Detailed Planning Makes Large-Scale Forging Possible

One of 2007’s largest finished forgings is a kiln tire produced at Ladish Forging in Cudahy, WI, for a European quarry operation. A kiln tire is a metal ring that surrounds and supports a tubular rotary kiln designed to process cement and other granular materials. In processing material in a rotary kiln, the tires attach loosely to the shell. Since the tire must fit the shell snugly, accurate design and manufacturing is critical. It also should allow thermal movement, riding on rollers that support the kiln but allowing rotation with the least degree of friction.

Shipped in late September, the finished seamless rolledring that became the kiln tire measured 21.5 ft.in diameter, 41 in. high, and 16.5 in. thick. Forged from raw material that arrived at Ladish as a 225,000-lb. ‘doughnut’, it was rolled and shaped to its final diameter on Ladish’s ringrolling mill, and then machined.

Detailed planning was a critical to the project, even in the acquisition of the raw material. Joseph Wilfert, the sales engineer who manages Ladish’s kiln tire business, related of the project: “Because it has been a while since we have been called upon to handle a project this big, we reviewed our entire process to make sure we were ready to accommodate a doughnut of this size.”

“For example, we had a section of railroad track outside our building that we knew needed to be upgraded and the kiln tire order provided the impetus to move that project forward. We also double-checked that our overhead cranes could comfortably handle a doughnut of this size.”

Wilfert acknowledged the other restrictions that Ladish planned for, including making sure the raw materials ordered did not exceed 12 ft.in diameter, so they could be routed by rail within the continental U.S.

In-house production time took about 12 weeks. “It typically takes six months or more for our suppliers to deliver the specialized raw material we need to forge a kiln tire,” said Wilfert about the overall manufacturing lead time that was needed. “Depending on the exact size and weight of the ring we launch into process, and on our exact internal production routing, manufacturing time at Ladish can take anywhere from eight to 14 weeks.”

Because of the size and weight of the kiln tire, shipping also required considerable planning. The kiln tire was shipped by barge from the Port of Milwaukee on the first leg of its journey to Europe.

The demand for forged kiln tires in increasing because buyers who consider other routes, such as casting, are unwilling to wait up to four years for the new kiln tire to be manufactured and delivered.

Wilfert says there are three reasons for this backlog: First, the necessary raw materials are difficult to acquire in a timely manner in the current market, which is at peak demand now in numerous industry segments.

Second, according to Wilfert, suppliers’ production capacity is booked farther into the future than at any time in recent memory and, along with long raw material lead times, this combination of conditions is stretching out manufacturing lead times to historic lengths. And third, demand for kiln tires by quarries has shot upward at a time when many of the kiln tires now in service are wearing out. For this reason, there is simultaneous strong demand for spare or replacement parts and components for brand new systems.

Wilfert also points out that some buyers of quarry kiln system components have been around for only a decade or so, and may not be aware there are alternatives to cast kiln tires. Although forged kiln tires are sometimes more expensive than cast kiln tires, the price differential is insignificant when the alternative is an entire system out of commission for extended lengths of time as a replacement tire located.

“Some of our customers have expressed a preference for forged tires because, in their experience, forged tires are more durable than cast tires, and for this reason, actually offer lower life-cycle cost,” said Wilfert.

With proper maintenance, which essentially means keeping a good, clean surface on the ring, a forged kiln tire can last 30 to 40 years. In contrast, without an adequate level of attention to maintenance, the tire can wear out in as few as seven or eight years.

Because Ladish specializes in forging large components — they boast the world’s largest ring-rolling mill — and is now producing some of the largest kiln tires. The company is currently planning production for a seamless rolled ring in the 62,000-lb weight range, which will be about 14 ft in diameter. In all, Ladish has orders for eight seamless rolled rings to be manufactured during the next 12-18 months.

Although the 21.5-ft diameter ring Ladish just produced required the largest input weight in more than 20 years, its recent evaluations have confirmed that the company can handle raw material input weights up to 350,000 lbs, as well as produce rings as large as 28 ft in diameter and 10 ft in face height.

Pointing to Ladish’s 50-year involvement with NASA, Wilfert tells potential customers that “we know how to build quality into a forged, seamless rolled ring. That experience translates into measurable value for quarry operators, because it’s built into every kiln tire they buy from us.”

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