Types Of Belt Conveyor Drives | Belt Conveyor Drive Arrangement

Types and Selection of Drives:

• Single Unsnubbed Bare / Lagged pulley Drive
• Snubbed Bare / Lagged Pulley Drive
• Tandem Drive
• Special Drives

Single Unsnubbed Bare / Lagged Pulley Drive:

This is the simplest drive arrangement consisting of a steel pulley connected to a motor and the belt wrapped round it on an arc of 180°. This can be used for low capacity short center conveyors handling non-abrasive material. The pulley may be lagged to increase the coefficient of friction.

Snubbed Bare / Lagged Pulley Drive:

Here the angle of wrap is increased from 180° to 210° or even up to 230°, by providing a snub pulley to the driving pulley. In majority of medium to large capacity belt conveyors, handling mild abrasive to fairly abrasive materials, 210° snub pulley drive with load pulley lagged with hard rubber is adopted.

Tandem drive:

Here belt tension estimated to be high; the angle of wrap is increased by adopting tandem drives. Both of tandem pulleys are driven. The tandem drive with arc of contact from 300° to 480° or more can operate with one or two motors. The location of such drive is usually determined by the physical requirements of the plant and structural constraints.

Special Drive:

Special drives with snub pulleys and pressure belts used in heavy and long conveyors.

Pulley | Belt Conveyor Pulley | Belt Conveyor Pulley Types | Belt Conveyor Power Calculation

Pulley:

The diameters of standard pulleys are: 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1400 and 1600 mm. pulley may be straight faced or crowned. The crown serves to keep the belt centered. The height of the crown is usually 0.5% of the pulley width, but not less than 4 mm. The pulley diameter D_p depends on the number of plies of belt and may be also be determined from the formula:

D_p > K.i (mm)

Where

K = a factor depending on the number of plies (125 to 150)

i = no of plies

The compound value should be rounded off to the nearest standard size. While selecting the pulley diameter it should be ascertained that the diameter selected is larger than the minimum diameter of pulley for the particular belt selected.

The drive pulley may be lagged by rubber coating whenever necessary, to increase the coefficient of friction. The lagging thickness shall vary between 6 to 12 mm. The hardness of rubber lagging of the pulley shall be less than that of the cover rubber of the running belt.

Pulley types:

Pulleys are manufactured in a wide range of sizes, consisting of a continuous rim and two end discs fitted with hubs. In most of the conveyor pulleys intermediate stiffening discs are welded inside the rim. Other pulleys are self cleaning wing types which are used as the tail, take-up, or snub pulley where material tends to build up on the pulley face. Magnetic types of pulleys are used to remove tramp iron from the material being conveyed.

Typical welded steel pulley-Drum conveyor pulley

Spun end curve crown pulley

Spiral drum conveyor pulley

Welded steel pulley with diamond grooved lagging

Welded steel pulley with grooved Lagging

Spiral Wing Conveyor pulley

Power calculation for the drive unit:

The horse power required at the drive of a belt conveyor is derived from the following formula:

H.P = T_e . V

Where

T_e is the effective tension in the belt in N

V = velocity of the belt in m/s

The required effective tension T_e on the driving pulley of a belt conveyor is obtained by adding up all the resistances.

CONVEYOR TAKE UP ARRANGEMENT

Conveyor Take-up Arrangement:

All belt conveyors require the use of some form of take-up device for the following reasons:

• To ensure adequate tension of the belt leaving the drive pulley so as to avoid any slippage of the belt
• To ensure proper belt tension at the loading and other points along the conveyor
• To compensate for changes in belt length due to elongation
• To provide extra length of belt when necessary for splicing purpose.
• Usually there are two types of take up arrangements.

  • Fixed take up device that may be adjusted periodically by manual operation
  • Automatic take up devices for constant load type

  In a screw take up system the take up pulley rotates in two bearing blocks which may slide on stationery guide ways with the help of two screws. The tension is created by the two screws which are tightened and periodically adjusted with a spanner. It is preferable to use screws with trapezoidal thread t decrease the effort required to tighten the belt.

