New Shell Sand Improves Core Production, Enhances Working Conditions

July 29, 2006
Coremaker Sees Benefits, too

Tyler Pipe’s North Plant in Tyler, TX, produces cast iron soil pipe, soil pipe fittings, drains, and valve boxes used in multi-story commercial building drain systems around the world. The McWane Inc. division is a large-volume operation, too, producing in excess of 500 tons/day of cast iron products. Producing on that scale makes it difficult to institute effective environmental updates and improve product quality, until recently.

But, Tyler Pipe recently adopted a new Technisand Inc. shell-sand formulation, and according to the plant’s operators the results have made the operation more productive and efficient, and improved working conditions.

Shell cores are an important component of the Tyler North Plant’s casting operation. 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.” Allen adds that because Tyler’s North Plant currently operates a total of 26 shell-core machines, the large volume of shell-core sand it uses in the process represents a considerable expense.

The resin-coated sand supply contract came up for renewal at Tyler Pipe last October, 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. Other problems they sought to reduce or eliminate were lamination, peelback core defects, and uncured sand inside the shell cores. And, they wanted their finished shell cores to show more strength, 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 that has been a longtime supplier of shell-sand products. Porter Warner’s technical sales specialist, Don Markham, recommended converting to Technisand Signature Series, a low-emission resin-coated sand developed by Technisand Inc., a Fairmount Minerals subsidiary. 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 the other 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 peel-back core defects, lamination problems, and uncured sand inside the shell cores.”

The assistant general manager at the 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.”

Coremaker Sees Benefits, too

Another recent convert to Technisand is Bender Foundry Services, a Sigourney, IA, supplier of cores to ferrous and nonferrous jobbing foundries, as well as manufacturers of agricultural, pump, and gearbox castings. The company uses several binders in its coremaking processes, which includes the shell-sand process.

In fact, more than half of all Bender’s output is produced by the shell-sand process, and recently Bender adopted the Technisand Signature Series product.

“Our previous supplier had some real consistency issues,” according to Doug Bender, owner of Bender Foundry Service. “Peel-back was a big problem and we had to make heavier cores, which increased our cycle times. Since switching to Technisand products, those problems have been eliminated. We’re running the new Signature Series sands and they’re great.”

Bender has noted free phenols reduced to an exceptionally low 0.3% level. Additionally, free formaldehyde and tar pitch in the coreroom’s ductwork have been reduced, and Bender has had no problem staying below permissible emissions limits (PEL).

When the Signature Series sands were being tested, Bender Foundry Service was in the process of a large-scale expansion, bringing its total number of shell-core machines to 20. Not only did the operation remain below the PEL throughout the expansion, but the in-plant environment has shown improvements, too.

“Even after adding several new shell-core machines, we had no problem staying under the PEL. We actually saw a decrease in our emissions,” says Bender. “We also see a noticeable reduction in smoke and cleaner-running core boxes. This significant improvement in cleanliness has allowed me to reassign a full-time worker who used to just clean core boxes.”

All of these improvements were realized without sacrificing core quality. Bender Foundry Service still achieves good core production speeds and invests, and hasn’t seen any reduction in tensile strengths or changes in core weights. In fact, throughout the launch and continued use of Signature Series, Bender has never changed a single core machine setting.

Consistent core quality, low smoke, easier cleaning, and ultra-low organic emissions aren’t the only benefits. The Neozien odor-abatement technology has actually eliminated the shell process’s strong, annoying odor. “With Neozien (patent pending), our operators can literally put their faces in the invest area and they are not taken aback by bad odor,” Bender claims. “The air is easily breathable and there is no longer that noticeable ammonia smell. Technisand has been able to neutralize the odor.”

“I had six customers through the plant this week, and they’re all asking when they can get cores produced with Neozien. This product is great! We won’t go back to the old coated sands.”