40 important question & answers on belt conveyor for ...

1-What equipment is utilized in a coal handling plant (CHP)?

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Beginning with the coal shed

• Coal elevator

• Coal grizzly hopper

• Coal vibro feeder

• Coal conveyors (belt conveyor)

• Coal vibro screen

• Coal crusher

• Coal dust extraction system

• Shuttle conveyor

2-What are the various components of belt conveyors?

• Belt

• Carrying idlers

• Return idlers

• Impact idlers

• Transoms

• Pulleys

• Vertical gravity take-up system

• Power transmission system (Motor, Gearbox, couplings)

• Main structure & trestles

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3-How do you specify a conveyor belt?

Belt specifications are based on the following criteria:

• Material composition
• Number of plies
• Belt rating
• Belt width

4-What materials are typically used to manufacture belts?

Nylon, Polyester, Aramide, Polyester-Nylon, Steel fabric

5-What types of pulleys are used in belt conveyors?

• Head pulley
• Tail pulley
• Snub pulley
• Bend pulley
• Take-up pulley

6-Identify the largest and smallest pulleys mentioned above.

• Largest pulley: Head pulley
• Smallest pulley: Snub pulley

7-What are the different troughing angles used for transoms?

Depending on use and load capacity, various troughing angles are implemented. These include:

• 180 degrees: For flat belts and lighter loads
• 45 degrees: For increased capacity
• 35 degrees: For medium capacity
• 20 degrees: For low capacity
• 10 and 15 degrees

8-What protection systems are available for belt conveyors?

• Pull Cord Switch (PCS):

  Utilized for emergency stopping of the belt.

• Belt Sway Switch (BSS):

  Protects the belt from swaying or excessive lateral movement.

• Zero Speed Switch (ZSS):

  This system is fitted to the tail or snub pulley to prevent further damage to the belt in case of a belt cut.

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9-What does transoms mean in the context of belt conveyors?

Transoms: These are brackets that support the idlers and ensure their proper placement.

The following types of transoms are typically noted in belt conveyor systems:

• Carrying idler transom
• Return idler transom
• Self-aligning carrying transom
• Self-aligning return transom
• Garland idler transom

10-What are the roles of carrying idler, return idler, impact idler, and side guide idler?

• Carrying idlers:

  Located on the carrying side of the belt (top side).

• Return idler:

  Positioned on the return side of the conveyor (bottom side) and typically the largest idler used.

• Impact idlers:

  Fitted on the carrying side, below the discharge chute of the preceding conveyor.

• Side guide idler:

  Placed on self-aligning transoms to prevent swaying of the belt to one side.

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10a-What different grades of belts are there and what are their applications?

• M Grade:

  Heavy-duty, resistant to sharp rugged materials, operates in normal ambient temperatures, primarily for coal, bagasse, and biomass applications.

• N Grade:

  Used for coal and biomass, less resistant to sharp rugged materials.

• B (G) Grade:

  Operates in normal temperatures and suitable for light duty only.

• HRS:

  Used for high-temperature applications up to 100 °C surface temperature and 200 °C material temperature.

• HRE Grade:

  Suitable for high temperatures up to 150 °C surface with 400 °C material temperature.

11-What issues might you encounter with belt conveyors?

• Belt misalignment at head pulley due to improper troughing idlers.
• Misalignment at tail pulley due to material build-up on return idlers.
• Excessive wear on the bottom of the belt.
• Excessive wear on carrying and return sides.
• Overstretching of the belt due to excess tension.
• Slipping on tail pulley.
• Damage to pulley hub keyway.
• Belt tracking on one side only.
• Fuel leakage from improper scraper and skirting arrangements.
• Conveyor Drive Issues: Vibration from gearbox and motors, unusual sounds in gearbox, loose coupling bolts.

12-What conditions trigger a Zero Speed Switch (ZSS) to activate?

The ZSS operates under conditions such as:

• Belt cut
• Belt slip on head pulley

13-What causes excessive wear on the carrying side of the belt?

• Dirty, frozen, or misaligned return idlers.
• Excessive sag between troughing idlers causing load movement.
• Abrasive skirt boards.
• Poor loading practices.

14-Why does excessive wear occur on the bottom of the belt?

• Slippage between belt and drive pulleys: Check the wear on pulley rubber lagging.
• Stuck troughing idlers: Inspect belt cleaners (scrapers).
• Material accumulation between pulley and belt: Regularly remove collected debris.

15-What are common reasons for belt misalignment at the head pulley?

• Material build-up on return idlers.
• Unequal loading on the belt.
• Improper alignment of head pulley.
• Malfunctioning self-aligning transoms near the head pulley.

16-What causes a conveyor belt to track towards one side over a distance?

This is typically due to improper loading of the belt and failure of self-aligning transoms.

17-What steps would you take if you notice continuous wear on the carrying side of the belt?

