Steel cord belt splice length check
Check the splice length you copied from your belt maker’s diagram and work out the belt over-length — for Sempertrans, NILOS and Fenner Dunlop layouts.
Result
How it works
A steel cord splice is laid out in one to four steps, with cords from both belt ends interleaved and butted with a gap. The number of steps and the lengths depend on the ST rating — and on the maker: for an ST 2000 belt, NILOS and Sempertrans publish a 1150 mm splice, while Fenner Dunlop publishes about 1675 mm.
So this page does not choose lengths. You enter the values from your belt maker’s splice diagram; it recomputes the length with that maker’s layout to catch copying mistakes, and gives the belt over-length you need including the bias.
Formula
Sempertrans: Lv = n·Lst + 200 + (n + 1)·50 NILOS: Lv = n·Lst + 2·e + (n − 1)·50, e = 100 / 150 / 200 / 250 mm for 1–4 steps Fenner Dunlop: L = n·S + 2·B + (n − 1)·G + 50 Over-length = Lv + W × tan θ Cord-end gap ≥ 3d (NILOS) or ≥ 4d (Sempertrans); filler ≥ 1.2 + 0.1d (Sempertrans)
| Symbol | Meaning | Unit |
|---|---|---|
| n | Number of steps on the diagram | — |
| Lst, S | Step length from the diagram | mm |
| B, G | Dunlop end zone and gap between steps | mm |
| W | Belt width | mm |
| θ | Bias angle from the diagram | ° |
| d | Cord diameter (belt data sheet) | mm |
Worked example
Inputs: Splice diagram from = nilos ; Belt rating ST (optional) = 2000 N/mm; Belt width W = 1200 mm; Bias angle = 16.7 °; Number of steps = 2 count; Step length from the diagram = 400 mm; Dunlop: end zone B = mm; Dunlop: gap G = mm; Splice length on the diagram = 1150 mm; Cord diameter d (optional) = 5.6 mm; Planned cord-end gap (optional) = 20 mm; Planned filler strip (optional) = 2 mm.
- NILOS layout, 2 steps of 400 mm: Lv = 2 × 400 + 2 × 150 + 50 = 1150 mm — matches the 1150 mm on the diagram
- Bias offset = 1200 × tan 16.7° = 360 mm
- Belt over-length = 1150 + 360 = 1510 mm
- Planned cord-end gap 20 mm: ≥ 3d = 16.8 mm (NILOS) but below 4d = 22.4 mm (Sempertrans) — follow your own maker (cord diameter is an illustration)
Assumptions and limits
- Values come from your belt maker’s splice diagram for this belt. The page never supplies step counts or lengths as defaults.
- The layout formulas reproduce the published tables of each maker; if your diagram length does not match, re-check the copied step length, step count and zones (one maker table has a misprinted step length).
- Cure temperature, time, pressure and rubber compounds come from the same instruction. Finger splices (e.g. Ferroflex) use a different layout and are not covered.
- Isolate and lock out the conveyor before any splice work.
Screening estimate, not a design approval. Verify measured inputs, current standards, manufacturer limits and site procedures before purchasing, cutting or installation. Isolate and lock out equipment before any hands-on measurement.
Questions
How many steps does an ST 2000 splice have?
Two, in the Sempertrans, NILOS and Fenner Dunlop instructions — but the step lengths differ by maker. Use your own maker’s diagram.
Why does the page not give me the splice length?
Because makers publish different lengths for the same rating; only your belt maker’s diagram is valid for your belt.
Source notes
- Layouts back-calculated from the makers’ diagrams: Sempertrans Sempercord General Splicing Instruction V a / 12.2020 pp.9–13; NILOS steel cord splicing instructions (NAA-VSG_EN) p.10; Fenner Dunlop steelcord hot splice procedure v10.4 p.7. Cord-end gap and filler rules: NILOS p.10; Sempertrans p.19. Summarised in original words; no table reproduced.
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