7.2.6 Troubleshooting and Problem-Solving
If you find something wrong with a chain during start-up or regular inspection, it may require treatment as shown in Figure 7.19, or you may need to change to a different type of chain.
| Symptom | Possible Causes | Remedy |
|---|---|---|
Excessive wear at the inside of the chain's link plates or the teeth surfaces. | Improper centering of the sprocket. | Remove the chain and correct the centering of the drive and driven sprockets. |
| The chain is being pushed to the side. | Remove the cause of the push and/or install a guide roller. | |
| Vibration caused by the inaccurate finishing of the sprocket's axle hole. | Check and correct the faulty locations and replace the sprocket with a new part. | |
| Improper flex or bending of the chain. | Rusting or corrosion. | Install a partition to protect the chain. Select a chain of suitable specification (for example, MT type). |
| Particles of the conveyed material have contaminated the pin, roller, and bushings. Otherwise, contamination from foreign particles. | Install a partition to protect the chain. Select a chain with large clearance between the pin, bushing, and roller. | |
| Deformation of the chain caused by improper installation. | Inspect and correct the installation of the sprockets and axles. | |
| Inadequate lubrication. | Inspect the lubrication or look into wear-resistant chain (for example, CT or BT specification). | |
| Operation in extremely high temperatures (over 400°C). | Provide adequate clearance. | |
| Seizure from excessive loads. | Provide periodic lubrication. Reduce load. | |
| Pin bending due to excessively high loading. | Reduce load. | |
| The chain is winding on the sprocket. | Too much slack in the chain. | Adjust the chain length or distance between axles, or install a tensioner. |
| Excessively worn sprocket. The chain and sprocket do not match. | Replace the chain and/or sprocket with the correct-sized part. | |
The chain is climbing up on the sprocket. | The chain and sprocket do not match. | Replace the chain or sprocket with the correct-sized part. |
| The total arc of contact with the chain on the sprocket is insufficient. | Have the total arc of contact be at least three teeth on the sprocket. | |
| Excessive load. | Reduce the load (for example, by installing a shock absorber). | |
| Inadequate back-tension. | Adjust the catenary or take-up idler, or install a tensioner. | |
| Excessive elongation of the chain due to wear. | Replace with a new chain. | |
| The distance between the center of the chain and the sprocket do not match. | Inspect and correct. | |
| Unusual noises. | Inadequate lubrication to the contacting portions of the pin and bushing. | Provide sufficient lubrication. |
| Inadequate lubrication to the contacting portions of the bushing and roller. | Provide sufficient lubrication. Use a bearing roller or plastic roller. | |
| Winding or rising on the sprocket. | See previous symptom. | |
| Loose chain casing or axle bearing. | Tighten all nuts and bolts. | |
| Interference of the casing with the chain or other moving part. | Inspect and correct. | |
| Excessive wear in the chain or sprocket. | Replace the chain or sprocket. (Replace all chains connected.) | |
Improper setting of the guide rail. | Inspect and correct. | |
| Rusting of the chain. | Inappropriate selection of material. | Select a more suitable chain material. Protect the chain from the environment. Apply a rust inhibitor. |
| Condensation. | Eliminate the temperature difference between inside and outside of conveyor (using insulation, etc.). | |
| Improper roller spin and uneven roller wear. | Excessive load on roller. | Provide sufficient lubrication. Consider bearing roller or GT chain specification. |
| Particles of the conveyed material, or other foreign particles, have gotten between bushing and roller. | Periodic cleaning. Install partition to protect chain. | |
| Particles of the conveyed material, or other foreign particles, have built up onto the rail. | Periodic cleaning. Install partition to protect chain. | |
| The lubricant is falling on the roller surface and rail without entering between the bushing and roller, and between the roller and link plate. | Select the appropriate lubricant and lubrication method. | |
| The bushing and roller have rusted together. | Select the appropriate specifications (RT, etc.). | |
| The inner plate is moving sideward. | Replace with a new chain. Re-inspect the installation and load conditions. | |
| The bushing is cracked. | Reduce the load and lower the speed of rotation. | |
| The side surface of the roller is contacting the side of the link plate due to a thrust load. | Eliminate the cause of the thrust load. | |
| The chain and sprocket do not match. Excessively worn teeth. | Check for tooth deformation. |
Figure 7.19 (i) Troubleshooting Large Pitch Conveyor Chain
| Symptom | Possible Causes | Remedy |
|---|---|---|
| The roller is opening up. | Excessive load. | Reduce the load, provide adequate lubrication, remove any large steps in the rail. |
| The roller or bushing is split (falling off). | Excessive load. | Reduce the load. Provide adequate lubrication. |
| The number of teeth is to few with respect to the conveyor speed. | Increase the number of teeth. Decrease the speed. | |
| The roller is becoming hour-glass shape. | Excessive load or inadequate lubrication. | Increase the lubrication, improve loading conditions, and replace the chain with a new one. |
| Excessively worn rail. | Correct or replace the rail. | |
