Designing Inclined Screw Conveyors for Upset Conditions

Download PDF

Question

I have an inclined screw conveyor that continually has problems. The motor will trip out at the worst time and shut down my process. What can I do to get the inclined screw conveyor to work consistently?

View Details

Answer

Using an inclined screw conveyor to convey bulk materials is very advantageous and solves layout problems. One inclined screw conveyor can be used to occupy a minimum of space instead of a multiple conveyor arrangement.

However, as the degree of incline increases from horizontal, the efficiency of a screw conveyor is reduced and torque requirements increase due to the influence of gravity and fallback of the bulk material.

KWS recommends that screw conveyors located on inclines over ten degrees be designed to start and operate under upset conditions. An upset condition is the worst case scenario of the trough being 100-percent full in cross-section for the full length of the conveyor. Sufficient horsepower and torque is required to start the screw conveyor in the upset condition.

An upset condition could occur if normal flow is interrupted (example: a plug develops at the conveyor discharge) and the screw conveyor becomes completely full for the entire trough length. Another example of an upset condition is if a free-flowing bulk material falls back down the incline when a screw conveyor is shut down, completely filling the unit.

All KWS inclined screw conveyors are designed to start and operate under upset conditions, eliminating the chance of the motor stalling out and shutting down the process. Engineers at KWS study the characteristics of bulk materials for various applications and incorporate many features into the design of inclined screw conveyors to guarantee effective conveying.

Basic Design Rules

Use Proper Conveyor Design &#; KWS performs calculations for normal operating conditions to determine the operating speed of the inclined screw conveyor at the desired capacity, density, and level of trough loading. Conveyor diameter, pitch, trough type and speed are selected based on bulk material characteristics such as flowability, angle of repose and degree of abrasiveness.

Consider Various Trough Loading Conditions &#; Under normal operating conditions inclined screw conveyor trough loading is typically between 30 and 45-percent. However, when the inclined screw conveyor is shut down, bulk materials fall back and fill up the trough area. When restarted, the unit will instantaneously convey a larger capacity. KWS considers the larger capacity due to upset conditions in all calculations.

Design for Additional Horsepower and Torque &#; Bulk materials can compress and pack when an inclined screw conveyor is shut down, causing more demand on the drive unit. KWS designs inclined screw conveyors with the additional horsepower and torque to overcome upset conditions. Bulk density and flowability are considered in packed condition for all horsepower calculations.

What is Inclined Screw Conveyor?

Inclined screw conveyor typically operates from slightly above the horizontal position to 45 degrees from the horizontal position. It can complete conveying, mixing paint, quantitative ingredients, etc., and is mostly used in conjunction with filling and packaging machines as a completed powder packaging machine system. The inlet and outlet of the inclined screw conveyor can be made into the required inclination angle according to the work site, and can be linked and fixed with other supporting equipment.

Inclined screw conveyors are designed with an incline that allows for an inclination angle of 60 degrees in height and take up less space than horizontal screw conveyors. The most common style of inclined screw conveyors is when the feeder is attached or integrated with a hopper, silo or silo This design is the most economical when used, and allows the inclined screw feeder to meter and deliver flow from the inlet to the desired height, but requires more horsepower to feed the product upwards.

What is maximum angle for Inclined Screw Conveyor

1. Shaft series

The conveying angle of the shafted tube screw conveyor is about 45°, while the conveying angle of the shafted U-shaped screw conveyor is about 20°-30°.

2. Shaftless series

The conveying angle of the shaftless tubular screw conveyor is about 30°, while the conveying angle of the shaftless U-shaped screw conveyor is about 20°-30°.

The larger the angle of the inclined screw conveyor, the worse the conveying effect (there is no effect within 15°, and the conveying efficiency will decrease by 15% for every 5° increase). At this time, the following items need to be considered:

More horsepower is required for inclined screw conveyors: This is due to both lifting the product and "reconveying" product that falls back.

Hangers should be eliminated: They create a "dead flow" area that is emphasized with inclined conveyors. This often results in the use of longer screws which require their own design considerations.

