In industries such as grain, building materials, chemicals, and mining, steel silos often experience long-term inactivity due to off-season shutdowns, project reorganization, and capacity adjustments. This can result in prolonged periods of inactivity lasting months or even years. Many enterprises resume production by directly feeding materials into the silos, believing that the silos will not cause any problems when left idle.
However, from on-site operation experience, the hidden dangers of long-term idle silos are far greater than those of operating equipment. Problems such as rusting, settlement, residual materials, and equipment aging during the idle period do not manifest immediately. Once the silos are put into operation with faults, they can easily cause blockages, equipment damage, structural deformation, and even safety incidents such as dust explosions and material spontaneous combustion.
Why can’t the silo after long-term deactivation be put into use directly
Silos that are operating normally have equipment in a continuous running state, and the silo body is evenly stressed, with ventilation and unloading systems remaining unobstructed. Hidden dangers can be detected and addressed promptly during daily inspections. However, idle silos are in a completely static state, and various wear and hidden dangers will accumulate slowly.
The steel structure of the silo walls and bolted connections are exposed to air, rain, snow, and humidity for a long time, leading to natural rusting, oxidation, and aging of the steel, with slight reduction in strength. The foundation, when under no or light load for a long time, may experience uneven settlement, disrupting the original force balance.
Residual materials in the silo will absorb moisture, form lumps, mold, and breed pests, not only contaminating new materials but also potentially blocking unloading channels. The accompanying motors, conveyors, dust removal, and other mechanical and electrical equipment will experience problems such as dry lubricating oil, damp circuits, and stuck components when left idle for a long time. These hidden problems cannot be quickly detected with the naked eye and direct production can easily trigger various faults and safety accidents.
Overall inspections to be conducted before the silo is reactivated
Inspection of the silo structure
The silo structure is the core load-bearing component. Before reactivation, a comprehensive inspection of the appearance and deformation issues should be carried out. Pay special attention to whether there are rust, bulges, depressions, or cracks in the wall plates of the silo. Particularly focus on the stressed areas in the middle and lower parts of the silo and the joint positions of the wall plates.
Carefully inspect the vertical reinforcement ribs and the circumferential wind-resistant rings to ensure there are no bending, deformation, or detachment issues. If severe rust is found locally, the remaining wall thickness should be measured to determine if it meets the load-bearing standards. If the rust exceeds the limit, rust removal, welding repair, or replacement of the plates must be carried out first.
Inspection of the silo top and bottom
The silo top is often overlooked during routine inspections. After long-term inactivity, it is necessary to check whether the top plate is rusted or damaged, and whether the rainproof sealing strips are aged and fallen off. This is to prevent water from seeping into the silo in the future. At the same time, check whether the ventilation ports and dust removal interfaces on the silo top are unobstructed, and whether there is any debris blocking or rusted sealing.
The silo bottom and the hopper are areas prone to blockage and accumulation of dust. They are also key stressed areas. Check whether the hopper plates are deformed, and whether the weld seams are cracked. Check the sealing flanges and sealing components of the discharge ports for aging and damage. Also, remove the accumulated debris and water on the periphery of the silo bottom to avoid long-term soaking of the foundation and the bottom structure of the silo.
Inspection of the foundation settlement
The foundation settlement of the silo is the most concealed safety hazard. After long-term inactivity, the soil stress state changes, and uneven settlement is very likely to occur. By comparing the original horizontal reference line of the silo, check whether the silo is tilted, whether the foundation concrete has cracks, peeling, or water seepage marks.
If there are minor cracks in the foundation or slight tilting of the silo, the reactivation operation must be suspended, and the foundation should be rechecked and reinforced. Imbalance in the foundation load will cause the silo to be subjected to uneven stress, and after feeding, the structural deformation will be significantly exacerbated, leading to safety risks.
Inspection and adjustment of connection parts and bolts
The stability of the silo relies on a large number of bolts and connection parts. After long-term static storage and moisture absorption, bolts are prone to rust, looseness, and stuck threads. Need to inspect the tightening status of the connecting bolts of the silo wall, the fixing bolts of the columns, and the foundation anchor bolts in sections.
For rusted bolts, rust removal treatment should be carried out. If the rust is severe or the threads are worn, they must be replaced directly. After the inspection of all bolts is completed, they should be tightened uniformly according to the standard torque to avoid uneven stress caused by loose connection parts.
Inspection and debugging of mechanical and electrical equipment
The failure rate of mechanical and electrical equipment after long-term inactivity is extremely high. First, check the distribution cabinet and control lines to identify potential moisture, aging, loosening, short-circuit hazards in the lines. Confirm that the electrical insulation performance meets the standards.
