A number of considerations should be made before settling on the screening plant that best fits your needs.
Portable screening plants are a major part of the business for aggregate producers, road builders and contractors. Any of these operators can tell you how important quality screeners are to a business, but what’s right for one operator may lead to production issues for another.
From small, highly customized design modifications to the overall type and size, there are a multitude of factors to sift through. Selecting the right screener takes time, research and clearly outlined goals for the operation. Here are a few key things to consider.
Analyze everything
It’s important to factor in everything from output capacities to business goals before you buy.
The first thing you need to do is size the equipment to match the operation. This is not an option. Understanding the application and materials will help you determine the ideal production, capacity and number of end-size products. This is the first step in outfitting a screener that aligns with the goals of the operation.
Next, make sure you fully understand the company’s goals and projected sales to determine what size screener you’ll need. For example, if an operation can sell 500,000 tons per year, its screeners need to sort nearly 42,000 tons per month.
If the screener is in operation two days each week (about eight days each month) 10 hours each day, the operation will require a machine capable of screening around 525 tph. A screener that processes 300 tph would limit profits and cap growth potential. A machine with a potential output of 900 tph would come with extra expenses and no added value.
Scalp or screen
Several main differences separate a scalping plant from a standard screening plant. Standard screens are often considered “finishing screens” because they’re capable of producing specific-sized end products. Operators can adjust the speed of the feeder belt to help produce a clean, sized finished product. These units typically have two or three screen decks and are ideal for use in sand-and-gravel pits, on asphalt jobs and in quarries.
Scalping screening plants are built to handle the toughest materials but are not as precise as standard screening plants. Material is fed directly onto the screen. Scalpers are ideal for sorting materials before crushing, processing scrap metals and recyclables and to extract rock from dirt on construction sites.
Hopper size
Industry standard hoppers are 12 ft. wide with an option to upgrade to a 14-ft.-wide hopper. Just an extra two feet can capture more product and prevent spillage. The size of the hopper is perhaps most pertinent when pairing the screener with the loading machine, especially if you use a large wheel loader.
Live head and tipping grid
Operators can add a live head or tipping grid to a screener above the hopper for additional sizing. While they perform a similar duty, they are very different. A tipping grid is essentially a hinged grid that blocks larger materials from entering the hopper. This is an affordable option but can become a chore, particularly in wet or dirty applications where the tipping grid may become plugged frequently.
A live head is essentially a vibrating screen that attaches to the hopper and is ideal for heavy-duty, dirty, wet and sticky applications. The unit can be used for two purposes: to scalp dirty material off and eliminate the need for manual cleaning, or to size material going into the machine so operators can produce an additional sized product.
While these are generally very efficient, operators should know that screeners with 14-ft. hoppers would not be used to the full potential. A typical live head measures 12 ft., making two feet of the hopper unusable.
Apron feeder versus belt feeder
A belt feeder is another key element to evaluate, as different products vary in durability. The standard belt feeder is perfect for sand-and-gravel operations, but is likely to tear or break when working with metal, large rock or extremely abrasive material. An apron feeder, which is essentially a belt made of metal, is durable and can handle nearly anything an operator throws at it.
Screen media
Operations working with abrasive materials may want to consider stainless steel as an alternative to regular wire mesh. Stainless steel costs nearly twice as much but offers longer wear life.
Additional options are appropriate for some operators. For example, bofar bars, formed of long bars with spaces between, are designed for miscellaneous dirty material. Punch plates, used for heavier applications, are essentially a piece of sheet metal with spaced holes. These plates are very durable, customizable and affordable. Finger decks are ideal for reclamation, landfill jobs or any other type of screening where clogging, blinding or breakage might be an issue. Finger decks can easily accommodate high-impact loads mixed with recycled waste and debris.
Stockpiling
There’s not much mystery behind the stockpiling of sorted, saleable product. The higher you’re able to stockpile, the less time it will take your operators because they’ll be able to run for longer periods without having to move material. Even an additional 8 to 10 in. of stockpile height can make a significant difference.
Conveyors
Conveyor rollers commonly break under pressure and belts become punctured. As an alternative, some manufacturers offer an impact or sleigh bed conveyor. The impact bed is solid and runs the width of the conveyor to best accommodate the impact of material and prevent belt damage. These conveyors provide additional support and are more durable so they can handle heavy products.
Most discharge conveyors are about 48 in. wide, but the industry offers belts up to 63 in. wide to help prevent clogging. Because the screener is wide and funnels down to the conveyor, machines with smaller conveyors create a bottleneck effect. The material begins blinding in the corners, narrowing the opening. This creates productivity and maintenance problems, forcing operators to shut down and clean it out.
Look for a machine that has less – or no – restriction as it transitions onto the discharge belt. A free-flowing machine with a low drop height is the best option to minimize wear and keep productivity elevated.
Countdown to the purchase
Purchasing the wrong screener can cause problems, slow production and result in revenue losses. Taking time to sift through the facts and separate the good from the bad at the front end will prevent headaches, downtime and loss of production later.
Sean Donaghy is the national sales manager at IRock Crushers. He has more than 20 years of crushing and screening experience and has been with IRock for seven years.