For materials with poor fluidity, the inclination angle can reach 50°, but to convey materials in this way, a certain pressure needs to be applied to the feed inlet, and the added materials are squeezed into the conveying main body, and the bearing at the bottom of the equipment needs to bear huge pressure , The bearing is easily damaged.

Working Priciple of Inclined Screw Conveyor

The inclined screw conveyor uses the motor to drive the screw to rotate through the reducer, and through the rotation, the material is pushed along the fixed casing to carry out the conveying work, so as to be conveyed to the predetermined position. According to various uses, installation locations, models, and conveying methods, the installation locations of the reducer and motor can be diversified and unlimited.

Application of Inclined Screw Conveyor

The inclined screw conveyor is suitable for inclined conveying of powder, granules and small block materials. The inclined angle is generally not more than 90°. It is used to convey and lift bulk materials from one layer to another. It can be directly connected and fixed with its supporting equipment. Bulk materials from bulk bags, hoppers or silos to overhead processes can also be metered via screw conveyors while conveying and lifting product.

Common industry uses:

Industry Real Use Industry Real Use Foundry Sand treatment Salt Mine Mix, convey, mix Brewery Grain and Hops Handling/Storage Steel Mill Dust and storage Wooden Waste and sawdust Sewage Treatment Plant Sludge conveying and storage Paper Pulp and Wood Chip Handling Chemical Plant Prevent pollution Plaster Wallboard Gypsum Conveying Feed and Grain Various applications Leading Lead recycling Render Widely used, rinse well Food Handling Various food grade applications Glass Factory Conveying and metering

Related Videos

Conveying pulverized coal

Conveying grain

Conveying wheat bran (with screening and dust removal equipment)

Benefits of Inclined Screw Conveyor

Large inclination conveying

0-90 degree inclination angle, suitable for connecting with hopper, silo or silo to achieve the purpose of conveying and lifting.

High conveying efficiency

There can be multiple inlets and outlets, and the bulk materials can be transported and distributed to various positions as required, and the process arrangement can be customized according to customer needs.

Uniform feeding

In the process of conveying materials, blocking and jamming are not easy to occur, and the feeding is uniform. Sliding gates or valves can be added to control the flow in and out of the screw conveyor.

Link to dahe

High speed

Higher screw speed, which increases the forward momentum of the product and reduces back-off, especially for granular, free-flowing products such as dry sugar, refined sugar.

Low cost

Product can be conveyed and lifted at the same time, it covers two operations with one piece of equipment, thus saving space and reducing downtime, maintenance costs, etc.

Flexibility

The moving wheels can be installed under the support frame, providing flexibility to meet the installation requirements of most applications and moving systems, allowing for in-plant flexibility.

Structural Characteristics of Inclined Screw Conveyor

1. The inclined screw conveyor produced by Dahan Machinery is a non-foundation fixed type. It is connected in turn by the spiral body of the casing of the drive motor reducer and combined into a whole.

2. The shaft end is connected with the involute spline (or rectangular spline) of the rotating body, which is easy to assemble and disassemble, and has a large bearing capacity, safety and reliability.

3. The outer casing of the conveyor is connected by steel pipes through flanges to form a whole, so its overall rigidity is good, so that the working position and working posture can be selected at will, and can be disassembled and moved at will.

4. The inlet and outlet of the material can be made into the required inclination angle according to the situation of the work site, and the connection with other supporting equipment is fixed.

5. The helical blades of this machine are integrally connected blades rolled by disc-shaped steel strips, with high helicoidal degree, helical pitch size of inner hole and outer diameter, and good conveying conditions. (If the single-piece welded blade meets the above requirements) .

