Screening & Separation

Screening equipment in bulk applications allows bulk material handling operations to refine and purify their materials. Without any screening equipment, oversized and foreign materials remain in the material stream. This can degrade the product quality and sometimes damage machines. In size reduction applications screening is used to protect the machines resulting in an efficiency increase. Screening equipment is used in a lot of different industries such as agricultural products, pet food, pharmaceutical processing, and many more. Most screening equipment requires low maintenance and can be used continuously, sometimes even being self-cleansing.

Screening equipment

There is a lot of different screening equipment offering a variety of sorting solutions. This includes different types of screening machines and industrial sieving machines, also commonly referred to as gyratory separators. These are a traditional part of processing dry bulk powders. The most popular screening equipment for bulk solids are the following:

• Trommel screens
• Vibrating screens
• Disc screens
• Grizzly screens

Screening dry bulk powders

For screening dry bulk powders, a vibratory screen is the most common screen and is a traditional part of processing dry bulk powders. This type of screen is commonly known as a gyratory separator or vibrating screening machine. It separates materials by using a combination of horizontal and vertical movements forcing particles to pass through a mesh screen.

Many industrial sieves are used for a variety of different applications, not simply for screening and separating. The most common industrial sieve is the check sieve. The check sieve is often used to remove bits of packaging and lumps from the product. Check sieves are usually a single screen and typically the fine product that passes through the mesh is kept.

Another common industrial sieve is the grading sieve, the grading sieve is similar to the check sieve but offers more precision of the sieving process. The aim of a grading sieve is to take exact cuts of different particle sizes.

Powder sifting

Powder sifting can be described as separating, sieving, de-lumping, and screening, but each description is a different method of sifting requiring a different type of sifting motion.

The centrifugal sifter is a popular powder sifter specifically designed for sifting high capacities of product and removing unwanted material from the material stream. In addition to the centrifugal sifter, the vibratory sifter is a sifter that shakes the body of the machine, transferring this vibration to a high tensioned screen cloth. It is designed to size or classify powder. The gyratory sifter uses a non-vibratory motion that is gentle on friable powders and therefore can utilize ball cleaning of the screens.

Magnetic separators are important, especially in the mining industry, where they can be used to separate (non-)ferrous metals. A magnetic separator can prevent harmful bits of metal from entering machinery further down the line and can remove unwanted materials from a stream. The magnets pull out the unwanted material as the bulk materials pass by on a conveyor.

A magnetic separator uses magnets to capture and retain ferrous contaminants from the flowing material stream during processing. The magnets attract and hold contaminants passing over or near the separator. The captured contaminants then accumulate on the separator. The contaminants are then cleaned off.

Many factors influence magnetic separator selection, including:

• The size of the contaminants
• The specifics of the process
• Your material’s characteristics

Metal detectors work by transmitting an electromagnetic field from the search coil into the ground. Any metal objects within the electromagnetic field will become energized and retransmit an electromagnetic field of their own. The detector’s search coil receives the retransmitted field and alerts the user by producing a target response.

In the food industry, metal detectors are primarily used for the purpose of consumer protection. Metal particles that enter the product during the production process or already are contained in the raw material may cause serious injuries to consumers. Metal detectors for food provide effective protection against ferrous and non-ferrous metals, such as aluminum, stainless steel, etc.

Metal detection equipment is a highly sensitive piece of equipment and needs to be protected from environmental interferences such as vibration and other electrical fields. Detection equipment often consists of a handheld unit with a sensor probe which can be swept over the ground or other objects. The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field.