Screw Conveyor Design

Contents

CONTENTS

Terms of Reference

Introduction

1 DEVICE AND PRINCIPLE OF OPERATION OF WINDING CONVEYOR

2 DESIGN CALCULATION OF SCREW CONVEYOR

2.1 Determination of the main dimensions of the conveyor

2.2 Determination of engine shaft power

2.3 Selection of transfer device

2.4 Greatest Longitudinal Force on Shaft

2.5 Screw shaft strength calculation

2.6 Calculation of screw shaft for rigidity

3 CALCULATION OF SCREW LINE DEPLOYMENT

4 RATIONALE FOR DESIGN DECISIONS

5 CALCULATION OF KEY CONNECTIONS

6 END SUPPORT SHAFT CALCULATION

6.1 Calculation of reactions in supports

6.2 Calculation of bending moments of shaft

6.3 Calculation of the shaft for static strength under action

peak load

6.4 Calculation of shaft for fatigue strength

7 CALCULATION OF INTERMEDIATE SUPPORT SHAFT

6.1 Calculation of reactions in supports

6.2 Calculation of bending moments of shaft

6.3 Calculation of the shaft for static strength under action

peak load

6.4 Calculation of shaft for fatigue strength

8 CALCULATION OF PIN JOINTS

9 CALCULATION OF BEARINGS

6.1 Calculation of end support bearings

6.2 Calculation of intermediate support bearings

6.3 Calculation of head support bearings

10 CALCULATION OF BELT TRANSMISSION

11 JUSTIFICATION OF ACCEPTED LANDINGS

12 LIST OF STANDARDS USED

Conclusion

List of sources used

Paper

Course project: 48 p., 7 drawings, 8 sources.

Graphic part: 4 sheets of A1 format.

KEYWORDS

(Screw conveyor, conveyor, corn)

SCREW CONVEYOR

The project object is a screw conveyor.

The purpose of the work is to master the design and calculation of lifting and transportation equipment, consolidate knowledge in the disciplines: lifting and transportation equipment, machine parts, machine and mechanism theory, metrology, material resistance, interchangeability basics, etc., design a vibration conveyor.

During operation, calculation of the main parameters of the screw conveyor, check calculation of rolling bearings, calculation of the shaft, check calculation of key connections were carried out. A screw conveyor was designed.

COURSE ENGINEERING ASSIGNMENT

Topic of work Screw conveyor design.

The contents of the task shall be designed and calculated by the screw conveyor.

Scope:

a) explanatory note 3040 s.

b) graphic part 4 of A1 sheet

Recommended literature Kovalevsky V.I. Design of technological equipment for food production; Kovalevsky V.I. Ensuring assembly accuracy during the production and repair of machines.

Introduction

The object of the course project is a screw conveyor.

Screw conveyors belong to the category of continuous transport machines, its traction organ is an auger. They serve to move loose, dusty and powdery, less often small-piece cargoes over short distances (usually up to 40 m horizontally and up to 30 m vertically) at a productivity of usually up to 100 t/h in the chemical and flour mills industry and in construction materials enterprises.

It is not advisable to transport sticky and strongly compacted weights with winding conveyors.

The advantages of screw conveyors include the simplicity of the device and ease of maintenance, small overall dimensions, convenience of intermediate unloading, tightness, which is especially important when transporting dust, hot and spiky loads.

Disadvantages of screw conveyors are method-related

high specific energy consumption, significant attrition and grinding of the load, increased wear of the screw and trough, as well as sensitivity to overloads, leading to the formation of a cluster of loads inside the trough (especially at intermediate bearings).

Screw Conveyor Arrangement and Operating Principle

The horizontal screw conveyor consists of a screw in the form of a screw shaft located in bearings with screw turns fixed on it, a trough with a semi-cylindrical bottom in which the screw is placed coaxially, and a drive, which is a motor reductor, rotating the screw. Bulk cargo is fed into the chute through one or more holes in its cover and, when the screw rotates, slides along the chute, just as the nut held from joint rotation with it moves along the screw. Joint rotation of the load with the screw is prevented by the gravity of the load and its friction against the trough. Unloading of the trough is carried out through one or more holes in the bottom, equipped with gates.

