Prevention is the most effective method to ensure the integrity and continued operation of your silo. Regular maintenance and inspections can increase the life of your silo and ensure the safety of those working around your structures.
Though frequent inspections should be conducted in-house to catch warning signs early on it is important to understand the accompanying limitations. Many serious issues can only be identified by experienced silo inspectors or silo engineers during in-depth examination of empty silos free from material buildup.
The routine examination of your silo is effective in increasing facility safety and ensuring smooth operations only when it is conducted in conjunction with professional inspections as part of a regular preventive maintenance schedule. When used in place of professional services, in-house inspection, cleaning, and repair procedures increase safety risks. Failed silos can sometimes be repaired and some stored material can be recovered. However, companies often face additional costs from cleanup, possible environmental damage, injury, or loss of life.
While working on welding and fabricating metal bins for a concrete silo in December 2016, a fire broke out and resulted in the death of one crew member. After determining the crew did not have the required confined space permit, a general negligence action was settled for $1.75 million. (Michigan Lawyer Weekly, April 2017)
In August 2013, employees at an Ohio-based concrete facility attempted to remove material buildup of fly ash clumps in a clogged silo. After cleaning attempts of the interior using “a metal bar and air hose failed” an employee, who entered the silo without a lanyard and harness, died when a fire erupted. During the investigation, OSHA noted 10 serious safety violations, which resulted in a fine of $55,800. (OSHA News Release, November 2013)
Both of these accounts highlight preventable accidents where the necessary confined spaces permit was not held and the workers did not have the necessary safety training. Confined space permits and safety training are essential for safe inspections. While there are no inspection recommendations specific for silos, OSHA does have policies regarding confined space entry that are essential for interior inspections.
The effective inspections, however, depend on more than this permit. Inspectors must also have field experience and an understanding of the unique properties that effect silo material flow and structural integrity. Industry experience further enables trained silo and bin inspectors to recommend preventative maintenance to address issues before they become serious problems. Only inspectors with industry experience and proper silo engineering, design, and construction training can anticipate these issues to increase the effectiveness and safety of your silo.
It is recommended that you conduct professional inspections at two- to five-year intervals to help identify any issues that could lead to structural failure. Silo inspections should include examining the main aspects known to be potential areas of failure. These inspections should include the foundations, walls, cones, discharge configuration, floors, shelves, tunnels, and roofs.
The Mine Safety and Health Administration (MSHA) and OSHA have consistently emphasized a focus on silo processing and activity, but in recent years, one of their primary efforts has been on the importance of workplace safety and accident prevention. When it comes to the enforcement of safety policies, if there is an issue within a facility, the MSHA and OSHA are expecting to see a current silo inspection report for reference and assessment. Many insurance companies are also now requiring silo inspections on the facilities they insure.
Inspections can uncover problems that require immediate remediation. The most important thing to remember when conducting silo inspections is to consult a professional silo inspection and repair company if you discover anything alarming. You should also defer to a professional inspector if you do not have personnel with the necessary permits for closed space entry.
The importance of having regularly scheduled inspections by a professional silo company is even more evident in a recent case study in Florida where multiple discharge asymmetric flow failures were present.
Concrete stave silos are reinforced with exterior, galvanized steel hoops, which help compress the walls and provide necessary tension for structural integrity. The concrete staves act to distribute the load of the material over the hoops.
The hoops are the primary structural stabilizer of the silo and for this reason; it’s essential to inspect the condition of the exterior hoops, as they are vital to the health and safety of the silo. The exterior hoops shouldn’t be bent, broken, falling off, or lying on the ground. It’s also important to make sure the hoops aren’t heavily corroded. Hoops are bolted together with a lug, which can lead to issues if it begins to corrode. The hoops are tensioned to a specific rating and pressure, so it’s essential that the hoop has not been welded to and stands independently.
Since stave silo construction utilizes steel galvanized hoops for structural integrity of the bulk storage system, failure to protect these hoops properly will shorten the designed stability of the entire system. A cementitious silo coating is ideal on concrete stave silos, protecting the steel galvanized hoops and preventing leakage. These bonding and waterproofing agents seal the joints between the staves and add a level of corrosion protection to the exterior steel hoops, ensuring long lasting defense against corrosive elements and deterioration.
One recent case study examines a concrete stave silo with rusted and broken hoops, showing further evidence that failing to inspect your silo regularly will put your silo’s structural integrity, operability, and safety in jeopardy and require costly repairs in the future.
The quality of your stored cement can be compromised by the conditions on top of and inside your cement silo. In fact, no matter the design or the materials stored, silos are susceptible to material flow issues. Material flow that is unimpeded by moisture or other issues is essential for smooth operations and the continued functionality of your silo.
To prevent stored cement from setting inside the silo due to moisture and humidity levels, the structure must be completely watertight. Even the smallest leaks in silo roofs and walls can damage your stored cement and result in material flow issues. Ambient humidity levels can also cause some materials to set. If you do aerate stored materials, it is essential to use an air dryer system to help lower the ambient humidity level in your silo. You should also avoid over aerating stored materials as excess aeration can pump unneeded moist air into the silo, which may lead to hydration of the cement. Hydrating occurs when moisture mixes with stored material and causes it to solidify within the silo (cement is highly susceptible to hydrating). When this happens, the cement can expand and cause added wall pressure, increasing the likelihood of structural failure.
Silo Maintenance Schedules
Verify during inspections that regular preventive maintenance measures are being followed. Essential maintenance includes exterior waterproof coatings and keeping your air pad and air stones in good operational condition. Silo maintenance should also include a routine professional cleaning and regular, complete silo emptying.
Of these measures, one of the most important is regular emptying. Silos that are regularly emptied and refilled are less likely to experience buildup issues that can be seen in silos that are kept topped off. Regularly emptied silos need professional cleaning less frequently and are less likely to experience problems, such as material compacting and hydrating.
The importance of inspecting your silo on a regular basis and making sure your structure is protected from the elements, especially the roof, is the focus of one of our recent case studies, which specifically examines a leaking concrete silo roof, with cement stored inside.