Getting a handle on the ins and outs of wire rope
lubrication can be almost as tough as holding a well-lubricated rope while it's
in use. A collection of experts in the field make the subject a bit easier
Envision wire rope as a complex mechanical system. Whether used as a
dragline, tow line, elevator cable, or bridge guy line, it is made up of moving
parts. Those parts are forced to continuously adjust to one another during
often high stresses in hostile environments.
Consider a hoist rope on a large dragline. As the rope moves over the
sheave, it is pulled, bent and compressed simultaneously. Metal to metal
contact stresses the outside of the rope as it enters and leaves the
sheave. Inside, wires contort and abrade one another.
Sometimes the hoist rope is forced to then move over another sheave in a
reverse bend. The closer the two sheaves are, the more stress the rope
will experience because the strands will not re-adjust themselves.
The best lubricant for the job
Almost anyone in the wire rope industry would agree that, with few
exceptions, wire rope needs lubricant protection. According to the
Roebling Wire Rope Handbook1, fatigue tests were conducted with two sections of
9/16" diameter 6 x 19 wire rope. One was lubricated and one was dry.
The lubricated rope lasted 2.4 times longer on the 10" tread diameter sheave,
and 5.2 times longer on the 24" tread diameter sheave.
||Sheave/Rope Dia. Ratio = 18
||Sheave/Rope Dia. Ratio = 43
But when users and manufacturers begin to discuss specifics, such as types of
lubricants, additives, environmental issues and application methods, opinions
For instance, here are some basic lubricant compounds used for
manufacturing or re-dressing:
And here are some of the additives:
- petrolatum based
- combination (asphaltic and petrolatum)
- soap (stearate) thickened
- inorganic thickened
- greases (pumpable)
- amorphous polypropylene
- resin based
- linseed/castor oil
Lubricants must not be highly
acidic or alkaline, which can deteriorate the rope and threaten the environment.
- corrosion inhibitors
- anti-wear additives
- water displacing additives
- polymers (tack and adherence)
- plasticizers (low temp)
- polar additives (wetting)
Key to choosing the correct lubricant is
knowing the rope's application and in what environment it will be used.
For instance, with applications like the dragline discussed above, the
lubricant must have additives that cause it to remain pliable as the rope is
used. As the strands inside the rope move against each other, the
lubrication can wear off in spots. "A good lubricant will re-distribute
itself evenly between the strands — a characteristic known as ‘self healing',"
says Bill McAlaine.
The marine environment is one of the most hostile for wire rope. At
sea, the wire is subjected to high corrosion from wind-blown salt air, as well
as from short immersions in salt water during lowerings. The zinc corrodes
first, and how quickly it corrodes depends on a number of factors:
of water in which the rope is used. Oxidation is a kind of
corrosion. The closer the rope is to the surface of the water, the higher
the temperature, and the more reactive the oxygen is. So, the rope will
corrode faster when it is closer to the surface of the water.
The temperature and chemical content of the water. In a 1969 study,
with the assistance of the Woods Hole Oceanographic
Institution, Oregon State University, the Halan Company and U.S. Steel, an
experiment was performed where specimens of bright steel wire, galvanized wire
and electromechanical cable were submerged for three months in three different
locations. The results showed "accelerated rates of corrosion...ultimately
traced to a combined effect of chemical levels in the water and the temperature
of the sea water."3
||3.71% Total Solids
||44 Degrees F|
||3.61% Total Solids
||40 Degrees F|
||3.98% Total Solids
||84 Degrees F|
How thick, how hot?
In many applications, the lubricant's
tolerance to fluctuations in temperature is a major concern. In hot desert
climates, for instance, the wrong lubricant will literally drip off the
wire. At low temperatures, it may flake or crack.
very in viscosity, and viscosity always varies with temperature.
"There are many different standards for measuring lubricant viscosity,",
explains Bob Kirkpatrick, President of The Kirkpatrick Group,
Inc. Most commonly used are: "NLGI" (National Lubricating
Grease Institute), "Saybolt" (Sus), and "Centistoke" (Cst). Laymen and experts
alike have difficulty making conclusive comparisons between the standards.
There are few, if any, complete comparison charts that provide accurate cross
reference between the standards. Most lubricant manufacturers use only one
or two measurement specifications when preparing technical data. To avoid
confusion...we...use the terms "Pourable" for low viscosity and "Nonpourable"
for high viscosity when referencing given wire rope dressing ranges.
Pourable (Low Viscosity) wire rope dressings range from SAE 90 weight oil
density upwards to NLGI #0 a near equal to molasses. Nonpourable (High
Viscosity) wire rope dressings range from NLGI #1 (consistency of soft butter)
to NLGI#3 (consistency of thick peanut butter).
