39 0 4MB
A Project Report ON
“DESIGN AND MODEL OF BUCKET ELEVATOR” Under The Guidance Of
Prof. .................... Assistant Professor, Kalpi Institute of Technology In partial Fulfillment for the award of the degree Of Bachelor of Engineering In Mechanical Engineering
Prepared By
AMIT JAISWAL (5808614) Submitted to
Kalpi Institute of Technology, Ambala Sep, 2015
DECLARATION
I, AMIT JAISWAL hereby declare that the report on entitled “Design and Model of Bucket Elevator” is a result of my own work and my indebtedness to other work Publications, if any, have been duly acknowledgment.
Place: - Ambala, Haryana, India th
Date: - 5 Sep, 2015
Amit Jaiswal
i
ACKNOWLEDGEMENT
I deem it a privilege to have been the student of Mechanical Engineering stream in Kalpi Institute of Technology, Ambala. My heartfelt thanks to Prof..........., my project guide who helped me to bring out this project in good manner with his precious suggestion and rich experience. I gratefully acknowledge my sincere thanks to my friend Rohit Kumar for working as Co-partner and all other friends who help me in this project in such critical situations and make my project memorable.
I hardly thank to my principle sir Dr. ............ who grant us permission for economic help for model making also Mr. Karimbhai, Mr. Samirbhai, Mr. Anandbhai, Mr. Sureshbhai, Mr. Manishbhai, Mr. Harshadbhai, Mr. Mineshbhai, Mr. Yogeshbhai, Mr. Bharatbhai, Mr. Birenbhai and Mr. Aashishbhai the staff’s members of KIT workshop, without help of them this work is not possible.
ii
ABSTRACT
In this modern competitive industrial world one can get a step ahead of his competitor by selection of proper material handling equipment. Material handling process is overhead for the production but it is heart of any process plant. Still people prefer most advanced material handling equipment even though they are costly. But cost can be justified after prolonged usage of that equipment.
Bucket elevator has evolved as advanced material handling equipment in mechanized bulk material handling industry. The effective use of different type of bucket elevators are completely depends on its design and type of bulk material. In this report different types of bucket elevator are discussed along their different parts and the design of centrifugal discharge bucket elevator with simultaneous buckets for lifting wheat at a certain height is reported for a particular output rate. Detailed design, CAD parts, coding for the design procedure of bucket elevator, fabrication related data and future scope of work and at last satisfactory conclusion is worked out in successive chapters.
iii
LIST OF TABLE Table No.
Table Description
Page No.
2.1
Recommendation for selecting bucket elevators
23
2.2
Main characteristics of buckets
26
2.3
Recommendation for selecting bucket Dimension by Maxi-lift
34
3.1
Bill of material for bucket elevator
45
4.1
Design inputs for prototype model
49
4.2
Design outputs for prototype model
49
4.3
Fabrication processes for bucket elevator
51
5.1
Observation table for 10.00 kg of wheat
63
5.2
Observation table for 24.75 kg of wheat
63
iv
LIST OF FIGURE Figure No.
Figure Description
Page No.
1.1
Simple belt conveyor
3
1.2
Simple bucket elevator
4
1.3
Parts of simple belt bucket elevator
5
1.4
Belt bucket elevator
6
1.5
Positive discharge bucket elevator
9
1.6
Gravity discharge bucket elevator
10
1.7
Horizontal discharge bucket elevator
11
1.8
Centrifugal discharge bucket elevator
12
1.9
Twin legged discharge bucket elevator
13
1.10
Single and double bucket elevator
14
1.11
High or Super capacity bucket elevator
15
1.12
Bunge Russia – Oilseed bucket elevator
17
1.13
New Zealand - Bins plant bucket elevator
17
1.14
Cimbria (Egypt) - Bins plant bucket elevator
18
1.15
Bahrain-Coke calcining plant bucket elevator
18
1.16
Jordan - Fertilizer plant bucket elevator
19
2.1
Diagram to calculate the pole distance
20
2.2
Forces acting during bucket unloading
21
2.3
Diagram to determine the paths of ejection of material from buckets
21
2.4
Effect of bucket width B on io/tb ratio
25
2.5
Diagram for elevator calculation
28
2.6
Diagram for bucket calculation
34
3.1
Bucket
40
3.2
Ball bearing
40
3.3
Belt
41
3.4
Shaft
42
3.5
Pulley
43
3.6
Bucket elevator assembly
45 v
3.7
Mechanism of bucket elevator
46
3.8
Mechanism problem-1 of bucket elevator
47
3.9
Mechanism problem-2 of bucket elevator
47
3.10
Mechanism problem in case study
48
4.1
Side part of bucket
53
4.2
Bend part of bucket
53
4.3
Sheet metal planning for all bucket
53
4.4
Loading and bending moment diagram for upper shaft
56
4.5
Fabricated bucket elevator prototype model
58
5.1
Variation based on lifting height
59
5.2
Variation based on pulley diameter
60
5.3
Variation based on capacity
61
5.4
Variation based on efficiency
62
vi
LIST OF SYMBOLS, ABBREVIATIONS AND NOMENCLATURE R P, F
Resultant Forces
Rp
Pulley radius
hp
Pole distance
ra
Bucket circle radius
β
Bucket angle
Q
Capacity
H
Lifting height
ρ
Wheat density
ν
Belt speed
Dp or dp
Pulley diameter
N
Rotational speed of pulley
B
Bucket width
V
Volume
Bb
Belt width
tb
Bucket pitch
Ψ
Average coefficient of bucket filling
mrb
Linear mass of belt
g
Gravitational constant = 9.81
mb
Mass of bucket
T
Tension
ζ
Resistance on take-up pulley
Ksc
Scooping resistance
K
Safety factor
W
Pulley resistance
μ
Coefficient of friction
P
Power
η
Efficiency
Bp
Width of pulley
vii
t
Pulley rim thickness
L
Belt length
C
Centre distance
τs
Allowable shear stress
w
Width of key
h
Height of key
rh
Hub radius
d
Inner diameter of bearing
D
Outer diameter of bearing
b
Width of bearing, Projection of bucket
Co
Static load
C
Dynamic load
h1
Depth of bucket
θ α
п
Angle of contact Angle subtended by each common tangent
3.14
viii
TABLE OF CONTENTS
Page No.
1.
2.
3.
Declaration
i
Acknowledgement
ii
Abstract
iii
List of Tables
iv
List of Figures
v
List of Symbols, Abbreviations and Nomenclature
vii
Table of contents
ix
Introduction 1.1
Material handling equipments
1
1.2
Bucket elevator
5
1.3
Classification of bucket elevator
8
1.4
Application of bucket elevator
15
1.5
Presently installed bucket elevator in abroad
17
Design of bucket Elevator 2.1
Bucket elevator geometry
20
2.2
Design input data for bucket elevator
22
2.3
Flow chart for coding of design
35
Modeling of elevator 3.1
Introduction of modeling and its significance
39
3.2
CAD parts of bucket elevator
40
3.3
Assembly of bucket elevator
44
3.4
Bill of material
45
3.5
Mechanism of bucket elevator
45
ix
4.
5.
Fabrication of prototype 4.1
Selection of prototype dimension
49
4.2
Fabrication of bucket elevator prototype
51
4.3
Selection of power pulley
55
4.4
Bending moment diagram of upper shaft
55
4.5
Problems occurred during fabrication
57
4.6
Fabricated prototype of bucket elevator
58
Results analysis 5.1
Effect of operating variables on performance
59
5.2
Result analysis of prototype model
62
6.
