In most areas of southern China, the southwest region, and along the coast and riverbanks, there are many rainy days throughout the year, and the relative humidity of the air remains high for an extended period. During the plum rain season and flood season, there are also continuous moisture backflows and oppressive weather conditions. Under such climatic conditions, grains, feed, and powdery materials are highly susceptible to moisture problems. High-humidity external air can seep into the silos through gaps, ventilation openings, and loading/unloading channels, causing condensation, material self-humidification, and water seepage backflow issues to occur successively. After the silos get damp, grains will mold and clump, and powdery materials will become compacted and deteriorated. This not only causes material loss but also breeds pests and molds, corroding the steel structure and concrete structure of the silos and shortening their service life.
The core reason for frequent dampness of silos in rainy areas
The continuous moisture erosion brought by regional climate
The most core characteristic of rainy areas is high saturated humidity of the air and large diurnal temperature difference. Under continuous rainy weather, the moisture content of the external air remains at a high level, and even when the weather clears up, the moisture in the ground and air is difficult to quickly dissipate.
The temperature difference between day and night causes a temperature difference between the inner and outer walls of the silo. When warm and humid air contacts the cooler silo walls, condensation occurs. This is the main reason why many silos do not have water seepage but the internal materials still get damp. The backflow of moisture during the plum rain season also causes air backflow, and external moisture will continuously seep into the silo through various gaps, forming continuous moisture accumulation.
The silo structure itself has inherent shortcomings of moisture accumulation
Whether it is a steel structure or a concrete silo, it inherently has design flaws, which will be greatly magnified in a rainy and high-humidity environment. Steel structure silos have a fast heat conduction rate, and the silo wall temperature changes rapidly with the external temperature, resulting in a much higher probability of condensation than other structures.
Concrete silos have many pores in their walls and possess certain moisture absorption properties. They will continuously absorb water vapor when in a humid environment, and the moisture will slowly penetrate into the silo. At the same time, most silos’ roof nodes, ventilation openings, and foundation gaps are prone to moisture absorption and cannot resist the long-term moisture penetration of rainy weather.
Internal moisture generation during daily storage operations
In addition to external moisture intrusion, improper storage operations will generate moisture in the silo, exacerbating the dampness problem. During rainy weather, materials will absorb water vapor from the air, and the moisture content will gradually increase. After entering the silo, it will continuously release moisture into the silo.
Frequent loading and unloading operations will disrupt the air pressure balance in the silo, forming a negative pressure state, and actively inhaling external humid air. Some factory areas have overly dense material piles, and the water vapor inside the materials cannot escape, continuously accumulating and causing internal dampness and deterioration problems from the inside of the silo.
The hazards caused by moisture in silos
The quality of materials deteriorates, resulting in direct economic losses
When grains and feed materials get wet, they will quickly undergo phenomena such as clumping, mold growth, deterioration, and pest infestation, completely losing their usability. For powder industrial raw materials, if they get wet and become compacted, it will affect the production ratio and lead to substandard product quality.
The problem of moisture in rainy areas is persistent. Once the control is not in place, the entire silo’s materials will suffer losses. For large-scale storage enterprises, repeated material scrapping and downgrade processing will increase production and storage costs, directly affecting the overall profit margin.
It corrodes the structure of the silo and shortens the service life of the equipment
Moisture not only affects the materials but also continuously erodes the structure of the silo. When the silo is in a high-humidity environment for a long time, the inner walls and weld seams will rust, and long-term rusting will reduce the structural stability and pose safety hazards.
Concrete silos will have problems such as wall cracking and weathering due to moisture penetration. The foundation of the silo will suffer from long-term moisture soaking and settlement, and become loose. Silo equipment that was originally expected to last for more than ten years will be significantly shortened in service life due to continuous moisture and corrosion in rainy environments.
Create potential safety hazards and trigger compliance and production risks
The moisture-contaminated and moldy materials will produce a large number of mold and harmful bacteria, and if they accumulate for a long time, they will breed mosquitoes, pests, and rodents, damaging the storage hygiene environment. Food and grain will also face non-compliance inspection issues.
