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CEMENT AMERICAS • Winter 2015 • www.cementamericas.com 20 FEATURE ASH GROVE CEMENT or special mounting plates, and dis- charge nozzles are embedded directly in the refractory lining of the pre- heater tower. All of the air cannons in the main pro- duction line network are equipped with the Martin Engineering XHV Valve, designed specifically to deliver premium performance and long serv- ice life in preheater towers, clinker coolers and other high-temperature applications. The negative pressure-firing valve was developed to provide reliable op- eration and long service life in chal- lenging applications. The cannons discharge in a timed se- quence that moves in an upward spi- ral around the tower firing about 20 seconds apart, with the entire cycle taking just over eight minutes to complete. Control room operators can alter the schedule to accommo- date a range of kiln pressures and operating conditions, extending the sequence to as much as 45 minutes. A crew from Martin Services installed the entire system, including cannons, air lines and controls, as well as the company's Thermo Safety Shields on each unit. Operating like trap doors, the sliding shields bolt in between the air can- non valve and mounting flange, help- ing to protect workers from exposure to severe heat, gases and high-tem- perature materials. STAGE II Based on its success with the initial air cannon system, Ash Grove started planning a similar system for the plant's second production line. For that opera- tion, engineers designed a network of 15 additional air cannons, equipped with Martin Tornado Exhaust Valves. Described as the latest advancement in air cannon valve design, the patent- pending Tornado Exhaust Valves fires in response to a positive air pressure surge delivered by a solenoid valve, which can be located as far as 200 ft. away. The unique design improves air can- non safety, since the discharge se- quence requires a positive signal. Unlike negative pressure-firing de- signs, a cannon equipped with the Tornado valve will not discharge ac- cidentally in response to a pressure drop, so an air supply failure or bro- ken line won't trigger its firing. In addition, this positive-acting valve amplifies the discharge force, deliv- ering up to 20 percent greater force than a standard XHV-equipped air cannon of the same size. RESULTS With the new air cannon network in place, the Louisville plant has been able to significantly reduce the need for water blasting. Material now flows more efficiently, and maintenance personnel have drastically reduced the man-hours that were spent on manual removal. "We still hydro-lance occasionally, because of changes in raw material or fuel," Junkins explained. "But we don't have the issues we had before. We can see that the air cannon sys- tem has paid for itself, by allowing us to maintain production rates without many of the interruptions and issues that water blasting created." F Information courtesy of Martin Engineering.