The conveyor screw is made with the right or left direction of the spiral, single, two- or three-start. The surface of the screw may be solid, band or discontinuous in the form of shaped blades. A screw with a solid surface is used mainly when moving a dry fine-grained load that is not prone to fusion; with tape, vane and shaped - when moving fusing weights. In addition, blade and shaped screws are used in cases where a certain technological process must also be performed when moving the load, for example, mixing is more intense.

Turns of full-wall and band screw are made by stamping from steel sheet or strip and then welded to shaft. Spiral of band or blade screw is fixed on rods passing through holes drilled in shaft.

The screw shaft may be solid or tubular for ease of assembly from separate sections. The tubular shafts have a smaller mass and are more conveniently fastened together by means of short connecting rollers inserted at the ends. Screw shaft lies in intermediate and end bearings. intermediate bearings are suspended from above on transverse bars fixed in the gutter. They should have as small a diameter and length as possible (since the turns of the screw have to be interrupted for this length), as well as a reliable seal to avoid contamination with cargo particles. Often these are sliding bearings in which the connecting rollers rotate. lubricant is supplied to bearings via tubes from presses located on top of the strips. end bearings are reinforced in end walls of trough. One of them is made stubborn and is installed usually on the side into which the load moves, to receive the axial tensile load acting along the shaft.

The performance of the screw conveyor depends on the diameter of the screw, the pitch of the screw, the speed of rotation thereof and the filling ratio of the screw cross section.

The filling ratio of the screw cross section in order to avoid congestion of the load at the intermediate bearings is taken to be relatively small: it depends on the properties of bulk loads.

On inclined conveyors with upward movement of the load, productivity decreases with increasing angle of inclination, especially in the presence of intermediate bearings .

The pitch of the screw for relatively easily movable loads is taken equal to the diameter of the screw, for difficult to move it is reduced to 0.8 D or two- and three-screw screws are used.

The rotation speed is selected depending on the type of weight to be moved and the diameter of the screw; it must ensure a calm, without pouring cargo through the shaft; speed decreases with increase of screw diameter, density and abrasiveness of weight.

The total resistance to the movement of the load on the screw conveyor is composed of the forces of friction of the load against the trough and against the surface of the screw, resistance in intermediate and end bearings (including the thrust bearing), as well as resistance to lifting when moving up the slope. If friction coefficients are known, these losses can be calculated. However, in addition, additional, difficult-to-take-into account resistances occur on the screw conveyor due to the accumulation of weight at the intermediate bearings, friction on the edge of the screw against particles tightened into the gap between the screw and the trough, and mixing the load. Therefore, when determining engine power, it is most convenient to use the general resistance coefficient obtained experimentally, depending mainly on the properties of the transported load.

The shaft of the screw, which can be considered as a multi-support split shaft with a distance between the supports l, is calculated for the complex twisting resistance under the influence of the torsion moment, longitudinal stretching by axial force, bending by the bending moment, as well as bending along the length l from its own weight. The screw is also checked for bending deformation, and the deflection should not significantly change the gap between the edge of the screw and the trough.

Design calculation of screw conveyor

The task of the design calculation of the screw conveyor includes:

- selection of conveyor circuit depending on process requirements and conditions;

- determination of the main dimensions of the conveyor;

- determination of drive motor power;

- selection of drive device elements;

- selection of electric motor type;

- calculation of screw shaft for strength.

Justification of the adopted design decisions

The conveyor I am developing moves the load at a length of 40 m at an angle of 0 to the horizon. The trough has a semi-cylindrical bottom and vertical walls and consists of 3 sections connected to each other by M16 bolts tightening welded flanges. At the beginning and end, the chute is attached to the steel sheet with the same bolts .

For ease of assembly, small metal sheets are welded to the end sheets for ease of assembly. This design makes it possible not to waste time and effort in getting bolts into the holes on the flange and in the sheet. During assembly, the bullet-cylindrical part of the welded flange is centered relative to the end sheet by basing it on metal plates welded to this sheet.

