7.1.6 Troubleshooting and Problem-Solving

If you find something wrong with a chain during start-up or regular inspection, it may require treatment or you may need to replace it with a new chain. A variety of problems and their solutions is shown in Figure 7.14.

Symptom	Possible Causes	Remedy
Chain is riding up on the sprocket.	The chain and sprocket do not match.	Replace the chain or sprocket with the correct size.
	Excessive load	Decrease the load, or increase the number of strands or size of the chain.
	Elongation of the chain due to chain wear or excessively worn sprocket teeth	Replace with new chain and sprockets.
Unusual noises	Improper installation of the sprocket or axle.	Inspect and correct.
	Chain casing or bearings are loose.	Tighten all bolts and nuts.
	Excessive or insufficient slack in the chain.	Adjust the distance between axles to obtain the proper amount of slack.
	Excessive worn chain or sprocket.	Replace the chain and sprocket with new chain and sprocket.
	Not enough lubrication.	Provide proper lubrication according to the operating conditions.
Excessive vibrations in chain.	Chain is resonating with a periodic external force.	Change the chain's mode of vibration. Preventing resonance. To change the natural frequency of the chain. Alter the effective tension either by applying an initial tension or adjusting the existing one. Install a tensioner to change the chain span. Replace the chain. Choose a different quality and spring coefficient. Change the vibration frequency. Change the speed of rotation of the sprocket. Re-evaluate the device set-up. Mechanically reducing the vibrations. Install a guide shoe. Install a self-adjusting tensioner on the slack side.
Excessive vibrations in chain.	Load fluctuations are excessively large.	Reduce fluctuations with fluid coupling or similar technique.
The chain winds onto the sprocket (poor separation from the sprocket teeth).	Span between axles is too large.	Install an idler.
	Excessive slack in chain.	Adjust the chain length or distance between axles. Install a tensioner.
	Elongation of the chain due to chain wear or excessively worn sprocket teeth.	Replace with new chain and sprocket.
Rusting of the chain.	Improper lubrication or poor environment.	Replace chain and protect it from the environment with chain casing or proper lubrication.
Excessive wear at the inside surface of link plates and sides of sprocket teeth.	Improper installation.	Correct sprocket and axle installation.
Excessive wear at the link plate side surfaces and pin heads.	Improper installation of guides, etc.	Check the condition of the guides, and increase the gap between the guides and chain.

Figure 7.14 (i) Troubleshooting Chain Symptoms and Remedies Transmission Chain, Small Conveyor Chain

Symptom	Possible Causes	Remedy
Improper flex or bending of chain, tight joints.	Chain is not installed correctly.	Inspect the installation and correct as necessary.
	Contamination from metal dust or dirt because of improper lubrication.	Remove the chain, wash it thoroughly, and provide proper lubrication.
	Excessive load or bent pin.	Reduce the load or increase the number of or size of chains. Replace chain with a larger size.
	Corrosion or rusting.	Install a chain casing to protect the chain.
	Seizing from improper lubrication.	Provide proper lubrication according to the operating conditions.
	Seizing of pin and bushing. Pin and bushing seized from high-speed operation. This causes improper bending and can lead to chain breakage.	Provide the proper operating conditions.
Spreading of link plates	Uneven or excessive loading caused by improper installation.	Replace with new chain and correct installation.

Figure 7.14 (i) Transmission Chain, Small Conveyor Chain (Cont.)

Symptom	Possible Causes	Remedy
Breakage of link plate	Excessively large shock load.	Reduce shock loads by making the start-up, stopping, and other actions smoother (installing a shock absorber, etc.). Increase the size or number of chains.
	Vibrations in the chain.	Install an anti-vibration device (for example, tensioner or idler). Refer to "Excessive vibration in chain."
	Large inertia in the driven machine (excessive load).	Increase the size or number of chains.
	Corrosion.	Replace with a new chain. Install a casing to protect the chain. Otherwise, periodically clean the chain.