Scope of further work
64
7.
Conclusion
65
Appendix: A
xi
Bibliography
xxv
x
Chapter 1:
INTRODUCTION
1.1. MATERIAL HANDLING EQUIPMENTS Expressed in simple language, Material handling equipment is relates to the movement, storage, control and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption and disposal. One of the definitions given by the American Material Handling Society is: “Materials handling is the art and science of moving, packaging and storing of substance in any form.” To do it safely and economically and efficiently, different types of tackles, gadgets and equipment are used, when the materials handling is referred to as mechanical handling of materials.
Material handling also should be considered with in a system context. Rarely, if ever, are activities performed in a one area or department of a facility without having an impact on other operations. Example: The efficiency of store room will affect the efficiency with which the production operations are performed out on the shop floor. The positioning of conveyor line in plant might improve material flow through the facility or it could present a hindrance to plant traffic. A significant improvement in the efficiency of one operation, without a corresponding improvement in a subsequent step in the work sequence, may only result in a piling up of materials down the line.
These simple examples illustrates the point that to maximize overall productivity of the plant or warehouse, the material handling steps that supports production, order assembly, and other operations must be integrated in to a system of activities rather than being viewed as a number of isolated independent procedure. In addition to considering time and place utility and system approach, a through definition of material handling must also include the human aspect. People are always a part of material handling weather the operation is simple one, involving only a few items of equipment, or a large, complex, automated system. Maintenance personnel keep the equipment working properly and keep downtime to a minimum. Foremen and supervisors oversee overall operations, making sure they meet the objectives of the department or plant. Training in operating procedure, and in safety practice, is usually required to make handling operation pay off as expected. 1
Finally, the definition of the material handling must contain an economic consideration. Certainly the delivery of parts and materials to a specific time, it not completely meaningful unless accomplished at an acceptable cost so that an adequate return is realized. Material handling is a system or combination of methods, facilities, labour, and equipments for moving, packaging and storing of materials to meet specific objectives. A materials handling operation can be simple and small, and involve only few pieces of basic equipments. Or, it may be large, complex or automated. Material handling equipment is generally separated into four main categories. Storage and handling equipment. Engineered systems. Industrial trucks. Bulk material handling.
Bulk material handling is an engineering field that is cantered around the design of equipment used for the handling of materials such as ores, coal, cereals, wood chips, sand, gravel and stone in loose bulk form. It can also relate to the handling of mixed wastes. Bulk materials handling plants and processes quite often require the elevation (lifting) of bulk materials to other parts of the plant or process. Numerous technologies and equipment are currently available for this purpose to the designer and practitioner. Generally they are classifying in to three main categories. Pneumatic conveyor or air lifter. Conventional screw conveyor. Bucket elevator.
Conveyor is almost universal in application. It can travel for miles at speeds up to 5.08 m/s and handle larger amount of weight in metric tons with the help of belt. It can also operate over short distances at speeds slow enough for manual picking, with a capacity of only a few kilograms per hour. Generally they are use in inclined position and not preferable for vertical transport. However, it is not normally applicable to processing operations, except under unusual conditions. Belt conveyors inside the plant may have higher initial cost than some other types of conveyors and, depending on idler design, may or may not require more maintenance. However, a belt conveyor given good routine maintenance can be expected to outlast almost any other type of conveyor. Thus, in terms of cost per ton handled, outstanding 2
economy records have been established by belt conveyors. However, these methods of elevation can experience a range of problems and limitations, such as in case of: Pneumatic conveying or lifting: Relatively high operating costs e.g. blower and compressor Product velocities and wear rates especially for dilute-phase conveying. Screw conveying: Relatively high operating speeds due to slippage between the screw flight and particles and also due to the back-flow of material through the screw flight and casing clearance, Increased particle attrition, Undesirable casing or screw contact.
Figure 1.1: Simple belt conveyor (Source: www.enviro-abrassion.com) 3
Bucket elevator is a type of vertical or inclined transport equipment that efficiently moves goods between floors, vessel or other structure. Elevator is generally powered by electrical motors that either drive traction cables or counterweight system like a hoist or pump hydraulic fluid to raise a cylindrical piston like jack. Generally it is preferred for short in distance compared to belt conveyor. It is more preferable to transport the materials vertically. The detail explanation of bucket elevator is given in next chapter.
Figure 1.2: Simple bucket elevator (Source: www.swo-conveyors.com) 4
1.2. BUCKET ELEVATOR Bucket elevators are the simplest and most dependable units for making vertical lifts. They are available in a wide range of capacities and may operate entirely in the open or be totally enclosed. The trend is toward highly standardized units, but for special materials and high capacities it is wise to use specially engineered equipment. Main variations in quality are in casing thickness, bucket thickness, belt or chain quality, and drive equipment. The main purposes of bucket elevators are used to lift bulk materials from one height to another. They are a reliable and well-proven piece of equipment. The various major parts of bucket elevator are shown in figure. Inspection panel
Relief
Bridge tree
vent
Head
Boot pulley
Motor
pulley
Casing
Take-up assembly
Hood
Boot section
Head section
Friction material
Belt
Bucket Short trucking
Discharge
Boot bearing
Adjustable throat plate
Boot
Boot inlet
Figure 1.3: Parts of simple belt bucket elevator (Source: www.BEUMER.com) 5
The detail description of various parts of bucket elevators is discussed bellow. The major components of belt bucket elevator are Drive head Bottom head Inlet Outlet Buckets Casing Drive unit Take up Drive head
Drive unit Or Motor
Outlet
Bucket
Casing
Take-up Inlet
Figure 1.4: Belt bucket elevator (Source: www.motridal.com) 6
Drive Head and Bottom Head: Drive head section made with high thickness steel sheets heavily stiffened. Steel split upper cover easily removable for inspection and maintenance of drive pulley or wheels. Dust or relief vent on top and inspection panel located at some height of the outlet. Bottom head is made with high thickness steel sheets is equipped with a removable bolted door for inspection and cleaning.
Inlet and Outlet: Openings prearranged for the connection with other machines; chutes lined with wear resistant material when required.
Buckets: On the basis of the conveyed material characteristics the buckets are generally made of: Carbon steel Wear resistant steel Stainless steel Plastic material Buckets are made with bent and welded steel plates, properly reinforced with welded plates in wear resistant material for heavy duty application, drawn or pressed for light materials. The buckets are also available in various sections, which are listed below. Square V Trapezoidal Circular
Casing: It is the cover part of elevators which is made of welded and bolted sections, designed to obtain a self supporting structure of the machine for the vertical loads. The assembling sections are done by bolted flanges, with seals between each section. There is a bolted door for easy bucket inspection and mounting.
Drive Unit: This configuration may vary depending on the application. The typical drive unit for installed power of 22kW or more includes an electric motor, hydraulic coupling and right angle gearbox with backstop and torque arm directly mounted on the drive shaft. Additional
7
electric motor for creeping can be installed, upon request, on the gearbox. As an alternative, drive units can be equipped with a belt drive between electric motor and gear unit. Take-Up: The gravity take-up system of the bucket elevators is equipped with additional dust-tight seals between the casing and the guide of the idle shaft belt bucket elevators realised for heavy duty application are equipped with a self aligning system which ensure the safe parallel guidance of the pulley. Method of Operation: Bucket elevators operate by using an endless belt or chain on which rectangular buckets are mounted. The belt or chain revolves between a top and bottom pulley and the buckets move with it. At the bottom the buckets pick up product fed into the elevator boot and at the top the product is discharged as the bucket turns downward over the head pulley.