End bearing support is installed on inclined welded frame made of channels of the 14th profile. The frame itself is attached to an inclined concrete foundation using anchor bolts.

Drive representing motor reducer and initial bearing support have common frame made also of channels of 14th profile and fixed to foundation in the same way as frame of end support.

The intermediate bearing support is bolted to the corners screwed to the cylindrical part of the trough by M16 bolts.

Due to the small length of the conveyor, it is not necessary to provide intermediate unloading, so its design provides only two hatches: a loading one located on the cover of the conveyor made of steel sheet; and unloading, welded directly to the cylindrical part of the unloading section of the trough.

To avoid contamination of the load, the conveyor cover has corners welded on the sides, which, in turn, rest on corners welded outside the trough and filled with some kind of insulator.

Above the intermediate support there is a manhole in the cover, which allows you to have access to this support if necessary.

Justification of accepted landings

Justification of selected rolling bearing fits

It has been established by many years of practice that the connection to the shaft or housing of rings rotating relative to the load must be carried out with tension, which excludes the turning and rolling of the mating part with the ring and, as a result, the flaring of the mounting surfaces and contact corrosion.

The seats of the rings fixed relative to the load are designated as freer, allowing for a small gap, since the rings of the mating parts do not roll in this case. Irregular rotation of the non-rotating ring is useful because the position of its loading zone changes. In addition, such coupling facilitates axial movements of the rings during installation, when adjusting clearances in bearings and during temperature deformations of shafts.

The bearing is the main component product that should not be further refined during assembly. The required fits in the rolling bearing connection are obtained by assigning the corresponding tolerance fields to the shaft diameters and holes in the housing .

For internal rings of bearings we assign fits L0/k6, for external rings - H7/l0.

Justification of selected rolling bearing cover fits

Install the blind bearing cover by non-essential fit with clearance H7/d11.

Justification of selected fits of screw shaft connection with end support shaft

It is necessary to provide a gap at this point, because during assembly these parts will have to be rotated relative to each other in order to attach them with pins. landing - H7/k7.

Justification of selected threaded joint fits

It is recommended that 6H/6g be assigned to fit the threaded connections.

List of standards used

GOST 833875 - "Ball radial single-row bearings."

GOST 779870 - "Bolts with hexagonal head of accuracy class B."

GOST 640270 - "Spring washers."

GOST 2336078 - "Prismatic keys."

GOST 1394186 - "Spring thrust flat internal eccentric rings and grooves for them."

GOST 1394286 - "Spring thrust flat outer eccentric rings and grooves for them."

GOST 875279 - Rubber reinforced collars for shafts.

GOST 1208066 - "Cylindrical shaft ends."

GOST 1952381 - "Three-phase asynchronous motors with increased sliding of the 4AS series."

GOST 105088 - "High-quality carbon steel."

GOST 278973 - "Parameters for surface roughness rationing."

GOST 2464281 - "Deviations and tolerances of cylindrical surfaces shape."

Conclusion

This course project completes the study of the discipline "Lifting equipment." The main purpose of the work was to master the design and calculation of lifting and transportation equipment.

In the course of the work, the acquired knowledge was fixed in such disciplines as lifting and transportation equipment, the design of technological equipment and lines, machine parts, material resistance, the calculation and design of machines and apparatus of food production, the theory of machines and mechanisms, metrology, the basics of interchangeability, etc.

The topic of the course project was chosen during the technological practice at the enterprise for the storage and processing of grain products (OJSC Krasnodarzernoproduct). Real equipment operating at the enterprise was taken as the basis.

During the course project, practical skills were gained in the design of lifting and transportation equipment. In particular, a screw conveyor was designed in this project. First of all, the principle of its operation was studied. Then the screw conveyor was calculated according to the available method.

The acquired skills in the design and calculation of equipment are undoubtedly necessary for the subsequent training of the future engineer.

Proektirovanie_vintovogo_konveyera.dwg