Field Tool
Pull Planner
Estimate cable pulling tension through straights and sweeps, compare both directions, and find a mid-route split.
Lower estimated peak: reel at A. Peak 98 lbf. 16% of the 600 lbf rating.
Good: 16% of the 600 lbf ratingLower Estimated Peak: Reel at A
98.0 lbf peak
With the reel at B, the pull would peak at 158 lbf, 61% higher.
- Reel at A (solid)
- Reel at B (dashed)
Each step up is a sweep. The 600 lbf rating is far above this pull, so it is off the chart.
Table View: Tension after Each Segment
| # | Segment | Reel at A | Reel at B |
|---|---|---|---|
| 1 | 100 ft straight | 22 | 158 |
| 2 | 90° sweep | 30 | 157 |
| 3 | 50 ft straight | 30 | 114 |
| 4 | 90° sweep | 42 | 114 |
| 5 | 50 ft straight | 42 | 83 |
| 6 | 90° sweep | 58 | 82 |
| 7 | 2,500 ft straight | 98 | 60 |
Tension in lbf as the cable leaves each segment. With the reel at B the cable travels from B to A, so read that column from the bottom up.
Show the Math
straight: T₂ = T₁ + μ·W·L sweep: T₂ = T₁·e^(μθ) θ in radians snaking κ: T₂ = (T₁ + W/κ)·e^(μκL) − W/κ
W is the cable weight in lb/ft, L the straight length in ft, μ the coefficient of friction and θ the sweep angle. Duct snaking κ is entered in degrees per 100 ft and converted to radians per foot. A sweep multiplies the tension that reaches it. As a rule of thumb, set the reel at the end nearest the sweeps; the tool's comparison of both directions (reel at A and reel at B) decides, and it reports the lower peak.
Status
- Peak below 80% of the cable rating: good.
- 80% to 100% of the rating: warning.
- Over the rating: critical.
- The 80% warning band is a FAHMY planning threshold, not a standard; the owner's design rules govern.
- At 80% or more, the tool tests a split at every segment boundary three ways (reel at A then figure-8; reel at B then figure-8; reel at the split pulling both ways) and suggests the lowest peak.
Defaults and Where They Come From
- Cable weight 0.08 lb/ft and feed tension 20 lbf are example values. Use the spec sheet and your setup.
- Friction μ 0.20 is a common planning value for lubricated pulls in HDPE innerduct (presets 0.15, 0.20, 0.30). Use the lubricant and duct maker's data where you have it.
- Cable rating: 600 lbf minimum for OSP cable. Drop and micro cables are rated far lower: use the cable's own rating.
- Minimum bend radius: 20 × OD while pulling, 10 × OD at rest.
Assumptions
- Level route. Elevation changes and sidewall pressure in sweeps are not checked.
- Field pulls often run higher than this estimate because continuous duct snakes in the trench or bore. Use the snaking input or keep extra margin.
- Owner pulling procedures and the cable manufacturer's instructions govern: pulling limits and methods.
Source
FAHMY tools give planning estimates. The owner's specifications, the authority having jurisdiction and the manufacturer's data govern every job. Values marked "Planning assumption", "Planning default", "Typical maximum", "Rule of thumb" or "Example" are editable starting points, not requirements; "Per owner spec" fields take the owner's value.