| The chain sticks and slips. (This can be caused by a combination of many problems. Therefore, the listed remedies may not solve the problems.) | Change the rolling friction coefficient of the chain. | Lubricate the chain and clean the rail. Lubricate with Tsubaki oil. Change to a bearing roller chain. |
| The conveyor speed is too slow. | Increase the speed. | |
| Insufficient rigidity in the frame. The conveyor chain is small compared to the device. | Increase the frame rigidity, increase the chain model number. Decrease the slack in the drive roller chain. | |
| The force of friction is excessively large. | Lubricate the chain. Change to a bearing roller chain. | |
| The machine is too long. | Divide the conveyor system into sections to decrease the length. | |
| Inconsistent speeds due to movement along a polygon-shaped path. | Use a 12-or-more-toothed drive sprocket. | |
| Excessive wear of the sprocket teeth valleys and drive sides. | Excessively worn chain. | Replace both the chain and sprocket. |
| Insufficient number of teeth. | Increase number of teeth. | |
| A BF chain (no rollers) is being used. | Change to an RF chain (with rollers). | |
| The hardness of the teeth is insufficient with respect to the load and conveyed material or foreign particles. | Use a sprocket with hardened teeth or changeable teeth. | |
| The chain and sprocket do not match. | Replace the chain or sprocket with one that is of the correct size. | |
| Excessive wear of the inside link and pin on one side of an NF block chain or BF chain (no roller). | Increase internal tension when meshing with the sprocket. | Attach the supporting block to the sprocket. Reduce the load. Lubricate the chain and sprocket. |
| Sudden fracture of the link plate. | Excessive load. | Eliminate causes of the overloading. Install a safety device (for example, Shock Relay). Increase chain size. |
| Weakening of chain caused by excessive wear or corrosion. | Replace with new part. Install a cover to protect the chain. Periodically lubricate the chain. Select a chain with the proper specifications for the application. | |
The link plates are pressed outward by the sprocket. | Check and correct the installation. Excessively worn chain or sprocket. Check if the chain and sprocket match, and correct as necessary. | |
| Crack in the link plate. (1) Fatigue breakage.  | Excessive load or excessively large repetitive load. | Eliminate overloading or large repetitive loads. |
| The factor of safety is not sufficient. | Increase the size or specifications of the chain to increase the factor of safety. | |
| Repetitive load on attachment. | Eliminate overloading or large repetitive loads; increase the chain size to increase the allowable load of the attachment. |
Figure 7.19 (ii) Troubleshooting Large Pitch Conveyor Chain
| Symptom | Possible Causes | Remedy |
|---|---|---|
(2) Corrosion stress crack. (Bow-shaped crack in heat-treated metal plates.) | The chain is being used in an acidic or alkaline environment. (This is not caused by a repetitive load.) | Install a cover to protect the chain from the environment. Replace with new part. Use a chain with a high resistance to corrosion stress cracks. |
Deformed link plate holes and pin rotation (the pin is shifted from its normal position). | Excessive load. | Eliminate the cause of overloading and replace chain with a larger size. |
| Improper installation of the connection link. | Replace connecting link with new one. | |
| Excessive load and inadequate lubrication. | Replace with a new chain and improve the lubrication and loading conditions. | |
| Seizure of the pin and bushing, improper bending or flex of the chain. | Increase the chain size. Increase the clearance between the pin and bushing. | |
| (1) Pin fatigue fracture. (2) Pin corrosive fatigue. (3) Pin brittle fracture. (4) Pin sudden fracture.  | The factor of safety used for calculation of the peak load was too small. The peak load acted like a repetitive load on the chain. | Recheck the size of the peak load, and eliminate its cause. Replace the chain with a larger size (larger pin diameter). |
| The pin was subject to a tensile load at the side of the fracture origin, where the break then progressed. Chain is especially susceptible to this when the pin surface is corroded and weak against bending stresses. | Recheck the size of the peak load, and eliminate its cause. Replace the chain with a larger size (larger pin diameter). Use a pin made of an anti-corrosive material. | |
| Poor environment. | Use an appropriate pin material. | |
| Excessive load. | Eliminate the cause of overloading, and replace chain with a larger size. | |
Excessive wear caused by the conveyor material. The surface is worn away. | The chain is contaminated with especially abrasive materials, such as mineral powders, etc., being worn away by the chain surfaces itself. | Prevent material from falling onto the chain. Use a wear-resistant chain. |
Excessive wear from corrosion. Links plates not made from an anti-corrosive material are corroding. | The chain is exposed to acidic or alkaline substances, and, therefore, more susceptible to machine wear, which then progresses much faster. | Use a material not affected by the chemicals. Use a wear-resistant material for the machine-worn parts. |
Excessive wear from electro-chemical corrosion. Only the contact surfaces are worn. | When the chain is covered with water or passes through a solvent, the portions in contact suffer galvanic corrosion. | Use a material not effected by the chemicals. Use a wear-resistant material for the machine-worn parts. |
Figure 7.19 (iii) Troubleshooting Large Pitch Conveyor Chain
