Explanation 1.2:
If the conveyor chain should be elongated more than 1/4" per foot, it will not feed properly through the drive unit. The drive unit's caterpillar drive dogs cannot properly engage the conveyor chain. Instead, the point of the dog rides on or near the top of the lateral link, thus forcing the link downward and eventually bending the center guide.
To determine the actual amount of chain elongation, measure twenty 6" chain pitches. For instance if the pendants are on 12" centers, measure from the center of one pendant to the center of the tenth pendant. This will normally be 10'-0". If it should be 10'-2 1/2" the chain is elongated 1/4" per foot. Chain needs to be tight and have some tension on it when this measurement is made.
If time permits, one side of the drive chain track should be removed. This will show the action of the drive chain dog engaging the conveyor chain. You may also inspect the chain very well at the inspection section. Simply open the conveyor and inspect the general condition of the chain.
Correction 1-2:
Replace the chain the system. Also, replace the drive caterpillar chain. You will also need to check the condition of the curves. Vertical curves and horizontal curves tend to wear the fastest because they create the most friction.
Explanation 1.3:
Conveyor chain which is allowed to run without lubrication will often require 50% or more effort for movement and pins may shear or clutches may slip. This is the reason that the chain is dipped in lubricant before it leaves the factory. Unless lubrication is provided on a regular basis, rapid wear will occur and the chain life will be reduces drastically, because of chain wear and elongation.
We recommend that you purchase some type of automatic lubricator to help solve this problem. If you have a high temperature application, we suggest that you use a high temperature lubricant.
Correction 1-3:
Better Lubricate the Chain; or purchase an automatic lubricator.
Explanation 1.4:
In single drive systems, the slack or loose chain will collect immediately in front or downstream from the drive unit, unless there is a decline just beyond. In this case, the slack will accumulate at the bottom of the decline. In a level system without an automatic take-up or where there is an incline in front of the drive, the loose chain will gather immediately in front of the drive and eventually it will crowd back into the caterpillar chain and jam it. Usually, this will bend or damage the drive chain guide and possibly the caterpillar chain.
Correction 1-4:
In a multi-drive system the two or more drives may not be properly spaced. The drive unit with the lightest load will tend to run a little faster so all of the system's slack chain will gather in front of it. In this case, an automatic take-up downstream of the drive is indicated.
If it is a flat or level system, install a spring loaded or air take-up. In either arrangement, the drive unit should be located just upstream of the take-up so that chain will feed directly into the take-up. Should the drive be upstream of an inclined track section, the drive should be relocated to a point just upstream of a downward slope. Also, the drive chain should be replaced if worn.
Explanation 1.5:
The conveyor track, straight and curved has a 5/8" slot at the bottom when manufactured. However, being thrown on and off of trucks and rough handling at the job site plus welding often causes the slot to be decreased. When this happens, the track width is reduced in some cases to a point where the chain will not pass freely. The restriction can jam the chain.
Correction 1-5:
Passing a 10'-0" section of chain through the track will locate the pinched sections of track. Also a visual inspection will detect the narrow points. If the slot, at any point, is less than 9/16" wide, it is too narrow. To correct, the slot can be widened with a pry bar and hit with the spherical end of a ball peen hammer on the top of the track in the center opposite the pry bar. This will spread the track side walls to the desired slot widths.
Explanation 1.6:
An instruction sheet accompanies all take-up units. The direction of chain travel is shown. If the instructions are not followed and the sleeves are reversed, the vertical wheels must climb upon the end of the moveable inner track. This causes a rough passage of the conveyor chain and can result in a pulsation, and possible chain stoppage.
Correction 1-6:
Remove the take-up units and replace as described in the instructions provided with the equipment.
Explanation 1.7:
The caterpillar drive chain after long wear and overloads will become a source of trouble resulting in jamming of the drive unit. Removal of the drive track lips or the drive cover will usually identify the problem.
Correction 1-7:
Replace the drive caterpillar chain. While certain chain can be repaired, it is usually advisable to install a new one. It may also be necessary to install a new head shaft and idler sprocket.
A damaged caterpillar chain can shut down a conveyor system. Therefore, all users are seriously urged to keep a spare caterpillar chain on hand.
Explanation 1.8:
The head shaft and the idler shaft of the drive unit get out of alignment as a result of the drive take-up adjustment. If one pillow block bearing is advanced more than it's mate, the two shafts are no longer parallel. This tends to cause the caterpillar dogs to twist sideways and they often move down into the side plate of the conveyor chain. Thus jamming the drive. Even though the dogs manage to move in between the side plates, the strands of the caterpillar chain can wear prematurely resulting in a shut down.