"Ambient temperature must be considered when measuring dressing viscosity..As
an example: NLGI pourable dressing grade #0 at 85 degrees may easily become #1
or #2 nonpourable at 40 degrees. Prior to operation, check you
viscosity...In extremely cold temperatures, it may be necessary to pre-heat wire
rope dressing to assure it is easily pumped and applied to the wire rope."
Where ropes are being stored, Nonpourable lubricant may protect the rope with
a heavier film. Relatively recent advancements in pressure lubricators
manufactured by companies like The Kirkpatrick Group make it possible to force
heavier oils into the inner parts of the wires. When this is possible, it
is sometimes preferable, since more highly viscous lubricant affords greater
But, for certain applications, and where a pressure lubricator is not
available, thinner oils are preferred. They can be applied by spraying or
simply pouring, and drip into the inside of the rope readily. Lower
viscosity lubricants must be re-applied frequently.
In confined spaces, or
where motors might produce sparks, avoid using inexpensive petroleum
solvents. They have a low flash point, which can present a serious fire
From the first drawing
Before considering field dressing
(relubricating), a user may need to start where lubrication begins: with the
wire rope manufacturer (OEM). At intervals while the rope is manufactured,
the OEM applies lubricant. This lubricant differs from the type used to
re-dress the rope. But it is important to be aware of the OEM lubricant
applied, since the re-dressing lubricant may interact with it, causing
The type of lubricant and the amount added is
determined by the manufacturer based on his information about the future use of
"A wire rope may be lubricated at three intervals during its
manufacture," explains Bill McAlaine, Vice President and Business Manager of
Allied Kelite, "once at ‘stranding' (when the wires are joined to form strands),
once at ‘closing' (when the strands are formed to make rope) and sometimes after
the rope is made, to provide an added level of protection."
wire is drawn, it passes through a ‘soap', Bill adds, "which is designed to
facilitate lubrication between the wire and draw dies.
"However, it is not
designed to protect the wire in use. If anything, it actually causes us
problems, because the soap left on the wire often absorbs water. (Many drawing
soaps contain borax, which is highly hydrophilic). Applying a lubricant at
stranding over a moisture laden soap/borax film can cause moisture encapsulation
and result in premature corrosion. We build water displacing properties
into our stranding lubricants, which helps address this problem. However,
the best practice is to take the last wire reduction without lubricant to help
minimize the amount of water-absorbing residual film left on the wire surface."
If a termination is added, lubrication should be re-applied. It is
important that the juncture of the strand and socket be inspected periodically,
because of torsional twisting, which subjects it to corrosion.
The core of the problem
Once the customer receives new rope, he
should store it inside a building and away from direct sunlight, or at least
cover it with a tarp if it has to be left outside. Turn the storage reel
periodically to prevent the lubricant from seeping to the bottom, especially
where temperatures are high or the lubricant is very fluid.
When the rope is put to use, field dress it immediately. Like devious
enemies, moisture and pollutants can invade the wire quickly, corroding the core
of the rope. (Note that we are referring to a wire, rather than fiber, core.)
"Corrosion damage is impossible to estimate and must be avoided in order to
maintain necessary strength and safety. A corroded rope is reduced in
strength for various reasons. First, metallic area is lost by chemical or
electro-chemical action. Second, corrosion mars the smooth finished wire
surfaces, resulting in erratic contours which form stress raisers. These
stress concentrations are very susceptible to failure by crack propagation as
the rope bends and stretches during operation. Third, corrosion hinders
normal movement between wires, creating a binding condition which increases
stresses to an indeterminable extent and speeds corrosion-fatigue fracture
A major concern in re-dressing should be the compatibility
of the lubricant with the OEM lubricant. Incompatible materials can cause
dangerous results: the re-dressing lubricant may not penetrate the wire
sufficiently; components of the OEM lubricant may leach out; or the re-applied
dressing may flake away.
If in doubt, consult the OEM. According to law, the wire rope
manufacturer should tell the customer how to field dress the rope.
And, cautions Al Lucht, President of Wire Rope and Metallurgical Engineering
Services, "a basic requirement for all lubricants is that it must stick to the
rope and not fall off. Strange as it may seem, this is not always an easy
problem to resolve. One can read all the advertisements and listen to the
vendor, but the only way to find out is to use the wire rope and try it in the
intended application. If the lubricant does not stick (adhere), it will do
absolutely no good at all."
Here are some lubricant related field problems:2
- Film is too heavy for the rope speed.
