Blain sand and Gravel screens out unnecessary costs at new plant

The Blain Company Mount Olive, Mississippi

Blain's Natchez operation begins with an 8' by 20' triple-deck Deister screen. Material between 1/8" and 2" goes to the 48" by 30' log washer

The dewatered mason sand drops out of the cyclone into Blain's self-designed "see-saw trough." When one pile of sand has been filled, the trough tips and fills another pile.

Every new sand and gravel plant goes through a shakedown phase when equipment and methods are fine-tuned for efficient operations. But when the concrete sand product from Mike Blain’s new plant failed to meet spec, he wasn’t happy with the apparent option–a six-figure capital equipment purchase.

Founded in 1965, the Blain Company opened its first sand and gravel plant in Crystal Springs, Mississippi, to supply materials for highway construction. The company has grown across Mississippi since then. Its headquarters are in Mount Olive, Mississippi, with other operations in Crystal Springs, Natchez, Hattiesburg, and Columbia.

A few years ago, Blain’s operation in Natchez was nearing the end of its old deposit. A new deposit had been found five miles outside of town. Instead of moving the old plant, Mike Blain decided to build a new plant with all new equipment. Since the new site was projected to give the company over 30 years of sand and gravel reserves, the new plant was worth the investment. The new Natchez plant was designed for input of 600 tons of pit run gravel per hour, with output of 250 tons of washed gravel per hour. Annual production was estimated at approximately 250,000 tons of washed gravel and a supplementary 150,000 tons of sand.

The first product the plant was set up to produce was Mississippi DOT spec concrete sand. Processing begins when pit run material is dumped into a 75-ton hopper, and conveyed on a 36-in. belt to a slurry box set up over an 8-ft. by 20-ft. screen box equipped with a Dur-X-Snapdeck® urethane modular system. The top deck takes off material larger than 2 inches, which is stockpiled.

The material smaller than 2 inches, but larger than 1/8", is run through a 48-in. by 30-ft. log washer, then stockpiled for processing. Material passing the 1/8" slotted bottom deck originally ran directly into the sand screw-but that created a problem.

“We couldn't clean out all of the fines, mud, and silt,” Mike Blain said. “Extra fine sand ended up in the final concrete sand product, throwing it out of spec.” Equally bad, Mike added, was that water overflow loaded with extra fines discharged into the settling ponds and filled them faster than normal.

Blain’s Natchez crew tried using a 30-in. cyclone from their old plant, locating it over the sand screw and feeding sand to it with an 8 x 8 slurry pump driven by a 60 hp motor. With the cyclone, 60% to 63% of the product passed, meeting the MDOT spec for concrete sand. But using the cyclone didn't prove to be an efficient solution. To increase production and efficiency, Mike Blain was looking at a $300,000 investment in a sand classifying tank.

Fortunately, the local Durex dealer, thought that there had to be a better-and considerably less expensive way to improve the quality of the sand, and reduce the amount of fines sent to the settling pond. The dealer called Rick Beduhn, the Durex regional manager of dealer services, and together they consulted with the company engineers. The Durex team recommended installing a urethane curved sieve between the screen and the sand screw.

Durex had previously proven the cost-efficiency of its Dur-Elast® urethane curved sieves in several coal slurry applications. The molded tapered openings on the Durex curved sieves provide an effective water cutting design which produces more efficient, and consistent, dewatering. The coal slurry applications also demonstrated that Durex urethane screens have a wear life about 10 times longer than profile wire, and require turning about five times less often, which means far less downtime. With Durex engineering and field experience behind them, the dealer and Rick knew that a curved sieve would work for Blain.

The installation took just one day, with Blain’s Natchez crew doing the work themselves. They started with a Durex 0.75mm urethane screen, with 1-in. long slots, attached to a stainless steel frame. The material coming off the top of the sieve, then into the sand screw, produced concrete sand which met the MDOT spec at production levels better than the cyclone method. Eventually, the sieve was changed to a 1mm slotted opening for slightly coarser sand.

Not only did the Durex sieve solve Blain’s concrete sand problem, it provided an unexpected bonus: mason sand. The Blain crew simply pumped the underflow from the 100-mesh curved sieve to a 15-inch cyclone for separation.

By making a relatively small investment in a Durex urethane curved sieve, Blain's Natchez operation now produces two high quality products: concrete sand and mason sand. The cost of electricity alone, for operating the slurry pump and 30-inch cyclone, added up to about $5,000 per year-versus almost no annual cost for the curved sieve. The settling ponds are a lot cleaner, which also reduces maintenance time and costs. And best of all, Mike Blain got the products he wanted without buying a very expensive classifying tank.

“This is a perfect example of Durex partnering,” Rick Beduhn says. “It‘s our customers, dealers, and Durex engineers working together to help our customers solve problems, save money, and increase production.” Mike Blain agrees. “We‘ve been pleased with the whole setup of this plant, and the production as well. Durex worked with us directly, and through their regional dealer, who provided on-the-spot attention to our needs. They made sure we were satisfied with all of their products and recommendations.

“The curved sieve was a dramatic example of cost saving at our Natchez plant. But Durex screens are also used in many other areas of our plants. You add it all up and the Durex products make a nice contribution to our bottom line.”