To reduce wear, consider implementing the following measures:

• Install belt-cleaning plows at both ends of the conveyor.
• Regularly clean, repair, and align return idlers.
• Increase belt tension if it is excessively low.
• Reduce spacing between idlers.
• Regularly inspect and repair skirt board rubbers.
• Feed loads consistently on the belt in the same direction and speed.

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18-If a belt exhibits excessive tension, what measures should be taken?

In the case of excessive belt tension, consider:

• Reducing belt tension by altering lagging on drive pulleys.
• Increasing the arc of contact with the drive pulley.
• Where feasible, increasing speed while maintaining same tonnage.
• Reducing tonnage while operating at lower speeds.
• Adjusting the screw take-up just enough to prevent belt slippage.
• On gravity take-ups, decrease counterweights to the minimum sufficient to avoid slippage.

19-What is the preferred speed for coal belt conveyors in power plants?

For medium capacity power plants (10 to 50 MW), a speed of 0.9 to 1 m/sec is recommended.

For larger thermal power plants, the speed can range from 0.9 to 1.5 m/sec.

20-What does transition distance refer to?

Transition distance is defined as the space from the center line of the first fully troughed idler roll to the center line of either the head or tail pulley.

21-Can you elaborate on belt cleaners/scrapers?

Belt cleaning methods are aimed at removing a high percentage of carryover at the source, specifically at the head/discharge pulley. It is crucial for belt cleaners to operate without damaging the belt.

Types of Belt Cleaners:

Contact Type:

Primary, secondary, and tertiary belt cleaners are largely utilized.

Primary belt scraper: Installed inside the head chute beneath the natural material trajectory where the belt contacts the pulley. They are typically contact scrapers.

Secondary belt scraper: Commonly positioned within the head chute to contact the belt leaving the head pulley. Usually, these are contact scrapers and may take the form of blade-type scrapers or rotating brushes.

Tertiary scrapers: Not often used but can be present outside the head chute where the removed material must be redirected back to the chute.

Belt washing systems may also be employed when carryover materials are particularly stubborn or where washing water handling is manageable. These systems are largely deemed non-contact cleaners as water is utilized to clean the belt, subsequently dried by squeezing rollers.

22-What is the purpose of a Take-up unit (TU)?

The take-up device's function is to maintain adequate tension for the conveyor drive pulley to effectively drive the belt during all operational states (whether loading or empty).

23-What are the primary types of Take-up unit (TU)?

1-Fixed type: screw take-up unit (STU)

2-Vertical gravity take-up (VGTU)

24-What percentage of belt tension adjustment is normal during operation?

It typically ranges from 0.8 to 1.2% of the total length.

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25-What is the minimum length required for the take-up system?

The minimum length for the take-up is 1.5% of the conveyor length (Center to Center).

26-For a 100-meter long belt conveyor requiring a VGTU system, compute the minimum length of the take-up.

Minimum length of take-up = 1.5% X 100 = 1.5 meters.

27-If a conveyor measures 200 meters in length and operates at a speed of 1 m/sec, how long will it take to complete one full rotation?

Total approximate length of the belt = 2 X conveyor length + Conveyor length X 1.5%.

The calculation is as follows:

2 * 200 + 200 * 1.5% = 403 meters

Time taken for one full rotation of the belt = 403 m X 1 sec = 403 seconds = 6.71 minutes.

28-Define transition distance.

Transition distance refers to the measurement from the center line of the first fully troughed idler roll to the center line of either head or tail pulley.

29-Describe the VGTU system in belt conveyors.

The primary role of the take-up device is to create and maintain appropriate pre-tension needed for the conveyor drive pulley to effectively drive the belt throughout various operational conditions. Generally, there are two primary take-up types: fixed type typically known as screw take-up (STU) for shorter conveyors (up to 50 meters) and the automatic gravity take-up (GTU) for longer conveyors, ensuring constant pre-tension. The specific length of the take-up will rely on both the conveyor's center distance and the belt type. The screw take-up is generally positioned at the tail end for shorter belts. It is advisable to reserve tracking adjustments with the screw take-up for last resort as it may induce permanent stretching of the belt.

The GTU works optimally when sited near the drive pulley. The GTU's bend pulleys will have a minimum diameter based on belt specifications, and both vertical and horizontal movements should be limited to prevent excessive displacement and tracking issues. The GTU should have protection against return belt retraction and requires adequate guarding.

30-What is the significance of counterweight?

The counter weight of a GTU aids in maintaining consistent belt sag between idlers. Proper weight is crucial, as insufficient weight will result in excessive sag, increasing belt resistance and shortening the lifespan of both the belt and idlers. Conversely, overly heavy weights can lead to excessive tension, which stretches the belt and joints.

31-What purpose do covers serve on the belt?

Covers in conveyor belt designs protect the underlying belt carcass and enhance its lifespan. Moreover, covers grant the complete belt a range of favorable characteristics, such as:

32-For a 100-meter belt conveyor requiring a VGTU system, calculate its minimum take-up length.

