🔹 Introduction

A belt conveyor system operates efficiently only when its key components — such as pulleys, idlers, and take-up devices — are well designed and properly maintained. Each component contributes to smooth operation, load support, tension regulation, and overall system reliability.
The pulleys transmit power and guide the belt, while idlers support and shape the loaded belt into a trough for increased capacity. Take-up devices maintain proper tension, preventing slippage and sag. Together, they ensure safe and steady material transport.
Understanding these components is critical for DGMS mechanical examinations as they directly influence conveyor performance, belt life, and maintenance intervals.
This blog provides detailed DGMS notes on the types of pulleys (drive, tail, snub), idler classifications (impact, disc, troughing), and take-up systems (screw, gravity, winch) with illustrations, functions, and practical design points.
A deep understanding of these fundamentals equips mining engineers to design conveyors that are safe, efficient, and long-lasting under all industrial conditions.

🔹 1. Types of Pulleys

1️⃣ Drive Pulley (Head Pulley) – transmits torque.

2️⃣ Tail Pulley – returns belt.
3️⃣ Snub Pulley – increases wrap angle.
4️⃣ Bend Pulley – changes belt direction.

Minimum Pulley Diameter:Dmin=K1K2ZpD_{min} = K_1 K_2 Z_pDmin =K1 K2 Zp

🔹 2. Idlers

Type	Use
Carrying Idlers	Support upper run
Return Idlers	Support lower run
Impact Idlers	Absorb shock at loading point
Rubber-Coated Idlers	For wet or dusty areas
Self-Aligning Idlers	Correct belt misalignment

🔹 3. Maintenance Tips

• Lubricate bearings regularly.
  
• Keep alignment & balance checked.
  
• Replace damaged rollers immediately.
  
• Avoid overloading and material spillage.
• 
  

🔹 4. 25 DGMS-Style MCQs

1️⃣ The main function of idlers in a belt conveyor is —

a) Transmit power
b) Support the belt and material load
c) Change belt direction
d) Reduce belt tension
e) Control spillage
✅ Answer: b) Support the belt and material load
Solution: Idlers provide continuous support to the belt, reducing sag and maintaining alignment.
2️⃣ Carrying idlers are located —

a) Below the return run
b) Along the top carrying run
c) Near the head pulley only
d) Near the take-up device
e) At motor shaft
✅ Answer: b) Along the top carrying run
Solution: They support the loaded portion of the belt between pulleys.
3️⃣ Return idlers support —

a) The loaded belt
b) The empty return belt
c) The drive pulley
d) The snub pulley
e) None
✅ Answer: b) The empty return belt
Solution: They are mounted under the conveyor to carry the return run.
4️⃣ The purpose of impact idlers is —

a) Prevent slippage
b) Absorb shock at the loading point
c) Reduce belt speed
d) Guide the belt
e) Control spillage
✅ Answer: b) Absorb shock at the loading point
Solution: Installed below loading chutes to prevent damage to belt surface.
5️⃣ Troughing idlers are used to —

a) Flatten the belt
b) Form the belt into a trough shape
c) Increase pulley grip
d) Support pulley shaft
e) None
✅ Answer: b) Form the belt into a trough shape
Solution: They prevent spillage by increasing cross-sectional area of material.
6️⃣ Transition idlers are placed between —

a) Tail pulley and carrying run
b) Troughing and flat belt sections
c) Return idler and drive pulley
d) Take-up and tail pulley
e) None
✅ Answer: b) Troughing and flat belt sections
Solution: Transition idlers gradually change belt shape to reduce edge stress.
7️⃣ Idler spacing for a 1000 mm belt conveyor is usually —

a) 0.2 m
b) 1.0–1.2 m
c) 3–5 m
d) 6–8 m
e) 10 m
✅ Answer: b) 1.0–1.2 m
Solution: Closer spacing prevents excessive belt sag under load.
8️⃣ Which pulley transmits motion to the conveyor belt?

a) Tail pulley
b) Drive (head) pulley
c) Snub pulley
d) Take-up pulley
e) Bend pulley
✅ Answer: b) Drive (head) pulley
Solution: The drive pulley powered by motor pulls the belt forward.
9️⃣ The tail pulley is located —

a) At the discharge end
b) At the loading end
c) Midway of belt
d) Near take-up
e) Above the drive pulley
✅ Answer: b) At the loading end
Solution: Tail pulley guides the return belt into the carrying run.
🔟 A snub pulley is used to —

a) Reduce take-up tension
b) Increase the wrap angle of the belt on the drive pulley
c) Change belt inclination
d) Support the return belt
e) Act as idler
✅ Answer: b) Increase the wrap angle of the belt on the drive pulley
Solution: Improves friction between pulley and belt, reducing slippage.
11️⃣ The bend pulley is used to —