In addition, when powder materials get wet and clump, they will block the discharge ports and conveying equipment, causing equipment jamming and shutdown failures. In severe cases, there will be overheating of the materials, fermentation, spontaneous combustion, and excessive dust, causing major safety risks to the production and operation of the factory.
Three common misunderstandings about moisture prevention in silos
Blindly ventilating at fixed intervals, mistakenly believing that ventilation can remove moisture
Many maintenance personnel are accustomed to turning on ventilation equipment at fixed times to keep the silo dry, completely ignoring the climatic characteristics of rainy areas.
The air humidity during rainy days, foggy days, and re-moistening days is close to saturation. At this time, ventilation not only cannot remove moisture but will also introduce a large amount of high-humidity air into the silo, rapidly aggravating condensation and moisture problems. Un-differentiated timed ventilation is the core reason why silos in rainy areas become more humid with ventilation.
Only focusing on waterproofing at the top, ignoring the foundation and hidden cracks getting wet
Most enterprises’ moisture prevention focus is entirely on waterproofing at the silo roof and protection of the silo walls, believing that as long as there is no leakage, there will be no moisture. However, in rainy areas, the groundwater level is high, and the foundation gets wet and the floor leaks are long-term existing hidden problems.
At the same time, the splicing seams of the silo body, pipe perforations, door and window rubber strips, etc., are difficult to be noticed with the naked eye, but they will continuously seep moisture. Only doing waterproofing at the top, ignoring the bottom drainage and gap sealing, the moisture prevention work always treats the symptoms but not the root cause, unable to solve the problem fundamentally.
Over-reliance on equipment for dehumidification, ignoring the internal moisture of the materials
Some factories invest a large amount of cost in configuring dehumidification equipment, but still cannot control the humidity in the silo. The core problem lies in ignoring the internal moisture of the materials. In rainy weather, the materials entering the silo will continuously release water vapor, far exceeding the processing capacity of regular dehumidification equipment.
Relying solely on equipment for dehumidification, without controlling the moisture content of the materials entering the silo and optimizing the stacking method, is equivalent to dehumidifying while generating moisture, and the equipment operates under a high-load condition for a long time, resulting in not only poor dehumidification effect but also a significant increase in energy consumption and equipment wear and tear.
Ensure the waterproofing of the silo structure at the physical level to isolate external moisture
Properly waterproof the roof joints of the silo to prevent water penetration and accumulation
For rainy environments, the roof of the silo needs to undergo layered waterproofing and insulation treatment. After cleaning the base layer, lay insulation boards to block the temperature difference conduction and reduce condensation on the inner wall of the roof. Then, apply waterproof coatings on the outer layer to achieve complete coverage without any blind spots.
The exhaust holes on the roof, the base of the lightning rod, and the pipe perforations are high-frequency points for water leakage. They cannot be uniformly coated with waterproofing paint. Instead, local reinforcement with sealant is required. At the same time, additional rain caps and water-blocking edges should be added to prevent rainwater from flowing into the silo through the gaps in the components. Before the rainy season each year, focus on checking the waterproof aging of these special nodes and promptly repair damaged areas.
Seal and block the opening and closing parts of the silo to block the convection channels of moisture
Most of the doors, inspection ports, and ventilation ports of the silos have only simple closed structures with large gaps. During rainy weather, humid air will continuously and slowly penetrate the silo. Over time, this leads to excessive humidity inside the silo. Especially on rainy days with large temperature differences between day and night, the air convection between the inside and outside of the silo will carry a large amount of moisture, causing condensation on the wall of the silo. All opening and closing parts should be upgraded with sealing upgrades. The silo doors and inspection ports should be equipped with double-layer sealing strips, and additional rain caps and water-blocking edges should be added to completely block the air circulation.
The joint seams of the steel plate sections of the steel structure silo need to be regularly filled with flexible sealing materials to compensate for the tiny cracks caused by structural expansion. These gaps are difficult to be noticed with the naked eye, but they are the main channels for moisture penetration. Fine sealing can significantly reduce the probability of moisture infiltration inside the silo.
