Introduction
Screening plays an essential role in aggregate production. It is the process of separating aggregate materials according to their appropriate size using various types of screens.
Whether it’s crushed stone, sand, gravel, or other materials, screening is necessary for ensuring material consistency and quality. Without it, there will be a lack of production efficiency, increased maintenance costs, and reduced equipment durability.
To successfully navigate through the screening process, it is vital to avoid making even the slightest mistake. Next time you are using screening equipment, keep these five costly mistakes in the back of your mind to ensure your screening process goes smoothly.
1. Selecting the Wrong Type of Screen Media
Picking the correct screen media for your material can be challenging. Some of the most commonly used screening media include woven wire cloth, urethane, or a combination of urethane and wire cloth, or urethane and rubber.
Screen media is the backbone and impacts the entire screening process. Choosing the wrong screen media leads to the improper separation of materials, which cross-contaminates various sizes of material into one pile.
Using the wrong screen media can lead to bigger and more costly mistakes, including frequent screen replacements, material fragmentation and inconsistent material quality.
To avoid making this mistake, analyze the material you are screening and determine its characteristics. From there you need to consider the factors that determine the correct screen media, such as the size, shape, wetness and abrasiveness of material, as well as if material is free flowing or sticky.
2. Improper Screen Media Installation
Screen media installation determines the performance quality of the screening process. The installation relies on the correct media selection and can compromise the way material is processed through the equipment.
Improper screen media installation can mean different things - installing a broken screen, incorrect tensioning or misaligning screen media are some key examples. Any one of these mistakes can compromise the entire operation, which is why it’s important to take the time to correctly install the screen media.
The mistake of improperly installing the selected screen media can cause uneven material distribution. Poor installation can also lead to alignment issues, producing gaps between panels that allow material to sneak through.
To ensure that this mistake doesn’t happen, double check every aspect of the equipment before starting the screening process. Frequently inspect and monitor the equipment, looking for gaps, worn out screen panels and other loose ends that need to be fixed.
3. Distributing Feed Unevenly
To properly separate materials into their appropriate sizes, material needs to be distributed evenly throughout the deck.
A common and easy mistake to make when distributing the feed is to overload one side of the screen with material. Overloading the screen increases the risk of blinding and pegging, which are when material gets clogged and stuck in screen media openings.
Clumping material onto one side of the screen can lead to damage to springs and side sheets of a screen. This is the result of putting too much stress on the screen with heavy forces.
When you are distributing the feed onto your equipment, be sure to evenly spread the material to avoid damaging the equipment. Examine the feed rate and feed speed to understand if something needs to be changed.
Unevenly distributing feed can be one of the costliest mistakes and can slow down the distribution process. If not done properly, screens and other equipment will need replaced, which will minimize efficiency.
4. Operating at the Wrong Speed and Angle
How effective a screen is highly depends on the speed and inclination angle. These parameters impact the ability for material to pass through the screen deck and rely on the screen type, material characteristics and stroke.
Setting the speed too fast can cause the materials to bounce and be ejected from the screen deck, potentially hitting equipment operators. High speed also generates strong and loud vibrations that can damage hearing if not wearing the proper protection. Not only can fast speed cause injuries, but it limits and reduces the amount of time a particle has to penetrate through the opening of the media, which results in carryover.
Setting the speed too slow minimizes the amount of material that is processed through the screen deck and accumulates material buildup from a lack of vibration. The overload of material generates equipment issues and can damage the screen.
Accounting for the screen type and material, the screens speed can vary from 1,000 rpm for ¼" material to 600 rpm for 6” material.
The inclination angle can impact the amount of stratification that happens during the screening process. Material that is larger needs a lower incline while material that is smaller needs to be set at a higher angle. If an angle is too high, materials will move too quickly and separate improperly, but if the angle is too low, materials will pile up.
Operating at the wrong speed and angle can have damaging implications. To prevent this mistake, conduct test runs with small batches of material to know how to adjust the parameters and follow a guide.
5. Lack of Equipment Maintenance
Throughout the entire screening process, it is important for all screening equipment to be maintained regularly and after every use. Neglecting to clean, replace or monitor different parts of equipment will reduce production efficiency and promote safety hazards.
Different pieces of equipment require specific attention and inspections. When examining screen media, check for holes and tears and be sure to clean out old material. Similarly, for the screen deck, look for wear and tear, and clean off any dirt or buildup. For all screening equipment, taking extra precautions can keep your operation running smoothly and on time.
While it can be difficult and time-consuming to constantly assess your machinery, taking the steps to avoid this mistake will be well worth it. Conducting regular inspections will increase equipment lifespan, lower repair costs and increase safety.
This mistake can be prevented by creating an organized schedule that breaks down what to inspect on what day. Be sure to take notes of what needs to be replaced, any issues and things that require follow-up. Consider doing some research and reaching out to equipment maintenance support resources, such as the OEM of your equipment.
