Roller chain drives transmit power or convey products through diverse environments in applications such as material handling, agriculture, construction, mining, food processing, and automotive manufacturing. With simple periodic inspections, proper lubrication, and regular maintenance, these chains will give long service and may even outlast the machinery on which they’re installed.

Why lubricate?

Lubrication is the most effective method of extending the service life of chain drives. Its primary mission is to provide a film of lubricant between the pins and bushings in the chain links, thus preventing metal-to-metal contact and wear. But, it offers other benefits as well:
• Dissipates heat generated during operation.
• Helps flush wear debris and contaminants from the chain joints.
• Protects the chain against corrosion.
• Cushions the impact when a chain engages a sprocket.
• Enables smooth movement of the chain over sprockets.

Without lubrication, metal-to-metal contact causes rapid wear and elongation, reducing a chain’s service life. In addition, excessive heat generated by metal-to-metal contact can destroy the benefits of component heat-treatment.

With sufficient lubrication, chain parts function without generating excessive heat. Elongation due to wear is reduced. And, it is both uniform and predictable. As a result, chain life can be many times that of unlubricated or inadequately lubricated chain.

Selecting a lubricant

Roller chain lubricant is applied to the outer surfaces and allowed to flow into the pin-and-bushing joint. For this reason, coating the chain with a heavy, thick grease does little toward supplying the joint with the lubricant it needs. Oil does the job better.

The oil grade, viscosity, and purity are the most important factors for proper chain lubrication. Because some grades of oil contain additives or detergents that may foam or leave a residue in the chain’s joints, it is best to use nondetergent, single- viscosity petroleum oils selected primarily for the drive operating temperatures, Table 1. If available, antifoam, anti-rust, and extreme-pressure additives in the oil are beneficial. Impure or used oil may have degraded in service and may contain contaminants which can increase wear or damage the chain components. Therefore, this oil should be replaced.

Synthetic or food-grade lubricants are available for extreme temperature or food-handling applications. Generally, the cost of synthetic oil is significantly more than petroleum-based oil, so that petroleum oils have historically provided the best cost/performance ratio in most applications.

Choosing a lubrication method There are four primary methods of chain lubrication — manual, drip, oil bath and slinger disc, and oil stream applied under pressure.

Manual. Appropriate for drives operating at low speed (defined by Table 2), manual methods generally involve applying oil with a brush or spout-can approximately every 8 hr depending on the drive conditions and duty cycle. Oil should be applied to the inside of the chain loop so it won’t be thrown off by centrifugal force. The chain drive should always be stopped and power locked out before manually lubricating the drive.

Drip feed. A more continuous form of lubrication, the drip method is also adequate for low-speed drives. Oil is supplied to the chain from a reservoir or manifold system, typically at at rate of 4 to 20 drops per minute, Figure 1.

Oil bath and slinger disc systems. For moderate-speeds, the entire drive is contained in a housing with an oil sump. A short section of the chain travels through the sump to pick up oil, Figure 2. This method is often used in conjunction with a slinger disc which picks up small amounts of oil from the sump and slings it onto the chain.

Oil stream. For high-speed applications, a pump directs lubricant under pressure onto the chain at a high flow rate, Figure 3.

Horsepower rating tables published by the American National Standards Institute (ANSI) provide guidelines for selecting the correct type of lubrication system based on the size (number of teeth) and speed (rpm) of the smallest sprocket. Table 2 is a modification of this ANSI table. As a general rule, higher speeds and loads require more sophisticated lubrication systems.

Continue on Page 2