The waterproofing of the silo floor foundation, to block the upward return of underground moisture
In rainy areas, the groundwater level is high, and during the rainy season, the soil moisture is saturated. Groundwater will penetrate upward through the foundation of the silo and the capillary pores of the floor, causing the silo floor materials to become damp and compacted. Many factories only focus on waterproofing the upper part of the silo and ignore the moisture prevention of the bottom, resulting in long-term damp and deteriorated materials at the bottom.
New silos should be equipped with waterproof membranes as a waterproof layer during the foundation construction stage to block the capillary infiltration of groundwater. When pouring the floor, use anti-crack and anti-seepage concrete to reduce the generation of fine cracks.
For the silos that have been in use, the gaps on the floor and cracks in the floor can be sealed and repaired. At the same time, drainage ditches can be excavated around the silo to promptly drain the accumulated water and avoid long-term soaking of the silo foundation by the water. This can reduce the upward return of underground moisture from the root cause.
Optimize the ventilation control logic to prevent the backflow of wet air during rainy days.
Distinguish weather conditions to adjust the ventilation strategy
Ventilation is a common method for controlling humidity in silos, but in rainy areas, ventilation should not be blindly activated. Forced ventilation during rainy, foggy, or humid days will directly introduce high-humidity outside air into the silo, exacerbating the moisture problem. The core principle of ventilation is to only carry out ventilation operations when the outside temperature and humidity are lower than those inside the silo.
On clear and dry days, natural or mechanical ventilation equipment can be activated to replace the humid air inside the silo and remove the water vapor emitted by the materials. During continuous rainy periods, all ventilation ports and windows should be closed throughout the process to prevent outside moisture from entering the silo. Adjust the ventilation plan flexibly according to daily weather and temperature/humidity changes.
Standardize the start and stop procedures of mechanical ventilation equipment.
For silos with mechanical ventilation systems, it is necessary to establish equipment operation norms adapted to rainy seasons. Before starting the fan, compare the temperature and humidity data inside and outside the silo to confirm that the outside air is dry before starting the equipment. During ventilation, operate at a constant speed to avoid rapid convection with large air volume causing condensation on the silo walls.
In case of sudden temperature drops or rises during rainy days, immediately shut down the ventilation equipment and close the ventilation channels. If there is a rainy weather after ventilation, the residual flowing air inside the silo will form a convection with the outside moisture, easily forming condensation on the surface of the materials.
After ventilation, promptly check the sealing status of the ventilation ports to confirm no gaps for air leakage, and record the humidity data inside the silo to provide reference for subsequent moisture prevention control.
Prevent moisture backflow caused by negative pressure suction
During the silo’s loading and unloading operations and equipment start-stop processes, a negative pressure state is prone to form inside the silo. High-humidity outside air will be sucked into the silo through various gaps. The negative pressure absorption of moisture in rainy weather will significantly intensify in such rainy and humid conditions.
During rainy and high-humidity weather, try to reduce silo loading and unloading operations to avoid drastic fluctuations in silo pressure. When operations are necessary, reduce the equipment’s operating speed to decrease the negative pressure difference inside the silo.
Standardize the entry and storage of materials, reducing the risk of moisture absorption from the source
Strictly control the initial moisture content of the materials entering the silo
In rainy areas, the air humidity is high. During the transfer, storage, and transportation of materials, they will naturally absorb water vapor from the air. If damp materials are directly entered into the silo, they will continuously release water vapor into the silo, increasing the overall humidity and causing condensation and clumping problems.
For various stored materials such as grains, feed, and powders, the moisture content must be tested before entry. Materials exceeding the standard need to be pre-sun-dried or dried, and then re-enter the silo for storage. Avoid transporting materials outdoors in rainy weather to prevent them from being directly exposed to rain and getting damp.
The entry of materials into the silo should be scheduled during sunny and dry periods to reduce the input operations in high-humidity weather. This way, the increase in moisture in the silo can be reduced at the source, and the subsequent control pressure for moisture prevention can be alleviated.
