Sidewall Pressure & Cable Pulling Tension Calculator (AEIC CG5)
Sidewall pressure and pulling-tension calculator using the AEIC CG5 (2nd Ed.) pulling-guide method. Build the duct run section by section, walk the tension through, calculate SWBP at every bend, and check the pull in both directions.
Sidewall Pressure & Pull Tension Calculator
Build the duct run section by section. The tool walks the tension through, works out sidewall pressure at every bend, and checks the pull in both directions.
Cable and duct
K = 0.45 straight, 0.15 in high-pressure bends
Limits
From the eye, grip or conductor stress — whichever is lowest
Tension limit helper and options
Eye limit ≈ 16000 lb (two cables sharing)
Reel to duct entrance
Duct run in the A → B direction
- Max tension
- — lb
- Tension limit
- 8,000 lb
- SWBP limit
- 2,000 lb/ft
- Weight corr. Wc
- 31622.777
| # | Section | K | T out (lb) | SWBP (lb/ft) |
|---|---|---|---|---|
| 1 | Straight, level | 0.45 | 205,769,457 | — |
| 2 | Bend, concave, pulling up | 0.15 | — | — |
| 3 | Slope, pulling up | 0.45 | — | — |
| 4 | Bend, convex, pulling up | 0.15 | — | — |
| 5 | Straight, level | 0.45 | — | — |
| 6 | Bend, concave, pulling up | 0.15 | — | — |
Simplified tension equations, valid within about 5% where the WR/T₁ check passes. Where a section fails that check, or where tension or SWBP lands within 20% of a limit, run the exact equations before committing to the pull. Aim for a calculated maximum tension no higher than 80% of the allowable to leave room for start-up and surging.
Overview
Sidewall pressure (SWBP) is not a lookup number. It depends on the tension arriving at the bend, and that tension depends on everything the cable has already been dragged through: straight sections, slopes, bends, the duct–cable friction pair and how the three cables ride on each other inside the duct.
This tool follows the AEIC CG5 (2nd edition) underground extruded power cable pulling guide. You build the duct run section by section in the A → B direction, the solver walks the tension along, then checks both ends (A → B and B → A) and shows the better pull direction automatically. On a marginal run that one choice is often the difference between a pass and a re-design.
Use it alongside cable sizing (to pick the cross-section in the first place) and voltage drop (to verify drop after the cross-section is fixed). The three together give you: size → drop → field feasibility.
How it works
- 1. Describe cable + ductCables per duct (1 / 3 / 3-triplex), weight, O.D., duct I.D., duct material and outer covering.
- 2. Set the limitsSWBP construction limit and the pulling-tension ceiling from the eye/grip or conductor stress.
- 3. Build the run+ Straight, + Slope or + Bend section-by-section in the A → B direction; edit angles (0–90°, R in ft or m).
- 4. Read both directionsThe solver walks tension through the run once, then flips slopes and runs B → A, reporting the easier end to pull from.
FAQ
What is a safe sidewall pressure limit?+
There is no single figure — published values spread 4:1 depending on construction. Start with the dropdown (AEIC CG5 Table 5) then confirm with the cable manufacturer before committing to a marginal pull.
Why check both directions?+
Tension compounds over every bend and hill. Feeding from the side with the most bends or the uphill side usually gives the harder pull. Flipping the direction can change the result by 30 % or more.
Why does friction drop in a tight bend?+
High contact pressure squeezes the lubricant film thin, and you go from shearing a thick compound to proper boundary lubrication. The transition is around 150 lb/ft — this is why the tool has two K values.
Why is there a weight correction factor Wc?+
For three cables in a duct, they push not only on the wall but also on each other. That raises the effective friction. Skipping Wc in a three-bend pull can under-report tension by ~1/3.
What does the WR/T₁ asterisk mean?+
The simplified bend equations are only valid inside the WR/T₁ band. Rows marked * need the exact (iterative) equation run before committing to the pull.
My SWBP limit is lower in the 3-cable dropdown than the single one. Why?+
For some constructions (e.g. unjacketed wire shield) AEIC CG5 publishes a 3-cable figure lower than the single-cable value, because the three cables press harder on each other.