Many mining and aggregates operations have used traditional products, such as woven wire cloth, for years with great results, but for operations experiencing high wear and frequent screen change outs, it’s worth looking into engineered screen media.
Materials such as polyurethane, rubber and perforated steel plates often handle heavy and abrasive materials better than woven wire, but operators need to know how to choose the best screen media for their operation.
The difference between using “good-enough” screen media instead of the “optimal” screen media for the application can be unwanted downtime and expense. Consider three things when selecting the best engineered screen media for an application.
The right screen media saves money.
First, look at all aspects of an aggregates or mining operation and any challenges to increasing production rates and profitability. Second, look at the composition of the material going through the vibrating screen and consult an expert from a reputable company to match the best screen media to the application, and finally, learn to properly install and maintain the screen media.
Have a Look Around
The first step toward selecting the most productive screen media involves answering several questions. What material is being processed? Is the screen media reaching a suitable lifespan for the operation? And what sort of challenges are occurring with the current screen media? Consider the types of materials going through the vibrating screen. Factors such as material size, weight and abrasiveness all come into play during the selection process.
For example, screening gravel typically requires media with higher wearability to handle the material’s abrasiveness. On the other hand, materials with top sizes as large as 10 inches require more durable screens because of the constant high impacts.
Next, look at the vibrating screen itself and complete a vibration analysis. Some analysis systems are designed to safely monitor vibrating screen performance in real time and detect irregularities before small problems lead to diminished performance or bigger issues. In some cases the machine may be running perfectly, but changing the screen media can prevent screening irregularities and the resulting damage.
Consider the three phases material goes through within the vibrating screen, from layered to basic to sharp. Producers can customize the screen deck with various types of screen media through each phase by accounting for open area and wear life to maximize productivity in each phase.
In the layered phase, as material of all sizes hits the screen deck, the media should handle a deep bed depth, high impact and a mix of coarse and fine particles. Material should stratify in the middle of the deck during the basic phase, and near-size and oversize particles should be at the top of the material being screened. Virtually all undersize material should have fallen through the screen media by the time it reaches the sharp phase at the discharge end, where near-size and oversize particles should be in direct contact with the media.
A vibrating screen operator should also examine wearability to determine whether media in the three phases is reaching maximum potential. If it seems like screen media has to be changed too often, consider switching to something more durable.
Next, look at the screening challenges. Examine discarded screen media for signs of problem areas, such as broken wires, premature wear due to heavy material along with large amounts of abrasive fines. Screening problems can cause carryover or contamination, resulting in unwanted material in the screened pile, or the added cost of rescreening. Also, broken screens mean costly unscheduled changeouts. All of these signs indicate there’s likely a better screen media option for at least one phase of screening, if not all three.
A Lot to Choose From
Manufacturers create engineered screen media out of several different types of materials, such as polyurethane, rubber and perforated plates. Polyurethane offers a long lifespan and durability. Look for a polyurethane screen media manufacturer who blends their own material and who pours their polyurethane open cast rather than injection-molded. The open cast process takes about 9 hours to complete and typically lasts about 1.5 to 2 times longer than injection-molded products. In addition, open cast polyurethane permanently hardens when cured to maintain its chemical properties, so it resists wear and tear. Injection-molded screens, though faster to manufacture, can soften when the temperature rises during screening, resulting in less wear life.
Engineered screen media is made with thicker material for increased durability, but this results in less open area. This is ideal for screening many small aggregates materials or for decks with mixed media. Hybrid screens are an option that combine woven wire with polyurethane to achieve open area closer to wire cloth but with four to six times longer wear life while weighing less than woven wire. Other polyurethane screens achieve additional durability with thicker wire to hold up to deep bed depths, large top sizes and wide bar rail spacing. There are misconceptions that polyurethane is strictly for dry applications, whereas there are others that it is only for wet applications; in fact it works well in both.
Look for rubber screen media when screening material with a top size larger than 12 inches, or when an application requires an opening bigger than 4 inches. Manufacturers can create rubber screens thicker than polyurethane for improved durability. The screens also dramatically reduce noise, handle high-impact applications and resist abrasion.
Consider perforated steel plates for heavy-duty operations that require a large amount of open area. Some manufacturers customize each plate’s thickness to a customer’s application and can create almost any size opening. The screens should be manufactured with tapered openings to resist pegging. Many perforated plates come in different abrasion-resistance levels, so be sure to choose a plate appropriate for the application.
Make the Best Choice
If an operations manager finds traditional screen media isn’t working and unscheduled change outs are eating into profits, it might be time to consider a polyurethane, rubber or perforated plate product. Engineered screen media has the advantage of being versatile while bringing improved durability and longevity to a wide range of applications.
Perhaps most importantly, look for a company that takes pride in its work and provides great service and has integrity. That, too, will save time and money. Following these tips will improve an operation’s screen media life, profits and satisfaction for years to come.
Information for this Special Report provided by Steve Fair, Engineered Media Manager at Haver & Boecker Canada.