Overhead Conveyor Configurator

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Troubleshooting
Article Index
Troubleshooting
Problem 1: Slipping of Clutches
Problem 2: Pulsating Chain
Problem 3: Premature Wearing of Chain
All Pages

McGinty Conveyors, Inc. strives to keep our customers systems up and running. We have provided a list of the three most common problems that may occur. There are several possible causes that could contribute to each one of these problems. Each problem and its solution are identified in this manual.


Problem 1: Slipping of Clutches

Causes:

  1. Conveyor Overload
  2. Conveyor Chain Elongated more than 1/4" per Foot
  3. Conveyor Chain not Properly Lubricated
  4. Slack Conveyor Chain Backing into the Drive Unit
  5. Pinched Track
  6. Take-Up Sleeves Installed Backwards
  7. Drive Unit Caterpillar Chain Damaged
  8. Drive Head and Idler Shaft out of Alignment
  9. Drive Unit Installed Backwards
  10. Drive Unit Clutch Friction Liners Worn Out
  11. Worn Conveyor Track Curves
  12. Pendant, Hook, or Load Hang-ups
  13. Chain Corrosion from Process Equipment
  14. Sub-freezing Temperatures

Explanation 1a: Slipping of Clutches – Conveyor Overload
The friction clutches are designed to accommodate the starting load so the slipping of clutches occurs at approximately 650 lb. chain pull on older 400 lb. drives. The 600 lb. clutches begin to slip at 900 lb. chain pull. Therefore, if a conveyor is actually overloaded, the clutch slips to protect the chain and drive mechanisms from damage.

Correction 1a: Slipping of Clutches – Conveyor Overload
A chain pull dynamometer may be connected to the chain upstream from the drive unit in the first available straight section to determine the actual chain pull. If this is not practical, the product and the product hook should be weighed accurately and a chain pull calculation should be made. Should the calculated chain pull exceed the rated capacity, an additional drive or drives should be added.

Explanation 1b: Slipping of Clutches – Conveyor Chain Elongated more than 1/4” per Foot
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 1b: Slipping of Clutches – Conveyor Chain Elongated more than 1/4” per Foot
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 1c: Slipping of Clutches – Conveyor Chain not Properly Lubricated
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 1c: Slipping of Clutches – Conveyor Chain not Properly Lubricated
Better lubricate the chain; or purchase an automatic lubricator.

Explanation 1d: Slipping of Clutches – Slack conveyor Chain Backing into the Drive Unit
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 1d: Slipping of Clutches – Slack Conveyor Chain Backing into the Drive Unit
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 1e: Slipping of Clutches – Pinched Track
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 1e: Slipping of Clutches – Pinched Track
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 1f: Slipping of Clutches – Take-Up Sleeves Installed Backwards
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 1f: Slipping of Clutches – Take-Up Sleeves Installed Backwards
Remove the take-up units and replace as described in the instructions provided with the equipment.

Explanation 1g: Slipping of Clutches – Drive Unit Caterpillar Chain Damaged
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 1g: Slipping of Clutches – Drive Unit Caterpillar Chain Damaged
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 1h: Slipping of Clutches –Drive Head and Idler Shaft out of Alignment
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 its 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 1h: Slipping of Clutches –Drive Head and Idler Shaft out of Alignment
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 1i: Slipping of Clutches – Drive Unit Installed Backwards
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 1i: Slipping of Clutches – Drive Unit Installed Backwards
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 1j: Slipping of Clutches – Drive Unit Clutch Friction Liners Worn Out
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 1j: Slipping of Clutches – Drive Unit Clutch Friction Liners Worn Out
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 1k: Slipping of Clutches – Worn Conveyor Track Curves
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 1k: Slipping of Clutches – Worn Conveyor Track Curves
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 1l: Slipping of Clutches – Pendant, Hook, or Load Hang-ups
A clutch may slip if the product hook or product catches and hangs up on a conveyor guard, building steel, washer, etc. Also, a production worker will often accidentally jam the drive by hooking the product carrier on a column or other stationary object.

Correction 1l: Slipping of Clutches – Pendant, Hook, or Load Hang-ups
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 1m: Slipping of Clutches – Chain Corrosion from Process Equipment
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 phosphoric 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 1m: Slipping of Clutches – Chain Corrosion from Process Equipment
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 1n: Slipping of Clutches – Sub-freezing Temperatures
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 1n: Slipping of Clutches – Sub-freezing Temperatures
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.


