8 Go-To Resources About Screw Conveyor Flight Types | Helicoid Screw Flight | Ribbon Flight Conveyor System: It’s Not as Difficult as You Think

Screw Conveyor Flight Types

The screw of the conveyor flight may be right hand or left hand, the right hand type being the usual design. The threads of the screw may be single, double or triple.

The flight of the screws may be made in either of the two ways:

1. As Helicoids

2. As Sectional flight

Helicoids Flight | Screw conveyor Flight types:

They are formed from a flat bar or strip into a continues helix. The threads are thinner at the outer edge and thicker at the inner edge.

Sectional flights | Screw conveyor Flight types:

Sectional flights are formed from a flat disc and the thickness of the thread is uniform throughout. A continuous helix is made by joining a number of sectional flights together on a piece of pipe and butt welded them. Various styles of screw flights are in use, depending on the service required.

Some of the typical configurations in screw conveyor Flight types are:

1. Short pitch or continuous flight | Screw conveyor Flight types:

If the conveyor is required to handle dry granular or powdered materials that do not pack, this style of flight may be selected. It is of regular construction and recommended for inclined conveyors having a slope of 20 or more, including vertical conveyors. This style is extensively used as feeder screw.

2. Ribbon flight  | Screw conveyor Flight types:

If the conveyor is to handle lumpy, clinging, sticky, gummy or viscous substances, this type flight may be selected. It consists of continuous helical flight formed from steel bar and secured to the pipe by supporting lugs.

  Design of Screw Conveyor | 40 Ways To Eliminate Your Fears and Doubts About Size of Screw Conveyor | Screw Conveyor Capacity Calculation | Screw Conveyor Design Calculation

3. Cut Flight | Screw conveyor Flight types:

In this type of flight screws have notches cut in the periphery of the flight. These notches supplement the conveying with moderate mixing action. They are recommended for conveyors required to handle light, fine, granular or flaky materials.

4. Cut and folded flights | Screw Conveyor Flight Types:

This type of flight is characterized by notches as in cut flight, together with folded segments. This type of flight creates agitation and aeration resulting in better mixing. This type of flight is used to handle light or medium weight materials having fine, granular or flaky materials.

5. Some screw conveyors have cut flight with paddles mounted at regular intervals. The paddles counteract the flow of material past the flight resulting in greater agitation and mixing.

6. Sometimes screws are made of stainless steel to suit special requirements, like the sanitation requirements for handling food, drugs and other hygienic materials.

7. Standard Screw conveyor flight | Screw conveyor Flight types – Screws sectional flight with a pitch spacing equal to the diameter are considered standard and are suitable for most screw conveyors of conventional horizontal design.

Standard-screw-conveyor-flight-design

8. Screw conveyor tapered flight | Screw Conveyor Flight types – Tapered flight spirals provide a continuous incremental change in swept volume of the screw conveyor auger. This promotes even draw down in a full hopper situation. Tapered flights leave residual material in the screw conveyor unless the casing is tapered to suit.

Screw-conveyor-tapered-flight

9.  Screw conveyor short pitch flight | Screw Conveyor Flight Types – Short pitch screws are used in inclined screw conveyors. They are also used to control the feed at the inlet and to reduce flushing of free flowing materials. The shorter the pitch the more efficient is the screw augers.

Screw-conveyor-short-pitch-flight

10. Screw conveyor paddles | Screw Conveyor Flight Types – Paddles are set in a helical form around a square or round center tube to form a segmented spiral. They are used in mixers and pug mills to mix and condition dry products when liquid is added during the process.

Screw-conveyor-paddles

11. Variable pitch flights | Screw Conveyor Flight Types – The screw conveyor with Variable pitch flights are used to control the amount of material drawn down along the length of a hopper. By increasing the pitch at each flight along a screw you can incrementally increase the volume of product that is allowed to enter the screw.

Variable-pitch-flights

12. Screw conveyor double start flight | Screw Conveyor Flight Types – The screw auger conveyor with Double start flights are used to accelerate the conveying process at the conveyor inlet and even out the pulsing effect at the outlet. They are also typically used in drilling and post-hole augers to equalize the torsional forces on the screw auger.

Screw-conveyor-double-start-flight

13. Screw conveyor notched and folded flights – The screw augers with Notched and folded flights provide a more aggressive mixing action where material that passes through the notch is lifted and mixed with the trailing material. They can also be used for aerating or cooling materials.

