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Screw conveyor calculation excels are of different types depending on the application's needs. These include the following:
Horizontal Screw Conveyors
Horizontal-type screw conveyors are designed to transport bulk materials over short and medium distances, usually within processing facilities. With a pitch-less screw conveyor, the material is transported in a straight line, typically installed on a horizontal plane. The conveyors are extensively used in industries like agriculture, food processing, and chemical manufacturing for moving grains, powders, and other bulk materials.
Inclined Screw Conveyors
An inclined screw conveyor is designed to transport bulk materials at an angle to the horizontal, usually within a range of 15 to 60 degrees. These conveyors are installed where elevation change is required in the material handling system. They are, therefore, common in construction, mining, and wastewater treatment industries to move materials such as cement, rocks, and sludge, among others.
Variable Pitch Screw Conveyors
Variable pitch screw conveyors feature a changing pitch along the length of the conveyor is designed. This conveyor type helps transport different bulk materials with varying flow characteristics. Such conveyors are used in industries with varying material densities and textures, like food and chemical processing, to manage the material flow more efficiently.
Vertical Screw Conveyors
Vertical screw conveyors are developed to lift bulk materials straight up, saving floor space. Bulk materials are charged into the vertical screw conveyor at the bottom and discharged at the top. The conveyors are mostly found in the mineral extraction industry to transport materials like ores and concentrates and to elevate materials like powders and granules in food and chemical processing.
Shaftless Screw Conveyors
Shaftless screw conveyors are designed with no central screw shaft, thus enabling easier loading and cleaning. Of these conveyors, however, the design features a solid, rugged trough, making it ideal for handling sticky or difficult-to-convey materials. Commonly, shaftless screw conveyors are used in wastewater treatment plants, pulp and paper, and food processing industries to convey dewatered sludge, waste, and other heavy materials.
Screw conveyor systems are developed using different materials, each with pros depending on the operating environment and the material to be conveyed, such as:
Stainless Steel
A common choice for many industries is stainless steel, which has good corrosion resistance, strength, and durability. This is also known to be resistant to rust and chemical activity. This, therefore, makes it ideal for food processing, pharmaceuticals, and chemical manufacturing industries where sanitation and corrosion resistance are very critical. Also, stainless steel conveyor screws provide a long operational life and require minimal maintenance.
Carbon Steel
In many applications, carbon steel is the most used material due to its strength and affordability. Although carbon steel can be coated or treated to prevent corrosion, it is commonly used in environments where they are exposed to a minimal chemical activity. Carbon steel conveyor screws are used in industries such as agriculture, mining, and construction, where the conveyed materials are not highly corrosive.
Auger Flight
A conveyor screw can also be made using artificial flight plastic. Plastic screw conveyors are lightweight, corrosion-resistant, and cost-effective. These conveyors are commonly used to convey bulk materials like plastic granules, powders, and small parts. Plastic screw conveyors are also used in such industries as electronics and packaging, where the conveyed materials require minimal maintenance and have light damage.
Chrome Plated
Chrome-plated screw conveyors are known to have enhanced wear resistance and corrosion. Chrome plating of screw conveyors creates a smooth, easy-to-clean surface that reduces material adhesion. This is mostly applied in the most hostile environments, such as mining and mineral processing, where abrasion is common. Also, chrome plating prolongs the life of the conveyor and reduces the need for frequent replacements.
Hardened Steel
Hardened steel screw conveyors are extremely durable and wear-resistant, ideal for heavy-duty applications. Commonly, hardened steel is used where abrasive materials are conveyed, such as in mining, cement, and power generation industries. These industries help minimize the risk of damage to the conveyor, encourage longevity, and, as a result, require little maintenance.
The choice of the type of screw conveyor system for any application should involve several key factors to ensure efficiency and durability. Below are the key factors:
Conveying Capacity
The conveyors' capacity should be able to handle the volume of bulk material to be conveyed per unit time. Screw conveyor engineers have to evaluate the material's density and viscosity to establish the proper conveyor size and speed in order to achieve the desired capacity. Go for a horizontal tubular conveyor to achieve higher capacity.