Problem 2: Pulsating Chain

Causes:

  1. Slack Chain
  2. Misaligned Track Joints
  3. Excessive Chain Pull
  4. Pinched Track
  5. Excessive Chain Length
  6. Defective Drive

Explanation 2a: Pulsating Chain – Slack Chain
If too much slack chain is allowed to develop in a conveyor, and especially in a long system, the chain will accelerate and coast enough to telescope. This stops it momentarily, after which it surges ahead. The action described is due, in large part, to the normal elasticity of the chain. The longer the chain, the more pronounced is the surge. Also, the greater the chain pull, the greater the surge.

Correction 2a: Pulsating Chain – Slack Chain
Adjust the take-up to remove slack. In a long or level conveyor, it is preferable to use a spring loaded, counterweighted or an air operated take-up located just downstream from the unit. The automatic take-ups may be adjusted to keep a slight tension on the chain which absorbs some of the elasticity, thus reducing the surge.

Explanation 2b: Pulsating Chain – Misaligned Track Joints
Misaligned track joints interrupt the free movement of the chain wheels. While the chain may not jam, a step at the juncture of the tracks causes the wheels to stop momentarily until chain tension increases enough to pull through. Again, elasticity allows the chain to stretch until the wheels break loose. If this is the problem, the chain will surge in 6" increments, which is the vertical chain wheel centers. Usually, the offending joint can be located by inspecting the chain movement, starting at the drive and moving downstream to where the surge stops or lessens.

Correction 2b: Pulsating Chain – Misaligned Track Joints
If one track is actually offset from the other, correction is made easiest by sawing through the joint and re-welding after alignment with a TR-155 welding jig. Care should be taken to remove any weld deposits from inside the track prior to rewelding.

Explanation 2c: Pulsating Chain – Excessive Chain Pull
Systems having excessive chain tensions will often pulsate. The condition is usually more evident just downstream from the drive. Also, it will be noted that the erratic action diminishes gradually all the way back to the drive where the movement is smooth. Again, the longer the chain the worse the pulsating will be.

Correction 2c: Pulsating Chain – Excessive Chain Pull
To locate the cause of the excessive chain pull, the conveyor chain should be inspected first to insure that it is adequately lubricated and that the lateral chain wheels are not worn sufficiently to cause the vertical chain wheel to slide around the horizontal track curves. If the latter is the case, the chain must be replaced. Should the problem be lubrication, the chain must be lubricated thoroughly. Should the pulsation persist, determine the product loads (by weighing), load centers and then calculate the draw bar pull. This will probably indicate the need for an additional drive. Also, in the process of determining the pull, the second drive unit can be located.

Explanation 2d: Pulsating Chain – Pinched Track
At start up of a new or revised conveyor, very often a damaged piece of straight or curved track finds its way into the system. This is usually discovered when the conveyor chain is installed. At other times, the track is shifted after erection and possibly re-welded. In any event, the track side walls may close in at one point to create an obstruction sufficient to produce pulsation in the chain.

Correction 2d: Pulsating Chain – Pinched Track
The pinched track may be located by following the instructions set forth in #2.2. Once located, the problem is easily corrected by hitting the center of the track on top with the spherical end of a ball peen hammer. If the track sides should be bent inward, the piece in question must be replaced.

Explanation 2e: Pulsating Chain – Excessive Chain Length
Any given conveyor with an unusual number of vertical and horizontal curves plus great length will have a tendency to pulsate, regardless of the draw bar pull. As indicated earlier, the chain is elastic to a degree and the elasticity is accentuated by length. Therefore, lubrication must be adequate, chain slack must be held to a minimum and the track joints must be smooth.

Correction 2e: Pulsating Chain – Excessive Chain Length
Corrective action may be taken as outlined in #2.1. If this fails to achieve a proper operation, an additional drive must be installed.

Explanation 2f: Pulsating Chain – Defective Drive
If a conveyor should be pulsating just back or upstream of the drive unit, it would indicate a problem in the drive.

Correction 2f: Pulsating Chain – Defective Drive
By removing the caterpillar chain and one side of the drive chain track, it may be found that the caterpillar dogs are not seating down into the lateral chain links. This can occur if the chain is elongated beyond 1/4" per foot; the caterpillar chain is damaged or out of alignment; the drive chain guide is bent or; the motor drive chain is loose and bouncing up and down. An inspection of all drive components is necessary and corrections made as indicated.


