Conveyor belt splice length calculator
Step-splice geometry for textile (EP, NN) multi-ply belts: number of steps, bias offset, splice length and the extra belt to order.
Result
How it works
A step (stepped) splice joins the plies of two belt ends in staggered steps along a bias line. The geometry is the same in every maker’s instruction: one step fewer than the number of plies, a bias of about 0.3 × belt width, and a splice length equal to the steps plus the bias.
What differs between makers is the step length (it depends on the strength per ply), the cure schedule and the splice materials. This calculator does the geometry and leaves those values for you to enter from your own belt maker’s splice instruction — it contains no maker table.
Formula
Ply strength = belt rating ÷ number of plies Steps = plies − 1 (enter your maker’s count if it differs) Bias offset La = B × tan θ (0.3 × B ≈ 16.7°) Splice length L = step length × steps + La (single ply: overlap length + La) Belt per splice = L + finishing allowance + trim; order length = endless length + splices × belt per splice
| Symbol | Meaning | Unit |
|---|---|---|
| B | Belt width | mm |
| θ | Bias angle (match your press) | ° |
| S | Step length from the belt maker | mm |
| La | Bias offset across the belt | mm |
| L | Splice length along the belt | mm |
| trim | Trim allowance per splice (≥ 50 mm in one manual) | mm |
Worked example
Inputs: Belt width B = 800 mm; Nominal belt rating = 315 N/mm; Number of plies = 3 count; Bias angle θ = 16.7 °; Step length (overlap for 1 ply) — from your belt maker = 250 mm; Steps, if your maker differs from plies − 1 = count; Finishing / chamfer allowance = 0 mm; Trim allowance per splice = 50 mm; Splices in the belt = 1 count; Endless belt length (optional) = m; Material temperature (optional) = 100 °C.
- EP 315/3: ply strength = 315 ÷ 3 = 105 N/mm; steps = 3 − 1 = 2
- Bias offset La = 800 × tan 16.7° = 240 mm
- Splice length L = 250 × 2 + 240 = 740 mm (250 mm step is an illustration only)
- Belt per splice = 740 + 50 trim = 790 mm
- No supplied maker table covers 315/3 (105 N/mm per ply): use your belt maker’s step length, cure data and, for a heat-resistant cover, the matched heat-grade splice kit.
Assumptions and limits
- Geometry only. Step (or overlap) length, cure time, temperature, pressure and materials must come from the belt maker for this exact belt and cover grade.
- Match the bias angle to your vulcanising press. Calculate the angle from the offset — some manuals print wrong angle labels (e.g. 0.37 × B is 20.3°, not 22°).
- Two-ply belts: the generic rule gives 1 step; some makers use 2. Single-ply belts use an overlap splice.
- Material above 125 °C: makers specify longer steps and heat-grade materials.
- Steel cord belts use a different splice (cord layouts by stage). Use the steel cord maker’s splice diagram.
- Isolate and lock out the conveyor, clamp the belt and secure the take-up 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 long is a splice on an EP 315/3, 800 mm belt?
About 240 mm of bias plus 2 × the step length. With a 250 mm step that is 740 mm, but the step length must come from your belt maker.
Why is the bias 0.3 × belt width?
It spreads the joint so the whole splice does not cross a pulley at once. Makers use 0.3 B (16.7°) to 0.4 B (22°); match your press.
Can I use this for a steel cord belt?
No. Steel cord splices are laid out in cord stages from the maker’s diagram for the ST rating.
Source notes
- Steps = plies − 1 and L = step × steps + bias: SIG Multiply Conveyor Belts – Installation Handbook Rev.5 (2018) pp.12–14; Mercurio Manual of Conveyor Belts and Splices REV.08/22 p.80. Bias ≈ 0.3 B: SIG p.12; REMA TIP TOP cold splice instructions 07/2021 p.4. Trim ≥ 50 mm per splice: ContiTech fabric splice manual (2015) p.6. Method summarised in original words; no maker table reproduced.
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