Introduction Conveyors are one of the transport equipment in material handling Transport equipment Conveyors Cranes Industrial Trucks

Conveyors are used Where material is to be moved frequently between specific points To move materials over a fixed path When there is a sufficient flow volume to justify the fixed conveyer investment

Classification of conveyors Type of product being handled unit bulk Location of the conveyor overhead on-floor in-floor Whether or not loads can accumulate on the conveyor (Pls follow this web link: http://www.mhi.org/learning/cicmhe/resources/taxonomy/TransEq/Conv/index.htm

Type of Conveyors 1. Chute Conveyors 2. Wheel Conveyors 3. Roller Conveyors a) Gravity roller conveyor b) Live (powered) conveyor 4. Chain Conveyors 5.Slat Conveyors 6.Belt Conveyors a) Flat belt conveyor b) Magnetic belt conveyor c) Trough belt conveyor

7.Bucket Conveyors 8. Vibrating Conveyors 9. Screw Conveyors 10. Pneumatic Conveyors a) Dilute-phase pneumatic conveyors b) Carrier-system pneumatic conveyors 11. Vertical Conveyors a) Vertical lift conveyors b) Reciprocating vertical conveyor

c) Sliding shoe device 12. Cart-on-track conveyors 13. Tow conveyor 14.Trolley conveyor 15.Power-and-free conveyor 18.Monorail 19.Station conveyor a) Diverter d) Tilting device b) Pop-up device e) Cross-belt transfer device c) Sliding shoe device

Belt Conveyors Characteristics Very Efficient Damage to the products is very low High Carrying capacity Long distance conveying Long service life

Elements of a belt conveyor Feeder Belt Idler Pulley Pulley Discharge Drive

1) Belt -consists of one or more layers of material 1) Belt -consists of one or more layers of material. Many belts -two layers. An under layer (carcass) for linear strength and shape an over layer (cover). The carcass is often a woven fabric -polyester, nylon and cotton. The cover is often various rubber or plastic compounds specified by use of the belt.  2) Drive - Drive the mechanism -Located at the end of the discharge to prevent the sag

3. Pulley - Large enough to provide enough contact surface with the belt to ensure a positive drive 4. The Take Up - Automatic or manual adjustment for contraction or expansion of the belt due to moisture and temperature.

5. Idler Pulleys - Material – Plain wood or light steel - Multiples to increase carrying capacity 6. Feeder - Free flow – Single funnel with a gate valve - Not a free flow - Screw feeder, vibrating feeder , Star feeder

7) Discharge - Placed at the end of the belt - Types a) Tripper b) Angle Scrapper

Types of belt conveyors Flat belt conveyor

Transport Medium and light weight loads Inclined or decline when it is required Provide considerable control over the orientation and placement of the load No smooth accumulation, merging and sorting on the belt The belt is roller or slider bed supported

Magnetic belt conveyor For transporting ferrous materials

Trough belt conveyor

Designing Belt Capacity Determination BLTCAP = 0.8 * CSA * BLTS BLTCAP – Conveyor belt capacity (bu/min) SI units can be used m3, m2 & ms-1 Belt capacity vary according to the belt width and surcharge angle CSA – Cross sectional area (ft2) BLTS – Belt speed (ft/min) (1bushel = 1.2444 cubic feet)

Horse Power Requirement Determination 1. Horse power to drive = BLTS * (A+BL)/100 empty conveyor BLTS – Belt speed (ft/min) L - Conveyor length in feet A, B – Constants depend on belt width 2.Horse power to convey material = tons of material * (0.48 +0.00302 L)/100 on level per hour (Metric tonne = 1000kg ton = 2240 pounds or 1016kg) 1 t = 1.1023 t

1hp =745.7 W 3. Horse power to = Lift * 1.015 * tons of lift the material in ft material per h/1000 Simplified SI calculation Power (kW) = (Capacity (t/h)* lift (m)* 3.75)/1000 **** True for <10% slope **** If efficiency of drive mechanism is < 95% use 4 instead 3.75 1hp =745.7 W

SI detailed calculation

The basics of the Calculations of Conveyor Belt Design Parameters Belt tension: The belt of the conveyor always experience a tensile load due to the rotation of the electric drive, weight of the conveyed materials, and due to the idlers. The belt tension at steady state can be calculated as: Tb = 1.37*f*L*g*[2*mi+ (2*mb + mm)*cos (δ)] + (H*g*mm)…….eqn.1.1

Where, Tb is in Newton. f = Coefficient of friction L = Conveyor length in meters. Conveyor length is approximately half of the total belt length. g = Acceleration due to gravity = 9.81 m/sec2 mi = Load due to the idlers in kg/m. mb = Load due to belt in kg/m. mm = Load due to the conveyed materials in kg/m. δ = Inclination angle of the conveyor in Degree. H = vertical height of the conveyor in meters.