Technical Parameters of Inclined Screw Conveyor

LS Model 100 160 200 250 315 400 500 630 800 GX Model     200 250 300 400 500         Spiral diameter&#;mm&#; 100 160 200 250 315 400 500 630 800 Pitch&#;mm&#; 100 160 200 250 315 355 400 450 500 560 630 Rotating speed&#;r/min&#; 140 120 90 90 75 75 60 60 45 35 30 Throughput QΦ=0.33&#;m3/h&#; 2.2 7.6 11 22 36.4 66.1 93.1 160 223 304 458 Power Pd 1=10m&#;KW&#; 1.1 1.5 2.2 2.4 3.2 5.1 4.1 8.6 12 16 24.4 Power Pd 1=30m&#;KW&#; 1.6 2.8 3.2 5.3 8.4 11 15.3 25.9 36 48 73.3 Rotating speed&#;r/min&#; 120 90 75 75 60 60 45 45 35 30 20 Throughput QΦ=0.33&#;m3/h&#; 1.9 5.7 18 18 29.1 52.9 69.8 125 174 261 305 Power Pd 1=10m&#;KW&#; 1.0 1.3 2.1 2.1 2.9 4.1 4.7 6.8 9.4 14.1 16.5 Power Pd 1=30m&#;KW&#; 1.5 2.3 4.5 4.5 7 8.9 11.6 20.4 28.3 42.2 49.5 Rotating speed&#;r/min&#; 90 75 60 60 45 45 35 35 30 20 16 Throughput QΦ=0.33&#;m3/h&#; 1.4 4.8 15 15 21.8 39.6 54.3 97 149 174 244 Power Pd 1=10m&#;KW&#; 0.9 1.2 1.9 1.9 2.5 3.4 4.3 5.4 8.1 9.5 13.3 Power Pd 1=30m&#;KW&#; 1.2 2.2 3.8 3.8 5.4 6.8 9.2 16 24.4 28.6 39.9 Rotating speed&#;r/min&#; 75 60 45 45 35 35 30 30 20 16 13 Throughput QΦ=0.33&#;m3/h&#; 1.2 3.8 11 11 17 31.7 46.5 73.0 99.3 139 199 Power Pd 1=10m&#;KW&#; 0.75 1.1 1.6 1.6 2.1 3.1 3.7 4.6 5.7 7.7 11 Power Pd 1=30m&#;KW&#; 1.1 1.8 3.4 3.4 4.4 5.6 8 14 16.7 23.2 33

Selection Notes:

1. Material characteristics: material name, material particle size, whether the material has hardness, whether the material has viscosity, material temperature, etc.;

2. Determine the oblique angle

3. Determine the material: 1) Stainless steel material - stainless steel material can also be divided into 304, 310, 310L, 316, 316L models (all models can be made of stainless steel, but when the conveying distance is long, the surface area increases If the difficulty of grinding increases, sandblasting is generally selected, and it will not be as bright as common stainless steel visually, but the quality will not be affected). 2) Carbon steel material&#;Carbon steel material is a commonly used material for inclined rotary conveyors. This material has a low cost and can also realize the normal transportation of materials.

4. Rotation speed selection "The rotation speed of the inclined screw conveyor is generally r/min. The rotation speed of the inclined screw conveyor can be adjusted by itself. The larger the angle, the greater the required rotation speed.

5. Determine the size: such as pipe diameter, length, length of the discharge port, distance from the discharge port to the ground, height of the bracket, width of the hopper, etc.

Note: The rotation speed of the screw conveyor cannot be infinite. When the rotation speed reaches a certain limit, the material will be thrown outward due to excessive centrifugal force, resulting in failure of the conveying process. The larger the angle of the screw conveyor, the same speed ratio and type of conveyor, the conveying capacity will be weakened.

Design and Construction Features to Consider for Inclined Screw Conveyors

1. Incline Up to 10-Degrees: At an inclination of up to 10°, the loss of conveying efficiency is minimal. Screw conveyors with U-shaped grooves and full-pitch screws are sufficient for most applications. The efficiency loss can be overcome by increasing the speed of the screw conveyor, increasing the diameter of the screw conveyor or reducing the pitch of the propeller.

2. Incline Between 10 and 20-Degrees: The loss of transmission efficiency is usually between 10 and 40%. Screw conveyors with U-shaped grooves and 2/3-pitch spirals are sufficient for most applications. The loss of efficiency can also be overcome by increasing the speed or diameter of the screw conveyor. Additional power is required to overcome gravity and loose material falling.