a) Bend the belt to another direction
b) Increase load capacity
c) Guide the belt at the drive end
d) Change motor torque
e) None
✅ Answer: a) Bend the belt to another direction
Solution: Used where the belt needs to change its running plane.
12️⃣ Rubber lagging on pulleys serves to —

a) Reduce pulley weight
b) Increase frictional grip with belt
c) Make pulley smooth
d) Reduce belt wear only
e) None
✅ Answer: b) Increase frictional grip with belt
Solution: Lagging prevents slip and increases torque transmission.
13️⃣ The take-up pulley maintains —

a) Power transmission
b) Correct belt tension
c) Motor speed
d) Belt curvature
e) None
✅ Answer: b) Correct belt tension
Solution: Compensates for stretch and keeps the belt taut.
14️⃣ Two main types of take-up systems are —

a) Mechanical and gravity
b) Hydraulic and pneumatic
c) Fixed and floating
d) Manual and electric
e) Static and dynamic
✅ Answer: a) Mechanical and gravity
Solution: Mechanical (screw) type for short belts, gravity type for long conveyors.
15️⃣ The wrap angle on the drive pulley affects —

a) Power factor
b) Tension ratio (T₁/T₂)
c) Belt width
d) Belt weight
e) None
✅ Answer: b) Tension ratio (T₁/T₂)
Solution: Greater wrap angle increases friction and grip, reducing slippage.
16️⃣ The usual wrap angle in head drive conveyors is —

a) 90°
b) 120°–210°
c) 270°
d) 360°
e) None
✅ Answer: b) 120°–210°
Solution: Enough for good frictional contact and torque transfer.
17️⃣ The idler roll diameter depends primarily on —

a) Belt speed and load
b) Motor size
c) Pulley lagging
d) Belt color
e) None
✅ Answer: a) Belt speed and load
Solution: Higher speed and heavier loads require larger diameter rollers.
18️⃣ The main cause of idler failure is —

a) High belt tension
b) Poor lubrication or bearing failure
c) Incorrect pulley speed
d) Small pulley diameter
e) Water in belt
✅ Answer: b) Poor lubrication or bearing failure
Solution: Lack of grease and misalignment are major failure causes.
19️⃣ Idler misalignment results in —

a) Reduced belt speed
b) Belt sway and uneven wear
c) Increased capacity
d) Reduced vibration
e) None
✅ Answer: b) Belt sway and uneven wear
Solution: Misaligned idlers cause belt mistracking and edge damage.
20️⃣ Idler shell is commonly made of —

a) Cast iron
b) Mild steel
c) Aluminum
d) Rubber
e) Plastic
✅ Answer: b) Mild steel
Solution: Steel provides strength, impact resistance, and low wear.
21️⃣ DGMS recommends idlers should rotate freely with a torque not exceeding —

a) 1 Nm
b) 2 Nm
c) 3 Nm
d) 5 Nm
e) 10 Nm
✅ Answer: c) 3 Nm
Solution: Ensures low friction and energy-efficient belt operation.
22️⃣ In the return run, self-aligning idlers are used to —

a) Change belt speed
b) Correct belt misalignment
c) Increase power
d) Hold take-up
e) None
✅ Answer: b) Correct belt misalignment
Solution: They pivot automatically to center the belt path.
23️⃣ The maintenance of idlers should include —

a) Regular cleaning and lubrication of bearings
b) Painting only
c) Tightening bolts only
d) No routine checks needed
e) Replacing every month
✅ Answer: a) Regular cleaning and lubrication of bearings
Solution: Prevents seizure, noise, and drag.
24️⃣ Which pulley is generally lagged?

a) Tail pulley
b) Drive pulley
c) Bend pulley
d) Snub pulley
e) None
✅ Answer: b) Drive pulley
Solution: Lagging provides better grip and reduces slippage under load.

25️⃣ DGMS recommends conveyor pulleys be guarded —

a) To prevent dust
b) To prevent accidental contact with moving parts
c) For aesthetic appearance
d) To reduce noise
e) None
✅ Answer: b) To prevent accidental contact with moving parts
Solution: Mandatory guarding ensures worker safety near drive and return pulleys.

                      🔚 Conclusion

Idlers and pulleys are the heart of conveyor stability. Regular maintenance reduces power loss and downtime. DGMS insists on standardized pulley diameters and alignment.

📘 Download “Belt Conveyor Design & DGMS Mechanical Notes” from OnlineMiningExam.com

🎯 Practice MCQs & design numericals online.