  

  The main problem with the use of manual take-up is that it requires a vigilant and careful operator to observe when take up adjustment is required. Perfect tension adjustment with this system is also not possible. For this reason these devices are used only in case of short conveyors of up 60 m length and light duty.

  In automatic take up arrangement the take up pulley is mounted on slides or on a trolley which is pulled backwards by means of a steel rope and deflecting pulleys. The carriage travels on guide ways mounted parallel to the longitudinal axis of the conveyor, i.e., horizontally in horizontal conveyors and at an incline in inclined conveyors. Hydraulic, pneumatic and electrical take up devices are also used.

  Automatic take-up has the following features:

  • It is self adjusting and automatic
  • Greater take-up movement is possible.

Belt Conveyor Take Up Design | Conveyor Belt Take Up System | Horizontal Take Up In Belt Conveyor

Belt Conveyors for bulk materials:
Take up Arrangement:
All belt conveyors require the use of some form of take up device for the following reasons:
1. To ensure adequate tension of the belt leaving the drive pulley so us to avoid any slippage of the belt.
2. To ensure proper belt tension at the loading and other points along the conveyor.
3. To compensate for changes in belt length due to elongation.
4. To provide extra length of belt when necessary for splicing purpose.

Usually there are two types of take up arrangements.
These are:
1. Fixed take up device that may be adjusted periodically by manual operation
2. Automatic take up device (constant load type)

Manual Screw Take Up:
The most commonly used manual take up is the screw take up. In a screw take up system the take up pulley rotates in two bearing blocks which may slide on stationery guide ways with the help of two screws. The tension is created by the two screws which are tightened and periodically adjusted with a spanner. It is preferable to use screws with trapezoidal thread to decrease the effort required to tighten the belt.

The main problem with the use of manual take up is that it requires a vigilant and careful operator to observe when take up adjustment is required. Perfect tension adjustment with this system is also not possible. For these reason these devices are used only in case of short conveyors of up 60m length and light duty.

Automatic Take Up:
In automatic take up arrangement the take up pulley is mounted on slides or on a trolley which is pulled backwards by means of a steel rope and deflecting pulleys. The carriage travels on guide ways mounted parallel to the longitudinal axis of the conveyor, i.e., horizontally in horizontal conveyors (Ex.: Gravity type automatic take up arrangement) and at an incline in inclined conveyors. Hydraulic, Pneumatic and electrical take up devices are also used.

Automatic take up has the following features:
1. It is self adjusting and automatic
2. Greater take up movement is possible

For the perfect conveying of materials, adding a resistance with the peripheral forces on the driving pulley of a belt conveyor is important. Some of the resistances are:
1. The inertial and frictional resistance due to acceleration of the material at the loading area
2. Resistance due to friction on the side walls of the skirt board at the loading area.
3. Pulley bearing resistance applicable for other than the driving pulley
4. Resistance due to the wrapping of the belt on pulleys
5. Special resistances include

a. Resistance due to idler tilting

b. Resistance due to friction between material and skirt plate

c. Frictional resistance due to belt cleaners

d. Resistance due to friction at the discharge plough

Special resistances are usually small. Here the resistance due to idler tilting and skirt resistance is ignored. There being no discharge plough the resistance due to plough is ignored. For belt speeds greater than 3 m/s, the edge clearances are applicable.

Idling Stop Technology | i-stop

Idle stop systems save fuel by shutting down a vehicle’s engine automatically when the car is stationary and restarting it when the driver resumes driving. Especially in urban areas, drivers often let their car’s engine idle at traffic lights or when stopped in traffic jams. Switching off the engine to stop it idling in these situations enhances fuel economy by about 10% under Japan’s 10-15 mode tests.

