By switching to a new diverter system, Capitol Cement has seen reduced electric costs and air consumption, increased storage capacity, and improved productivity

Over the years, Capitol Cement Corp.'s Martinsburg, W.Va. plant spent millions of dollars on electrostatic precipitators and dust collection equipment to control air pollution. More recently, maintenance and production teams collaborated to invest in valves that positively affected the company's bottom line.

In 1888, Standard Lime and Stone Co. was incorporated, and by 1965 it became Capitol Cement Corp., an operating division of Martin Marietta. The plant site is on 1,400 acres, which includes raw material reserves of about 80 years. Its labor force includes workers who are second- and third-generation employees. The company's marketing area stretches from Pennsylvania to North Carolina.

Capitol's 48 concrete silos, together with the truck facility bins, provide storage for nearly 75,440 tons of cement. When production changes to one of its nine types of portland cement or Brick-Lok masonry cement, they ideally divert the end of the completed run to the fringe bin. The line to the silo is then blown clear of cement preparing for the next product run. The diverter valve is then switched for flow to the appropriate silo.

This is the cement in the books; let's focus on the cement in the pipes.

Capitol Cement habitually repaired diverter valves that were included in the plant design when it was modernized in 1965. The fringe bin should be empty to accommodate the tail end of a production run when changing to the next product. Once the previous run is purged, you switch back to the silo and find the closed port has leaked and cement has built up downstream of the valve plugging this leg.

The decision must be made to either divert the off-spec product to several other silos for blending or to the fringe bin. Then, because both ports of the diverter have leaked, you discover the fringe bin is full and cannot accept this off-spec cement. Time is lost bleeding the contaminated silo diverting this to another silo reserved for off-quality product. This is the way it always has been done.

About every three months, maintenance would remove a leaking valve, replacing it with a rebuilt spare. The failed valve would then be sent to the shop for refurbishment and stored until it was again returned to service. To do this repair, production has to agree on when to shut down and schedule down time, and maintenance must plan the job.

Once shut down, it usually takes four hours to blow out the line. Removing the leaking valve and installing a rebuilt valve with shop time to fix the failed (with shop time to fix the failed valve) is another 12 hours, and you have only fixed one valve. Add to this the rental cost for a crane. Not typically considered in the maintenance costs is what happens to production and plant profitability when these diverters have seat leaks.

While cement is being blown to several silos to blend off-spec cement or to the off-quality silo, compressors are running, as is your electric meter, causing a shortage of compressed air at the plant. Time and money are lost to the detriment of making saleable product because of leaky diverter valves.

Opportunity for change

Tom Cluchey, maintenance manager for the three-kiln, 943,000-tpy Martinsburg plant, saw an opportunity in 1993 to change a 28-year-old habit by removing a single diverter and installing a pair of 8-in. BMV Everlasting Valves to divert flow from the silos to fringe bins and back. (The Everlasting Bulk Material Valve was introduced to the industry in 1991.) Maintenance inspects the valves once a year, and Cluchey said that after seven years in service, there has been no maintenance required on any of the valves installed, including the very first one.

Benefits at Capitol Cement from this tight-sealing, switch-on-the-fly valve are that compressed air is conserved, electric costs reduced, and increased storage capacity and productivity. According to Cluchey and Frank Sowers, production superintendent at the plant, the cement in the pipes is now more like the cement in the books.

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This article was adapted from material provided by Everlasting Valve Co., South Plainfield, N.J., (908) 769-0700.