Material Compatibility
In choosing a screw conveyor, pay attention to the material to be transported, the material it is made from, and its compatibility with the conveyed material. This will include the humidity, temperature, and abrasiveness of the material. For example, in industries with high corrosive activities, such as chemical manufacturing, food processing, and pharmaceuticals, go for stainless steel. Hard and abrasive materials, which are common found in mining and mineral processing, are also best conveyed in hard steel or chrome-plated conveyors.
Incline Angle
Select a screw conveyor based on the required incline angle. Horizontal screw conveyors are meant for flat transportation. Inclined screw conveyors, on the other hand, are meant for short vertical transport. The angle of incline should be no more than 60 degrees.
Environment Conditions
Installation and operation environments are important factors to be considered when choosing the screw conveyor system. Where temperature varies widely, go for a thermal screw conveyor made from suitable material to withstand temperature variation. In wet or abrasive environments, please install protective housings around the screw conveyor system or use shaftless screw conveyors.
Maintenance Requirements
Some screw conveyors have low maintenance requirements, whilst others require more frequent inspections and repairs. Shaftless screw conveyors, for example, are easier to maintain. Conversely, the conveyor has a central shaft that may require periodic greasing.
For longevity and reliability in the performance of screw conveyor systems, routine maintenance has to been done. Below are some ways to maintain and repair the conveyors:
Routine Inspection
Inspections have to be done routinely to be able to detect and repair problems early. Such inspections should particularly focus on the condition of the auger shaft, flight, and wear liners, for instance. In the case of shafted conveyors, look out for signs of bending or wear on the screw. On shaftless conveyors, watch out for wear on the flight and significant material buildup. Also, check for signs of ruture on the conveyor casing, as well as any unusual noise or vibration during conveyor operation.
Lubrication
Lubricating the conveyor system helps minimize friction, reduce wear, and thus safeguard the overall system from damage. This is especially true for tailed conveyors where the drive end and screw shaft bearings have lots of friction. Lubication has to be done frequently as shafted conveyors have a lot to be ungreased while shaftless ones are easy to grease.
Repair or Replace Worn Components
As the maintenance or wear happens, so does the need to replace worn out conveyor parts. Well, minor damages on the screw can be repaired using welding or specialized hardfacing materials. In case the wear is severe enough to warrant replacement, then the concerned parts, which can be conveyor flights, shafts, or augers, will need to be replaced. Conveyor screws and flights as well may also feature wear liners, which are protective wear surfaces. They too should be replaced the moment they start wearing out.
Controlling Material Flow
Overloading a screw conveyor will affect its components. Those impacts will cause significant wear to the screw flights and motor damage, among other effects. Underloading a conveyor has its own effects, which include wastage. Conveyors should be installed with appropriate inlets and outlets. In addition to preventing material buildup, controlling material flow will end up minimizing wear on the system.
Regular Cleaning
Regular cleaning of screw conveyors, especially for shaftless ones, should be observed for them to last long. Accumulation of material on the conveyor can cause either blockage or corrosion. Both of them have detrimental effect on the conveyor system. Cleaning tools like brushes or pressure washers could be used to easily clean most of the conveyors. However, for some complicated ones, they may require to be disassembled before cleaning them effectively.
A. Screw conveyors are extensively used in almost all industries that handle bulk materials. Such industries include agriculture, food processing, chemicals, mining, cement, and power generation, among others. These industries move, store, and process various materials from powders, grains, and sludge to ores, rocks, and even bulk chemicals.
A.Yes. There are screw conveyors that can handle abrasive materials. These conveyors are made of hard-wearing materials like wear-resistant steel or chrome-plated steel. Besides, a conveyor's design may incorporate features like hardened surface treatments or replaceable wear liners to further enhance durability against abrasion.
A.High temperatures can affect the material being conveyed, damage the conveyor system, or even do both. Screw conveyor systems are usually fabricated from special materials and alloys to resist heat. For example, stainless steel and other materials will be affected by high temperatures. They are unsuitable for high-temperature environments.
A.Maintaining the right speed and power, as well as the proper installation of inlets and outlets, can help keep the efficiency of screw conveyors. Also, regular maintenance is key to ensuring the reliability of screw conveyors.