33-A 200-meter belt conveyor with a drive pulley size of 510 mm OD and a connection to a 40:1 planetary reduction gearbox is driven by a motor. Determine the time required for one complete rotation of the conveyor.

The following values apply: Conveyor length = 200 meters Pulley OD = 510 mm = 0.51 m Motor output speed = [RPM] (used as a reference) Gearbox reduction ratio = 40:1 Gearbox output speed N = [RPM]/40 = 36.87 RPM

Head pulley speed = Gearbox output speed (as the head pulley is directly coupled to the gearbox)

Pulley speed in m/sec = V = Pi X D X N/60 = (3.142 X 0.51 X 36.87/60) = 0.98 m/sec

The calculated belt speed is 0.98 m/sec based on a 200-meter conveyor. Consequently, the total conveyor length computation is:

The total length of the belt = 2 X conveyor C/C length + Conveyor C/C length X 2 X 1.5% (VGTU) + 0.5 X Number of pulleys (Assuming a contact radius length of 0.5 meters per pulley)

= 2 X 200 + 200 X 2 X (1.5/100) + 0.5 X 6 (6 pulleys) = 409 meters

Time required for one complete revolution = Belt length/Speed = 409/(0.98 X 60) = 6.95 minutes.

34-A 7.5 kW inclined belt conveyor with a width of 800 mm operating at 0.95 m/sec, how do you calculate the maximum tension at the start?

Belt rated power (P) = 7.5 kW

Belt Speed (V) = 0.95 m/sec.

Belt Width (W) = 800 mm = 0.8 meters

Maximum tension at start of the belt = (3.2 X P)/(V X W) = (3.2 X 7.5)/(0.95 X 0.8) = 31.5 kN/m

35-An 800 mm wide inclined belt conveyor has its head pulley elevated 22 meters from the ground and is tasked with carrying 45 TPH coal. The head pulley connects to a motor with a specific RPM through a planetary gearbox of 80% efficiency. Calculate the required motor power to operate the conveyor. Include a 15% safety margin when determining the motor rating.

Belt Width (W) = 800 mm

Vertical lift = L = 22 m

Conveyor Capacity (Q) = 45 TPH

Gearbox efficiency = 80%

Motor efficiency = 90%

Power needed to drive the incline belt P = (4.7 X L X Q)/[insert units] = (4.7 X 22 X 45)/[insert units] = 4.65 kW

Motor Input Power = 4.65/(Gearbox Efficiency * Motor Efficiency) = 4.65/(0.8 * 0.9) = 6.45 kW

Motor Rated Power = Motor Input Power X 1.15 = 6.45 * 1.15 = 7.42 kW (15% margin considered)

Thus, select a 7.5 kW motor.

36-Determine the total length of a 3-ply 800 mm width conveyor belt coiled around a 100 mm pipe. The belt thickness is 10 mm and it is coiled 65 times.

Let:

Diameter of coiled belt center hole, d = 100 mm = 0.1 m

Belt Thickness T = 10 mm = 0.01 m

Number of turns N = 65

Outer Diameter D = 2 * 65 * 0.01 = 1.9 m

Length of belt = (d + (D - d)/2) X π X N = (0.1 + (1.9 - 0.1)/2) * 3.142 * 65 = 204.23 meters

37-Address the significance of operational checks for conveyor belts.

Belts:

Ensure that any material spillage is removed from the return pathway where it can become trapped between the belt and pulleys.

Confirm that the belt remains aligned correctly and doesn't come into contact with structural components, particularly the lower return track.

Document any breaks or damage for timely repairs.

Eliminate any large debris (coal lumps, rocks, foreign materials) on the belts; if present, carefully remove them.

Idlers and Pulleys:

Monitor frozen or damaged idlers needing repairs or replacement.

Check both troughing and return self-aligning idlers for efficient operation.

Inspect scrapers and plows for gold condition.

Watch for material build-up beneath idlers or pulleys. This is critical at self-aligning idlers.

Chutes and Hoppers:

Identify and rectify any material obstruction or bridging.

Prevent large objects from dropping onto the unprotected belt.

Check that material is centered on the belt and that overloads are avoided.

Always replace any damaged impact idlers; do not substitue them with regular idlers.

38-What is the purpose of pulley lagging?

Lagging enhances pulley traction by being bolted or vulcanized onto the pulley face. This prevents slippage at the head pulley and cushions the wear between the belt and the pulley surface, particularly useful in wet situations with grooved lagging.

39-What does a hold back device do in conveyor belts?

The hold back device is designed to prevent the conveyor from reversing or rolling back during sudden stops or trips.

40-Define belt splicing and describe its different types.

Splicing refers to the technique of joining two trimmed ends of a conveyor belt through specific chemical or mechanical methods. Common methods include Vulcanized Splicing (both cold and hot) and Mechanical Splicing.

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