For transmission equipment such as bucket elevators, screw conveyors, discharge valves, and dust removal equipment, manual turning tests are required to confirm there are no sticking or jamming problems. The lubricating oil and hydraulic oil of the equipment will deteriorate and settle over time. All oil quality should be checked, and deteriorated oil should be replaced promptly. After replenishing the oil volume, the equipment should be tested and run.
Cleaning work required before reopening the silo
Clearance of residual materials
It is difficult to completely empty the silo before it is shut down. Small amounts of residual materials will remain on the silo walls, cone hoppers, and in the corners. These residual materials, left to stand for a long time, will absorb moisture from the air and cause dampness and accumulation problems.
Before restarting, all residual materials in the silo must be thoroughly cleaned. No blind spots should be left. Residual materials not only contaminate newly stored materials but also reduce the effective volume of the silo. Excessive accumulation can alter the original force state of the silo and affect the smoothness of unloading.
Handling of agglomerated and moldy materials
Long-term residual of grains and powder materials will absorb moisture and form agglomerations, and may also develop mold and deteriorate. They will adhere to the silo walls and the inner walls of the cone hoppers. Simple manual cleaning cannot completely remove them. Professional tools are needed to clear the agglomerated materials to avoid residual agglomerations causing arching and blockage in the future.
After cleaning, the silo walls should be wiped thoroughly and dried. For silo bodies that are severely moldy, low-toxicity disinfectants should be sprayed for disinfection to completely eliminate mold residues and prevent secondary pollution of new materials after they are stored in the silo.
Solving pest and dust problems
The idle silo is closed and humid, which is easy to breed eggs, mites and mice, especially the problem of grain silo is more prominent. Before restarting, thoroughly inspect the pest traces in the corners and crevices of the silo, and carry out fumigation and disinfection treatments to prevent pest residues.
At the same time, remove the accumulated floating dust in the silo. Excessive accumulation of powder dust not only affects the purity of the materials but also poses a dust explosion hazard. After cleaning the dust, turn on the ventilation system to keep the silo air dry and circulating, meeting the safety conditions for production.
Startup test procedure for silos
Full-load no-load test run to confirm no abnormal vibration or noise
After all inspections and emptying work are completed, start the full-load no-load test run without feeding. Turn on all supporting equipment such as conveying, discharging, and dust removal, and run continuously for 1 to 2 hours.
During the operation, pay close attention to the operating status of the equipment, listen for any abnormal sounds, jamming, or frictional noises, and check if there is any abnormal vibration or shaking of the silo and equipment. Once any abnormalities are detected, immediately stop the machine for troubleshooting and thoroughly resolve the issues before continuing the test run.
Small-load trial feeding to test the force on the silo and the smoothness of discharging
After the no-load test run shows no abnormalities, start small-load trial feeding. The feeding volume should be controlled at 20% to 30% of the silo capacity. Small-scale feeding can test the force state of the silo and the smoothness of the discharging system.
During the feeding process, observe if there are any local bulges or deformations in the silo and if the equipment is running smoothly. After standing still for half an hour, attempt to discharge the material and check if the material discharging is smooth, if there are any blockages, arching, or leakage problems.
Gradually increase load to complete staged full-load production and operation
After no abnormalities in the small-load test run, use the staged feeding method to gradually increase the load. Increase the feeding volume to 50%, 70%, and 100% successively. Run each level for 1 to 2 production cycles stably.
Monitor the structural stress of the silo, equipment temperature rise, operating noise, and discharging speed throughout the process to ensure stable parameters under full-load conditions. Once no abnormalities are confirmed, it can be transferred to regular continuous production.
Key points for re-activation of different types of silos
Key inspection areas for grain silos
The core of restarting grain silos is to prevent moisture, pests, and mold. Focus on inspecting the ventilation system at the silo roof and the sealing structure of the silo walls, ensuring there are no channels for water leakage. Thoroughly check the corners and weld seams inside the silo, and completely remove residual grain residue and insect eggs.
Also, test the temperature and humidity sensing equipment to ensure real-time monitoring of the grain pile status after commissioning. Adequate disinfection and ventilation must be carried out to prevent heating, mold growth, and pest infestation after new grain is introduced.
What to pay attention to for cement silos
Cement powder is highly prone to absorbing moisture and forming lumps. For cement silos that have been idle for a long time, the inner walls will usually be covered with hard cement layers. Before restarting, it is necessary to thoroughly clean the lumps on the silo walls and the hard-encrusted materials in the hopper to prevent blockages and uneven discharging in the future.
