It's not an easy job cleaning a silo. These structures can be up to 200 feet tall and 90 feet in diameter. Cleaning the interior of these silos are a challenge and require special training and techniques to enter these confined spaces.
Zach Cato, one of our Blackwell's supervisors wrote a description of the work done just to get ready for cleaning a food silo recently. Zach describes the work below.
"The entire bottom air agitation system had been disassembled so the silo was completely open at the bottom. I hung plastic over the equipment that was directly below the bottom opening and let the rest fall to the floor. We set up red danger tape in Xs on all of the doors leading to the bottom room of the silo house.
All confined space procedures begin with monitoring the air inside with a gas monitor and completion of required permits. Once the air quality inside the silo is determined, only then is the entrant allowed in to the confined space.
The confined space attendant continually observes the entrant
for signs of distress or needs while the entrant is inside the silo.
When the filters on top of the silo were removed from the housing, we set up our entry equipment. We used a tripod to enter the silo from the top hatch. The tripod legs had to be adjusted to different lengths to compensate for the dome shaped roof of the silo. Attached to the tripod was a winch that lowered theboatswain's chair (or bosun's chair) up and down. This is a device used to raise or lower and suspend a person from a rope or cable to perform work aloft.
Attached to the tripod was another winch for primary fall protection. This winch’s cable was attached directly to the D ring on the back of the entrant’s full body harness. We also took advantage of a basic safety life line rope with a rope grab connected to the entrants' harness for a secondary fall protection measure. We utilized an explosion proof light with a shatterproof bulb and a large Copus blower to ventilate the space.
A checklist was made of every piece of personal protective equipment that was on the entrant once his pockets were emptied and all jewelry removed. The entrant wore a Tyvek full body suit with coverings for the boots. He wore his full body harness along with a respirator, hairnet, safety goggles, and ear protection.
Setting up the equipment for the entry took us about an hour and a half from the time we arrived at the plant.
While inside the confined space of the silo, the confined space attendant would keep eyes on the entrant at all times to assist him with things such as raising and lowering the winch, adjusting the lighting and ventilation, and giving helpful calming advice. The attendant wears the industrial facility's required plant PPE along with a full body harness of his own. The entrant and the attendant communicate verbally and confirming short commands using hand signals.
Once the air quality inside the silo is determined,
only then is the entrant allowed in to the
confined space of the silo.
Once we had completed the brush down, men from the industrial facility assigned to assist us brought us a sanitizing solution in the pump up sprayers that we provided. I put on a new Tyvek suit and sprayed 3 gallons of the solution evenly on the interior of the silo including the roof and bottom cone. After completing the spray down, we packed up our equipment and lowered it down to ground level using the crane. We made sure to remove all of our locks and caution tape and sweep up the flour that had fallen through to the bottom floor.
When our work was checked and signed off on, we returned to Lagrange".
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