1.3. CLASSIFICATION OF BUCKET ELEVATOR Generally bucket elevators are classified in mainly two types. Belt type bucket elevator. Chain type bucket elevator. Now a day there are many types of bucket elevators are available and each one is different from other according to their feature, application, and design. The major classifications of bucket elevators are as follows.
bucket elevator according to type of discharge
according
positive
single
single
low
gravity
twin
double
medium
mediu m
heavy
heavy
to types of
leg
according to types of
bucket use
horizontal centifugal 8
depending
depending
on load
on capacity
low
1. Positive Discharge Bucket Elevator These types of bucket elevators are widely used for elevating light, fluffy, fragile materials like free flowing powders and granular products in a range of industries in vertical as well as inclined position. Buckets are mounted at a well spaced interval, are loaded by digging material from the boot or by feeding the material in to them. After passing over head wheels, the buckets are inverted over the discharge spout, providing a positive discharge material. Generally they have higher conveying capacity. Figure shows the typical diagram of positive discharge bucket elevator.
Figure 1.5: Positive discharge bucket elevator (Source: www.fmctechnologies.com and www.rexnord.com)
2. Gravity or Continuous Discharge Bucket Elevator: In these types of elevators head shafts are fixed, the foot shafts takes up are screw type. Gravity takes are available. This elevator consists of a series of steel made buckets mounted on spigot pins between two chains or on the belt with the help of special types of screw. Also some time the buckets are mounted continuously on the normally friction surface belts. 9
Continuous type steel buckets are used leaving minimum clearance between the buckets. The buckets retain the material being carried and travelled vertically, until they are mechanically tipped at discharge positions. Gravity discharge elevators supplied as close bucket discharge type, central discharge type, or Idler wheel discharge. Generally a slow speed design gravity bucket elevator is primarily installed for elevating large lumpy, free-flowing material, sluggish material and abrasive material. Our standard units are usually chain driven, either friction drive or toothed sprocket. These elevators offer reliability with minimum wear & a positive discharge emptying of the bucket. The figure shows the vertical arrangement of gravitational discharge bucket elevator.
Figure 1.6: Gravity discharge bucket elevator (Source: www.integratedbulksystems.com.au and www.swrewconveyor.com)
3. Horizontal Discharge Bucket Elevator These elevators are designed and engineered to conform to general practice in the handling of grain. In particular they are found in flour mills and animal feed mills, where whole grain is being transferred into intake silos. Also these types of bucket elevators are widely used for 10
elevating aggregate, hard rock, coal from mine in vertical horizontal as well as inclined horizontal position. Head and foot shafts are provided with roller bearings. Buckets are made of steel and mounted on the belt with special types of screw. Casing of steel are welded and dust tight. The curve hood is designed for proper discharge of the grain. The boot can be loaded from the front or back side or both. Generally they have higher conveying capacity. Figure shows the typical diagram of horizontal discharge bucket elevator.
Figure 1.7: Horizontal discharge bucket elevator (Source: www.ryson.com)
4. Centrifugal Discharge Bucket Elevator Centrifugal elevators are the most common type of elevator installed to most industries supplied in both belt type and chain type depending on material characteristic and the capacity being elevated and in some case the feeding method of the elevator. Centrifugal discharge type elevators are offered as boot take up and head take up. In this types of bucket elevators buckets are mounted on chain or belt and will handle free-flowing materials with small to medium size lumps. The standard inlet chute and standard curved bottom plate direct the material into the buckets and reduce the “digging” action. The speed of the elevator is 11
sufficient to discharge the material by centrifugal force. The feed point is lower, loading is simpler and fewer buckets are required than for the Continuous Type Bucket Elevator. Buckets on chain or belt travel at speeds high enough to discharge materials by centrifugal force as they pass around the head pulley or sprocket. Bucket spacing and speed is important for centrifugal discharge bucket elevators. Usually buckets are made from malleable iron. Generally these types of bucket elevators are more preferable in grain industries.
Figure 1.8: Centrifugal discharge bucket elevator (Source: www.screwconveyor.com and www.go4b.com) 12
5. Twin Leg Bucket Elevator The twin lagged or double trunk legging bucket elevator has been designed and engineered to provide efficient high capacities for handling various grains, feeds, mill stock and similar free flowing granular materials. The elevator is self-supporting with extra large heads and boot pulleys. They are fabricated from heavy gauge steel and are dust and waterproof and with provision for easy clean out. It is manufactured in many different sizes to suit individual requirements. It has double trunk legging construction with connecting angles provided on each 10 foot flange section. Vertical angle supports are included on taller units.
Figure 1.9: Twin legged discharge bucket elevator (Source: www.screwconveyor.com, www.integratedbulksystems.com.au and www.rexnord.com) 13
6. Single and Double Bucket Elevator The construction of these types bucket elevators are same as other types accept that the number and types of buckets are use is different. The capacity of double bucket elevators is more compare to single bucket elevator and also high capacity motor is required in operation. The size of double bucket elevator is large compare to single bucket elevator since two buckets are use in one raw as shown in figure. The double bucket elevators are used lift heavy materials and also where, the higher output is required. Generally these types of bucket elevators are used in aggregate plant, hard rock plant, cement plant where the lift of heavy material is possible.
Figure 1.10: Single and double bucket elevator (Source: www.screwconveyor.com and www.indiamart.com)
14
7. High or Super Capacity Bucket Elevator Super capacity bucket elevators are a continuous discharge type with buckets mounted between two strands of chain or on the belt. This type of elevator is used where higher capacities, severe service or higher shaft centres are required. The high or super Capacity Bucket Elevators are designed to provide efficient high capacities for handling various grains, feeds, mill stock and similar free flowing granular materials. It is manufactured in many different size stop suit individual requirements. It has double trunk legging construction with connecting angles provided on regular interval flange section. Vertical angle supports are included on taller units.
Figure 1.11: High or Super capacity bucket elevator (Source: www.feedandgrain.com and www.screwconveyor.com)
1.4. APPLICATION OF BUCKET ELEVATOR For stable work and application widely bucket elevator are used. By using this one should get high Productivity. This bucket elevator is normally designed and made for metallurgy, 15
chemical industry, building materials, mine, pulp and paper industries, ports and terminal, grain and vegetable oil, food, fodder, plastic and medicine related application. Bucket elevator systems are used for the following industrial fields.
Cement factories: For lime, clay gypsum, clinker and cement additives like pyrite, silicate, oxide etc Environment and water treatment: Waste for combustion, biomass, sludge, ashes etc. Power plant: For coal, lignite and desulphurization product like gypsum, ashes, sludge. Fertilizers and Chemical: For raw materials and additives handling, phosphate, nitrate. Steelworks and Aluminium smelter: For coke, ashes, blast furnace slag, coke, alumina, crushed bath, covers material. Food industry: For sugar, flour, vegetables pulp, slaughterhouse waste etc.
Z type bucket chain material elevator is Suitable for lifting puffed food, fried food, nuts, sugar, candy, hardware, medicines and so on. It is easy to operate fast transfer speed with low noise. For grain or Seed application bucket elevator are used. This bucket elevator can be equipped multi-channel explosion-proof mouth if required which can prevent dust explosion. The system of speed monitoring, automatic running deviation alarm, anti-blockage alarm also can be equipped to ensure the good running.