Figure 7.14 (ii) Link Plate

Symptom	Possible Causes	Remedy
$Static fracture$ (1) $Fatigue fracture$ (2) (3) (1) Static fracture. Stretching the link plate with a tensile load beyond its breaking load will cause it to stretch and then break. (2) Fatigue fracture. By repeatedly applying a load past its fatigue limit (fatigue strength), the fatigue will start at holes and then suddenly break. (3) Offset plate fatigue. Offset plates are bent at the center, and the resulting concentration of stress at the bend can cause a fatigue break. Avoid using offset links in high-stress applications.
Cracks in the link plates (fatigue), which are perpendicular to the direction of pull.	Loads are greater than allowable.	Remove all large or excessively repeating loads. Otherwise, increase the size or number of chains. Replace with a new chain.
Deformation in the link plate holes.	Excessive load.	Remove the cause of the excessive load. Replace with a new chain.
Corrosion stress cracks appear, usually as bow-shaped cracks in the link plate.	The chain is being used in an acidic or alkaline environment. (This is not caused by a repetitive load.)	Install a casing to protect the chain from the environment. Consider a chain with a high resistance to corrosion stress cracks. Replace with a new chain.

Figure 7.14 (ii) Link Plate (Cont.)

Symptom	Possible Causes	Remedy
Breakage of pin	Excessively large shock load.	Reduce shock loads by making the start-up, stopping, and other actions smoother.
	Subject to a repetitive load greater than the fatigue limit of the pin.	Remove the large repetitive load. Otherwise, increase the size or number of chains.
	Corrosion.	Install a casing to protect the chain. Periodically clean and lubricate the chains.
$Static fracture$ (1) $Fatigue fracture$ (2) $Shock-induced bending fracture$ (3) (1) Static fracture. The type of fracture found when subjecting the chain to the breakage test. Occurs when chain is subjected to a load greater than its breakage strength. (2) Fatigue fracture. Occurs when the pin is repetitively subjected to loads greater than its fatigue limit. Recheck the size of the peak load and formulate a countermeasure. (3) Shock-induced bending fracture. The pin is subjected to a large shock load. A pin is especially susceptible to this when the surface is corroded.

Figure 7.14 (iii) Pin

Symptom	Possible Causes	Remedy
Pin rotates or begins to stick out.	Excessive load or improper lubrication.	Replace with new chain. Improve the lubrication or loading conditions.
Pin rotates or begins to stick out.	Operating a chain at high load without proper lubrication can create friction between the pin and bushing, causing the pin to rotate. In this condition, the pin may come out, leading to chain breakage.	Replace with new chain immediately. Do not weld or reuse the pins. (Dispose of the old chain to be sure that it is not used by mistake.) Also, if the pin head or link plate surface is worn, check the installation.
Wear or rust occurs only at the connecting pin in a tension application or similar operation.	Improper initial lubrication at installation.	Replace the connecting link. If pin wear is excessive, replace the chain also. Take special care to properly install the connecting section for devices such as terminators used for tension applications.

Figure 7.14 (iii) Pin (Cont.)

Symptom	Possible Causes	Remedy
Roller and/or bushing splits and falls off.	Excessive load or speed of rotation.	Choose a different chain according to the transmission capacity table.
Roller and/or bushing splits and falls off.	Inadequate lubrication.	Replace the chain. Provide adequate lubrication according to the operating conditions.
Fatigue fracture $Fatigue fracture$ Reached the point of fatigue during operation and eventually broke. Impact by the sprocket teeth at a force exceeding the chain's transmission capacity.
Roller does not rotate.	RS11SS, RS15, RS25, RS35.	A bushed chain and not a roller chain is being used.
	The inner plate is moving inward, or the bushing is cracked.	Replace with a new chain. Re-inspect the installation and load conditions.
	Foreign particles have gotten between the bushing and roller.	Periodically clean the chain. Install a casing to protect the chain.
Roller is opening up	Excessive load.	Reduce the load. Provide adequate lubrication.
Roller is becoming hourglass shaped	Excessive load or inadequate lubrication.	Replace with new chain. Improve the lubrication or loading conditions.

Figure 7.14 (iv) Bushing/Roller Problems