433A Conveyor Systems 2 — Questions and Answers
Question 1: What is a screw conveyor and what materials is it typically used for?
- A conveyor held together with screws
- A conveyor using a helical screw (auger) rotating inside a trough to move bulk materials such as grain, cement, and powders (Correct answer)
- A conveyor that moves fasteners
- A belt conveyor with a screw take-up
Correct answer: A conveyor using a helical screw (auger) rotating inside a trough to move bulk materials such as grain, cement, and powders
A screw conveyor consists of a helical screw (flight) rotating inside a U-shaped trough or enclosed tube. It efficiently moves bulk granular, powdery, and semi-solid materials horizontally or at slight inclines. Common applications include grain, cement, chemicals, and sludge.
Question 2: What is the purpose of a gravity take-up on a long belt conveyor?
- To increase belt speed using gravity
- To automatically maintain constant belt tension using a weighted carriage that moves to compensate for belt stretch and thermal changes (Correct answer)
- To slow the belt when going downhill
- To take up floor space
Correct answer: To automatically maintain constant belt tension using a weighted carriage that moves to compensate for belt stretch and thermal changes
A gravity take-up uses a weighted pulley carriage that rides on tracks. The weight applies constant tension to the belt, automatically compensating for belt stretch, thermal expansion/contraction, and load variations without manual adjustment.
Question 3: What is a bucket elevator and what is it used for?
- An elevator for maintenance personnel
- A vertical conveyor using buckets attached to a belt or chain to lift bulk materials to a higher elevation (Correct answer)
- A screw conveyor mounted vertically
- A pneumatic conveying system
Correct answer: A vertical conveyor using buckets attached to a belt or chain to lift bulk materials to a higher elevation
A bucket elevator uses a series of buckets attached to a belt or chain loop running vertically between a head (top) pulley and a boot (bottom) pulley. Buckets scoop material at the bottom and discharge it at the top, providing efficient vertical transport of bulk materials.
Question 4: What causes belt slippage on the drive pulley of a conveyor?
- The belt is too heavy
- Insufficient belt tension, wet or worn pulley surface, or insufficient contact arc (wrap angle) between belt and drive pulley (Correct answer)
- The motor is too powerful
- The belt is too wide
Correct answer: Insufficient belt tension, wet or worn pulley surface, or insufficient contact arc (wrap angle) between belt and drive pulley
Belt slippage occurs when the friction force between the belt and drive pulley is insufficient to transmit the required driving force. Causes include low belt tension, wet/smooth pulley surface reducing friction coefficient, and insufficient wrap angle around the drive pulley.
Question 5: What is the purpose of a belt conveyor training idler?
- To train new operators
- To automatically correct belt mistracking by pivoting in response to belt drift and steering the belt back to center (Correct answer)
- To train the belt to a specific shape
- To increase belt speed at certain points
Correct answer: To automatically correct belt mistracking by pivoting in response to belt drift and steering the belt back to center
Training idlers (self-aligning idlers) have a pivot mechanism that allows them to swivel when contacted by a drifting belt edge. The swiveling action creates a corrective steering force that guides the belt back toward center.
Question 6: What maintenance check is critical on a chain conveyor?
- Checking the color of the chain
- Measuring chain elongation (stretch) to determine wear and verifying proper tension and lubrication (Correct answer)
- Counting the number of links
- Checking the chain temperature
Correct answer: Measuring chain elongation (stretch) to determine wear and verifying proper tension and lubrication
Chain elongation due to wear on pins and bushings is the primary wear indicator for chain conveyors. Regular measurement of chain pitch against original specifications indicates when the chain should be replaced. Proper tension and lubrication are also critical to chain life.
433A Conveyor Systems 2
What is a screw conveyor and what materials is it typically used for?