Set project inputs and get spacing quickly. Verify tension and sidewall pressure across bends today. Download clear reports that crews can trust onsite always.
| Scenario | Total run | μ | Cable weight | Bends × angle | Min radius | Recommended spacing |
|---|---|---|---|---|---|---|
| Street lighting feeder | 450 m | 0.25 | 1.1 kg/m | 2 × 90° | 1.0 m | ~120 m |
| Campus fiber pathway | 900 m | 0.20 | 0.35 kg/m | 4 × 45° | 0.8 m | ~150 m |
| Industrial power duct | 300 m | 0.30 | 2.0 kg/m | 1 × 90° | 1.2 m | ~90 m |
Handhole spacing is a pull-planning control that limits mechanical stress and installation time. For long duct routes, dividing the run into shorter segments reduces peak tension and improves lubricant distribution. A practical spacing target is the maximum segment length that still stays below cable tension and bend sidewall limits with margin. Use consistent assumptions for friction, weight, and bends so crews can reproduce the plan consistently.
Spacing depends on total length, conduit condition, and cable mass per length. Higher friction or heavier cable increases the longitudinal drag term, so allowable segment length drops. In mixed terrain, treat each segment as its own pull and keep bends, elevation changes, and tight radii concentrated near access points. When data is uncertain, apply a conservative rule cap and verify with trial pulls on representative sections.
Bends amplify tension because the cable must slide against the wall while changing direction. This calculator uses an exponential factor based on the sum of bend angles and the friction coefficient. Two 90° bends are more demanding than four 45° bends when radii are similar, because local contact pressure increases near tighter curvature. Reducing bend count in a segment can often increase allowable spacing without changing cable selection.
Sidewall pressure is checked at the tightest bend by dividing predicted tension by bend radius. Even if straight-run tension is acceptable, a small radius can push sidewall pressure above the jacket limit. If sidewall governs, increase bend radius, add an intermediate handhole before the bend group, or change routing to spread direction changes. Always apply a safety factor to both allowable limits when setting construction spacing.
In the field, document segment lengths, bend counts, and handhole locations on a simple pull sheet. Record measured tension at the winch, lubricant quantity, and any observed binding points for future optimization. Exporting results to a file supports submittals, crew briefings, and as-built records. After installation, compare planned and observed values to refine friction assumptions and improve the next design iteration.
A handhole is an access box used to pull and route cable in conduit. It creates intermediate access so long runs can be divided into safer pull segments.
Friction coefficient, cable weight per length, and total bend angle typically drive spacing. Higher friction, heavier cable, or more bends reduce the allowable segment length and increase handhole count.
Use values based on duct condition, lubrication, and cable jacket type. If uncertain, start with a conservative value, then refine after trial pulls or measured tensions from similar installations.
Reduce segment length by adding handholes, increase bend radius, reduce bends per segment, or improve duct preparation and lubrication. Recalculate until both tension and sidewall checks are within limits.
No. It is a planning estimator for spacing decisions. For critical or high-value pulls, confirm assumptions using manufacturer guidance, detailed pull calculations, and site-specific installation constraints.
It provides a practical cap when inputs are incomplete or variability is high. The cap helps prevent overly long segments that can be difficult to lubricate, stage, and control during construction.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.