Optimize the stacking method of materials in the silo
If the materials are overfilled or have uneven density, the air circulation in the silo will be blocked, and the moisture will be difficult to dissipate, easily accumulating inside the materials. Especially in the center of the pile and the areas close to the wall, the ventilation conditions are poor, and the internal moisture is most likely to be affected.
After entering the silo, keep the stacking height of the materials reasonable, reserve a small amount of ventilation space, and ensure that the air in the silo can circulate slowly. Avoid stacking the materials closely against the silo wall, reducing the direct infiltration of wall condensation into the materials.
For long-term stored materials, regular turning and loosening of the surface layer can be carried out to break the dense and compact structure, release the accumulated moisture inside, and prevent the materials from becoming damp and deteriorating due to internal condensation.
Prevent the accumulation of moisture from new and old materials
During rainy seasons, there is a significant difference in moisture content between new and old materials. The moisture content of newly entered materials is generally higher, while the old materials are relatively dry. Storing them together will lead to the cross-penetration of moisture, causing the overall materials to become damp and deteriorate.
Try to store new and old materials in separate batches and areas, stack them separately, and control the humidity independently. Different moisture content materials must not be stored in the same silo to avoid the transmission of moisture.
At the same time, shorten the storage period of materials during rainy seasons to reduce the problems of moisture absorption and condensation caused by long-term static accumulation of materials, and reduce moisture-related losses.
Establish regular inspections to identify latent moisture-related risks in advance
Conduct regular humidity monitoring at key points
The moisture accumulation in silos is a gradual process. Initially, there won’t be obvious lumping or mold formation, which is difficult to detect with the naked eye. It is not until the surface materials deteriorate that the internal moisture problem becomes more serious.
It is necessary to set up temperature and humidity monitoring points at key locations such as the top of the silo, the side of the silo wall, the middle layer of the materials, and the bottom of the silo. Regularly record the data. Once local humidity abnormally increases, promptly investigate potential leakage, water seepage, and condensation issues, and intervene in advance for handling.
During rainy seasons, increase the monitoring frequency and record the humidity data inside and outside the silo at fixed times. Analyze the changing patterns to accurately grasp the material condition inside the silo and avoid delayed detection of potential risks.
Special inspections of the silo structure and sealing areas
Long-term rain erosion and temperature differences can cause aging of sealing rubber strips, cracking of waterproof coatings, and loosening of gaps. These hidden damages are the main reasons for moisture infiltration and are often overlooked in daily life.
During the inspection process, focus on checking areas such as roof waterproofing, door and window sealing, ventilation openings sealing, and silo joint gaps to check for any traces of water seepage, fallen rubber strips, or peeling coatings.
Fix any minor damages promptly. Do not wait until there are obvious water seepage or moisture accumulation problems before addressing them. Timely rectification of small issues can significantly reduce the probability of large-scale moisture accumulation.
Layered sampling verification of material conditions
The surface materials of silos are affected by ventilation, and their humidity is relatively stable. Middle and bottom layers of materials are prone to accumulate moisture, resulting in internal moisture accumulation and lumping. The surface shows no obvious abnormalities, and simply observing the surface cannot determine the true storage condition.
During the inspection, conduct layered sampling checks of the material conditions, focusing on the bottom and central areas, and check for any lumping, moisture accumulation, or odors.
For the identified localized moisture accumulation points, take measures such as ventilation to loosen, local dehumidification, and batch turnover to prevent the moisture accumulation area from expanding and causing greater material loss.
Conclusion
The moisture problem of silos in rainy areas is not caused by a single factor. Instead, it is the result of multiple factors such as the infiltration of external moisture, the loss of control of the internal environment, improper material management, and inadequate operation and maintenance protection. There is no one-size-fits-all solution for moisture prevention. The key lies in establishing a full-process, regularized full-process protection system that takes into account the high humidity, frequent rainfall, and variable temperature differences in the climate of rainy areas. This aims to reduce problems such as mold growth, loss, and compaction of materials, lower the operation and maintenance costs of the factory, and long-term protect the structure and equipment of the silos and ensure the stable operation of silo operations throughout the year in rainy areas.