Screw-conveyor-notched-and-folded-flights

14. Screw Conveyor Notched Flight – The screw conveyors with Notched flights are used to provide a gentle mixing action. Notched flights are useful in blending different materials during the conveying process.

Screw-conveyor-notched-flight

15. Screw Conveyor Center-less Flights (Shaft-less) –  The Screw conveyor Center-less  flights (Shaft-less) are used for extremely sticky or fibrous materials that tend to wrap around or build up on a center pipe.

Screw-conveyor-centreless-flights-shaftless

16. Screw conveyor hollow spiral flight – The screw conveyor with Hollow spiral flights are used to pass heating or cooling liquids around the helix. Typically both the hollow center pipe and the hollow spiral flight are used as a heat exchanger to cool, heat or thaw the material being conveyed.

Screw-conveyor-hollow-spiral-flight

17. Screw conveyor ribbon flight – The screw conveyor with Ribbon flights with integral support legs are used for sticky or cohesive materials that tend to build up on the flight-pipe interface.

Screw-conveyor-ribbon-flight

  10 Fundamentals About Screw Conveyor Working | The Complete Beginner's Guide to Screw Conveyor Applications | Screw Conveyor Pdf

18. Screw conveyor Coned flight | Screw Conveyor Flight Types – The screw conveyor conical flight centers provide a continuous incremental change in swept volume of the screw. This promotes even draw down in a full hopper situation. Combined with variable pitch the coned screw provides the best possible solution to even hopper draw down. Standard troughs can be used with coned flights.

Screw-conveyor-coned-flight

Design of Screw Conveyor | 40 Ways To Eliminate Your Fears and Doubts About Size of Screw Conveyor | Screw Conveyor Capacity Calculation | Screw Conveyor Design Calculation

Design of Screw Conveyor:

The size of screw conveyor depends on two factors

1. The capacity of the conveyor

2. The lump size of the material to be conveyed (Maximum dimensions of the particle)

For the transportation and dispensing of bulk materials, screw conveyors are one of the most often used machinery. The size of a screw conveyor must be calculated in numerous projects in order to attain the required capacity. An existing screw conveyor's capacity might need to be checked in the event that material handling or capacity requirements change. From this brief engineering reference, some few formulas are explained.

Screw conveyors are a convenient, economical, and extremely efficient means of transporting the goods, when the conveyor is properly constructed or designed, according to the consumer requirements. Material flow rate, material dispensing, and overworking of the motor are all governed by the screw conveyor's design and construction. Consider the following methods and techniques for screw conveyor design, in more detail.

Screw Conveyors Have a Long History

The screw conveyor was invented by Archimedes in the 3rd century B.C.  The first screw conveyor was used to irrigate crops and remove water from ships. Spiral flights were attached to the inner wall of a hollow cylinder and were powered by a central shaft in the initial model. Water was transported and raised from one point to the next as the assembly revolved. The spiral project is focused on the inclined plane principle. In contemporary times, the screw conveyor has evolved and is currently utilised in virtually every major sector.

Selection of Screw Conveyor

Screw conveyors are constructed with a central shaft encircled by screw flights as its fundamental design. This mechanism is enclosed by an enclosure that is open on both ends, allowing materials to be collected and discharged from it. While screw conveyors and screw feeders have a similar architecture, screw conveyors are intended to move material from one area of the process to another, while screw feeders are intended to measure the material as it passes through the process.

Internal Parts of Screw Conveyor

Many different screw conveyor designs are available for customization. The following are a few examples of how screw conveyor designs may be tailored to meet the specific requirements of a particular application or material. Please keep in mind that this is not a comprehensive list; there are additional methods to modify the screw conveyor to suit your specific material handling requirements.

• Pitch is the distance between the screw flights on a given screw.
• Shaft refers to the size of the central shaft, or the lack of a central shaft.
• Construction: the materials used to construct the enclosure, shaft, flights, and other components.
• Capacity is measured by the amount of material that can be moved via a screw conveyor in a given amount of time.
• The speed at which the screw conveyor travels is referred to as the screw conveyor speed.
• The conveyor's entire length is referred to as its length.
• Incline: whether or not the conveyor must travel a vertical distance, and how much distance it must travel.