Conventional idling stop systems restart a vehicle’s engine with an electric motor using exactly the same process as when the engine is started normally. Mazda’s ”i-stop”, on the other hand, restarts the engine through combustion. Mazda’s system initiates engine restart by injecting fuel directly into a cylinder while the engine is stopped, and igniting it to generate downward piston force. This system not only saves fuel, but also restarts the engine more quickly and quietly than a conventional idle-stop system.

Piston stop position control and combustion restart technology

 

In order to restart the engine by combustion, it’s vital for the compression-stroke pistons and expansion-stroke pistons to be stopped at exactly the correct positions to create the right balance of air volumes. Consequently, Mazda’s ”i-stop” effects precise control over the piston positions during engine shutdown. With all the pistons stopped in their optimum position, the system restarts the engine by identifying the initial cylinder to fire, injecting fuel into it, and then igniting it. Even at extremely low rpm, cylinders are continuously selected for ignition, and the engine quickly picks up to idle speed.

Thanks to these technologies, the engine will restart with exactly the same timing every time and will return to idle speed in just 0.35 seconds, roughly half the time of a conventional electric motor idling stop system. As a result, drivers will feel no delay when resuming their drive. With the ”i-stop”, Mazda can offer a comfortable and stress-free ride as well as better fuel economy.

Direct Injection Gasoline Engine | DISI Engine

In developing the DISI engine, we aimed to cool the interior of the cylinder as much as possible by promoting fuel vaporization and uniform mixing of atomized fuel and air. This produces a high charging efficiency of the air-fuel mixture and a high compression ratio, which results in significant improvements in both torque and fuel efficiency.

Characteristics of the direct injection engine:

Fuel is injected from a tiny nozzle into a relatively large cylinder, so it has a high latent heat of vaporization, which efficiently cools the air within (in-cylinder cooling effect).

The air temperature in the cylinder decreases, which means:

• (1) more air may be charged into the combustion chamber, which produces increased torque.
• (2) the engine is less prone to knocking. This contributes to increased torque, and enables a higher compression ratio that also contributes to good fuel efficiency.

In a direct injection engine, however, the fuel skips the waiting period it would have to endure inside a standard engine and instead proceeds straight to the combustion chamber. This allows the fuel to burn more evenly and thoroughly. For the driver, that can translate to better mileage and greater power to the wheels.

In the past, direct injection posed too many technical hurdles to make it worthwhile for mass market gasoline automobiles. But with advances in technology and greater pressure to make cars run more cleanly and efficiently, it looks as if gasoline direct injection — or GDI as it’s referred to in industry lingo — is here to stay. In fact, most of the major car manufacturers make or plan to soon introduce gasoline cars that take advantage of this fuel saving and performance enhancing system. 

Miller Cycle | Sequential Valve Timing (S-VT) | Continuously Variable Transmission (CVT)

The key to improving fuel efficiency lies in raising an engine’s thermal efficiency. This can be done by increasing the expansion ratio. The expansion ratio is the amount of work the engine does each time the air-fuel mixture in the cylinders detonates. However, in conventional engines the expansion ratio is the same as the compression ratio, so increasing the expansion ratio will also raise the compression ratio. This is a problem because a high compression ratio causes abnormal combustion, or knocking.

The answer is the Miller-cycle engine. By delaying the closure of the intake valves, compression actually begins part way through the compression stroke, which results in a reduced compression ratio. At the same time, changing the shape of the piston crown decreases the combustion chamber minimum volume, resulting in a larger expansion ratio. In this way we can decrease the compression ratio and while increasing the expansion ratio. In other words, the Miller-cycle engine has a higher expansion ratio than compression ratio.

Mazda’s naturally-aspirated MZR 1.3L Miller-cycle engine delays the closure of the intake valves to improve the thermal efficiency (high expansion ratio). Sequential-valve timing (S-VT) is also employed to optimize intake valve timing and ensure sufficient torque for cruising and accelerating. Furthermore, the engine is mated to a continuously variable transmission (CVT) for a perfect blend of responsive acceleration, smooth gear shifts and top-class fuel economy.