Dispelling Myths About Cable Pulling and Blowing

Myth 1: “Any Lubricant Can Be Used for Cable Pulling”

The myth that “any lubricant can be used for cable pulling” is problematic for several reasons. However, it is primarily a falsehood because it assumes that all factors (e.g., lubricant chemistry, conduit and cable jacket materials, size, distances, number of bends in the conduit route, etc.) and conditions (e.g., temperature, wet environment, etc.) are equal with all cable-in-conduit installations.

Reality: Not all lubricants are suitable for cable pulling. Using non-engineered lubricants, such as mineral oil, wax, or soap, can potentially damage cable jackets, leading to swelling, weakening, or cracking of this protective cable layer. Specialized cable pulling lubricants are formulated to reduce friction and be compatible with cable jacket materials throughout the lifetime of the cable installation.

Myth 2: “More Lubricant Always Reduces Friction”

The myth that “more lubricant can reduce friction” is a slippery statement. This false declaration assumes that the lubricant is the only factor that reduces friction in a cable-in-conduit installation and that quantity influences friction. This statement is an oversimplification of lubricant use and performance.

Reality: While adequate lubrication is crucial during cable-in-conduit installation, simply adding more lubricant does not always equate to better performance. The lubricant is only functional if it gets to where the friction point is. This places the effectiveness of lubrication on the type of lubricant used and its proper application. In other words, over-application of lubricant doesn’t equate to lower friction, but the correct application of the right type of lubricant can significantly reduce the coefficient of friction (COF). It is important to note that the viscosity and chemistry of the lubricating agents, combined with the cable sheath and duct material play a larger role in COF determination.

Myth 3: “Friction Coefficient is the Only Factor in Pulling Tension”

If you have been reading in chronological order, you may be seeing a pattern. The myth that “friction coefficient is the only factor in pulling tension” does not consider other variables that affect pulling tension in cable-in-conduit installations.

Reality: Although the coefficient of friction (COF) is a key factor, other variables significantly influence pulling tension; these include cable stiffness, conduit condition, location of bends, temperature, and environmental conditions. Accurate tension estimation requires a comprehensive understanding of all these factors, not just COF.

Myth 4: “All Cable Jackets Perform the Same When Pulling”

The myth that “all cable jackets perform the same when pulling” is false because it assumes that all cable jackets are the same. The statement ignores the other materials that the cable jacket will encounter during the cable installation, such as the conduit material, rigging equipment, and the type of lubricant used for installing the cable. It also does not consider the variable factors that affect installation performance such as the pulling force, speed of the pull, cable weight, and the conditions (e.g., temperature, wet environment, etc.) that influence sidewall pressure and coefficient of friction.

Reality: Different cable or wire jacket materials exhibit varying friction characteristics. High-performance lubricants can mitigate some differences, but unlubricated pulls show significant variation in coefficient of friction (COF) depending on the jacket material in combination with the conduit material. Take for example the variation of plastic materials that are used for cable jackets. Harder plastics, such as polyvinylchloride (PVC), tend to have a slicker surface. Whereas softer plastics, such as low-density polyethylene (LDPE), can exhibit a stickier surface condition. Understanding the differences in cable jacket materials is crucial for planning successful pulls and avoiding potential damage to the cable, which could compromise the cable’s longevity.

Myth 5: “Lubrication is Unnecessary for Pre-Lubricated Cables”

The myth that “lubrication is unnecessary for pre-lubricated cables” is false because it does not account for the other factors in cable-in-conduit installation that impact installation performance. These include, but are not limited to, the conduit route design, condition of the conduit, environmental factors, and temperature.

Reality: Even pre-lubricated cables can benefit from additional pulling or blowing lubricants, especially in challenging raceway configurations or longer runs. The combination of pre-lubrication and specialized cable lubricants can optimize installation lengths and reduce pulling tension.

Dispelling these persisting myths about cable pulling can lead to more efficient, safer, and optimal installation practices. By factoring in the complexities of friction, lubrication, and the specific characteristics of the different cable and conduit materials, installers can ensure successful and damage-free cable pulls.

Have any questions?

For more information on cable pulling lubricant selection and friction management, contact Polywater.
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