In cement manufacturing, despite precautions taken by proactive managers, blockages are a common occurrence in storage vessels and throughout the production line. If neglected, blockages can reduce storage capacity, affect production, and lead to costly plant shutdowns.

As blockages are often caused by uncontrollable factors, such as weather, material volatility, or passing time, regular maintenance is one of the best counteractive measures managers can take. A plant production crew with the appropriate tools can effectively eliminate flow problems as soon as they are detected, keeping equipment, product quality, budgets and delivery deadlines in order. Implementing Cardox — a high-pressure, carbon dioxide blasting system offered by Mankato, Minn.-based Pneumat Systems — Cemex's Odessa, Texas, cement plant provides a case study in the successful application of tools right for the job.

Cemex discovers Cardox

For blockages in the preheater tower at the Odessa plant, material volatility is often the culprit. Sodium, sulfur, and chlorides enter the chamber in gaseous form; as these gases meet cooler temperatures, condensation occurs, and the materials return to a solid state.

Often the material condenses on the sides of the tower, causing a hard layer to form. Buildup of this type could take anywhere from 1½ to 10 hours to remove manually, depending on the location and extent of the accumulation. Not only is manual removal of the material a time-consuming task, it entails a significant safety hazard as well.

Tom McCoy, process engineer at Cemex, explains that when employees clean a tower manually they are exposed to hot dust that has reached temperatures of 1,500° to 1,600°F. Accordingly, he says, “To avoid someone getting burned, we want to minimize exposure to this dust.” Further, Plant Manager Kevin Kelley points out that if pressure is allowed to build in a plugged tower, the extremely hot dust can “blow and spray out like water.”

To prevent such hazards, Cemex performed regular maintenance with a blasting system throughout the production line. When the supplier's service was found lacking, Cemex invested in the Cardox System to safely clear blockages in the preheater, feeder systems, cooler systems or kilns. McCoy points out that the new system minimizes exposure to hot dust: “In the preheater tower, for example, the Cardox only needs a 2-in.-diameter entry port.”

Powerful enough to clear concrete and other rock-hard materials from a bulk materials handling line, Cardox instantaneously releases liquid carbon dioxide at up to 34,000 psi, creating a force that will dislodge tons of blockage with a single blast in milliseconds. Originally designed for use in coal mines where volatile methane gas poses the constant threat of explosion, the system works where other tools would be prohibited because its operation depends upon the controlled release of CO2, a gas that can be used in high-temperature production areas and where hazardous, flammable, or combustible materials are stored.

At the Odessa plant, 16 employees were trained to use the new system. McCoy reports, “The training was very helpful. I appreciated the open format where the agent fielded every question we threw at him.” Adds Kelley, “It is clear that Pneumat takes pride in their systems and wants customers to use their products to the full potential.”

Gentle blasting power

The heart of the Cardox System is a reusable, high-strength alloy steel tube, which holds a charge of liquid carbon dioxide and a safety heater. When the heater is remotely initiated by a small electrical charge, the CO2 reaches the shear pressure of the rupture disc (to 34,000 psi). High-pressure CO2 is instantly released through discharge-head ports, creating a force to dislodge the buildup. Heat generated within the cartridge is automatically cooled by sudden expansion of carbon dioxide, and there is no flame, so the Cardox cartridge cannot set off an explosion.

Once fired, the Cardox tube is rebuilt with a new safety heater, shear disc, and sealing washer and recharged with CO2 for another use. Designed to be used, rebuilt and recharged, each tube has a useful lifetime of more than 10,000 shots.

The manufacturer notes that Cardox is easy to use. First, the tube is charged with a critical amount of CO2 by means of a Rapid-Fill Station, employing a positive-displacement, air-driven pump to fill exactly the right amount so that no CO2 is wasted and a 50-lb. bottle lasts longer. The Cardox tubes are then inserted into the material they will dislodge. In areas where problems recur, a permanent Quik-Lok Socket Base and Plug provides convenient access. When placing tubes directly in the material to be dislodged through a porthole in the vessel, an exclusive threaded head accepts a heavy-duty eyebolt for secure retention and retrieval of the tube. Also, shafts can be added for easy placement in hard-to-reach areas.

Once the tubes are secured, a charge is initiated with a Remote Energizer, a mobile unit that allows the operator to remain at a safe distance. After firing and retrieval, the tubes are torn down, rebuilt, and recharged using the system's 360° Air Vise.

Maintenance a priority

Regular preventative maintenance is essential in the cement industry in order to prevent costly down time or safety hazards. A product like the Cardox system can be used online, making it an asset to cement manufacturers, developers contend. While a regular maintenance program carried out by a company's own employees is often the most practical solution, contract cleaning is also an option. Pneumat, for example, regularly uses its products in the field for contract cleaning services. In either case, quality service is an essential adjunct to a quality product.

This article was adapted from materials provided by Pneumat Systems, Inc., 1-800-458-9446.