Mill roll and ring manufacturer South Africa Roll Company (Sarco) has delivered what it believes to be the largest locally cast semi-autogenous grinding (SAG) mill trunnion casting to grinding mill manufacturer New Concept Projects (NCP).

NCP needed the cast for a client that experienced an “unfortunate operational failure” of its existing 10.97 m trunnion, which had to be replaced.

Sarco says the trunnion has successfully been delivered and will be installed and commissioned once the appropriate downtime period is scheduled.

“The trunnion casting for the 10.97 m SAG mill boasted a 75 t cast weight, which, on delivery, weighed a notable 55 t before machining,” says Sarco business development engineer Adelé Vorster.

Subsequent to the final machining of the trunnion, it weighed about 45 t.

Vorster adds that the trunnion was manufactured in a “record time” of 12 weeks, which included the development of the pattern, which took about six weeks; and the actual cast manufacturing, which took another six weeks, all while conforming to global quality standards.

The casting was produced by Sarco at its foundry in Vanderbijlpark, South Africa, and was made using spheroidal graphite iron, owing to its reputation of having a notable strength-to-weight ratio and its ability to withstand high operating pressures.

More about the Foundry

“Sarco offers a mix of sophisticated equipment, advanced technologies and a vast array of industry expertise,” Vorster enthuses.

The company can manufacture horizontal centrifugal cast mills for hot strip mill finishing stands, steckel mills and plate mills.

“We also manufacture static cast or monobloc rolls through carefully selected material specifications and heat-treatment cycles, in line with our clients’ requirements,” she says.

The foundry houses six coreless induction furnaces with a total capacity of 80 t, as well as thermal analysis systems to evaluate and optimise molten metal quality before tapping and casting.

A horizontal centrifugal caster, a vertical centrifugal caster for sleeves or rings and five continuous sand mixers are available on site.

Sarco boasts its own sand reclamation plant and sand testing station, with moulding equipment and chills for static and centrifugal casting.

“Our eight natural gas-fired, heat-treatment furnaces and various casting pits range in width and depth to accommodate large-size castings,” adds Vorster.

Sarco also offers a fully equipped technical laboratory, a machine shop with heavy and light bays, a research and development division, as well as a fully developed quality- assurance department.