Reliable Quality Chain Bucket Elevator is designed and made for metallurgy, chemical industry, building materials, mine, grain and vegetable oil, food, fodder, plastic and medicine application. The life is long, inflow feeding, none excavating with hopper and there is few extrusion and collision circumstance between materials. There is little materials sprinkling during feeding and discharging to reduce machinery abrasion.
Structure Simple Bucket elevator is used for perpendicular transport the grain, powder and disperse materials, and suitable for the oil, animal feed and chemical industry etc. This Bucket Elevator is a fixed elevator categorized as feeding device of delivering powdery and granular materials upward vertically. It has simple structure, smaller cover are, short 16
shipping route and low pollution. Wood chips are received from belt conveyor by a double led centrifugal discharge bucket elevator and delivered to a distributed belt conveyor over silos.
1.5. PRESENTLY INSTALLED BUCKET ELEVATORS IN ABROAD: Bunge Russia recently opened a new oilseed extraction facility featuring Brock steel bins.
Bucket elevator
Figure 1.12: Bunge Russia – Oilseed bucket elevator (Source: www.World-Grain.com)
Chief Industries installed two bins to increase storage capacity by 16,000 tonnes at this plant in New Zealand.
Bucket elevator
Figure 1.13: New Zealand - Bins plant bucket elevator (Source: www.World-Grain.com) 17
Cimbria recently installed bins with a combined storage capacity of 333,000 tonnes at seven facilities in Egypt.
Bucket elevator
Figure 1.14: Cimbria (Egypt) - Bins plant bucket elevator (Source: www.World-Grain.com)
Figure 1.15: Bahrain - Coke calcining plant (Source: www.motridal.com)
18
Figure 1.16: Jordan - Fertilizer plant (Source: www.motridal.com)
19
Chapter 2:
DESIGN OF BUCKET ELEVATOR
2.1. BUCKET ELEVATOR GEOMETRY: Pole Distance:
Figure 2.1: Diagram to calculate the pole distance (Source: Spivakovsy, A.O. and Dyachkov, V.K. (1985), Conveying Machine, MIR Publication,
Forth Edition)
As a bucket revolve on the pulley, the resultant R of the forces P and F varies in magnitude and direction. If however, the resultant force vector is prolonged to the vertical line passing through the pulley centre, it turns out that at any position of the bucket, and vector R intersects the vertical in one and the same point B to the pulley centre O is called the pole distance. The pole distance is denoted by hP. Bucket Unloading: At lower speed of the pulley, the effect of the gravity force on unloading become stronger and hP increases. When hP is not larger than rP the pole is inside the pulley circle (figures 2.2a and 2.2b), the centrifugal force is much higher than the gravity force and hence bucket unloading centrifugally.
20
(a) Centrifugal unloading; (b) gravity unloading; (c) Combined unloading Figure 2.2: Forces acting during bucket unloading (Source: Spivakovsy, A.O. and Dyachkov, V.K. (1985), Conveying Machine, MIR Publication,
Forth Edition)
Similarly if hP grater than rP the force of gravity is large and buckets are unloaded gravitationally. With rP < hP ≤ ra unloading of combined types takes place. Therefore, the method of unloading is determined by the ratio between the pole distance and pulley radius A= hP /rP . Trajectory of Partials Discharged From a Bucket:
Figure 2.3: Diagram to determine the paths of ejection of material from buckets (Source: Spivakovsy, A.O. and Dyachkov, V.K. (1985), Conveying Machine, MIR Publication,
Forth Edition) 21
As a bucket moves around the top pulley, a particle of load in it is acted upon by the gravity force, centrifugal force, and inertia force due to the relative acceleration of sliding the particle on the bucket wall. The path and velocity νS of sliding particle can be determined by solving equation of motion of the particle. The start of the motion of the particles depends on the method of unloading. 0
With centrifugal discharge the load beings to move in the bucket at an angle β0 = 15-30 . For elevators with centrifugal or combined unloading, it may be taken that β0 = 30-45
0
2.2. DESIGN INPUT DATA FOR BUCKET ELEVATOR: Assumption: During design of bucket elevator a few factors are consider for design and based on this for input data whole design calculations were carried out. The following factors are considered during design. Material for lifting: Wheat Average bulk density: 720-768 Kg/m
3
Application: In flour mills to transmitting large amount of wheat from ground floor to required destination (floor). Properties of material: Lighter than metal, Injection moulded, Flexible, Thick corners and digging lip. Specific requirements: It should have excellent chemical resistance and it should have higher transmission capacity. Calculation: Capacity (Q) = 30.00 Tonne/hour Lifting height (H) = 3.00 m Wheat density (ρ) = 0.768 Tonne/m
3
22
1. THE MAIN CHARACTERISTICS OF THE ELEVATOR By using Table 2.1 a belt elevator with widely spaced deep buckets and belt speed ν = 3.20 m/s is suitable for the transmission purpose. We select a four-ply belt; then the diameter of the drive pulley is given by DP = 125 * 4 = 500 mm = 0.50 m and its radius r P = 0.25 m. The rotational speed of the pulley at ν = 3.20 m/s is given by,
The pole distance hp is found by the formula,
Table 2.1: Recommendation for selecting bucket elevators KIND OF LOAD
DRY PULVERIZED MATERIAL
BUCKET
AVERAGE COEFFICIENT OF BUCKET FILLING
BELT
CHAIN
LOW SPEED GRAVITY UNLOADING
D
0.85
-
0.6 - 0.8
HIGH SPEED CENTRIFUGAL UNLOADING
D
1.25 - 2.0
-
TYPICAL EXAMPLE
TYPE OF ELEVATOR
PULVERIZED COAL CEMENT, ROCK, PHOSPHET MEAL GRAIN PRODUCTS (FLOUR)
FOOD GRAIN
HIGH SPEED CENTRIFUGAL OR GRAVITY UNLOADING HIGH SPEED CENTRIFUGAL OR GRAVITY UNLOADING
23
TYPE OF
0.80
SPEED m/s OF
S
0.85
1.0 - 2.0
-
D
0.75
2.0 - 3.2
-
GRANULAR AND FINE LUMP, LOW ABBRASIVE
PULVERIZED AND GRANULAR, WET POORLY FLOWING
SAWUST, WOOD CHIPS, DRY CLAY IN LUMPS, MILLED PEAT, FINE COAL
DITTO
D
0.8
1.25 - 2.0
1.0 – 1.6
LIME, SOOT
LOW SPEED GRAVITY UNLOADING
D
0.8
-
0.4 – 1.0
SOIL, SAND, POWDER CHALK, CHEMICALS
HIGH SPEED CENTRIFUGAL OR GRAVITY UNLOADING
S
0.6
1.0 - 2.0
0.8 – 2.0
(Note: Bucket types: D: Deep, S: shallow) (Source: Spivakovsy, A.O. and Dyachkov, V.K. (1985), Conveying Machine, MIR Publication,
Forth Edition)
