Chain lubrication. Snake oil or critical factor? - Leaf Chain

Chain lubrication. Snake oil or critical factor?

Why does chain need it?

Sometimes overlooked, lubrication should be considered as a major component in the chain’s construction. As well as being an important factor in prolonging chain life by slowing the wear between the pins and bushings in the chain joints, it also serves to flush out debris from wear and other loose foreign materials and to smooth sprocket engagement.  Lubrication by its very nature is an excellent inhibitor to rust and corrosion, it also cushions the forces of impact and can be used to diffuse heat.

Looking back

Evidence of lubrication in an industrial setting can be traced back to ancient Egypt where analysis showed that wheels were treated with tallow animal fat to reduce the friction on large sleds used to transport large heavy loads. Not to be outdone, the ancient Chinese had their own mixture of vegetable oils and lead.

The use of vegetable and animal oils continued up until the 8th Century when whale oil was used in lubricating rudders and pulleys on ships. Naphtha, a distilled hydrocarbon based flammable oil (like modern day lighter fuel) was also used by ship builders.

Fast forward to 1845 when the first use of crude oil is attributed to a cotton spinning mill in Pittsburgh, Pennsylvania. The mill owner experimented with this oil by mixing it with the sperm whale oil used to lubricate spindles on a weaving loom. Then in 1859 the American oil industry was born after the first American oil strike in Pennsylvania which formed the basis for most lubricants throughout the 19th and 20th centuries until the development of synthetic lubricants.

What makes a good lubricant?

Viscosity is the key word. It must be able to penetrate internal surfaces and have a high enough viscosity, or using necessary additives, be able to maintain an effective film at the required temperature and operating conditions. A good grade of nondetergent based petroleum oil usually is commonplace. Additives like antifoaming, antioxidizing and extreme pressure agents are often used.

A chain manufacturer often uses grease or petroleum jelly as a protective initial lubricant. However, greases should not be applied to chains in service because their viscosity prevents them penetrating the internal bearing surfaces of the chain.

Although we are regularly asked what the best lubricants are we always recommend talking to a tribologist (someone qualified in the study of how surfaces behave in relative motion) at a reputable lubricant company.

Same But Different

Numerous research articles on chain lubricants have existed for rotary power chains (think motorcycle, bicycles, and roller chain drives) however these types of chain and their intended use are very different from leaf chain in several ways.

Generally, these chains comprise four parts – links, roller, bush and pins. The lubrication required needs to penetrate between the bush and inside of the roller and and whilst that gap is small the clearance is bigger than that found between leaf chain pins and plates. Plus, they often operate at higher speeds and temperatures, with lubricant applied via an oil bath on the unloaded side of the drive. The lubricant required can therefore be quite different.

The Good Life

The longer the service life of the leaf chain the greater the positive impact on the total operating cost of the machine and additionally its safe operation.   Aside from lubricants there are two considerations we believe could have an equal or greater impact on leaf chain life than the selection of lubricant:

  • Many chain lubricants are engineered to have a creeping or capillary action, drawing the chain lubrication into tiny internal gaps inside in the chain. If shortly after lubricating any load is removed from the leaf chain and it is left in a slack condition for 15 to 20 mins it will open the clearances and greatly increase the amount of lubrication reaching the load bearing area inside the chain. 
  • Secondly, leaf chain lubrication applied with a brush allows for a more precise application to the points that most require it – namely the leaf chain pin and plate joint.  This method gives the lubricant the best possible chance to soak down deep into the chain. Spraying lubrication on and around a leaf chain is not nearly as effective as a large percentage will coat the non-moving components that do not need lubrication.

It’s your choice…

We have found several lubricants that are suitable for leaf chain:

Molykote MKL-N

Fuchs FLT Lube

Kluber Structovis BHD 75 S

They all share a high adhesion property, contain a water repellent and have a viscosity which allows for an efficient penetration of internal surface areas. Extreme pressure and anti-wear additives giving improved durability under heavily loaded applications are also common features.

We at FB Leaf Chain have chosen not to produce our own leaf chain lubricant. The choice of lubricant type is often a commercial decision based on service intervals and working environment involved. We would urge some caution when buying spray cans of chain lube as these may contain more propellant than chain lube and are often formulated for roller chains. All FB chains are immersed in a good quality leaf chain oil at the final stage of manufacture.

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