Considering Trommels

Trommels have been used in the recycling and scrap industries for many years. Due to the variable sizes of the screens and durability of the equipment, there are a host of applications. However, until recently, when used to separate smaller, finer material, as in the case of nonferrous residue from a scrap shredder, the trommel was seen as an inferior choice to a vibrating deck screen. The reason: many suppliers do not understand that trommel design is a calculated science, not merely a tube with holes inside.

Many suppliers only calculate the size of a trommel based on the tonnage they expect to process. However, there are variables that affect performance, especially in a scrap yard. Scrap yards are invariably one the toughest workplace environments for trommels to succeed.

The factors that a specialized trommel engineer looks at can vary from one operation to another. For instance, there are at least 30 calculations that need to be determined in sizing the proper trommel. Some variables that should be considered are:

Due to the advancement of designs recently, trommels are being selected to work in applications previously reserved for vibrating screens. For instance, large trommels are often used to effectively size 1 ½-inch product and under, but with a flexible, "self-cleaning" design, a trommel can be used to separate the 5/8-inch-and-under product that was previously done by deck screens. And, with a lower cost than a deck screen (and less maintenance) many operators are finding this an interesting option.

As in many mechanical operations, fine tuning and sound engineering is opening more doors to the trommel application in today’s scrap operations. Bill Tigner. The author is president of US Shredder and Castings Group. He may be reached at bill.tigner@usshredder.com, tel. 205-999-7670.