At lower speeds of the pulley the effect of the gravity force on unloading becomes stronger and hp increases. Now when hp is not longer than rp, i.e. the pole is inside the pulley circle as shown in figure 2.1, the centrifugal force is much higher than the gravity force; particles of the material in a bucket are displaced to the external (front) of the bucket and later are unloaded centrifugally. With hp greater than rp i.e. with the pole being the front edge of buckets as shown in figure the force of gravity is large compared with the centrifugal component and the buckets are unloaded by gravity over their back wall (closest to the pulley). Since hp> - 267.49 N. To ensure the certain margin, we take T 0 = 0 N and then,
29
The required number of belt plies is found for Kop = 55 N/mm and safety factor K = 10
Noting that belt is weakened by bolts and should ensure firm fastening of buckets, we can use the four-ply belt adopted earlier in the calculation. The circumferential force on the drive pulley, noting the pulley resistance is,
The power of drive motor, assuming the efficiency of drive mechanism η = 0.85 and a margin K = 1.25, will be
30
Hearse, we take finally a drive motor of a power P = 2.8 kW and rotational speed N = 51.95 rpm 4. PULLEY CALCULATION Width of the pulley is given by,
Thickness of rim is given by,
5. BELT CALCULATION Length of belt is given by,
31
Belt Tension,
Permissible Tension in belt per mm width (f),
6. SHAFT CALCULATION For 300 mm belt width and 500 mm pulley diameter, Diameter of shaft (d) is 83 mm. 2
Allowable shear stress for shaft and key material (mild steel), τsk = 70.4 N/mm then, allowable shear stress for shaft accounting keyway effect,
Now, Equivalent torque acting on shaft,
32
= 5.9 KN m Width of key,
Height of key,
Length of key = 22 mm and radius of hub is equal to diameter of shaft so, r h = 83 mm
7. BEARING CALCULATION By using series: 60 Inner diameter: d = 83 mm Outside diameter: D = 130 mm Width of bearing: b = 23 mm Static load: Co = 42 KN Dynamic load: C = 49 KN Permissible rpm for grease = 5187.5 rpm and For oil = 6536.25 rpm
33
8. BUCKET CALCULATION
Figure 2.6: Diagram for bucket calculation (Source: www.maxilift.com)
By using Table 2.3 given by Depth of bucket, h1= 156.00 mm Projection of Bucket, b= 156.00 mm Table 2.3 Recommendation for selecting bucket Dimension by Maxi-lift Width of Bucket Projection of Bucket Depth of Bucket B, mm
b, mm
h1, mm
108
79
79
133
105
105
159
105
105
184
105
105
181
130
133
206
130
133
232
130
133
238
156
156
264
156
156
289
156
156 (Source: www.maxilift.com)
34
Now, assume β=18˚
2.3. FLOW CHART FOR CODING OF DESIGN
Start
Lifting Height (H) in m = Wheat Density in Tonne/m3 = No. of Belt ply (Np) = Efficiency =
35
No
Yes
Want to enter Capacity (Q)?
Enter i0/tb in m-1
Capacity (Q) t/hr =
I0/tb = Q / (3.60 * v * ρ * Ψ)
Q = i0/tb * 3.60 *v * ρ * Ψ
No
Yes
Want to enter Pulley diameter?
Dp = 125 * No. of Belt ply
Pulley Diameter (Dp) mm
rp = Dp / (2000), m Belt velocity (V) = 3.2 m/s N = 60 * v * 1000 / (п * Dp), rpm hp = 895 / (N2)
No hp < rp
Unloading of bucket centrifugally is not possible
Yes Unloading of bucket centrifugally is possible
Bucket width (B) in mm Belt width (Bb) in mm Bucket pitch (tb) in mm Bucket volume (V) = (21* B) / 250 mm3
36
Stop
mrb = 2.4 * Np / 4; qrb = 9.81 * mrb; mb = 3.38 * B / 250;
q0 = qrb + (9.81 * mb * 1000 / tb); Tension T4 in N = q0*H; Tension T3 in N = 3.00*T4
Safety factor k = 10
Required no. of belt plies (i) = k * T3 / (Bb * 55); Pulley Resistance (W) in N = (T3 - T4) / 1.08
Motor power (P) in kW = 1.25 * W * 3.2 / (1000 * Efficiency)
Pulley width (Bp ) in mm = 1.25 * Bb Rim thickness (t ) in mm = Dp / 200 + 2 Belt length (L) in m = 2 * H + (3.14 * Dp / 1000) Belt tension (T) in Nm = (T3 - T4) * Dp / 2 Permissible Tension (f) in belt per mm width in N/mm = T3 / Bb
Projection of bucket (b) in mm Depth of Bucket (h1) in mm (h1 - h2) = b * tan(18) h2 = h1 - (h1 - h2), mm n = L * 1000 / tb
Shaft diameter (d) in mm Shaft load in kN Bearing No. Bearing bore diameter in mm Bearing outside diameter in mm Bearing width in mm Bearing static load (C0) in kN Bearing dynamic load (C) in kN Permissible rpm for Grease lubrication Permissible rpm for Oil lubrication Radius of hub (rh) in mm Key width (w) in mm Key height (h) in mm Equivalent torque acting on shaft (Te) in Nmm
Stop
38
Chapter 3:
MODELING OF ELEVATOR
3.1. INTRODUCTION OF MODELING AND ITS SIGNIFICANE Modeling is defined as the complete representation of an object or a system with the graphical and non graphical information. It is also known as geometric modeling. It generates the mathematical description of the geometry and non geometry of an object or a system in the computer database and the image of an object or system on the graphic screen. With the use of modeling the designer constructs the graphical image of an object on the computer screen with the use of following three types of commands to the computer. 1. Generates basic geometric elements such as points, lines and circles etc. 2. To accomplish scaling, rotation or other transformation of various elements. 3. Which cause various elements to be joined?
There are various types of drawing required in different field of engineering and science. In the field of mechanical engineering, the drawing of machine components and layouts are prepared. In the field of civil engineering, plans and layouts of power distribution system are prepared. The use of CAD process provides enhance graphics capabilities which allows any designer to, 1. Conceptualize his/her ideas 2. Modify the design very easy 3. Perform animation 4. Make design calculations 5. Use colours, fonts and other aesthetic features. Significance of modeling is as follows: 1. It makes the model a true replica of actual objects. 2. As the model is stored in mathematical form, the model modification can be carried out easily. 3. A geometric model can be use to evaluate the various properties of an actual objects. 4. A geometric model provides a sophisticated tool for 3D visualization of the objects. 39
5. A geometric model can be easily converted in to the two-dimensional views. 6. A geometric model can be used by Pro/Engineer software to perform the different types of analysis such as: stress-strain analysis, kinematic analysis, dynamic analysis, thermal analysis etc. 7. A geometric model can be used by the CAM software to generate a complete tool path required for the automatic manufacturing.
3.2. CAD PARTS OF BUCKET ELEVATOR: The important parts of bucket elevator are as under, 1. Bucket Command used: Extrude 1: Make solid cube of 250 x 156 x 156 mm. Extrude 2: Draw side view of bucket on Extrude 1 and remove excess material. Shell 1: Remove inside material of Extrude 2, so finally bucket shape is generated. Pattern 1 of hole 1: Make one hole of 15 mm diameter and done direction pattern for 75 mm distance. Function: Buckets are used to carry grain material from bottom to top.