Correction 1-8:
Readjust the drive take-ups so the head shaft and idler shafts are parallel. The take-ups should be extended to a point where no slack remains in the caterpillar chain.
Explanation 1.9:
By accident the drive is often installed backwards. This does not cause a problem until the drive caterpillar chain develops considerable slack. When this occurs, the slack gathers below where the caterpillar chain engages the conveyor chain. The caterpillar dogs will not meet the conveyor chain properly and a jam will occur.
Correction 1-9:
Reverse the drive or adjust the two caterpillar chain take-ups to remove the slack. DO NOT TIGHTEN TO A POINT WHERE THERE IS TENSION ON THE CATERPILLAR CHAIN. Also, be sure that the idler shaft is square with the centerline of the drive.
NOTE: If a given conveyor requires operation in either direction, the caterpillar chain must be adjusted at regular periods to prevent the unwanted accumulation of slack.
Explanation 1.10:
Frequent jams in a system will cause the overload friction clutch to slip. Eventually, the friction discs will wear out and the drive will stop functioning.
Correction 1-10:
Replace the friction clutch and readjust the new one as per instructions provided with the new assembly. Also, locate the problem area in the system and solve the problem. It is a good idea to keep a set of friction clutch liners on hand in case you may need to replace them immediately.
Explanation 1.11:
In older 400# systems, the horizontal and vertical track curves are not heat treated. When the chain pull in such a system exceeds around 500# at any given curve, the radial loading on the chain wheels is great enough to cause a deformation of the track wear surface. This is called peening. The top vertical curve is the most susceptible to this because the two lips are unsupported at the end of the slot. If the overload continues to exist, the lips of the top vertical curve will finally roll downward until the chain wheels come through and the drive will eventually jam. Meanwhile, the "tow in" of the vertical wheels causes the wheel bearings to deteriorate rapidly.
In horizontal and bottom vertical curves, the peening or rolling action is manifested by a definite bulge. In some cases, the hardened lateral chain wheels will finally cut through the wall of the horizontal or bottom curves.
Correction 1-11:
The reason for the high chain pull should be determined (See Item 1-1). This may necessitate an additional drive, better lubrication or a new conveyor chain. Along with these corrections, the damaged curves must also be replaced.
NOTE: It is not advisable to replace standard curves with heat treated curves to overcome the problems because the chain and the drive units will begin to fail.
Explanation 1.12:
A pin will shear or a clutch may slip because the product hook or product catches and hangs up on a conveyor guard, building steel, washer, etc. Also, a production worker will often purposely jam the drive by hooking the product carrier on a column or other stationary object.
Correction 1-12:
Locate the interference point or points. Sometimes, a simple sheet metal fender will serve to contain or prevent a product hook from swinging out to catch on a column or other stationary object.
Explanation 1.13:
Chain corrosion resulting from acidic washers and hot caustic paint strippers causes great harm to the conveyor chain, unless proper precautions are taken. The most common problem, and the worst, are the washers which use phosporic acid to etch the product for better paint adhesion. If the spray of this solution is allowed to reach the chain, the wheel races and the ball bearings will become etched and pitted. Continued exposure to the liquid or vapors will finally erode wear surfaces of the bearings until the balls drop out. Also, the connecting pin, the hourglass roller, and the lateral forged pin will wear rapidly.
In certain other processing equipment through which the conveyor passes, steam, water sprays, etc. also take their toll. Rusting results eventually and in some cases, very rapid chain replacement is necessary.
Correction 1-13:
The customer must be made aware of the problem and advised to install sanitary hooks with triple baffles through the critical areas or a Protectaire system.
It is also important to advise the customer that no overhead chain conveyor will withstand or endure attacks of acid.
Explanation 1.14:
When a conveyor is subjected to sub-freezing temperatures, the various parts tend to become coated with frost, and if allowed to stop, the chain will finally freeze. Wheel bearings coated with ice will not rotate and the drive unit will not develop enough force to start the conveyor chain. While this problem is more common in applications involving freezers, it also occurs when a conveyor is used both inside and outside of a building in sub-freezing conditions. Going from a heated area to a cold area, the moisture condenses on the chain and eventually freezes. However, a system that is entirely outside typically will not have problems because the condensation does not occur as easily. The only problem with outside applications lies in the drive unit and in the gearbox. The grease in the gearbox can and typically will congeal and become solid. When this occurs, the drive motor does not have sufficient power to drive the gearbox which is frozen up.
Correction 1-14:
When the drive unit appears to be frozen, the only solution is to warm the gearbox to a point where the lubricant can thaw out. Once the lubricant is thawed the system will operate fine as long as it does not freeze again.
