Roller Chain - Tsubaki

Roller ChainInstallation & Maintenance7. Precautions for Use in Damp, Corrosive and AbrasiveEnvironmentsWhere possible, roller chain should be used in clean environments. When roller chain is used in damp, corrosive or abrasiveenvironments follow these precautions:7.1 Use in damp conditionsIf the chain is exposed to water or steam the following problems may occur.1)An increase in abrasive stretch due to improper or insufficient lubrication.2) Decrease in fatigue strength from rust and corrosion (pitting) of the chain.A) Countermeasures(I) Reduce bearing pressure using a larger sized chain to improve wearresistance.(II) Use corrosion resistant roller chain for rust prevention.Drive Chain7.2 Use in corrosive conditionsIf roller chain is exposed to acids or alkaline conditions, such as battery acid andliquid used in plating processes, the following problems may occur.1) Embrittlement fracture of link plates and pins.2) Fatigue breakage of link plates and pins due to rust and pitting corrosion.3) Wear from usual mechanical abrasion and corrosion.4) Reduction in volume of the whole chain from corrosion.5) In special cases where the chain is underwater (immersed in liquid), electro-chemicalcorrosion may occur.6) There are also circumstances where even stainless steel roller chain will corrode.Fig. 31 shows an example of chain that was used in a plating apparatus. The chainfell to pieces within one month due to the affect of the acid.A) Countermeasures for embrittlement fractures (stress corrosion cracking):(I) Adopt a brittleness countermeasure that lowers crack susceptibility.(II) Install a cover or casing to prevent acids or alkalis from contacting the chain.(III) Adopt a high-grade material with anti-corrosive properties.B) Countermeasures for corrosion:(I) Use surface-treated chain.(II) Install a cover or casing to prevent acids or alkalis from contacting the chain.(III) Adopt a high-grade material with anti-corrosive properties.Fig. 31 Corrosion of stainless steelroller chainFig. 32 Hydrogen embrittlementcrackingIn general, embrittlement fractures (stress corrosion cracking) occur around the link plate holes. This is the area where the pin andbushing are press-fitted to the link plate. This area has the highest concentration of stress. Cracks are generated even when there isno tension on the chain. Roller chain in general is more susceptible to acids than alkalis, and in special cases, embrittlement fractures(stress corrosion cracking) are generated by seawater or pit water.7.3 Use in abrasive conditions where abrasion is a problemIf the chain is exposed to strong abrasive materials (eg. sand and metal particles), the following problems may occur:1) When the abrasive materials penetrate between the pins and bushings, chain wear is accelerated and poor articulation results.2) When the abrasive materials penetrate between the bushings and rollers, chain wear is accelerated and poor roller rotation results.3) When the abrasive materials penetrate between the link plates, poor articulation results.A) How to prevent abrasion.(I) Apply a dust-cover.(II) Remove foreign particles by regularly washing the roller chain.(III) Reduce bearing pressure by using a larger sized chain to improve wear resistance.(IV) Increase abrasion resistance by applying special processing to the parts of the chain where abrasion is a problem.A-117