flowing to difficult-to-handle millstock ingredients. Ensuring that the right ingredients go into the right bin will help avoid causing damage to the structure.
In addition to documenting events as they happen, it is important to conduct annual inspections and add any reports of unusual or troubling findings.
Preventive maintenance scheduling
Conducting preventive maintenance inspections are recommended not only to avoid structural collapse, but to ward off less critical problems that still have a big impact on your business. Properly maintained bins will, from a structural standpoint, reduce deterioration, and from an operational standpoint, prevent water and dust penetration, cutting down the potential development of molds, toxins and pests.
If a facility has a good record of performance or is new, inspecting concrete structures once a year should be appropriate. In general, you want to check for water seepage or spalling, cracks, corrosion and particles or aggregate (stones) in the product stream.
Small, regularly spaced vertical cracks in a fully loaded concrete structure are generally normal, but cracks that are vertical, more than 1/32 inch wide and 5 feet long and that appear suddenly should raise a red flag and can indicate more serious structural distress.
It is best to schedule your annual inspection when the bin is full.
“You want to look at the outside when it’s actually under load and being stressed,” says Kobetz. “In a concrete bin, once you empty it and take the load off of it, signs of distress or a crack that might be visible during unloading might appear much smaller when the bin is empty and may possibly become unoticeable.”
Additional items to look for include areas of exposed rebar combined with long vertical cracks over 1/16 inch wide, egg shaping of round silos and leaking hoppers. Egg shaping occurs when a bin that has been designed to discharge concentrically is discharged eccentrically either by improperly using off-center floor gates or through the installation of a side-draw without proper structural modifications to the silo. This is an operations error that can seriously damage a slip-form concrete silo.
The bin roof, deck, floor and grating should also be inspected annually as well as any time modifications to the structure have been made.
Some cracking in concrete floors may be normal, but if a crack suddenly emerges, especially after a piece of equipment has been added, Kobetz recommends calling a professional engineer to examine the crack. More importantly, an engineer should be called to verify the structural integrity of the floors before new equipment and their corresponding loads are added or new openings are cut in the floor.
A thorough bin inspection may take a few hours every year, but can translate to major savings by identifying potential structural problems early on before a system failure occurs.
Sticking to design
One of the most commonly overlooked ways to maintain concrete structures is to simply use the bin according to the original design specification and to use the bin only for its intended purpose.
No process further emphasizes this than the discharge design. A bin that’s been designed to discharge concentrically will have a discharge gate in the middle and additional gates closer to the walls, which are intended for cleanout purposes only. If the middle gate becomes plugged, opening a cleanout gate to discharge the bin will create an eccentric flow condition that could seriously damage a slip-form concrete silo; continued use of the bin in this manner may lead to a catastrophic failure of the structure.