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Posted by Dennis Blauser, November 2, 2020
Storage silos are used in almost every industry to store materials safely until they are needed for use, but no matter the design or the materials stored, silos are susceptible to material flow issues caused by blockages.
 
Blockages not only lead to a reduced storage capacity and disrupted or slowed operations, they also promote bad flow characteristics. When material flow is off, delamination, exterior concrete cracking and structural failure can result. There are numerous blockage types possible in storage silos, two common flow issues are bridging or caking.
 
If there is a blockage and your silo is plugged, here's how to know whether it's related to bridging or caking.
 
Bridging
When material is poured into the storage silo it exerts pressure on the material under and around it, and with some materials, this surrounding pressure can cause a structural bond. This bond results in a bridging effect, where the bottom of the bridge empties but a dome arch remains, preventing any further material from flowing. As more material is dumped on top of the bridge the pressure exerted increases and the bonds holding the bridge together will actually become stronger.
 
Caking
Caking occurs when powder, such as detergents, fertilizers and salts, become cohesive after storage, forming agglomerates comprised of individual particles that are bonded together. Caking results when the magnitude of interparticle forces increase over time. The most common cause of caking is moisture migration due to temperature changes with materials that are soluble. Caking creates resistance to flow in silos and can result in residue on walls.
 
You can help reduce the likelihood of material build-up through a number of ways, click here to watch and learn more. Depending on how easily stored material compacts or hydrates, your silo may need to be completely emptied on a regular schedule as often as once a month or as little as every year.
 
Silos that are regularly emptied and refilled are less likely to experience build-up issues than in those kept topped off. Regularly emptied silos need professional cleaning less frequently in comparison. They are also less likely to experience issues like compacting and hydrating. Hydration occurs when moisture mixes with stored materials and causes them to solidify within the silo. When this happens, materials can expand and cause added wall pressure, increasing the likelihood of structural failure.
 
The routine examination of your silo is only effective in increasing facility safety and ensuring smooth operations when it is conducted in conjunction with professional cleaning and inspection services as part of a regular preventive maintenance schedule.
 
Whether you have bridging, caking or plugging of any stored material, it’s essential to contact USA Silo Service, a division of the Marietta Group, which includes Marietta Silos and Marietta Inspection Services, to have the build-up removed quickly. This recent case study shows USA Silo Service using their proprietary equipment and cleaning methods to remove coal build-up in a silo and greatly improve material flow.
 
To learn more, be sure to check out our full library of silo inspection videos on silo maintenance, inspection and repair on our .
 

 
Posted by Dennis Blauser, October 1, 2020

The two most common systems for constructing a concrete silo are Jumpform and Slipform. Concrete storage silos from 10' to 65' in diameter can be built using the Jumpform technique, while Slipform silos are best for construction projects over 65' in diameter.

Jumpform construction is one of the most flexible silo construction methods available in the industry today. So is the Slipform method. There are absolutely no shortcuts to either method because safety and performance remain at the forefront of every silo project. So, what determines the construction approach?

Jumpform construction is not as time sensitive as Slipform. Jumpform is completed in stages, offering some economies of scale associated with equipment installation, reinforcing steel assembly, rebar inspection and concrete pour to cure.

Jumpform can be the most economical construction choice. The form can be set-up and ready to make the first pour of concrete within a week. Because Jumpform is poured in increments, pour costs can be reduced by as much as 20% over Slipform construction where a continuous pour is required.

The Jumpform silo framework is reusable. It takes just a few days to set up after delivery to the job site. This form provides a safe, circular deck to access and erect the silo from the interior, creating a smaller job site footprint. When construction is finished, the form is quickly removed from the job site.

Marietta Silos' standard Jumpform horizontal construction joint detail creates a leak-proof joint system and is the best choice for concrete storage silos less than 65’ in diameter. Jumpform silos are poured in multiple sequences as opposed to a single sequence in the Slipform method. Therefore, an allowance in the time schedule permits a thorough quality control inspections of the Jumpform, steel reinforcements and embedments. Only then is the concrete segment poured.

Marietta Silos is the only Jumpform manufacturer in the country that complies with OSHA 125' scaffolding requirements.

While Jumpform is an ideal method for building concrete silos less than 65' in diameter, Slipform construction offers many advantages in larger scale silo design and construction; these are described separately.

To learn the step-by-step Jumpform process and to understand its efficiencies, watch our Jumpform silo video.

Check out our full library of silo inspection videos on silo maintenance, inspection and repair on our .

 

 
Posted by Dennis Blauser, September 1, 2020

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.

To learn more, be sure to check out our full library of silo inspection videos on silo maintenance, inspection and repair on

 

 
 
 
 
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