3. Incline Between 20 and 30-Degrees: At an inclination of up to 30 degrees, the loss of transmission efficiency is usually between 10% and 70%. For most applications, it is recommended to use a screw conveyor with a tubular casing and a reducing screw (1/2 or 2/3). The efficiency loss can also be overcome by increasing the speed or diameter of the screw conveyor. Additional power is required to overcome gravity and loose material falling.

4. Incline Between 30 and 45-Degrees: At an inclination of up to 45 degrees, the loss of conveying efficiency is usually between 30% and 90%. For most applications, it is recommended to use a screw conveyor with a tubular casing and a reducing screw (1/2 or 2/3) and a larger diameter. It is also necessary to increase the speed of the large-incline screw conveyor. Additional power is required to overcome gravity and loose material falling.

Design and Selection of Inclined Screw Conveyors

The horsepower requirements of an inclined screw conveyor increase with the degree of inclination, requiring additional horsepower to overcome gravity and bulk material fall back. If a certain tilt angle is required, what should be paid attention to when using it? And listen to the manufacturer's analysis:

1. The fluidity of the conveyed product

If the material has good fluidity, it is easy to slide to the feed port during inclined conveying, which cannot meet the conveying requirements. The inclination angle of ordinary screw conveyor is about 45 degrees. If it exceeds this angle, the conveying effect of the material is not ideal. The material with poor fluidity can reach 50 degrees, and the larger inclination angle will also affect the conveying effect of the equipment. At this time, a tubular screw conveyor can be selected. The tubular screw conveyor can be used at 90 degrees, also known as the vertical screw conveyor. However, when conveying materials in this way, it is necessary to apply a certain pressure to the feed port to squeeze the added materials into the conveying body. Moreover, the bearing at the bottom of the equipment needs to bear huge pressure, and the bearing is easily damaged.

Material Name Pulverized Coal Cement Cement Raw Meal Gravel Sound Lime Material bulk Density 0.6 1.25 1.1 1.3 0.9 Fill Factor φ 0.4 0.28~0.33 0.28~0.33 0.25~0.3 0.35~0.4 Material Resistance Coefficient ω 1.2 2.2 1.8 2.5 3.0

2. Proportion of conveyed products

The specific gravity of the material also has a certain influence on the inclination angle. The material has a large proportion, and the inclination angle can be appropriately increased to make the screw conveyor complete the conveying operation. If the specific gravity of the material is light, it is easy to float in the air during transportation, so it is not recommended to use it.

According to the layout of the user equipment, if the screw conveyor needs to be inclined, the inclination angle is generally about 10 degrees to achieve better conveying effect. The larger the inclination angle, the worse the conveying effect. Therefore, when the user selects, the tilt angle needs to be estimated according to the layout design of the device.

Angle β o° &#;15° &#;20° &#;30° &#;40° &#;45° &#;50° &#;60° &#;70° &#;80° &#;90° Inclination factor C 1 0.9 0.8 0.7 0.65 0.7 0.67 0.6 0.53 0.47 0.4

Proof of Solutions for Our Wide Range of Products

The inclined screw conveyor generally operates at a certain inclination until 45 degrees, and can feed non-stick powder, granular and small granular materials from storage equipment such as silos to the receiving equipment evenly. The silos and conveying pipes are made of stainless steel. Material (material can be according to customer requirements) to ensure that the raw materials are completely pollution-free during the conveying process. The conveying pipeline adopts a closed design, which can effectively prevent dust and effectively isolate materials with high hygiene requirements or strong odor, with uniform feeding and sealing. Good, no dust pollution and other characteristics.

Inclined Screw Conveyor Manufacturer

Dahan Inclined Screw Conveyor Manufacturer covers design, drawing, modeling, processing, quality inspection, assembly, test machine, painting, delivery, etc. We have machining workshops (lathes, milling machines, boring machines, drilling machines), assembly workshops, painting workshops, warehouses, etc.

The manufacturer will help you select and design according to some parameters such as working conditions, material temperature, material granularity, material corrosivity, material conveying volume, material conveying distance and so on. Reasonable design and selection of conveying capacity, shell material (201, 304, 316), motor ratio power, reducer ratio speed, to meet user needs as the principle.