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
What do self aligning or training idlers do?
The pivot in the middle to help direct the belt back towards the center. It will correct small tracking problems along the length of the conveyor but will not correct severe misalignment problems
What are fixed side guides, and where are they used
They are located at various points along the conveyor where objects close to the belt may be damaged if the belt runs off. Their main function is to protect the frame of the conveyor or other objects from the damage. There are sometimes called guidelers
What are impact idlers
They’re installed directly under the loading point of the conveyor to protect the conveyor belt from damage caused by the loading impact of the material. They are also available in the standard angles 20°, 35°, and 45°
What are inclined return idlers?
Because most belt alignment problems occur on the return side the v style inclined idlers are used. They are inclined at 10° or 20°
If a belt slightly runs off what is one method to correct it if you can adjust your rollers?
You can knock over an idler roll in the direction the belt needs to move like handlebars on a bike. You cannot do it with one roll you need to move several
If the belt is out of alignment in one spot only what does that mean?
It means that the splice was not square
Where is most belt training done?
At the bottom
What is the most common belt scraper?
A V plough fitted with an adjustable rubber skirt. The skirting rubber should never be made of old belting
Why would a magnetic head pulley be used
Two separate out metallic material from a non-metallic material
What are two other ways to separate metal products from material being conveyed
A magnetic pulley on a separate belt to pull it out before discharge, or a magnet suspended right above the discharge
What is used on incline conveyor’s for a backstop to prevent roll back?
Usually a Spragg or overrunning clutch that allows rotation in One Direction only
What are the three main classes of chain conveyors?
Parallel strand, gravity drop drives, S drives
Describe parallel strand conveyors?
They usually have a trough and a flight attached to the chain which drags the material. A slight camber is preferable on the bottom carrying side.
What is a gravity drop chain drive?
They are usually slow speed and on a slope. They have no way to take up slack. The drive sprocket is on the return side of the head drum, which allows the weight of the chain to maintain contact with the drive sprocket.
What is a chain S drive used for?
Has a much larger area of contact with the drive sprocket being positioned in more of a V arrangement. This allows for long heavily loaded chains. They also have an adjustable take up incorporated
What keeps the chain straight in a parallel strand conveyor
Divider bars on the return side
What is a H class mill chain?
It is the same design as a Pintle chain but is a heavier construction, and has flanged wearing shoes cast on The bottom surface. It’s used for applications with Abrasive materials.
What is a drag or refuse chain
Drag chain links are one piece casting commonly have large pitches of 5 to 12 inches
What is the detachable chain commonly used for
It is used primarily for low speed One Direction conveyors. No pins are needed for attaching the different links
What is a rooftop or Camelback chain?
It’s main purpose is to allow the material to be transferred 90° from the main direction of travel. It has a domed or peaked top so things do not get caught on it when transferring the other direction
What is a roller top chain?
Similar to a rooftop or camelback except at the top rolls 90° from the direction of travel
What is the side flex chain?
It allows the material to go around bends. It is used mainly in the food industry
What is an example of a flight conveyor?
The clean out drag under a conveyor belt or waste conveyor
Describe a long link chain sprocket
Also called a star sprocket and has either five or seven teeth. is used very slow speed applications(boat anchors)
What is an apron or pan conveyor
Consists of two or more chains strands with formed flights attached that become like small pans or buckets. They are used to convey large amounts of heavy or very hot materials found in the mining and processing industry
What do bucket elevators do?
Transfer material up inclined or vertical planes
What are the main components of a bucket elevator?
The head assembly which has head shaft, bearings drive and discharge. The casing which supports the elevator and contains the buckets. The foot assembly also known as the boot which consists of the take up assembly and the feet shoot
What might be installed in the Boot section to keep the sprocket from the material build up
A deflector plate
Are the casings self-supporting?
Yes they are self-supporting but they must be attached to the building
What causes the chain and buckets to jump?
Broken teeth on the sprocket
What is the snub pulley used for in a bucket elevator?
It helps to discharge the material by inverting the bucket
What is attached to the casing to reduce fire hazard?
A grounding strip to prevent the buildup of static electricity, and prevent damage to the bearings
What is installed on a high lift elevator to prevent chain sway?
Chain guides
What is a continuous bucket elevator?
They’re designed and spaced so that as each bucket discharges over the back of the preceding which its bottom acts as a discharge chute. This design enables the elevator buckets to be fed directly from the loading shoot for the material maybe scooped up by the buckets.
What is a centrifugal discharge bucket elevator
These operate at high-speed’s. As the loaded buckets passover the head sprocket, centrifugal force throws the material from the bucket towards the discharge chute. Only to be used with dry free flowing material
What are the two bolted joints used to join the belt in a bucket elevator?