Figure 3.1: Bucket
Figure 3.2: Ball bearing
40
2. Ball bearing Command used: Revolve 1: Generate sphere of 4.27 mm radius by using revolve command. Revolve 2: Generate Bearing inside and outside ring shape of 83 mm inside diameter and 130 mm outside diameter of 23 mm width. Assembly: Finally done assembly of sphere and bearing ring shape assembly and put 16 spheres between inside and outside ring by using axis pattern. So finally Bearing is generated. Function: Bearing is used to reduce friction and to convert sliding contact in to rolling contact. 3. Belt:
41
Figure 3.3: Belt
Command used: Extrude 1: Make side part of belt and Extrude it up to 300 mm, So finally Belt shape is generated. Pattern 1 of hole 1: Draw first hole of 15 mm diameter and done curve pattern at 400 mm distance. Pattern 2 of hole 2: Draw second hole of 15 mm diameter at distance 75 mm to first hole and done curve pattern at 400 mm distance. Pattern 3 of hole 3: Draw third hole of 15 mm diameter at distance 150 mm to first hole and done curve pattern at 400 mm distance. Function: Belt is used to carry bucket and drive driven pulley (bottom pulley) by using driving pulley (top pulley). 4. Shaft
Figure 3.4: Shaft
Command used: Extrude 1: Draw 83 mm diameter circle and extrude it up to 600 mm length. So finally shaft shape is generated.
42
Extrude 2: Draw cube of 22 x 21 x 17 mm on shaft at 143 mm distance from centre to both side on opposite axis and done Extrude remove material to generate key way on shaft. Function: Shaft is used to transmit power, motion and torque. 5. Pulley
Figure 3.5: Pulley
Command used: Extrude 1: Generate 22 x 21 x 14 mm cube as key. Assembly 1: Put key on shaft key way and made shaft-key Assembly. Revolve 1: Generate hub shape of 166 mm outside radius and 83 mm inside radius with 48 mm total height and revolve it to get hub rough shape. Round 1: 5 mm fillet action are done at end of hub shape for its smoothness. Extrude 2: Generate cube of 8.63 x 21 x 45 mm cube is generated on inside part of hub shape and done Extrude remove material to generate key way in hub. Assembly 2: Combine hub and shaft-key assembly. Assembly 3: Put Bearing inside hub in previous done assembly. Extrude 3: Draw ring of 83 mm inside diameter and 130 mm outside diameter and extrude it to 6 mm, to generate bearing cover. Assembly 4: Assemble bearing cover on bearing in Assembly 3 outcome.
43
Extrude 4: Draw ring of 142 mm inside diameter and 500 mm outside diameter and extrude it to 6 mm, to generate pulley cover plate. Assembly 5: Assemble pulley cover plate on hub in Assembly 4 outcome. Extrude 5: Generate 500 mm inside diameter, 6 mm thickness and 375 mm pipe as pulley rim. Assembly 6: Assemble pulley rim on cover plate in assembly 5 outcome, so finally get Pulley. Function: Pulley is used to transmit power, motion and torque from one shaft to another shaft by using belt.
3.3. ASSEMBLY OF BUCKET ELEVATOR: Used Top to Bottom assembly approach to assemble bucket elevator as shown in figures earlier. Various steps includes in assembly of bucket elevator are as followed. The final figure of assembly of bucket elevator is shown in figure 3.6
Assembly 1: First call pulley at top and give fix constrain to it and take direction pattern of the same at distance of 3000 mm Assembly 2: Call belt and fix it on two pulleys. Assembly 3: Call buckets and fix it on belt by using nut bolts, And finally done curve pattern of bucket at 400 mm distance to get final bucket elevator assembly.
44
Figure 3.6: Bucket elevator assembly
3.4. BILL OF MARERIAL Table 3.1: Bill of material for bucket elevator
Serial Number
Quantity
Description
Material
1.
19
Bucket
2.
1
Belt
3.
2
Pulley
4.
4
Bearing
5.
4
Hub
Mild steel
6.
4
Key
Mild steel
7.
4
Cover plate
Mild steel
8.
2
Shaft
Mild steel
Mild steel Rubber Mild steel Stainless steel
3.5. MECHANISM OF BUCKET ELEVATOR The mechanism of bucket elevator is prepared by performing various stapes for that it required various joints between two respective parts. Joints required for mechanism is applied 45
during assemble the parts. Various joints required for mechanism are pin joint, sliding joint, belt joint. The detail procedure for mechanism is discussed under with the required figure.
First off all call the support on which the driving or driven pulley is going to be fixed and apply fixed constrain on it and take the direction pattern of the same at required distance. Call the driven pulley and assemble it with lower end support by pin joint. Same procedure is followed during assemble of driving pulley. Than call the belt bucket assembly and assemble it on outer surface of the pulley by sliding joint. Now go to the mechanism and apply the servomotor between the pin joint of support and driving pulley and give required input for rotation of servomotor in servomotor definition as shown in figure 3.7
Figure 3.7: Mechanism of bucket elevator
Click on the analysis definition and select the type of analysis also give the required input for respective analysis and run it. Here we select the kinetic analysis. During mechanism of belt elevator various problem occurred due to sliding joint of belt and pulley. Such problems occurred during mechanism are as under.
46
Problem: 1 From the figure 3.8 both pulleys are assembled by pin joint and belt is assembled by sliding joint, but during running of mechanism the driven pulley joint is suppressed and remain steady and driving pulley is rotate with belt like a clock hand.
Figure 3.8: Mechanism problem-1 of bucket elevator
Problem: 2 From the below figure 3.9 both pulley are assembled by pin joint and belt is assembled by sliding joint, but during running of mechanism one pulley joint is suppressed and driven pulley remain steady and driving pulley is rotate but the belt slides out from the both pulley surface.
Figure 3.9: Mechanism problem-2 of bucket elevator
47
To solve these problems, A belt drive as a case study is considered and parts are modeled using Pro/Engineer and the same problems are persisting in that assembly of mechanism. But same problem occurred during the mechanism of belt joints. In short the simulation of the belt-pulley system using Pro/Mechanism yet to be work out for its implementation in bucket elevator mechanism.
Fig. 3.10: Mechanism problem in case study
48
Chapter 4:
FABRICATION OF PROTO TYPE
4.1 SELECTION OF PROTOTYPE DIMENSION: Selection of dimension for prototype model is based on the input and output parameter of the C program shown in Appendix: A. The input and output data for the dimension of prototype model is shown in following tabular format. Input data: Table 4.1: Design inputs for prototype model
Lifting Height (H) - m Wheat Density (ρ) - Tonne/m
1 3
0.768
Number of belt ply
4
Efficiency
0.85
Want to enter Capacity (Q)? (Y/N)
N -1
Enter value of i0/tb (1.3, 2.0, 3.24, 5.0, 8.0) - m Want to enter Pulley diameter (Dp)? (Y/N)
2.0 Y
Pulley diameter (Dp) - mm
200
Output data: Table 4.2: Design outputs for prototype model
Capacity (Q) - Tonne/hr
13.271040
Pulley radius (rp) - m Belt velocity (v) - m/s
0.1 3.2
Rotation speed of pulley (N) - rpm
305.732483
Pole Distance (hp) - m Unloading of bucket centrifugally is possible?
0.001875 Y
Bucket width (B) - mm
160
Belt width (Bb) - mm
200 49
Bucket pitch (tb) - mm Bucket volume - mm
320
3
13.44
Tension (T3) - N
234.262802
Tension (T4) - N Required no. of belt plies
78.087601 0.212966
Pulley Resistance (W) - N
144.606674
Motor power - kW
0.783039
Pulley width (Bp) - mm Rim thickness (t) - mm
250.000000 3.000000
Belt length (L) - m
2.628000
Belt Tension (T) - Nm
17971.919922
Permissible Tension (f) in belt per mm width - N/mm
1.347894
Projection of bucket (b) - mm
79
Depth of Bucket (h1) - mm
79
h2 mm No. of bucket (n)
47.80 8.212500
Shaft diameter (d) - mm
30
Shaft load - kN
6
Bearing No.