- Field dressing or rig wash is softening the film.
- Stranding lubricant is wrong.
- Lubricant is poorly matched to the environment.
- Film thickness is wrong.
- Adhesion and film integrity are poor.
- low temperature flaking
- Lubricant is wrong for the application.
- Lubricant was overheated during application.
- Film thickness is wrong.
- dry rope
- Field dressing is inadequate.
- Penetration at the "point of twist"during the manufacturing process is
- dry core
- Melting point is low or viscosity is above the melting point.
- Film thickness is wrong for application or temperature at which it is
- internal wear
- Rope is dry.
- Contaminants are infiltrating rope.
worst scenario, the wrong re-dressing compound will form a solid film in the
valleys of the outer layer, insidiously trapping moisture and dirt in the rope,
and causing it to deteriorate faster.
- Field dressing or OEM lubricant is wrong.
Re-lubricating: how often?
Testing is key to finding out how well
the lubricant is protecting the rope, and establishing a re-lubricating
Since each rope application varies, it is impossible to specify a uniform
re-dressing time interval. It depends on many factors, including the type
of load, frequency of use, and kinds of environmental exposures.
For certain ropes used consistently in the same environment and under the
same conditions, rope re-dressing can be performed at reasonably predictable
intervals. For instance, when using a hoist dragline, frequent lubrication
is a must.
"As a general rule, the entire length of the rope should be lubricated every
eight hours on a machine operating continuously. This procedure will vary
depending on temperature. And lubricant temperature depends on ambient
temperature, which can be affected by wind, heat sources and humidity...An
average dragline uses about 55 gallons of wire rope lubricant per month."4
But in many cases, the rope needs to be visually checked frequently
for broken wires and corrosion. Even stationary wire rope like guy wires
and suspension cable should be inspected periodically because of damage caused
by atmospheric contaminants. It is vital that the lubricant is soft so
that it can be easily wiped from the rope surface. Lubricants that harden
cover defects, presenting a hazard. They can indirectly cause serious
injury or death.
Here is a sample visual inspection for galvanized
Periodically the wire rope should be visually inspected to determine the
condition of the strand, and if there is a question on the coating, the
following procedure should be followed:
Re-lubricating: how much?
- Remove the residue that is present with a pencil eraser or fine steel
wool, but don't use too much pressure that will remove the coating.
- Make a concentrated solution of copper sulfate with water (dark blue) and
apply it to the test area with a saturated cotton ball or cloth. Wear
- If there is no chemical reaction, the coating of lubrication is
present. If the test area turns black, the coating is not present, but
zinc is. If it turns copper color, then there is no zinc or coating
As a general rule, it
is better to re-lubricate lightly and frequently rather than heavily and
infrequently. The concern should always be keeping the inside strands
"Flooding a rope haphazardly, then permitting it to
run dry between these erratic applications, does not offer as good protection as
small, yet frequent additions of fresh lubricant."1
Traditionally, lab tests
have been used to evaluate lubricant effectiveness.
"The laboratory tests
often do not evaluate a rope under load. Consequently, they are not able
to determine the extension of rope life with proper lubricant usage."
"A better method of evaluating lubricant effectiveness is to test a rope by
the NDT procedure at periodic intervals throughout its service life. The
rope is passed through a sensor head that determines the rope's loss of metallic
area (LMA) and local faults (LF) such as broken or missing wires. The NDT
method, while not eliminating the visual rope inspection, provides advantages in
that it allows determination of the structural integrity of the internal rope
parts and requires less downtime for testing. Researchers at the Bureau of
Mines Spokane Research Center evaluated NDT date on various ropes by comparing
the LMA and LF and noting the trends."5
Once the wire rope is in use, a major concern
when re-dressing should be first removing the water and dirt that has become
trapped in the rope. If the rope is lubricated without first being
cleaned, the existing moisture and pollutants will still cause corrosion and
abrasion. And, they will prevent the lubricant from adhering to the rope
uniformly. As a result, the rope will deteriorate faster.
There are many cleaning methods. Any good method should remove dirt and
liquids not only on the surface, but in the "valleys" between the strands, where
it can become embedded, and work its way inside the rope.
As mentioned before, a primary concern in preparing a rope or cable to
receive a field dressing compound is that it is free from entrained water.
Re-lubricating rope without first removing internal moisture will, rather than
inhibiting corrosion, accelerate it. Some wire rope dressing compounds now
contain additives that will combine with water to prevent corrosion.
Here is a sample cleaning and re-dressing procedure:
recommendations concerning the temperatures of the rope and atmosphere required
when applying lubricant.
