Silo cleaning is a maintenance job that calls for special cleaning techniques. Whether a silo holds flour, grains, coffee, or even bulk cement, eventually it will need to be cleaned.
Periodic silo cleaning is necessary to:
• Remove the buildup of old residue inside a silo that reduces the volume of new product the filled silo will hold. In all silos, cleaning removes old product residue which in turn helps maintain the freshness of newly introduced product.
• In food product silos, cleaning controls fungal, bacterial, insect growth, and other sources of contaminants.
• Allow for inspection of the silo to determine areas that need repair and the overall condition of the structure. A coating system that is failing, or a water leak in the silo, is often undetectable when covered by product buildup.
• Wall and cone buildup of product inside the silo impedes the proper flow of the product to the auger or pneumatic conveyance system. This increases the likely hood of silo "bridging".
Cleaning the interior of a silo is not an easy job. These structures can be up to 200 feet tall and 90 feet in diameter.
Because it is a confined space, cleaning a silo is a challenge that requires special training, epecialized equipment, and techniques to enter.
In food product silos, confined space entry must also incorporate GMP (Good Manufacturing Practices) procedures and guidelines.
Dangers Associated with Silo Cleaning
Silo cleaning presents very real and potential dangers for anyone entering a silo for inspections, repairs, or cleaning. Falls, noxious gases, depleted oxygen levels, and entrapment are all associated with silo cleaning. Grain and flour dusts can form explosive clouds subject to spontaneous combustion due to suspended particulate matter, oxygen, and an ignition source all being present in the silo. Coupled with oxygen and particulate suspension, a spark can be devastating.
Silos, especially those in an outside environment, are affected by temperature, moisture, and vapor drive. The temperature differences in a silo or bin containing stored grains causes moisture to move from areas of warmer grain to areas of cooler grain. Moisture condensation can occur resulting in clumping of the grains. Mold can also cause the grains to clump together.
With enough moisture, limited flow, and time, the clumped grains can create "silo bridging".
Grains, flour, peanuts, beans, and other stored products, all have the potential to form a bridge that resists the downward gravitational pull as the product is removed from the bottom of the silo This creates an empty space or pocket underneath the bridge.
From a hatch opening at the silo top, the bridge may appear solid, but if a worker steps onto the bridge, it can collapse or cave in. This can create an avalanche of product that can bury the worker. A worker standing under a bridge can also be buried if the grain bridge were to suddenly and unexpectedly collapse.
Stored products clinging to the wall of a silo (which can be several feet thick) poses the same danger should the wall of product suddenly collapse on a worker inside the silo. Even though a wall of product attached to the sides of a silo may appear safe, a worker inside the silo could accidentally weaken the support of the wall buildup causing it to collapse onto the worker.
Cages built inside silos, and used as a platform for cleaning and servicing the silo, can have breaks or weakened support areas. These should be inspected before an OSHA trained and safety equipped worker steps onto the platform. These platforms allow only limited access to the silo interior. To gain complete access for silo cleaning, a safe suspension and retrieval method, as well as training, is required.
Cleaning Silos the Wrong Way
It is very easy to hose down or pressure wash the interior of a silo from the top down without ever having to conduct a confined space entry. A few food industry facilities have tried cleaning silos this way, and many still use this technique, and have paid a significant price in the form of major litigation and mechanical and manufacturing issues.
Moisture is a required component for the growth of a variety of organic problems in the food industry. Silos often have nooks and crannies where moisture can be trapped. When a food source is added to this trapped moisture, organic matter can start to grow. The resulting organic growth could poison or contaminate the product, resulting in serious issues for the manufacturer.
Pressure washing the interior of a silo is not a good idea unless there is absolutely no other alternative. If pressure washing is used to clean the interior of a food silo or other storage vessel, care should be taken to insure the cleaned silo is completely and thoroughly dried before filling.
CO2 (dry ice) Blasting is a Completely Dry Cleaning Method for Silo Cleaning
Mold spores are found everywhere. They are part of the natural environment. There is no reliable way to completely eliminate them. The best way to control mold growth is to control moisture.
Of the 4 basic requirements for mold growth (available mold spores, food source, temperature, and moisture), the availability of moisture is the easiest to control.
The advantages of blast cleaning food silos with CO2 instead of pressure washing:
• Mold growth is inhibited because no water is used
• Silo surfaces are decontaminated
• No secondary waste stream-food silo residues can be removed by vacuum
Good Manufacturing Practices (GMP)
Blackwell's, Inc. specializes in servicing the food industry and believes that the American food industry is the safest and best in the world. Our goal is to be a significant player in this industry. We strive to make sure we provide associates that are well versed in GMP and use equipment that is clean and sanitized for use in these food facilities.
Blackwell's, Inc. spends much time and effort to insure that our equipment is not a source of contamination or infestation and focuses on FOD (foreign object or debris) prevention within the confined spaces we enter in these facilities.