How to Estimate Dredging Production

Here are a few tips on how you can estimate the suction and discharge production of dredging and mining equipment yourself. It’s easier than it looks!

Taking the time to learn how to do this could save you millions of dollars down the line. Creating your own estimate will also greatly increase your understanding of upcoming projects. This insight is crucial for the timely delivery of projects as well as procuring or mobilising suitable equipment or contractors on site.

These tips and tricks will make it easy for you:

1. Convert units

The new release of the Pumps ‘n Pipeline (PnP v 1.5) tool comes in both metric and US imperial units of measure. You no longer need to find the conversion factor and correct prefix. If the unit is uncommon, you can always use the free offline tool Convert for Windows and Linux.

2. Take screen shots from the head, efficiency and NPSHr pump curves

The Windows Snipping Tool can take screenshots and save them as pictures in PNG format.
Note that the NPSHr curve is only required for the first pump and is an optional input.

3. Digitise head, efficiency and NPSHr pump curves

You can digitise the pictures of the curves using WebPlotDigitizer, a free online tool.
Make sure you collect at least five data points for each curve.

4. Find the regression coefficients
How to estimate dredging production. Finding regression coefficients in Microsoft Excel
How to find regression coefficients in Microsoft Excel

In MS Excel, paste the data points from Step 3 and then complete the following steps within Excel:

  • From the Data tab select the Text to Columns button.
  • Insert a Scatter Chart, then select the data points.
  • Right click and selected Add Trendline… from the menu box.
  • From the Format Trendline screen choose the Trend/Regression Type of Polynomial, the Order of 2 and tick the Display Equation on chart tick box towards the bottom on the screen
5. Fill in PnP’s Pumps tab

The hard part is now done and you can fill in the first tab, Pumps. Besides the regression coefficients, you’ll also need to provide values for the pumps and drives, such as power and revolutions.

6. Fill in PnP’s Pipeline tab
How to estimate dredging production. PnP's Pipeline tab in Imperial Units
PnP’s Pipeline tab in Imperial Units

Provide the length and diameters of the pipeline on both the suction and discharge side. Typical friction loss coefficients are provided in the PnP User Manual.

Tip: When suction production is the limiting factor or bottleneck, then the vertical distances have to be filled in accurately. One-tenth of a metre can significantly impact suction production although it won’t considerably affect your pipeline pressure loss.

7. Fill in the PnP’s Mixture tab

Fill in the properties of your mixture such as densities, temperature and particle size. If these values are unknown, the PnP User Manual can provide typical value ranges.

8. Fill in PnP’s Diagram tab

Provide the value range for the calculation and how you want to view your results. The range typically depends on the pump curves.

9. Calculate results

All done! Press on the calculator icon and analyse the results. All results can be viewed as easy to read graphs located on the Results tab

If you’re not sure about your results, contact us as we are keen to learn about your projects and very passionate about estimating dredging production. If that’s still too much work, provide us with the input data we need and we’ll do it for you!