6006
Bearing bore diameter - mm
30
Bearing outside diameter - mm
55
Bearing width mm
13
Bearing static load (C0) - kN Bearing dynamic load (C) - kN
8.30 13.30
Permissible rpm for Grease lubrication
12000
Permissible rpm for Oil lubrication
15000
Radius of hub (rh) - mm Key width (w) - mm
30 7.500000
Key height (h) - mm
5.000000
Equivalent torque acting on shaft (Te) - kNm
0.279774
50
4.2. FABRICATION OF BUCKET ELEVATOR PROTOTYPE After getting the above program output for prototype model design, fabrication of the model is carried out. Various processes involved in fabrication of the prototype model are as under. Table 4.3: Fabrication processes for bucket elevator 1. Cutting
6. Centering
11. Welding
2. Marking
7. Turning
12. Bending
3. Punching
8. Chamfering
13. Chipping
4. Drilling
9. Gas cutting
14. Boring
5. Facing
10. Grinding
15. Slotting
The procedure followed for the fabrication of model is as followed: For support structure: 1. Cut the L - channel, flat stripes of required height and length for the structure. 2. Marking and punching on each channel and flat stripes as per need of location of hole. 3. Drill on each punching location as per requirement of hole diameter with the help of drilling machine with respective drilling tool of 10 mm and 12 mm diameter. 4. By using bolts of 12 mm and 10 mm diameter at required hole joining various sections and make whole structure. For pulley shaft: 1. Cut the 32 mm diameter shaft as per the requirements of length. 2. Face the both end of shaft on lathe and centre on each end with the drilling tool. 3. Turning the whole shaft (both shaft) of 30 mm diameter. 4. Chamfer the each end of the shaft. For pulley: 1. Cut the 200 mm diameter, 6 mm thick pipe in two equal lengths of 250 mm for pulley rim. 2. According to the inner diameter of the pipe cut the four round circles for cover plate with the help of gas cutting. 51
3. Grind the outer surfaces of the plates to match with the inner surface of pulley rim. 4. Drill the hole of 30 mm diameter on centre of each cover plate. 5. Weld the cover plates on both shafts; two cover plates on each shaft. 6. Fix the pulley rim on shaft-cover plate assembly at required position and make just tag welding. 7. Check the proper fixing the pulley rim on the shaft-cover plate assembly carried out the full welding. For buckets: As per the calculation of the requirements of bucket, calculate the plate size of by developing the whole bucket as shown in figure 4.1 & 4.2 and calculate the area of sheet required for the one bucket. Prepare a bucket sheet metal planning for all buckets which is shown in figure 4.3. 1. As per the bucket sheet metal planning makes a marking on sheet. 2. Cut the plates in required shape for side parts (small in size) and bend parts (large in size) of the bucket with the help of tin snip. 3. Bend the large size of sheet in bending machine. 4. Cut the side parts (small in size) of the bucket in required shape. 5. Weld the bend parts of bucket with side parts. 6. Carried out grinding operation for batter surface finish. 7. Marking and punching on the surface on which the buckets are going to be bolt on the belt and drilling on that desired location with required drill tool. Calculation for material utilisation is as follows (Refere figure 4.3),
52
Figure: 4.1: Side part of bucket
Figure: 4.2: Bend part of bucket
Figure: 4.3: Sheet metal planning for all bucket
53
Area of front part, A = 231.13 ∗ 164 = 38889.32 mm2
Area of front part, A = 105 ∗ 105
= 11025 mm2
2
2
Total area of front part and side part is 9A mm and 18B mm respectively. Now total material used is given by, C = 9A + 18B
= =
9 ∗ 38889.32 + (18 ∗ 11025)
548453.88 mm
2
Total area available of sheet, D = 1800 + 750
= 2550 mm2
Now, material utilization factor is given by,
MUF = =
548453.88
=
40%
Area used C = Total area available D 2550
From the above calculation it is cleared that, only 40% of sheet is used from the whole sheet. So, in place of using whole sheet, use of scrap of particular size is advisable and also economical. For belts: 1. Marking on the belt for fixing the buckets at required bucket pinch distance. 2. Mark the holes position on this bucket pitch distance. 3. Punching on that holes location with the help of dot punch. 4. Drill the all punched marks on belt with hand drilling machine.
54
Assemble the all parts which are fabricated earlier with the help of suitable joints like nut-bolt, weld etc. the final picture of bucket elevator is shown in figure 4.4.
4.3. SELECTION OF POWER PULLEY To reduce the motor speed up to 305 rpm, it is necessary to use an extra pulley (power pulley) in conjunction with upper shaft of bucket elevator. For that calculation is necessary, calculation for speed reduction is given below. Where, D = Diameter of top power pulley attach with upper pulley of bucket elevator d = Diameter of bottom power pulley attack with motor N = Top power pulley speed = 305 rpm n = Bottom power pulley speed = 1400 rpm
To get this Diameter ratio, take D = 22.86 cm = 9 inch and d = 5 cm = 1.96 inch ≈ 2 inch
4.4. BENDING MOMENT DIAGRAM FOR UPPER SHAFT Bending moment diagram is shown in figure 4.4. Now, calculation for required length of v belt is shown as under. C = Distance between two pulleys = 89 cm D = Diameter of top power pulley attach with upper pulley of bucket elevator = 22.86 cm d = Diameter of bottom power pulley attack with motor = 5 cm
55
Figure: 4.4: Loading and bending moment diagram for upper shaft
56
4.5. PROBLEMS OCCURE DURRING FABRICATION The following problems ware faced during the fabrication of prototype model of bucket elevator. 1. Due to spring back effect in bucket sheet material, Elastic recovery occurs when press machine pressure is released. It is depends on type of material, thickness of material, band radius and band angle. 2. For pulley, used hollow pipe of 200 mm diameter, 6 mm thickness as pulley rim, this is slightly oblong during turning process. So to overcome this problem made pulley assembly like fabricated shaft, cover plate and pulley rim, than again done turning on pulley rim. 3. Purchased shaft from scrap so doesn’t know about its material property. Because of this purchased harden shaft’s machining is not possible. So replaced it by purchasing new shaft to get desired property of shaft material so once can machined it properly with in limited constraints. 4. Delay in getting of belt and pulley machining (Done outside due to less capacity of machine of ADIT workshop). 5. Problem due to pulley shaft alignment, Because of this belt is comes outside form pulley. To avoid this weld required thickness of strips or flange on pulley so that belt is fitted in required space and run within specific path.
