How to inspect your roller chain

Check our roller chain inspection list to find out the probable causes of roller chain wear and action suggested to take.

Check List 

1. Noise or vibration

Abnormal condition and inspection method – Abnormal noise or vibration occurs when chain is operating.

Correction – Check the chain tension, tightness and wearing. ; confirm whether the chain hit other parts during operating.

2. Chain tightness

Abnormal condition and inspection method – Rotate the sprocket to tighten one side of the chain, then measure the mid-span movement of the other side as below graph S-S’ slack span.

(1) When the angle is less than 45° between center line of the sprockets and the horizontal, the amount of S-S’ movement should be 2% ~ 6% of shafts center distance (A – B).

(2) When the angle is more than 45° between center line of the sprockets and the horizontal, the amount of S-S’ movement should be 1% ~ 3% of shafts center distance (A – B). 

(3) In following conditions, the amount of S-S’ movement should be 1% ~ 3% of center distance (A – B).

• Distance between the shafts is more than 1 meter.
• Frequently start and stop under heavy loading
• Chains is forwarder and reverse conversion motion

Correction – Adjust to the correct tightness or adjust with an idler.

3. Lubrication

Abnormal condition and inspection method – Visually check the appearance of the chain and whether there is enough oil in the chain links. If there is black or rust-colored iron powder seeping between the chain links, it shows that the lubricating oil inside the links is insufficient.

Correction – Re-lubricate the chains. Check the chain wear and see if there is tight joints, rollers proper rotation and turning pins. Replace the whole chains if necessary.

4. Rollers

Abnormal condition and inspection method – Check if the roller can be rotated freely by turning it by hand. Visually inspect the rollers for damage, cracks or wear.

Correction – Check if lubricating oil is sufficient. Re-lubricate if necessary. If the rollers are damaged or cracked, the chain must be replaced.

5. Chain wear inspection

Abnormal condition and inspection method – After the chain is used, the chain length would extend because of the friction and wearing between pins and bushings. By measuring the elongation, we can know if whether the chain has reached the service life or not.

How to measure chain elongation – Straighten the chain and apply some force to eliminate the gap between the chain links. Measure the length of 6~10 links with a caliper, as shown in the figure below.

The elongation limit (wear rate) of chain service life is related to the number of large sprocket teeth.

• Less than 60 teeth: 1.5%
  
• 61~80 teeth: 1.2%
• 81~100 teeth: 1.0%
• 101~110 teeth: 0.8%

Correction – If elongation reaches the limit, please replace the chain.

6. Tight joints

Abnormal condition and inspection method – Twist the chain links up and down to see if the chain can work freely. If the chain is stuck cannot twist freely, it shows that the chain may have tight joints.

Correction

• Please clean the chain if dirt or foreign substance is packed in joints. 
• Check whether the chain is worn out. 
• Check the lubrication status and re-lubricate if necessary. 
• If there is no improvement after re-lubricating the chain, please replace the chain.

7. Turned pins

Abnormal condition and inspection method – Visually inspect the direction of the pin riveting and check if there is any rotation.

Correction

• Check whether the chain is overloaded or insufficiently lubricated.
• If pins rotate, please replace the chain.

8. Enlarged Holes

Abnormal condition and inspection method – Visually check the chain link holes for elongated (elliptical) shapes.

Correction 

• Check whether the chain is overloaded.
• If the chain is overloaded, replace the chain with larger size or higher-strength chain

9. Cracked and fractured plates

Abnormal condition and inspection method – Visually check if there are cracked and fractured plates.

Correction

• Check whether the chain is overloaded.
• If the chain is overloaded, replace the chain with larger size or higher-strength chain.
• Check if the chain is exposed to corrosive environments or chemicals.
• If exposed to the harsh environment, replace the chain with corrosion resistant roller chain.

10. Worn plates

Abnormal condition and inspection method – Check plates height (H). The amount of side plates wear should not exceed 5% of the plate height (H). It would influence the strength of the chain.

Correction

• Use chain guide or wear strip
• Replace the chain if worn out exceed 5%.