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29.05.2017 Limestone silo unblocked – and kept that way

Martin Engineering, with worldwide headquarters in Neponset, IL, recently solved a blockage problem in a 486t capacity silo storing moist limestone. The vessel was becoming clogged on a regular basis, necessitating maintenance personnel to spend up to 12 hours each time to clear the blockage using tools and compressed air. Subsequently technicians from Martin Engineering were able to clear the blockage completely and then revised the existing air cannon system – which had previously coped effectively with dry limestone – to prevent the problem from recurring.
The silo, at the Drake Cement plant near Paulden, AZ, was unblocked by means of a Martin® Heavy Duty Whip. Powered by compressed air, the device can be equipped with a variety of flails and cutting edges to knock down accumulated material without damaging the silo’s walls or support structure.  Requiring no confined space entry, the device was set above the manhole opening at the top of the vessel and manoeuvred by remote control. Once the silo had been completely evacuated, attention was given to relocating the air cannons. Rather than the two cannons at the bottom of the limestone silo firing across the discharge flow, five cannons were strategically placed around the vessel. Three 70-litre Tornado Air Cannons were placed on the lower incline of the cone at a 30º downward angle against the 60º slope in the 6 and 12 o’clock positions (one side of the silo was inaccessible).  In the 3 o’clock position, one cannon was situated at the 60cm wide shaft, and another was added to the upper silo to aid in loosening material. A programmable logic control system centrally located in the facility coordinates and monitors the timing and firing sequence of each unit at all locations, including the limestone silo.  During the wet winter and monsoon months, the cannons are activated approximately every hour, but throughout the rest of the year the system has a firing sequence of only 4-5 times per day.  This pattern can also be manually activated from the weigh feeder, at the solenoid panel or in the control room. Martin Engineering has representatives or subsidiaries in most European countries.
The Heavy Duty Whip, which is remotely controlled, is set up above the access at the top of the silo; the lower silo air cannons (below) are shown strategically positioned around the 60-degree cone section

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