- Strands must be examined for any build-up of residue in the valleys
between the wires. If, upon examination, there is a build-up of residue
in the valleys between the wires, the valleys must be cleaned with a cable
cleaner to allow the lubricant to penetrate the outer wires into the core of
the cable and to combine with entrained water.
- If the residue of old lubricants and coating is just present on the crowns
of the wires, then a wire brush may serve the purpose.
- After the valleys are free of any residue that would restrict the flow of
lubricant, they should be dressed.
- If there is a large salt deposit in the valleys of the wires, a fresh
water wash forced air dry procedure should be used.
Cleaning systems are available to remove old lubricant and grit while the
rope is in use. Most scrape the rope clean as it passes through the
Lubricating can be done many ways, including wiping and spraying but a
lubricating system is usually preferred. A good lubricating system
re-dresses the rope uniformly with less lubricant waste. With pressure, it
forces the lubricant into the core, where it is needed most. And the
higher the pressure, the deeper the lubricant penetrates, especially if the
strand is under tension. Like a cleaning system, it can also be used while
the rope is in use, cutting down time dramatically.
lubricating wire ropes began only in fairly recent history, according to Al
Lucht. As Chief Wire Rope Engineer of American Steel and Wire (U.S. Steel)
in 1963, he first became aware of extensive problems with wire rope corrosion
and oxidation. Back then, lubricants applied while manufacturing wire rope
were basically asphaltic.
"AS&W had extensive files which dated
back to the late 1800's. In a random perusal one day, I read a report
dated around 1913. Wire ropes were used extensively with sailing vessels
(windjammers) used to carry freight across the oceans. At that time,
AS&W had a wire rope mill in Worcester, Massachusetts where it was the
practice not to coat wire ropes. They were furnished dry without any
lubrication. Naturally, these ropes, when used on sailing vessels
traveling the salt water seas, corroded rapidly."
The report stated that hemp ropes, which were coated with pitch, lasted much
longer, AS&W began coating their wire ropes with pitch obtained from
Jamaica. Life of the wire ropes remarkably improved.
Years later, the pitch was replaced by asphalt, which was a bi-product of oil
refining. Asphalt, the dregs of the refining process, didn't resist
corrosion well, was a poor lubricant, and differed from shipment to
shipment--but it was cheap.
"When I entered the scene," Al Lucht says, "[research and development] was
mixing different types of lubricants such as petrolatum (petroleum jelly) and
asphaltic and adding anti- oxidants, etc., to try to improve various
characteristics." But there was a problem in that the mix varied with the
"To help resolve our problems, our Monroeville, Pennsylvania Research
Laboratory developed a specification for a petrolatum-based general purpose
lubricant which was then used for 90% of our products. It was very
successful. Our rusting and corrosion problems and oxidation problems
disappeared as if by magic."
Various compounds were added to the mixture, including corrosion inhibitors,
anti- oxidants, water displacing additives and compounds designed to withstand
very high pressures.
Lubricants for the ‘90's
recent years, the spotlight has turned to environmental issues. In marine
use particularly, regulations require that the lubricant does not leave a sheen
on the water surface. Also, disposal of lubricant containers, and even the
lubricated wire rope itself, is now an environmental consideration.
"The use of additives is like going to the drug store and taking pills
to counteract whatever ailment you have or do not want to get," Al Lucht says.
"This era has seen a big change in the quality of lubricants used for wire
rope. The lubricants cost more but they are good and present a savings in
wire rope use."
Special thanks to
those who contributed information for this article:
- Roebling Wire Rope Handbook, The Colorado Fuel and Iron Corporation, 1966.
- Provided by Allied-Kelite, A Witco Company.
- Handbook of Oceanographic Winch, Wire and Cable Technology, Second
Edition, Alan H. Driscoll, ed. 1989.
- "Making Wire Rope Last Longer," by K. L. Barden and F.J. Klaus, Coal Age,
- "Evaluation of Lubricants to Increase Wire Rope Life," by Jack E. Fraley
and Grant L. Anderson, Spokane Research Center, Bureau of Mines, U.S.
Department of the Interior, Spokane, Washington.
Robert Kirkpatrick, President of The Kirkpatrick Group, Inc., Texas, which
designs and sells lubrication systems.
Wilbert A. (Al) Lucht, President of Wire Rope and Metallurgical
Engineering Services, California; and retired Chief Wire Rope Engineer of
American Steel and Wire (U.S. Steel).
William McAlaine, V.P. and Business Manager of Allied Kelite, A Witco
Company; and formerly General Manager of The Hodson Corporation, specializing in
formulating and marketing wire rope lubricants.