Efficient Plant July 2018 - 28
feature | lubrication strategies
brought on by overloading the chain with tension
which causes the chain to literally be pulled apart.
Roller Chain Pin Assembly
The illustration shows a cross section of a typical roller-type chain-link pin connection. Source: Practical Lubrication for Industrial Facilities, Heinz Bloch and Kenneth
Bannister, The Fairmont Press, 2017
Ken Bannister is coauthor, with Heinz
Bloch, of the book
Practical Lubrication for
Industrial Facilities, 3rd
Edition (The Fairmont
Press, Lilburn, GA). As
managing partner and
for Engtech Industries
Inc., Innerkip, Ontario,
he specializes in
reviews to ISO 55001
standards, assetmanagement systems,
and training. Contact
him at kbannister@
line contact of pins, bushings, and rollers that
create high surface pressure
intermeshing of chain links and sprocket teeth that
result in high shock loads.
Most chains fail as a result of ineffective lubrication. Arguably, the highest failure rate results
from pin and bushing wear caused by dry running
a chain. This condition can prevail even when
lubrication is attempted but the delivery fails to
place the lubricant in the bearing-surface area. It
also results when a non-chain-friendly lubricant is
used. Wear causes the chain to elongate which, in
turn, alters the pin-to-pin link pitch. When this occurs, the chain no longer mates smoothly with the
corresponding sprocket teeth, resulting in the chain
dragging and snatching and sometimes "skipping"
a tooth, thus changing the driver-driven timing and
causing the machine to fail dramatically.
Improper mating also wears/damages sprocket
teeth. Replacing worn sprockets can often be much
more expensive than maintaining or even regularly
replacing a chain.
When a chain demonstrates such behavior, the
tendency is to believe it has "stretched," but this
is not the case. Chain stretch is cause by fatigue
To meet the demanding service conditions in which
chains are used, combat premature wear, and stop
the chain from rusting, specialized lubricants are
needed with the following features:
Corrosion protection: Ferrite metals rust quickly
when moisture collects on unprotected surfaces. This
manifests itself as a reddish-brown staining on the
surface and throughout the oil when no anti-corrosion additive is present.
Wetting or creeping property: This allows the oil
to penetrate, displace water, and carry the lube to the
intended and most vulnerable part of the chain where
maximum wear occurs.
Adhesiveness: Tackifier agents are often added to
ensure the lubricant is not easily slung off the chain
by centrifugal action of the rotating sprockets and the
chain moving at speed.
Temperature stability: Whether a chain is used in
a refrigeration plant to carry product through a fastfreeze process or in a bakery to move dough through
a high-temperature oven, the oil must be able to function in a wide temperature range. This requires the
correct base oil with a high viscosity index (VI) rating.
Low-coking tendency: Coking leaves a residue on
the chain. Should it fall off, it can damage the conveyed product.
APPLYING THE LUBE
Chain lubricants can be applied in several ways,
depending on the work application.
Manually pouring, brushing, or spraying the
oil directly onto the chain whenever it appears to
be dry can be risky business if chain failure is an
unacceptable consequence. If manual lubrication
is an acceptable practice, always ensure the chain
is lubricated on the inside face as it moves into the
sprocket to ensure the sprocket receives adequate
lubrication at the mating faces.
Gravity-drip oilers are an inexpensive way to
apply lubricant to chains, either by dripping directly
onto the chain or onto a brush that touches the
chain surfaces. These types of systems, although