Conveyors Flashcards
What are the key components of conveyors?
Belts,idlers, pulleys,take ups and tensioning device, loading and unloading systems
What can be done to adapt to ground profile?
Bends in the frame, and the use of bend pulleys and idlers. Convex bends with high point in middle and bending down (like a flat bed trailer) and concave bending upward
What is a tripper?
It is a device that can discharge material from either selected points, or any point along the length of the conveyor. It’s purpose is for stockpiling material at several points along the conveyor. Some can rotate and unload on both sides
What is a feeder?
They are sometimes installed before the main conveyor, to provide a constant flow of material, and avoid overloaded spots which causes spillage. They are usually flat, and wider than conveyor belts
Where is the highest wear point found on a conveyor?
Usually the loading point. This is where most of the impact, and abrasion happen.
What is the best way to load a belt?
Have the material feed from the loading chute at the same speed, and in the same direction of the belt. It should also be loaded in the middle of the belt
What is a transition conveyor?
It is similar to a feeder, the material is properly centred to eliminate tracking problems, and the impact is reduced due to there diction in transfer height.
What is a side loader chute?
When the angles of the conveyor are changed, it can be dumped in a chute that takes it to another conveyor. Baffles are installed in the chute to slow the material and direct it to the center of the belt.
What things should be accomplished when designing a chute?
Material must be centred, flow in the direction of travel of the belt, reduce impact and abrasion of the belt, steep enough to avoid wet material from sticking inside, have chute liners if the material is abrasive
What is a rock box?
Located at the discharge end of the head pulley. The box fills with initial flow, then spills the material down the chute. The material absorbs most of the impact and abrasion.
What are Grizzlies?
It allows fine material to filter through them. The fine material acts as a cushion for the bigger pieces, reducing wear on the belt
What are skirt boards?
They extend off the bottom of the chute along the conveyor, to confine the material and prevent spillage. The mimumum clearance is 1” from bottom of skirt board to the belt. The rubber skirting at the bottom of the skirt board is to never be old belt material, it is too hard
What is a belt take up?
A tensioning device, usually found at the tail pulley
What is an automatic gravity take up?
Uses a counterweight design to tension belt. Needs to have sufficient travel to handle length changes from: startup, temperature changes, load variation. Same as belt system in shop
If there is not enough headroom for vertical gravity take up, what can be used?
Horizontal gravity take up. The back carriage is on wheels, that are attached to some pulleys and a weight. The disadvantage is the carriage wheels and track get dirty and material spilled on it
What is a screw take ups?
They are part of the tail pulley, found on short conveyors, and must be manually adjusted
What are the three main sections of a belt construction?
Top cover (thicker than bottom)
Carcass
Bottom cover
What are the three surface finishes for belts?
Smooth- to prevent material sticking to it
Rough- increase friction, prevent material slippage
Chevron or raised v- increases the angle of incline for wet conditions, or material having high water content
What are the four types of carcasses?
Solid woven, reduced ply, multiple ply, steel cord?
Describe a solid woven carcass
A single ply of solid woven fabric which has an interlocking weave
What is the purpose of the carcass?
It provides the strength, tension, and transmits the power of the belt
What is a reduced ply carcass?
Fewer plies than multiple ply. Plies have a wider separation between each layer. Due to fact they are not a standard construction, they have different load ratings than similar sized multi layers
What is a multiple ply?
At least 3 layers, but no more than 8. It has more flexibility
What is friction, in regards to belt construction?
It is a rubber adhesive compound that binds the plies together
What is breaker fabric?
It is an open mesh to reinforce against longitudinal breaking under impact. They run across the short direction of the belt
Describe steel cord belts?
Can be run in high tension, with little stretch. These belts must be hot vulcanized, and they are prone to longitudinal tears
What are the three types of joining methods for belts?
Mechanical, cold self vulcanizing, and hot vulcanizing
What are the different types of mechanical splices?
Riveted solid plate, bolted double plate, bolted hinge plate, riveted hinge plate, alligator clips. All of these splice methods must have both ends of the belt cut square, or the belt will track to the sides at the splice.
Which mechanical joining method can be used to repair tears in belts?
The bolted plate, or bolted double plate
What is the strongest most preferred method of splicing belts?
Hot vulcanized, and it can achieve 90% belt strength.
What are the four types of drive pulleys?
Lagged, smooth, self cleaning, or crowned.
The drive pulley is responsible to transmit power from the power unit to the belt
What is a lagged drive pulley?
Lagging is a rubber based compound. It’s main purpose is to increase the coefficient of friction between the belt and the pulley.
What is side lagging?
Also called slide lagging, it is when sections or strips of lagging can be slid into the side of the pulley without removing the pulley or belt
What is a self-cleaning pulley?
Also called wing pulleys they prevent the buildup of material between pulley and belt. Usually use on slow speed conveyors
What is the standard crown on a crown pulley?
1/8 inch per foot of pulley face. They should never be used on high tension steel cable belts or snubbed drive pulleys or multiple drives
What is the head pulley?
Always located at the discharge point, and usually the largest diameter pulley the drive is usually also at the head pulley end
What is the tail pulley
The opposite end of the belt from the head pulley. On small short conveyors it may also be used to help tension the belt through a screw take up
What is a snub pulley
It is simply used to increase the area of contact up to a maximum of 240°. Normal contact is 180°
What is an interlock?
It is a run permissive sequence of events for the conveyors. They shut down in the opposite order of the interlock
What are the three types of drive arrangements?
Single pulley Drive, tandem drives, dual drives
What is the difference between tandem drives and dual drives?
Tandem drives use one motor to drive two pulleys through a gear or chain drive, and dual drives have two motors controlling two drive pulleys
What are carrying and returning idlers?
Carrying idlers support the loaded side of the belt and they maybe troughed or flat. Returning idlers support the return side of the conveyor belt and are generally flat
What are the three angles for troughed rollers
20°, 35°, 45°
What is the advantage of the centre roller being slightly ahead of the angled rollers in a trough system
They have a larger load support area
Why did the idol rollers sometimes have 2° tilt off vertical in the direction of the travel?
It helps with keeping the belt centred
What are transition idlers
On the troughed belt they are used just before the head pulley and just after the tail pulley. The purpose is to gradually trough for flatten the belt from 45° to 35° to 20° and vice versa
How was the distance between idlers and the total transition distance determined?
Is determined by the belt tension, belts strength, and carcass composition