Busy cement manufacturers need their automated cement labs to be up and running 24/7 to keep up with production demands. In addition to the rigors of constant operation, these labs must often be able to run multiple samples at one time to ensure continuous process consistency within very close tolerances.

At Lehigh Cement Co's flagship plant in Union Bridge, MD, the automated cement laboratory is part of a recent modernization aimed at incorporating the latest technology for cement production, quality control, energy conservation, environmental protection, and worker safety. Serving the construction industry in North America for more than 100 years, Lehigh produces cements that are widely used by ready-mix concrete suppliers and for numerous highway, architectural, industrial and marine applications.

Boasting a capacity of 2 million metric tons of clinker per year, Lehigh's new facility is the largest and most modern in North America. A crucial component of the lab was a new European-made central vacuum system, added to evacuate excess sample and clean equipment from various sampling locations.

However, a number of vital factors were not taken into consideration when the system was originally specified, and when the lab was run under actual plant conditions, the system couldn't accommodate Lehigh's requirements for uptime. With as many as four and five stations open simultaneously, different types of materials being tested, and the heavy dust that was a byproduct of constant operation, the vacuum system quickly became overwhelmed.

With practically all velocity lost in the system, test material settled out in the lab's piping, stations became caked, and cross contamination occurred at various critical points. And, as the system became more and more clogged and contaminated, test results became skewed. In addition to unreliable test measurements and too frequent downtime, the lab also presented serious worker safety and maintenance issues.

In an effort to solve these problems and keep the lab up and running, Jeff Hook, Lehigh Cement's quality control manager, called on Dick Slechter of Gilro Associates, the Maryland Vac-U-Max representative, for advice.

"The vacuum system we were using was completely inadequate," Hook explains. "Rather than helping us, it was actually a hindrance. With uptime the key to our cement production, the lab needed to keep up with an unrelenting pace without losing any of its precision and accuracy."

Slechter visited Lehigh with a Vac-U-Max application engineer and performed a thorough audit of the lab's dedusting system. Using one of Vac-U-Max's local demo trucks equipped with a 15 hp portable vacuum unit, they soon determined that the system's pickup points were poorly designed and suggested a number of modifications that would help. And to increase airflow, they opted for a 20 hp, 700 cfm unit and found that it delivered the desired results.

In order to save plant floor space and still provide for proper filtration, a heavy duty weather-resistant Vac-U-Max 2120 receiver was installed outside, using a positive displacement pump that would be more durable under a constant load than the usual regenerative blower.

Providing direct dedusting and collection of debris into a 55 gal drum, the Vac-U-Max system features a 36 in. diameter receiver with 230 sq ft of filter area (providing a cloth-to-air ratio below 3:1 to minimize stress on the filters), and uses 19 long-lasting PTFE coated filters that filter down to 1 micron, and are relatively inexpensive to replace.

The system provides both continuous pulse filter cleaning and offline filter cleaning in order to accommodate its high-dust application; a severe-duty electric motor for continuous low maintenance, long-life operation; and UV-resistant tubing and paint to protect outside parts from the elements.

"Installed in January, after a few minor adjustments, the system has been running problem-free ever since," Hook reports. "Prior to changing over to the Vac-U-Max dedusting system, we had frequent system crashes caused by clogging in such central lab locations as the press, mill, receiving station, and x-ray machine. As the hours of lab downtime increased, our production output seriously suffered.

"Vac-U-Max helped us find a solution to these problems and was with us throughout the entire process, making sure that the system was properly installed and that the equipment performed according to its designed purpose. The bottom line? Vac-U-Max helped us turn our cement lab into a valuable asset, maximizing uptime and efficiency, while at the same time providing for improved environmental conditions."