Load due to idlers (mi): This can be calculated as below: mi = (mass of a set of idlers) / (idlers spacing) ……………..eqn.1.2 Power at drive pulley: The power required at the drive pulley can be calculated from the belt tension value as below: Pp = (Tb*v)/1000……………..eqn.1.3 Where, Pp is in kW. Tb = steady state belt tension in N. v = belt speed in m/sec.

Tb = the steady state belt tension in N. Ks = the start-up factor Belt tension while starting the system: Initially during the start of the conveyor system, the tension in the belt will be much higher than the tension in steady state. The belt tension while starting can be calculated as: Tbs =Tb*Ks………………..eqn.1.4 Where, Tbs is in N. Tb = the steady state belt tension in N. Ks = the start-up factor

Pp = the power at drive pulley in kw Kd = Drive efficiency. Sizing of the motor:  The minimum motor power can be calculated as: Pm = Pp/Kd………………eqn.1.5 Where, Pm is in kw. Pp = the power at drive pulley in kw Kd = Drive efficiency.

Acceleration :  The acceleration of the conveyor belt can be calculated as: A= (Tbs – Tb)/ [L*(2*mi + 2*mb+mm)]………eqn.1.6 Where, A is in m/sec2 Tbs = the belt tension while starting in N. Tb = the belt tension in steady state in N. L = the length of the conveyor in meters. mi = Load due to the idlers in kg/m. mb = Load due to belt in kg/m. mm = Load due to the conveyed materials in kg/m.

An Example of Conveyor Belt Calculations Input data: Conveyor capacity (Cc) = 1500 t/h = 416.67 kg/sec Belt speed (V) = 1.5 m/sec Conveyor height (H) = 20 m Conveyor length (L) = 250 m Mass of a set of idlers (m’i) = 20 kg Idler spacing (l’) = 1.2 m Load due to belt (mb) = 25 kg/m Inclination angle of the conveyor (δ) = 5 0 Coefficient of friction (f) = 0.02

Drive efficiency (Kd) = 0.9 Friction factor (Cr) = 15 Start-up factor (Ks) = 1.5 Drive efficiency (Kd) = 0.9 Friction factor (Cr) = 15 Breaking strength loss factor (Cv) = 0.75 First, we will use the eqn.1.2 for finding out the load due to idlers: mi = (20/1.2) = 16.67 kg/m We will use the eqn.1.1 for finding out the belt tension in steady state:

Tb = 1.37*0.02*250*9.81*[16.67+ {2*25+ (416.67/1.5)}*cos (5)] + (20*9.81* (416.67/1.5)) = 77556.88 N. The belt tension while starting the system can be calculated by using the eqn.1.4: Tbs = 1.5 * 77556.88 = 116335.32 N For calculating the power at drive pulley, we will use the eqn.1.3: Pp = (77556.88*1.5)/ 1000 = 116.335 kw We will use the eqn.1.5 estimate the size of the motor: Pm = 116.35/0.9 = 129.261 kw

A = (116335.32 - 77556.88)/ [250*{(2*16.67) + (2*25) + (416.67/1.5)}] We will use the eqn.1.6 to find out the acceleration of the motor: A = (116335.32 - 77556.88)/ [250*{(2*16.67) + (2*25) + (416.67/1.5)}] = 0.429 m/sec2

Chain Conveyors

Having a powered continuous chain arrangement If the chain at bottom is called the drag The chain at the top is called as the flight Operate at less than 200ft/min (Slow process) Noise is a problem

Trolley conveyor Overhead trolleys fastened by a chain Can have 1800 turn and steep elevations Commonly used in processing, assembly, packaging, and storage operations

Scraper conveyor A type of flight conveyor. It consists of a trough in which a continuous driven chain with flights is running. The flights are scraping the material over the bottom of the casing. The material is moving forward to the discharge point Used for granular or non abrasive materials Power requirement is high Use for many raw products

Apron conveyor Flights in scraper conveyors are replaced with the flat slats, steel plates or boards Have a moving platform or apron to convey sacked materials and large units The apron conveyor is an economical design for horizontal and inclined conveying up to 28°. Special features may be added to make inclinations of up to 60° possible. An extremely low-cost unit preferred for applications of up to 45° inclination.