Focus on inspecting the anti-corrosion layer of the silo body and the discharging breaker device. The breaker air discs and vibrators, which have been left to stand for a long time, are prone to malfunction and require individual debugging and testing. At the same time, check the dust removal equipment to avoid dust accumulation blocking the filter elements and affecting the dust removal effect.
Special requirements for chemical powder silos
Chemical powders often have slight corrosiveness, and some materials also have flammable and explosive properties. Before restarting, it is necessary to focus on inspecting the rust condition of the silo walls and rechecking the remaining thickness of the plates. If the corrosion exceeds the standard, it must be repaired in time.
Thoroughly clean the remaining chemical powder in the silo, as the mixing of different types of powders is prone to chemical reactions. At the same time, strictly check the anti-static, grounding devices, and explosion-proof dust removal system to eliminate the risk of static accumulation and dust explosion.
How to reduce the failure rate after re-activation of silos
Establish a regular inspection system
During the initial stage of restarting and commissioning silos, the equipment and structural conditions are not yet fully stable. Therefore, the inspection frequency should be increased. Daily inspections should be conducted to check the operating status of the silo structure, connecting parts, and mechanical and electrical equipment, and record basic data such as equipment noise, vibration, and discharging speed.
Through regular inspections, minor abnormal problems can be detected in time, and early intervention can be carried out to avoid the accumulation of small faults into major safety hazards. After long-term operation, the frequency of regular inspections can be adjusted according to the equipment condition.
Set equipment maintenance cycles
For conveying, transmission, dust removal, and electrical control equipment, establish fixed maintenance cycles. Regularly replace lubricating oil, clean filter elements, tighten bolts, and test circuits to ensure the equipment is always in good operation.
At the same time, regularly clean the accumulated dust and residual materials in the silo, check the integrity of the anti-corrosion layer, and reduce the failure probability from both the equipment and silo body aspects, thereby extending the overall service life of the silo.
Perform maintenance during shutdown
Most silo failures occur due to neglect during the shutdown period. After the equipment is shut down, the silo should be emptied of materials, dust should be cleaned, and the silo should be kept dry and ventilated.
Take precautions such as power-off, dust-proof, and moisture-proof for the mechanical and electrical equipment, and apply anti-rust treatment to the bolts and metal components. Regularly check the foundation condition and the sealing condition of the silo body to reduce static loss during the standstill period and significantly reduce the failure risk during the next restart.
Key precautions for restarting a silo after long-term inactivity
When restarting a silo, it is strictly prohibited to skip the inspection process and directly start feeding to meet the construction schedule. All potential static hazards must be thoroughly investigated and rectified before the silo is put into operation. During the cleaning operation, it is essential to implement the regulations for confined space operations, ensure proper ventilation, supervision, and explosion prevention measures, and eliminate the risk of poisoning or asphyxiation of personnel.
During the equipment trial run, it is necessary to strictly follow the hierarchical process of no-load, low-load, and full-load operation. It is forbidden to run the equipment at full load all at once. If any abnormal sounds, deformation of the silo body, or abnormal discharging are found, the machine must be stopped immediately, the hazards must be investigated and rectified, and only after the problems are resolved can it be restarted.
Silos of different materials and storing different materials cannot apply the same restart standards. They need to be inspected and debugged specifically according to their own working conditions to avoid personalized safety risks.
Key points for regular maintenance after silo restart
After the silo is successfully restarted and put into production, regular maintenance is the core for maintaining long-term stable operation. During daily production, ensure that the silo is ventilated and dry, avoid long-term accumulation of materials that absorb moisture and deteriorate, and ensure that the materials are advanced and used first.
Regularly inspect the anti-corrosion layer of the silo wall, weld seams, and bolt connections, and promptly handle minor rust and loosening problems. Mechanical and electrical equipment should be maintained according to the cycle, replace aging parts in time, and ensure that the transmission, dust removal, and control systems are sensitive and reliable.
Before each shutdown and stoppage, try to empty the materials in the silo, thoroughly clean the accumulated dust, and take measures to prevent dust and moisture from damaging the equipment, laying a foundation for subsequent shutdown and restart operations.
Conclusion
The restart of a silo that has been out of use for a long time does not merely involve simply starting up and feeding materials. The core lies in conducting a comprehensive inspection of the accumulated structural, material, and equipment hazards during the period of inactivity. Many silo safety accidents in enterprises are caused by the psychology and lack of procedures during the restart stage.
By strictly following the procedures of structural inspection, thorough cleaning of the silo, graded trial operation, and targeted debugging, and conducting regular maintenance and upkeep after restart, we can effectively avoid safety risks, reduce equipment failure rates, significantly extend the service life of the silo, and ensure the continuous and stable operation of production.