Silo maintenance method averts confined space entry
- Written by CP Staff
|The Commercial Acres ready mixed plant is located in Normal, Ill., adjacent to the Bloomington home base of owner Stark Excavating Inc.|
A central Illinois ready mixed concrete producer has resolved material build-up issues in three storage silos where accumulation had slowed production and increased internal pressures, eventually damaging the vessel walls and forcing a shutdown. By enlisting the Martin Engineering silo-cleaning crew, the Commercial Acres RMC facility, whic is owned by Stark Excavating, was able to have the vessels safely emptied and ready for repair in 10 working hours—without confined space entry.
Commercial Acres runs a Treyco model capable of producing more than 200 yards per hour. The plant includes three 125-ton storage silos measuring 30- x 30- x 57-ft., two for cement storage and one for fly ash/pozzolan.
“Over time, material dust in the three pneumatically-loaded silos gradually built up, first on walls and ridges and eventually clinging to all the interior surfaces,” says Concrete Production Manager Jeff Jackson. “As a result, the air flow became constricted, raising the pressure within the silos and exerting greater force on the structure, connections and piping.”
The compacted material build-up continued to collect particles, effectively shrinking the internal space as the pneumatic blower forced more material through the silos. The severity of the problem became apparent to system operators when they noticed the walls of the silos were actually starting to bulge outward. During a shutdown and inspection, staff observed interior damage and determined that over-pressurization had compromised the three vessels’ structural integrity.
|Bulging sidewalls were the most visible sign of material build up in the plant’s cement and fly ash silos. Martin Engineering crews remain outside silos thanks to the Martin Heavy Duty Whip, requiring an opening as small as 18in. to dislodge material through a vessel.|
The need for repairs was clear and immediate, but the material build-up presented a serious obstacle. Mindful of Martin Engineering’s silo-cleaning service, and familiar with its conveyor belt cleaners and related components, Jackson contacted the manufacturer about the problem.
WHIPPED INTO SHAPE
After a Martin field supervisor visually assessed the silos’ material build up, a two-man crew was dispatched ready to deploy a Martin Heavy Duty Whip, one of several technologies that make up the company’s Silo Solutions product line. A portable, remote-controlled tool that can be lowered into storage containers through a manhole opening, the whip is powered by compressed air and bears a proprietary motor that can use a variety of different flails and cutting edges to knock down accumulated material without damaging vessel walls. Abrasion-resistant steel chain is best suited for most applications; urethane flails can also be employed to protect lined vessels that could be susceptible to damage from metal tools.
Martin’s top-access cleaning technology eliminates the need to send a crew member inside a storage vessel and risk potential injury. The equipment is set up outside the silo, and is portable enough to maneuver around various bin sizes and shapes. The whip’s modular boom extends up to 28 feet and can clean vessels up to 60 feet across from a central, 18-in. diameter opening. The air hose is protected with double wire braid, and the pneumatic motor delivers powerful cleaning action from the rotating head to remove buildup.
“Part of the success of the Whip is its straightforward, air-driven design,” notes Martin Silo Supervisor Gregg Pickering. “Competing systems that run on hydraulics tend to be heavy and cumbersome. They also present the possibility of a fluid leak, which could damage otherwise-salvageable material. The pneumatic whip needs just 100 CFM at 90 psi, which can usually be supplied from a plant’s existing compressed air system.”
The technicians secured the equipment over an access hatch at the top of each Commercial Acres vessel. Though all Martin silo cleaning crews are OSHA and MSHA certified for confined space entry, they instead used remote control from outside the bin to safely guide the cleaning head. The two-man crew lowered the whip through an opening in the blockage, starting at the bottom and undercutting the material as they worked their way up. In most cases, the technique allows material to be recaptured and returned to the material stream; indeed, Stark was able to salvage the entire 40 tons of cementitious product removed.
The entire process limited downtime to a single day, the crew a) removing all internal horizontal supports; b) pulling all sidewalls back to their original flat position; and, c) replacing the horizontal bracing and adding further dimensional support. — Martin Engineering, Neponset, Ill., 309/852-2384; www.martin-eng.com