  Conveyor Take Up Arrangement | Take Up Pulley | Screw Take Up Conveyor | Quick Take Up Master Cylinder

There are many reasons and applications which require variation to standard screw conveyors. These are just some of the factors and conditions that will influence the design and construction of a screw conveyor.

• What material will be conveying?
• What are the material characteristics?
• What is the bulk density of the material?
• What through put capacity is the screw to be designed for and at what housing loading?
• Where will the material be coming from?
• Is the screw to be a feeder or a conveyor?
• Is the screw horizontal, incline or vertical?
• Is the screw reversing?
• How long will the screw be centreline of the inlet to the centerline of the discharge?
• Are intermediate hanger bearings for the screw acceptable?
• Housing construction information
  • Material of construction
  • Dust tight construction
  • Pressure tight construction (i.e. Will the housing have to hold pressure)
  • Will the housing requires a 'code stamp'?
  • Will the equipment be in wash down service?
  • Hinged covers?
  • Tubular or "U" trough housing?
  • Type of shaft seals?
  • Food grade polish
  • Welding requirements
  • How is the housing supported?
• What is the inlet size that we are connecting to and how many inlets are there?
• What is the discharge size that we are to connect to?
• Is the discharge a drop out, injector style or positive feed?
• Is there more than one discharge called out and do they have slide gates?
• What style are the slide gates and how are they operated?
• Is the screw service continuous, 8 hour a day, 24 hour a day, batching, intermittent etc?
• If there is more than one screw to a housing, how many drives?
• Is the screw to be portable?
• Will the screw be required to dewater or drain product?
• Will the screw be required to mix product while conveying?
• Will the product be abrasive?
• What material of construction in product contact?
• What type of welding in product contact?
• What finish or polish is required in product contacts?

Components of a Screw Conveyor

Material Characteristics of Screw Conveyors

The properties of the materials being carried have a major effect on the design of the screw conveyor. Various material qualities may have an effect on the design in a variety of ways, the most significant of which are listed below:

Flowability

Materials that flow smoothly will need less energy to move and will move more quickly. The power required to move materials that are thick and sluggish will be greater, and the materials will move more slowly.

Corrosive

It is possible for corrosive elements to eat away at a screw, shaft, and trough enclosure when they're not constructed from a resistant material. When dealing with corrosive compounds, some stainless steel grades or nickel alloys are the best options available.

Abrasive

Friction may eventually wear out at the screw, shaft, and enclosure as a result of the use of abrasive materials. Screw conveyors will benefit from the use of abrasion-resistant metals, which will assist to strengthen them.

The Angle of Repose

At different inclination levels, the angle of repose has an effect on the flow of the material. This will be especially essential if the screw conveyor is responsible for delivering goods across a vertical and horizontal range of distances.

Features that distinguish them from the other Material properties

Many specific features, such as levels of moisture or oil, agglomeration, toxicity, adhesion, dustiness, flammability, explosiveness, and other attributes, may have an impact on the functioning and design of a screw conveyor.

  6 Facts You Never Knew About Belt Conveyor Types | 5 Advantages Of Troughed Belt Conveyor And How You Can Make Full Use Of It | Flat Belt Conveyor

Flight Pitch, Number, Paddles, and Other Details

Pitch on the screw conveyor flights is an essential factor to take into account. Assuming the feeder is fully extended, the distance between each flight is equal to the diameter of the feeder. When the pitch is half pitch, the distance between the flights is equal to half the diameter of the feeder's diameter. If the pitch of the flights is the same throughout the board, pressure may build up towards the end of the conveyor's length. The pitch may also have an effect on how much material flows through the feeder at any one time.

There are a variety of options for customizing the screw conveyor pitch in order to accommodate the material properties, including the options listed below:

Types of Screw Flights

Progressive or Variable Pitch

A progressive or variable pitch is usually used for pulling items out of a hopper in an even and consistent manner. It is necessary in this situation to extend the distance between the flights in order to pull the material out of the hopper.

Double flight

A double flight is an additional spiral-shaped component that is added around the shaft to enhance the conveying power or quantity even more. Double flight screw conveyors are also available in progressive or variable pitch configurations.

Paddles

The use of paddles between screw flights may aid in the creation of a more gentle mixing and conveying action on the screw. This is particularly beneficial for materials that are brittle or fibrous, as well as those that cluster easily.

