Roller Chain Drives
Lubrication - Part 1

Roller chain consists of a series of connecting traveling metallic bearings, which must be properly lubricated to obtain the maximum service life of the chain. Although many slow speed drives operate successfully with little or no lubrication beyond the initial factory lubrication, proper lubrication will greatly extend the useful life of every chain drive. The chain drive requires lubrication for six purposes.
  1. To resist wear of the pin-bushing joint.
  2. To cushion impact loads.
  3. To dissipate any heat generated.
  4. To flush away foreign materials.
  5. To lubricate chain-sprocket contact surfaces.
  6. To retard rust or corrosion.
A good grade of clean petroleum oil without additives, free flowing at the prevailing temperatures, should be used. Some additives leave a varnish or gum deposit which prevents the oil from entering chain joints. Heavy oils and greases are generally too stiff to enter the chain joints and should not be used.

With proper lubrication, a separating wedge of lubrication is formed between the pins and bushings in the chain joints much like that formed in journal bearings. The viscosity of the lubricant greatly affects its film strength, and its ability to separate moving parts. The highest viscosity oil which will flow between the chain linkplates and fill the pin-bushing areas will provide the best wear life. This is essential to minimize metal to metal contact and, if supplied in sufficient volume, the lubricant also provides effective cooling and impact dampening at higher speeds.

    Note: Rotative speeds beyond the maximum recommended for chain operation are indicated in the horsepower rating tables with zero horsepower.

    Operation at these or higher speeds will result in excessing galling of the chain pins and bushings regardless of the volume of oil applied.

Chain drives should be protected from abrasive and corrosive conditions, and the oil supply kept free of contamination. Periodic oil change is desirable.

Chain Cross-Section Showing Exaggerated Clearances
Note: Oil should be applied to the lower span of chain on the upper edges of linkplates since access of oil to pin-bushing joints is possible only through the clearances between the roller chain linkplates.
 

   

 
Oil applied to rollers only cannot reach pin-bushing joints, and therefore, cannot retard chain elongation due to wear. The lengthening of chains in service results from wear on pin and bushing surfaces, not rollers.

When lubricating multiple strand chain, it is important that lubricant be directed to each row of chain linkplates.

In conveyor applications oil should be directed between the rollers and bushings as well as between the chain linkplates.

The following table indicates the lubricant viscosity recommended for various surrounding temperatures:


Recommended Grade Temperature, oF
SAE 5 -50 to + 50
SAE 10 -20 to + 80
SAE 20 +10 to +110
SAE 30 +20 to +130
SAE 40 +30 to +140
SAE 50 +40 to +150

There are three basic types of lubrication for roller chain drives. Close adherence to the recommended type of lubrication is essential to obtaining maximum service life of a chain drive.

The recommended type of lubrication as shown in the horsepower rating tables is determined by the chain speed and the amount of power transmitted.

Manual or drip lubrication. (Type A) 

Oil should be applied periodically between the chain linkplate edges with a brush, spout can, or drip lubrication.

Oil bath or oil slinger. (Type B)

With bath lubrication the lower strand of chain runs through a sump of oil in the drive housing. The oil level should reach the pitch line of the chain at its lowest point while operating. Only a short length of chain should run through the oil.
 

A typical drive arrangement for bath lubrication is shown in the illustration below.

Drive arrangements which permit long length of chain to travel through the oil should be avoided as overheating or foaming may result. 
 
Go to: Roller Chain Drives - Lubrication - Part 2
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