Chain conveyor design Generally flight speed – 75 -125ft/min Capacity decreases with inclination Horse power requirement Horse power = 2* V *Lc* Wc* Fc + Q(L *Fm +H) 33000 V – Speed of the conveyor Lc - Horizontal projection length of conveyor (ft) Lc = cos ( c) * TCL [ =cos(angle of elevation conveyor) * Total conveyor length]

Wc – Weight of flight and chain (lb/ft) Total conveyor length Conveyor length after loading Wc – Weight of flight and chain (lb/ft) Fc – Coefficient of friction for chain and flight Q – Material to be handled (lb/min) L - Horizontal projected length of loaded conveyor (ft) L = cos (c ) TLL =cos(angle of elevation conveyor) * Total Loaded length of conveyor

Fm – Coefficient of friction for material H – Height of lift (ft) H = Sin (angle of elevation conveyor) * Total length of conveyor

Bucket Elevators

A special adaptation of both belt and chain conveyors Very efficient in moving things vertically It consists of: Buckets to contain the material A belt or chains to carry the buckets and transmit the pull Means to drive the belt Accessories for loading the buckets or picking up the material for receiving the discharged material for maintaining the belt tension for enclosing and protecting the elevator.

Components of a Bucket Elevator Head pulley Head drive Components of a Bucket Elevator motor Garner Throat Head drive (Reducer) Leg Belts Leg Elevator Buckets Deflector pulley Take -ups Boot pulley Boot spout Boot

Discharging mechanisms Centrifugal action Gravity action

Types of buckets

Applications A bucket elevator can elevate a variety of bulk materials from light to heavy and from fine to large lumps Eg: Food products – grain, sugar, flour, coffee, salt.. Rock products – sand, gravel, cement, gypsum, limestone Chemical processing products – fertilizer, phosphate, agricultural lime , soda ash Pulp and paper products

Designing Power requirement determination Horse Power Requirement = Q.H / 33,000 Q = material handled (lb/min) = Belt speed * No of buckets per foot * Bucket capacity H = Lift (Ft)

- Theoretical value is increased by 10 to 15 % for, friction power for loading - Also additional power is needed for, starting under load peak load

Advantages Low power requirement Long service life Minimum maintenance requirement Ability to handle wet grains as easy as dry grains with negligible increase of power Relative quietness But Grain damage may be high in handling seed purpose grains!!!!

The 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/h 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 Screw Pitch: 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.

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 is large for free flowing and non abrasive, 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

The inclination factor C is determined by the angle of screw conveyor with the horizontal. http://www.mechanicalengineeringblog.com/tag/screw-conveyor-design-calculation/

Oscillating conveyors

Metallic trough carried on inclined arms fitted with rubber bushes to handle the reciprocating motion of the trough The oscillating motion of the trough is achieved via specially designed inclined arms and an eccentric shaft driven by a motor through v – belts

PRINCIPLE CONVEYOR TROUGH IMPARTS VELOCITIES IN x & y DIRECTIONS

F1 F2 F4 F3 Figure 2 Figure 1 FORCES ON ‘ Y ‘ DIRECTION F1 - ACCELARATION FORCE F2 - PARTICLE WEIGHT FORCES ON ‘ X ‘ DIRECTION F3 - FORCE IN THE X DIRECTION F4 - FRICTION

F1>F2 PARTICLE LIFTS & MOVES AXIALLY BY A SHORT TRAJECTORY F3>F4 PARTICLE MOVES MAXIMUM X DISTANCE DURING FLIGHT

DESIGN CRITERIA

END PART_1

Belt conveyor design following site for SI http://www.brighthubengineering.com/manufacturing-technology/83551-onsite-calculations-for-conveyor-belt-systems/