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Volume I

Fiber Optic Installation

How Much Lubricant is Enough?

Ask a field crew how much pulling lubricant they use on a fiber optic pull. Ask another, then another. You'd be surprised at the wide range of answers you'd receive.

Isn't there a right amount of lubricant, an amount that does the job, but doesn't waste by using excess? What is the right amount?

Let's Engineer It

One way to determine the amount (in gallons or quarts) of lubricant needed for a pull is to figure it theoretically.

For instance, we know that a 10-mil (.010 inch) film of Polywater® Lubricant F does a more than adequate job of minimizing cable tension. A 10-mil film looks like a thick coating of wet paint; you can easily see it and feel it.

Whether we cover the interior wall of the conduit or the exterior wall of the cable with a 10-mil film of lubricant ... that should be enough--the right amount.

We can calculate the volume of lubricant this takes. The results depend on both the length of the run and the conduit ID (or cable OD). The results of such calculations are as follows.

Get Real!!

Actually, these calculations aren't bad. They are in the right ballpark. American Polywater gets involved in a wide variety of fiber optic work; and when there is enough information to track it, the "typical" use is between 5 and 10 gallons of Polywater® F per mile of cable pulled, or .9 to 1.9 gallons per 1,000 feet. Since the "average" job is into 1 to 1.5" ID conduit with a .3" to .6" OD cable, we see actual use is in the right theoretical range.

More or Less?

There are a number of factors that may cause the right amount of Polywater® F to vary from our calculation. The most common is conduit type.

For instance, we usually use a higher quantity of lubricant in corrugated duct. This is not due to the greater surface area, but because in corrugated conduits, it's harder to keep lube in the area where the cable actually rubs; i.e., on top of the corrugations. In fact, the corrugations tend to wipe the lubricant off the cable. So ... we allow for this by using more lubricant.

This does not mean that corrugated conduit is more difficult to pull into or causes higher tension. In fact, the opposite seems to be true, but that is a subject for a future TeleTopics.

Other factors influencing quantity of lubricant use include the number of bends in the conduit system, the interior condition of the conduit, and conduit fill percentage.

Where It's At!

Once we have the right amount of lubricant, the challenge in fiber optic installation is to get it to all the points where the cable rubs--including those places 5,000 or more feet into the duct.

A good lubricant like Polywater® F helps here. By fully wetting on the cable jacket (and not dripping off over time), Lube F stays with the cable for long hauls.

A number of ingenious methods have been used to get lubricant to where it's needed. Our recommendation is to put lubricant into the conduit and then push and spread it with a sponge spreader as the cable is pulled. We've also seen:

• Lubrication at special T's or other points of conduit access.
  
• Pumping and/or blowing lubricant through the duct.
  
• Using a spreader or a similar device as a piston to pull lube into the conduit with suction.

The most common reason for using lubricant quantities above the theoretical guidelines is the need to get the lubricant everywhere. Sometimes an excess of lube is the only practical way to do this, and it's much less expensive than alternatives like shorter pulls.

Formula For Success

American Polywater developed the first guidelines for estimating lubricant quantities required for fiber optic pulling. The equation ...

... provides estimates similar to those discussed in this article.

American Polywater also offers a software program called the Pull-Planner™ 2000 that provides a convenient way to estimate cable pulling lubricant requirements (and much more) on a personal computer. Click here to order the software for $99, or contact American Polywater's Technical Service Department at 1-800-328-9384 if you have questions or wish to order over the phone.

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