Basics
Symptom (2) Corrosion stress crack. (Bow-shaped crack in heat- treated metal plates.)
Possible Causes The chain is being used in an acidic or alkaline environment. (This is not caused by a repetitive load.)
Remedy Install a cover to protect the chain from the environment. Replace with new part. Use a chain with a high resis- tance 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 connecting link.
Replace connecting link with a 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 versus the breakage load was too small. The peak load acted like a repetitive load on the chain. The pin was subjected to a tensile load at the side of the fracture origin, where the break then progressed. Chain is especially suscep- tible 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).
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.
The chain is contaminated with especially abrasive materials, such as mineral pow- ders, etc., being worn away by the chain surface itself.
Excessive wear caused by the conveyed material. The surface is worn away.
Prevent material from falling onto the chain. Use a wear-resistant chain.
Excessive wear from corro- sion. Link plates not made from an anti-corrosive materi- al are corroding.
The chain is exposed to acidic or alkaline substances, and, therefore, more suscepti- ble to machine wear, which then progress- es 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 affected by the chemicals. Use a wear-resistant material for the machine-worn parts.
Figure 7.19 (iii) Troubleshooting Large Pitch Conveyor Chain
84
Made with FlippingBook Digital Proposal Creator