Calculator
Formula Used
Pig velocity is estimated from effective volumetric flow and pipe cross-sectional area:
A = π × D² / 4
- Q is volumetric flow rate (m³/s).
- D is internal diameter (m).
- bypass is fraction of flow bypassing the pig.
- slip adjusts for leakage/inefficiency (1.0 = ideal).
How to Use
- Enter flow rate and internal diameter for your pipeline segment.
- Select a pig type to compare against typical speed ranges.
- Set bypass and slip if you have test or vendor data.
- Optionally add line length to estimate travel time.
- Submit to view results, then export CSV or PDF.
Example Data Table
| Flow | ID | Bypass | Slip | Length | Velocity | Travel time |
|---|---|---|---|---|---|---|
| 180 m³/h | 300 mm | 5% | 0.98 | 2.2 km | 2.04 m/s | 00:17:59 |
| 35 L/s | 12 in | 0% | 1.00 | 1.0 km | 0.48 m/s | 00:34:28 |
| 900 gpm | 200 mm | 10% | 0.95 | 500 m | 2.47 m/s | 00:03:23 |
Examples are illustrative. Confirm limits with project specifications and tool requirements.
Operating velocity window in field runs
Pig speed is primarily a flow-controlled outcome, but field constraints often define an acceptable window. Many cleaning programs aim for steady motion to maintain debris transport and avoid surge events. If velocity falls too low, the pig can stall in low spots, valves, or waxy sections. If it is too high, cups and discs may wear faster and tools can exceed their measurement limits.
Inputs that most affect calculated speed
The calculator converts your flow rate to an effective flow and divides by pipe area. Because area scales with diameter squared, small diameter changes can shift velocity noticeably. Use true internal diameter for lined pipe, older pipe, or heavy corrosion allowance. When flow is uncertain, run a sensitivity check by trying your expected minimum and maximum operating flows.
Bypass and slip as practical corrections
Bypass represents flow that moves around or through the pig without pushing it forward. Slip is a simple efficiency factor that captures leakage, cup deformation, or pressure losses that reduce net driving force. Together they convert the metered flow into a more realistic driving flow for the pig. Use vendor data, test history, or conservative estimates when exact values are unknown.
Reynolds number and stability checks
Reynolds number helps you judge whether the carrier flow is laminar, transitional, or turbulent. Turbulent flow typically improves mixing and debris suspension, while laminar flow may allow settling. This calculator reports the regime for awareness only; pig speed control still depends on flow control, pressure management, and consistent station operations during launch and receipt.
Example run data for reporting and briefings
Use this compact example set to verify units and communicate targets during toolbox talks and shift handovers. Adjust length to estimate arrival time at traps or intermediate stations.
| Scenario | Flow | ID | Bypass | Slip | Velocity | Length | Estimated time |
|---|---|---|---|---|---|---|---|
| Cleaning baseline | 180 m³/h | 300 mm | 5% | 0.98 | 2.04 m/s | 2.2 km | 00:17:59 |
| Tool run control | 35 L/s | 12 in | 0% | 1.00 | 0.48 m/s | 1.0 km | 00:34:28 |
FAQs
1) What velocity range should I target?
Target the range specified by your pig vendor and project procedure. Cleaning runs often tolerate higher speeds than tool runs. Use the built-in pig type checks, then confirm against site-specific limits.
2) Why does diameter change velocity so much?
Velocity equals effective flow divided by pipe area. Area increases with the square of diameter, so a modest diameter increase can significantly reduce velocity for the same flow rate.
3) What should I use for bypass if I do not know it?
Start with 0% for a conservative “best-case” speed estimate, then test 5–10% to see sensitivity. If your pig has bypass ports or leakage history, use those values for planning.
4) What does the slip factor represent?
Slip approximates efficiency losses between flow and pig motion, such as leakage past cups, deformation, or pressure losses. Use 1.0 for ideal behavior, or slightly lower when history indicates slower travel.
5) Is Reynolds number required to compute velocity?
No. Velocity comes from flow and diameter. Reynolds number is reported to describe flow regime, which can influence debris transport and stability, but it does not directly change the velocity equation here.
6) Why does the travel time show a dash?
Travel time is only calculated when a positive line length is provided. Enter length in any supported unit, submit again, and the calculator will estimate time using the computed velocity.
7) Can I export results for daily reports?
Yes. After you submit, use the CSV for spreadsheets and the PDF for site records. Exports include your inputs, key results, and any warnings so they can be attached to permits or shift logs.