Ribbon flight

The difference between a normal screw flight and a ribbon flight is that a typical screw flight is solid all the way through, while a ribbon flight contains gaps between the flight and the shaft. This makes it easier for sticky or viscous items to pass through the screw conveyor with less difficulty.

Screw conveyor design may be tailored to your specific needs to help prevent material from being trapped in the conveyor, avoid overworking the motor, and prolong the conveyor's usable life. Consider your materials, processes, and facility layout before collaborating with a seasoned manufacturer to create the perfect screw conveyor for your application.

Usually there are three ranges of lump sizes which are considered for selection of screw size. These are:

· A mixture of lumps and fines in which not more than 10% are lumps ranging from maximum size to one half of the maximum, and 90% are lumps smaller than one half of the maximum size.

· A mixture of lump and fines in which not more than 25% are lumps ranging from the maximum size to one half of the maximum, and 75% are lumps smaller than one half of the maximum size.

· A mixture of lump only in which 95% or more are lumps ranging from maximum size to one half of the maximum size and 5% or less are lumps less than one tenth of the maximum size.

The allowable size of a lump in a screw conveyor is a function of the radial clearance between the outside diameter of the central pipe and the radius of the inside of the screw trough, as well as the proportion of the lumps in the mixture.

  Screw Conveyors | Screw Conveyor Working Principle And It's Critical Components | Basic Screw Conveyor Systems Design

The lump size of the material affects the selection of screw diameter which should be at least 12 times larger than the lump size of a sized material and four times larger than the largest lumps of an un-sized material.

Example, if screw diameter is 250mm means radial clearance is 105mm, & Maximum lump size is 60mm of 10% lumps.

Capacity of Screw Conveyor:

The capacity of a screw conveyor depends on the screw diameter, screw pitch, speed of the screw and the loading efficiency of the cross sectional area of the screw. The capacity of a screw conveyor with a continuous screw:

Q = V. ρ

Q = 60. (π/4).D².S.n.ψ.ρ.C

Where,

Q = capacity of a screw conveyor

V = Volumetric capacity in m³/Hr

ρ = Bulk density of the material, kg/m³

D = Nominal diameter of Screw in m

S = Screw pitch in m

N = RPM of screw

Ψ = Loading efficiency of the screw

C = Factor to take into account the inclination of the conveyor

Design of Screw Pitch for Screw Conveyor:

Commonly the screw pitch is taken equal to the diameter of the screw D. However it may range 0.75 – 1.0 times the diameter of the screw.

 

Design of Screw Diameter for Screw Conveyor:

Nominal Size D	Trough height from center of screw shaft to upper edge of the trough	Trough width C	Thickness of Tough	Tubular shaft (d1 * Thickness)	Outside diameter of solid shaft	Coupling diameter of shaft
Heavy Duty	Medium Duty	Light Duty
100	63	120	–	2	1.6	33.7*2.5	30	25
125	75	145	–	2	1.6	33.7*2.5	30	25
160	90	180	5	3.15	1.6	42.4*2.5	35	40
200	112	220	5	3.15	2	48.3*3.5	40	40
250	140	270	5	3.15	2	60.3*4	50	50
315	180	335	5	3.15	–	76.1*5	60	50
400	224	420	5	3.15	–	76.1*5	60	75
500	280	530	5	3.15	–	88.9*5	70	75

RPM of Screw:

The usual range of RPM of screw is 10 to 165. It depends on the diameter of screw and the type of material (Max RPM of screw conveyor is 165)

Loading efficiency:

The value of loading efficiency should be taken large for materials which are free flowing and non abrasive, while for materials which are not free flowing and or abrasive in nature, the value should be taken low:

Ψ = 0.12 to 0.15 for abrasive material

= 0.25 to 0.3 for mildly abrasive material

= 0.4 to 0.45 for non abrasive free flowing materials

Inclination Factor:

The inclination factor C is determined by the angle of screw conveyor with the horizontal.

Angle of screw with the horizontal	0°	5°	10°	15°	20°
Value of factor C	1	0.9	0.8	0.7	0.65

---

Internal Resources:

---

1. Screw Conveyor: Definition, Function, Construction and Working Principle
2. Screw Conveyor: Applications
3. Screw Conveyor: Flight types
4. Screw Conveyor: Motor Power calculation and Conveyor Capacity Calculation
5. Screw Conveyor: Take up arrangement
6. Vertical Screw Conveyor