57
4.6. FABRICATED PROTOTYPE OF BUCKET ELEVATOR
Figure: 4.5: Fabricated bucket elevator prototype model 58
Chapter 5:
RESULTS ANALYSIS
5.1. EFFECT OF OPERATING VARIABLES For the purpose of handling, the effects of various operating conditions are being studied theoretically for working of bucket elevator. Effect of lifting height on number of bucket, motor power and belt length: Assume capacity (Q) = 30 Tonne / hr and Pulley Diameter (D p) = 500 mm as constant, than the effect of lifting height on number of bucket, motor power and belt length is shown in graph bellow. As the lifting height of bucket elevator increases the number of bucket, motor power and belt length is gradually increases (Refer figure 5.1). 90 80 70 60 50 40 30 20 10 0
15 m
3m
6m
9m
12 m
No. of Bucket
19
34
49
64
79
Motor Power (kW)
2.8
5.6
8.4
11.2
13.9
Belt Length (m)
7.6
13.6
19.6
25.6
31.6
Figure 5.1: Variation based on lifting height 59
Effect of pulley diameter on speed, belt length, number of bucket, and shaft diameter: Assume lifting height (H) = 3 m and capacity (Q) = 30 Tonne / hr as constant, than the effect of pulley diameter on speed, belt length, no. of bucket, and shaft diameter is shown in graph bellow. As the pulley diameter of bucket elevator increases the rotational speed of bucket elevator is decreases gradually and the belt length is increases. The number of bucket remains almost constant but the diameter of shaft slowly increases (Refer figure 5.2). 350
300
250
200
150
100
50
0 Roatational speed (rpm)
200
250
300
400
500
305.58
244.46
203.72
152.79
122.23
6.63
6.79
6.94
7.26
7.57
No. of Bucket
17
17
17
18
19
Shaft Diameter (mm)
40
50
60
80
100
Belt Length (m)
Figure 5.2: Variation based on pulley diameter
60
Effect of capacity on bucket width, bucket volume, belt width, bucket pitch, motor power and number of bucket: Assume lifting height (H) = 1.5 m and pulley diameter (D p) = 250 mm as constant, than the effect of capacity on bucket width, bucket volume, belt width, bucket pitch, motor power and number of bucket is shown in graph (Refer figure 5.3). As the capacity of bucket elevator increases the bucket width increases and hence the volume of bucket increase as its dimensions of bucket increases, the belt width also increases. As the capacity increases the bucket pitch increases but the motor power and number of required buckets decreases. 450
400
350
300
250
200
150
100
50
0
8.63
13.3
21.5
30
Bucket width (mm)
125
160
200
250
Bucket volume (mm3)
10.5
13.3
16.8
21
Belt width (mm)
160
200
250
300
Bucket pitch (mm)
220
320
400
400
Motor Power (kW)
1.14
1.02
1.02
1.24
17
12
10
10
No. of Bucket
Figure 5.3: Variation based on capacity
61
Effect of efficiency on motor power: Assume lifting height (H) = 1 m, pulley diameter (Dp) = 200 mm capacity (Q) = 13.3 Tonne / hr as constant, than the effect of efficiency on motor power is shown in graph bellow. As the efficiency of bucket elevator increases the motor power decrees gradually (Refer figure 5.4). 7 6 5 4 3 2 1 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Motor Power (Kw) 5.78 2.89 1.93 1.45 1.16 0.96 0.83 0.72 0.64 0.57
Figure 5.4: Variation based on efficiency
5.2. RESULT ANALYSIS OF PROTOTYPE MODEL Observation: Actual rotational speed of bucket elevator = 320 rpm 1 bucket capacity = 0.95 kg so, for 9 bucket capacity = 8.55 kg Case: 1 In this case bucket elevator is completely empty means no wheat inside the elevator for scooping effect on starting and wheat is finished during feeding without checking of scooping capacity for bucket elevator.
62
Table 5.1: Observation table for 10.00 kg of wheat Wheat at inlet for feeding (kg)
Wheat inside the elevator before starting of scooping (kg)
Wheat at outlet (kg)
Wheat inside the elevator after closing (kg)
Time (Second)
10.00
0.00
4.50
5.50
48.48
Efficiency (%) 45.00
Case: 2 In this case 5.5 kg of wheat is already remaining of case: 1 inside the bucket elevator to see scooping action from starting of feeding and feeding of wheat is finished within 1 min and after 1 min for 20.31 second bucket elevator run without feeding of wheat at inlet just to see the complete scooping action and switch off the power when scooping effect is finished. Table 5.2: Observation table for 24.75 kg of wheat Wheat at inlet for feeding (kg)
Wheat inside the elevator before starting of scooping (kg)
Wheat at outlet (kg)
Wheat inside the elevator after closing (kg)
Time (Second)
19.25
5.50
18.00
6.50
80.31
63
Efficiency (%) 72.72
Chapter 6:
FUTURE SCOPE OF WORK
The velocity analysis can be carried out to understand its effect with change in bucket angle. Coding of the C –Program can be refined for its faster and efficient way of its usage while editing input parameters. Use of fopen, fclose functions i.e. file operations using C- program will simplify the editing of the input and programming length. This leads to modular programming for bucket elevator. Existing program coding takes 325 lines results in difficulty of program modification and may be erroneous results. The mechanism of bucket elevator is not completed yet due to problem regarding to belt connection as a joint using Pro/Mechanism. The simulation of the bucket elevator assembly should be carried out to predict instantaneous velocity and components of the velocities in the required directions. Moreover, Torque and power calculations can be obtained using the dynamic simulation considering the gravity effect also. The obtained results can be compared with the practical one to understand the differences and subsequent remedial actions. The frictional considerations will be incorporated during the mechanism simulation along with gravity effect to predict the system behaviour more realistic. The effect of clearance between the bucket elevator belt mechanisms along with its outer casing will be lucrative to analyze for further improvement of its performance. The throttle plate arrangement for the prototype outlet will be more suitable for the existing configuration. The take-up system of the bucket elevators is equipped with additional dust-tight seals between the casing and the guide of the idle shaft belt bucket elevators realised for heavy duty application are equipped with a self aligning system which ensure the safe parallel guidance of the pulley. An idler mechanism should be also provided for tightening belt during running of bucket elevator.
64
Chapter 7:
CONCLUSION
1. This project was designed to study the design of bucket elevator also enhance the manufacturing idea about the processes and fabrication of the equipment. 2. Through this experience, we found the chance to apply our knowledge of previous courses like machine design, Kinematics of machinery, Product Design and Value Engineering. 3. The designed bucket elevator works having certain limitations. 4. When designing the system, we should make sure the material is cost effective, and durable. In the meantime, it should also be available in the market. 5. Dimensions should be realistic.
65
APPENDIX: A PROGRAM: /* Program about Bucket Elevator Design */ #include #include void main() { clrscr(); intNp, Dp, B, Bb, tb, b, h1, d, yes, no, Shaft_load, Bearing_No, Bearing_bore_diameter, Bearing_outside_diameter, Permissible_rpm_for_Grease_lubrication, Permissible_rpm_for_Oil_lubrication, rh; float H, Density, Bp, Q, a, ratio, v, rp, N,n,f, hp, V, mrb, qrb, mb, q0, T3, T4, k=10, i, W, Efficiency, P, t, L, T, h2, C0, C, w, h, Te; printf("Lifting Height(H) in m = \n"); scanf("%f", &H); printf("Wheat Density in Tonne/m3 = \n"); scanf("%f", &Density); printf("No of Belt ply (Np) = \n"); scanf("%d", &Np); printf("Efficiency = \n"); scanf("%f", &Efficiency); printf("Want to enter Capacity (Q)? Enter 1 for yes and 0 for no- \n"); scanf("%d",&yes); { if(yes) { printf("Capacity (Q) in Tonne/hr = \n"); scanf("%f", &Q); a=Q/ (3.60*3.2*Density*0.75); { if(1.1