The majority of chain drives will perform better and last longer when timely and adequate lubrication is provided. One rule-of-thumb is that proper lubrication can extend the chain life by as much as 100 times. Even if overall chain life is acceptable, lack of proper lubrication can cause other problems. When a chain starts to dry out due to lack of lubrication, you will notice the wear from one joint to another can vary greatly, causing erratic action.
A chain lubricant should have low enough viscosity to penetrate into critical internal surfaces and high enough viscosity, or necessary additives, to maintain an effective film at the prevailing temperature and pressure. The lubricant should have the capability to maintain the desired lubricating qualities under prevailing operating conditions, and be clean and free of cor-rodents.
A good grade of nondetergent petroleum base oil usually is acceptable. While detergents are not normally needed, antifoaming, antioxidizing and extreme pressure additives are often helpful. Impure oils should be avoided. Acids or abrasives in the oil can permanently damage the chain.
The chain manufacturer often uses grease or petroleum jelly as an initial lubricant. However, users generally should not apply greases to chains in service because they are too thick to penetrate into the internal bearing surfaces of the chain. Users should use grease only when fittings for injecting the grease into the chain joints are provided.
Lubrication of Chain Drives
The recommended method of lubrication for chain drives is indicated in the power rating tables published in ASME B29 Series Standards and in various manufacturers’ catalogs. The methods normally listed are manual, drip, oil bath, slinger disk and oil stream. In all methods, the oil should be applied to the upper edges of the link plate or sidebar in the lower span of the chain. This enables gravity and centrifugal force to carry the lubricant into the critical bearing areas.
In manual lubrication, the user applies oil periodically with a brush or spout can. The preferred frequency is once every eight hours, but a longer interval may be used if experience shows it is adequate for that particular drive. The amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints. Discoloration indicates that rust is being generated in the chain joints because they are not receiving sufficient lubrication.
In drip lubrication, oil is dripped between the link plate or sidebar edges at a rate from four to 20 drops per minute, depending on speed. Again, the amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints. In drip lubrication of multiple strand chains, a wick-packed distribution pipe may be used to uniformly distribute oil to all rows of link plates or sidebars.
Oil Bath Lubrication
In oil bath lubrication, a short section of the chain runs through the oil in the bottom of the chain casing. The oil level should extend only to the pitch-line of the chain at its lowest operating point. Having long sections of chain run through the oil bath can cause oil foaming and overheating.