Handling Roller Chain/Sprocket Maintenance and Inspection
(1) Need to Know When Installing
- Chain elongation is mainly caused by wear between pin and bushing.
- Roller chains are usually pre-lubricated with rust prevention oil before shipment. Don't wash out or remove this pre-lubricated oil when installing. Or don't put roller chain on the floor where dust or foreign material may exist.
(2) Guideline for Replacement
- When chain elongation reached ＋1.5% (except guideline may be less when sprocket has more than 60 teeth).
- When link plate has some damage like crack, distortion, etc.
- When any other parts has harmful damage like crack , or chain has irregular movement.
- When pin has bending or warped, or distortion of link is found.
- When substantial rust or improper flex of chain is found.
It is strongly recommended to replace whole chain. Replacing by some parts partially is never recommended.
(3) Check Oil Lubrication
- Periodically remove one chain, clean with Kerosene and apply fresh oil.
Never use acidic, alkaline liquid, gasoline, or benzine.
- Remove powdered and foreign material as these cause wear of chain.
- Washed out metal surface is easy to get rust, apply oil lubricant quickly.
- If surface of pin and bushing are keeping shiny and smooth surface, it is a evidence oil lubrication is appropriate and re-application with same manner is recommended.
(4) How to Measure Chain Elongation with Caliper
Roller chain length is usually measured applying one % of average tensile strength. In case chain installed, measure two dimensions shown by L1 and L2 in the following figure at tension side.
- To make accurate data, measure at least 6 links.
(5) How to Measure Chain Elongation with Tape Measure
To avoid inaccurate measurement, remove chains, put them in line, and measure all or almost all links.
Inspection of Roller Chains and Sprockets
(1) Running Inspection
- Are the chains and sprockets attached correctly ?
- Are the T pins etc. correctly attached at chain joints ? (Note the degree of pin bending).
- Is chain take up tension appropriate ? (Is the chain too slack or too tight ?).
- Are there any foreign bodies that impede the motion of the chain ?
- Is the chain properly oiled ?
- Does the chain make any abnormal sound (vibration, noise, etc.) when it moves ?
(2) Daily Inspection
- Is there any abnormal vibration or noise ?
- Is the chain visibly corroded, dirty etc. ?
- Are there any abnormalities in the chain components ? (Particularly damage, deformation, uneven wear, breakage etc. of link plates and rollers).
- Do the chains and sprockets mesh smoothly ?
- Does the chain flex and the rollers roll smoothly ?
- Is there any wear extension in the chain ?
- Is there any abnormally uneven wear at points of contact between the chains and sprockets (inner faces of inner plates, sides of sprockets) ?
- Is chain tension appropriate ?
- Is the chain oiled appropriately ? (Is meshing with sprockets noisy ?)
(3) Regular Inspection
- Carry out visual and measurement inspections as described in (1) and (2) above while the chain is running, at rest and removed.
- Regular inspection should be tailored to the environment and conditions of use. Increase the frequency of inspection when conditions are harsh.