Calculate the right amount of cable lube for your fiber-optic pull

If you ask several field crews how much pulling lubricant they use on their fiber-optic cable pulls, the answer will vary--and possibly widely. Is there a right amount of lubricant to use so that you can do the job without waste? And if so, how do you determine it?

Donald E. Larson, American Polywater Corp.

Problem

If you ask several field crews how much pulling lubricant they use on their fiber-optic cable pulls, the answer will vary--and possibly widely. Is there a right amount of lubricant to use so that you can do the job without waste? And if so, how do you determine it?

Solution

It is possible to predict how much cable lubricant you will need for a particular job. The table gives some theoretical quantities; use the formula to estimate your use of lubricant if one or more of the specifications fall outside the range of the table. Remember to factor in practical considerations once the theoretical value has been determined.

Procedure

1 Determine the outside diameter (OD) of the fiber-optic cable or the inside diameter (ID) of the conduit to be coated. The cable lube can be applied to either surface.

2 Measure or estimate the length of the cable pull.

3 Use the table or formula to calculate the theoretical amount of cable lubricant you should have on hand. For example, for a 1000-foot cable pull in 1.25-inch conduit, the table recommends two gallons of cable lubricant.

4 Experience shows that the tabular values are accurate for the typical cable pull, which uses between 5 and 10 gallons of cable lube per mile of cable pulled, or 0.9 to 1.9 gallons per 1000 feet. (The average pull is into 1- to 1.5-inch ID conduit using 0.3- to 0.6-inch OD cable, so actual use falls within the theoretical range.)

5 Many factors can impact calculated quantities of cable lube, raising or lowering the final amount used. The most common factor is conduit type. For instance, more lube is usually required in corrugated conduit, because the lube can be wiped from the cable by the corrugations as it is pulled. The number of bends in the conduit, the conduit`s condition and the fill percentage allowed for the conduit also influence quantity of lubricant used.

6 Calculations are based on applying a 10-mil film of fiber-optic cable lubricant; this amount is adequate to minimize cable-pulling tension. Ten mils is one-tenth of an inch; a 10-mil film looks like a thick coating of wet paint and can easily be seen and felt.

Donald E. Larson is national sales manager for American Polywater Corp. (Stillwater, MN), a manufacturer of cable lubricants. This tip is adapted from information in an issue of American Polywater`s TeleTopics newsletter.

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