Basics
5.4.2 Use in Acidic, Alkaline, or Electrolytic Conditions If chain is exposed to sulfuric acid or nitric acid, the following problems may occur: • Increase in wear due to chemical corrosion beyond normal mechanical wear. • Brittle failure of chain parts (especially plates). • Decrease in strength due to corrosion. • Shortened chain fatigue life due to oxidization or corrosion. A chain exposed to an electrolytic liquid, such as sea or mine water, may develop pitting corrosion, electrocorrosion, or electrochemical corrosion. There are chains that resist these types of corrosion. Table 5.3 shows examples of typical corrosion resistance of each chain type. In general, the corrosiveness changes based on the strength and temperature of the liquid. Use the informa- tion in Table 5.3 only as a reference. Select chains after thorough testing. 5.4.3 Use in Abrasive Conditions Strong abrasive materials, such as sand, coke, metal particles, or substantial amounts of dust in the air may affect the wear life of a chain. The particles may get into the chain’s working parts and engaging parts between the chain and the sprockets. In this case, you can take these steps: 1.Select a chain with hardened working parts. The parts need to be harder than the foreign objects. 2.Reduce the bearing pressure by using a larger-sized chain. This increases the abrasion-wear area. If you’re operating conveyor chains in abrasive conditions, consider the fol- lowing points: 1.Select a chain with thicker bushings to increase the abrasion-wear area. 2.Design the system so that the plates slide on the rails rather than roll on them. The bottom edge of the plate may accept much more abrasion wear than the area between the bushings and the rollers. 3.Install many small rollers in the equipment, instead of rails. This is especially useful when conveying objects that cause significant wear. In addition to causing wear, some objects may get into the working clear- ances of the chain, making it difficult or impossible for the chain to bend or rotate. In such cases, take the following steps: 1.Use seals, such as oil seal, labyrinth seal, or O-ring seals, to prevent particles from getting into the chain. (Applicable size is limited.) 2.Install a grease nipple and grease the chain regularly. Grease will force the particles from the chain. (Applicable size is limited.) 3.Increase the clearances so that particles will fall out, even if they get into the chain. This is the most common method.
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