Butt joints- bolting a layer of belting over the outside face and extending at least a half belt width past the joint on both sides
Lap joints- overlapping the ends of the belts over each other for at least one belt width and fastening them with elevator bolts. On belts with fewer than 10 plies the minimum length the belts splice is equal to the belt width
What is common maintenance done to bucket elevators
The buckets. When replacing them avoid removing and installing too many on one side, as it will cause an out of balance or runaway situation
What is the maximum RPM for a screw conveyor?
Approximately 450 RPM
What are the components of a screw conveyor?
Conveyor screw flights, couplings, bearings, housings, loading and discharge points, drives
What is the standard flight from a screw conveyor
It has the same pitch dimension as the screw diameter
What is the standard pitch, short pitch and long pitch on the screw conveyor flight
Standard pitch has the same pitch dimension as the screw conveyor diameter. Short pitch is less than standard pitch, long pitch has a longer pitch then the diameter
How was the screw conveyor coupled?
A coupling also referred to as a gudgeon shaft and gudgeon pin
What is another purpose of the gudgeon shaft in a coupling?
It serves as a bearing journal and is supported by a hanger that contains bearing shelves. Every coupling will have a supporting hanger as well
Where will the thrust bearing be in the screw conveyor?
It is normally located at the discharge end of the conveyor to keep the screw in tension
What are the two types of roller conveyors?
Gravity rollers, and live roller conveyors
What is a skate wheel conveyor?
It’s similar to a standard roll conveyor, but has smaller staggered wheels rather than one solid roller. These are often portable, such as ones to unload boxes from a truck
What is the smallest number of rollers, or skate wheels under a package?
Roll conveyors-3
Skate wheels -5
Based on the smallest package the conveyor is expected to travel
On smaller conveyors, what part of the bearing moves?
The shaft is locked in the pocket of the frame, so only the outer race can move
What is the typical conveyor pitch on a gravity roller conveyor?
1/4”-1/2” per foot are the limits
What is another name for double lane curves?
Differential roller curves. They can be either double lane in line, or double lane staggered.
What should the maximum pitch be on live roller conveyors?
Not more than 10° up or down because the product could slide on the rollers
Where are belt driven roller conveyors used?
Light loads, and applications where loads accumulate, because it allows for some slippage.
What are continuos chain drive systems used for?
Medium loads, more continual , not used for stop start applications.
What does a roll to roll drive system look like, and what is it used for?
Each drive roll will have two sprockets to join to the next roll. It is used in applications that require start and stop frequently, reversing loads, and heavy loads
Why are eccentric rollers used?
They are used to move a load 90 degrees to an end stop. These are used with chain drives which have the rooftop or camelback chain. This is similar to a bump roller
What is a bottle roller?
Another way of moving materials 90 degrees from direction of travel to an endstop. The tapered end faces upstream so nothing catches it. The chains that are moving product the primary direction, usually have lugs on them
What is the purpose of angling all the rollers one direction?
To align all the product to one side for another manufacturing step.
What are hourglass rolls primarily used for?
To carry cylindrical objects such as pipes or logs
What are Spurs?
Conveyors to transfer loads on or off the main conveyor
What is a deflector?
A moveable arm or plates that direct to the spur conveyors. They are usually powered hydraulically or pneumatically
What are the different multi conveyor configurations?
Converge, and diverge
What are end plates?
They are mounted at the end of the roll case, often with a photocell, so product doesn’t fall on the ground
What is often used with a rotating table?
A moveable stop/kicker to stop the product when it comes onto turntable, and push it onto the next conveyor when in position
What are the two types of pneumatic conveyors?
Negative pressure, and positive pressure.
Where does the most wear occur in a pneumatic conveyor system?
On the inside of the outside bend.
Explain a low pressure system?
It uses a lobe or roots type blower to supply the air. The material is then fed through a hopper and rotary feeder into the system. Limited to 12 psig
Describe a medium pressure pneumatic conveyor system
Operates from 15-45 psig, usually through a rotary blower or sliding vane compressor. The solids must be a uniform size and shape.
Describe high pressure pneumatic conveyors
Operate up to 125 psig. High pressure air and gas pressurize the tank and when it reaches pressure, a discharge valve is opened.
What prevents pressurized air from entering the hopper/rotary feeder?
Close clearances
What should be done before working on a jump system?
Ensure the roll case is in the lowered position.
What is an air slide conveyor?
The air is supplied by either a roots type blower or Centrifugal blower. The air slide is on a decline from entrance to exit it flows down hill
What are common maintenance inspections on a vibrating conveyor
Frame, Pan, springs, flexible plates and welds
Bearings or bushings, drive belts and couplings, gearbox
