News Articles


New Shell Sand Improves Core Production

By FMT Staff | Published January 31, 2007

Shell cores are an important component of the Tyler Pipe's North Plant casting operation in Tyler, TX — which produces more than 500 tons/day of cast-iron soil pipe, soil pipe fittings, drains, and valve boxes used in multi-story commercial building drain systems. In the shell process, coated sand is packed or blown into heated core machines, causing the viscosity of the coating to drop. The sand binder releases ammonia and formaldehyde, and begins to polymerize as it gradually locks the sand grains together while it cures into a resin.
Core-room manager Jimmy Allen explains: "The shell cores that we make are used to form the interior contours for many different sizes and shapes of low pressure gray-iron fittings, including p-traps, tees, y's, valve boxes, and extensions. Shell cores are also used on our hub-core machines to make the gasket seat end on a straight piece of pipe."

Not only are the cores critical to Tyler Pipe's product quality, but because the plant operates 26 shell-core machines, the large volume of shell-core sand it uses represents a considerable expense. In October 2005, the supply contract for resin-coated sand came up for renewal, and the plant's managers decided to consider new supply sources.

They set specific objectives to reduce costs and improve performance, and among their top goals was to cut down on core-machine scrap and reduce damage to finished cores during transport and handling. They also sought to reduce or eliminate lamination, peelback core defects, and uncured sand inside the shell cores. And, they wanted their finished shell cores to show more strength, have thinner walls, and better heat-transfer capabilities, all to reduce overall sand usage, shorten invest cycles, and reduce curing times.

During their evaluation, Tyler Pipe obtained a detailed cost analysis from Porter Warner Industries, a distributor of shell-sand products, whose technical sales specialist recommended converting to Technisand Signature Series, a low-emission resin-coated sand developed by Technisand Inc., a Fairmount Minerals subsidiary (www.fairmountminerals.com ).

The specialist, Don Markham, explains that "Technisand Signature Series grade S833R is a finer, denser material that gives better heat-transfer capability, eliminates breakage, and has much less odor than another resin-coated sand Tyler used previously. And, this resin-coated sand was actually lower in price than the material Tyler Pipe had been using in the past."

Since its introduction, Technisand Signature Series has exceeded Tyler Pipe's performance requirements. Allen observes that, "Technisand is a smaller-grain sand without the fines we had in our previous mixture, so it's a pure sand that coats much better. This results in greater tensile strength, better workability when the sand is made into a core, and a smoother surface inside the fitting."

He adds: "On the majority of jobs we are seeing faster cycle times. The ideal is a stronger core with reduced weight. When you reduce the weight of the core 20%, say from 10 to 8 lb, you reduce the cycle time. And, because the sand's formula has a higher melt point, there are fewer peelback core defects, lamination problems, and uncured sand inside the shell cores."

The assistant general manager at Tyler Pipe's North Plant, Kent Brown, confirmed the management's satisfaction. "We used to get quite a bit of shell-core breakage in the unit," Brown recalls, "but now I can tell from a visual inspection of the foundry that there is much less breakage — we no longer have piles and hoppers full of broken cores. We've also seen a reduction in the amount of core sand that we purchase. Our core department costs are down about 30.3% over the same period a year earlier."

Brown referenced the North Plant's improved working environment, too. "One of the other major benefits we received with Technisand Signature Series is that it has a pleasant, vanilla-like aroma rather than the strong, offensive formaldehyde or ammonia odor found in other resin coated sands. The product's patent-pending Neozien odor-abatement technology makes for a better working environment, and our employees comment frequently that they really like this feature."

Read the complete presentation, "New Shell Sand Improves Core Production, Enhances Working Conditions."


TECHNISAND SIGNATURE SERIES

  • Free phenol, less than 0.0015% in some formulations.
  • No strong ammonia odor.
  • Promotes a cleaner working environment, fewer organic emissions, and less smoke.
  • Greater core strength reduces breakage and scrap, and allows for thinner core walls that reduce invest and cure times.

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