Problem 3: Premature Wearing of Conveyor Chain

Causes:

  1. Lack of Lubrication
  2. Exposure to Abrasives
  3. High Temperatures
  4. Corrosion
  5. Drives out of Location
  6. Drives out of Coordination

Explanation 3a: Premature Wearing of Conveyor Chain – Lack of Lubrication
A customer may fail to lubricate the conveyor chain because of inadequate maintenance, lack of an oiler, or fear of drippage. In any case, when the chain is not lubricated, the useful life will be drastically decreased. Without an oil film, the connecting pin joints and bearings will wear rapidly. Also, the chain tension will mount to accelerate wear.

Correction 3a: Premature Wearing of Conveyor Chain – Lack of Lubrication
Ask the customer's lubrication supplier to recommend a proper lubricant, taking into consideration the operating conditions with special attention to temperatures. If the fear of contamination is great, recommend a #LU-669-A oiler which can be regulated to apply the proper amount of material. Also, the oiler should be placed in a section of conveyor where the product is not transported to.

Explanation 3b: Premature Wearing of Conveyor Chain – Exposure to Abrasives
Oftentimes the conveyor will be placed in or near a shot and/or sand blasting machine, or in an area where the air is heavily laden with abrasive particles. The abrasives do find their way into the chain wheel bearings. The oil on the chain actually attracts and holds the gritty substance. In some cases, the bearings clog and the wheels will not rotate. If they do continue to turn, the abrasive dust grinds away the bearing cones, races and balls. The chain will, of course, only function for a short period before replacement is necessary.

Correction 3b: Premature Wearing of Conveyor Chain – Exposure to Abrasives
In the case of shot or sand blast machine, the conveyor should be located over the machine cabinet tops. Product hooks can then be suspended through a very narrow slot in the cabinet top with rubber seals at both sides. In other situations, the Protectaire equipment can be used to prevent the abrasive dust from entering the conveyor track.

Explanation 3c: Premature Wearing of Conveyor Chain – High Temperatures
Burn-off and glass tempering ovens, plus certain other types of equipment operate at temperatures reaching 1000 Degrees F. and higher. When Zig-Zag, or any other overhead conveyor, is exposed to any temperature above 450°F., the hardening heat treated parts such as pins, wheel cones, races and balls, are softened by annealing. the drop in hardness is in direct relation to the temperature involved. Since the parts mentioned are heat treated (60 Rockwell, C scale) to accommodate certain loading, any hardness reduction accelerates wear.

Correction 3c: Premature Wearing of Conveyor Chain – High Temperatures
Remove the conveyor from the heat zone by slotting the top of the oven and installing continuous cover plates on the conveyor. Also, replace the conveyor chain.

NOTE: Please consult the factory for quotation and design for this application.

Explanation 3d: Premature Wearing of Conveyor Chain – Corrosion
Chain life is drastically shortened when it is exposed to corrosive substances, and particularly acids. The problem usually occurs when the conveyor is used to transport parts through certain washers, paint strippers, etc.

Correction 3d: Premature Wearing of Conveyor Chain – Corrosion
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 3e: Premature Wearing of Conveyor Chain – Drives out of Location
In multi-drive systems, the placement and number of drives is critical. An error in this procedure can cause replacement of conveyor chain at short intervals. It is easy to induce extra tension in the chain by placing a drive just upstream from a loaded decline. The force generated by the decline offers help to the drive motor and since all motors in a given system have equal torque, the chain tension is increased.

Correction 3e: Premature Wearing of Conveyor Chain – Drives out of Location
Relocate drives to eliminate the problem.

NOTE: Space does not allow for a complete instruction in drive placement. Also, each system presents its own requirements. Therefore, troublesome jobs should be submitted to the factory for analysis.

Explanation 3f: Premature Wearing of Conveyor Chain – Drives out of Coordination
In certain multi-drive systems, the drive motors fail to coordinate or work together. Resulting abnormal tensions accelerates wear of the chain.

Correction 3f: Premature Wearing of Conveyor Chain – Drives out of Coordination
This requires that a complete check of the drives be made as follows: Check all name plates. They must be identical except for the serial numbers. Check all motor drive sprockets. All must have the same number of teeth. Check caterpillar drive sprockets. These must all have the same number of teeth. If it is a constant speed arrangement with a three stage variable transformer, also check the settings. To adjust, the voltage should be reduced gradually until the conveyor stops. Push stop button, advance voltage control about one tenth of a revolution and push start button.

Check amperage at each motor. If any motor or motors should indicate readings much higher than the others, this motor should be sent to motor repair for checking and correction.