Clever combinations

Producing the most tons per hour, ensuring the product meets specifications and maximizing the wear life of screens can be difficult using only one type of media in aggregate, construction and demolition (C&D) and mining operations.

Getting the balance right

Finding the perfect balance of high wear and maximum longevity isn’t always an easy task. The feed end could wear out before the discharge end, or using a full deck of more durable screen media could reduce a processor’s tonnage per hour.

Many times, the ideal solution lies not in a single “screen-all” product but in a mix of screen media to ensure all phases of screening work correctly. Choosing that mix is best accomplished through careful analysis, which includes diagnostic analysis, an inspection of screen media and the vibrating screen itself, as well as a recommendation from an expert.

To find the best media for each phase of processing, operators should consider a few factors that could increase screening productivity:

• Vibration analysis – Vibration analysis systems can provide real-time, 24/7 monitoring of machine performance. The resulting data could help producers spot abnormalities the human eye cannot detect before they become costly problems, such as a hairline crack in a side plate or a twisting motion that will affect screening efficiency and the wear life of the equipment. This helps minimize downtime and maintenance costs, improving overall profitability.
• Inspection – A visual inspection of the vibrating screen and screen media could lead to better understanding of areas for improvement. The discarded screen media pile is one of the first places to look for problem areas, such as broken wires, wear areas, pegging or blinding. Premature wear often occurs in screen media that can’t handle heavy material or excessively abrasive fines. Screen media openings also should be a focus when looking for wear. For example, wear is apparent if the square openings in engineered media begin to round. Types of media unsuited for the application also can result in blinding, pegging or carryover, leading to added costs and time needed for rescreening. Additionally, broken screens mean costly, unscheduled change-outs.
• Phases of screening – Screen media manufacturers can help evaluate how material moves through the three phases of screening—from layered to basic to sharp—and recommend the best screen media for a given application. Producers can customize the screen deck by choosing screen media that maximizes productivity for each phase by blending the optimal combination of open area and wear life.

The material begins its path down the screen deck during the first phase—layered screening—where the screen media should be able to handle a deep bed depth, high impact and a mix of coarse and fine particles. Heavy-duty options, such as those using polyurethane, rubber or perforated plate, can excel in withstanding high-top sizes and abrasion.

Screen media with the ideal combination of wear life and open area is best for the next phase—basic screening—where most of screening takes place. Hybrid screen media, for example, pairs polyurethane’s durability with an open area similar to woven wire and often is a good choice for the middle of the deck.

Sharp screening takes place at the discharge end and requires the maximum open area to allow any remaining undersized particles to fall through and for near-sized material to pass, preventing contamination. Woven wire or self-cleaning media provide the best open area in this phase.

Screen media selection

Screen media inspections provide information required to identify the best type of media for each phase of screening. A certified screen media representative will work with you to decide what combination of media will provide the most efficient solution for each phase. This often means using a blend of different types of screen media to achieve the best combination of wear life with open area.

Implementation

The last step is to start switching out screen media one section at a time, beginning at the feed end of the top deck, to pinpoint where performance improvements are being made.

Careful selection and the correct blend of screen media can mean thousands of dollars in savings for operators. For the best results, work with a reputable screen media manufacturer or certified dealer for informed advice.

The author is the Tyler engineered media manager at Haver & Boecker Niagara, an Ontario-based provider of screening, pelletizing and primary crushing systems to the aggregates, mining, minerals, fertilizer, salts, recycling and cement industries. Contact him by email at sfair@haverniagara.ca.