CEDA Dredging Days 2021: Sustainable Dredging And Innovation

Promotional banner of the CEDA Dredging Days 2021 (Credit: CEDA)
Promotional banner of the CEDA Dredging Days 2021 (Credit: CEDA)

Tomorrow, another event with a long tradition will start: the CEDA Dredging Days1. Due to the Covid issues, this time, it will be a virtual event, just as a lot of other regular happenings. Hopefully, it will be the last days of this dreadful period. I can’t wait to meet people again in real life. Back at the office, we are slowly starting to get back. But meetings with people far outside the regular circle were difficult. For instance, I was a member of the Technical Paper & Program Committee and the preparation was completely digital.

Home page of your CEDA Dredging Days on the Swapcard platform (Credit: CEDA)
Home page of your CEDA Dredging Days on the Swapcard platform (Credit: CEDA)

Now, the event itself is also digital. Of course, this is still not the real thing. Having a coffee and a chat in the lobby is a much more enjoyable experience than sitting in front of your screen. I have to say that with the Sawpcard platform2 selected by the organising committee, it is much easier to arrange your own program, adapted to your personal interests. Moreover, it will also facilitate meeting people with the same interest. In a sense, this might be an opportunity to approach those. In the real world, people will not get seated next to you when they have the same interest. And certainly don’t have them captioned on their chest.

Pump design workflow (inspired by Suman Sapkota)
Pump design workflow (inspired by Suman Sapkota)

As member of the TPPC, I had the opportunity of a sneak preview of the articles and presentations and I can guarantee there are a lot of interesting sessions. For starters, there are three presentations by my colleagues. Suman Sapkota will have presentation on his research in various novel methods to apply numerical research into the design of dredge pumps3. We are happy to share with you some experiences and insights on the Dredging Days.

Testing the non-radioactive density sensor
Testing the non-radioactive density sensor

Another presentation will be by Frank Bosman4. He has been active in the development of an instrument that will measure the mixture density, without using a radio-active source. This intelligent solution is not only more sustainable, but will also provide easier access to this information. If you don’t know the density, you are very likely to underperform with your dredge. He will present some experiences and data gathered on the performance of this system.

Example of recent electric DOP dredge family

Our last presentation will be by René Sens3. Less technical, but surely an interesting perspective on the future of dredging equipment. Everyone in the dredging community is aware of the necessity to change and adapt to a more sustainable approach of our dredging business. There is an urgency to reach the goals set by the UN to leave the world behind as a better place than we received it. Although usually an increase in size also increases the efficiency of a dredge, the UN goals look beyond that single parameter. With that in mind, small and medium size dredges will be far more interesting than at first sight.

Session 7: Young CEDA ask a CEO (Credit: CEDA)
Session 7: Young CEDA ask a CEO (Credit: CEDA)

There will be a lot more going on and I could produce a long list of other interesting presentations. I think you should also check out: Edwin de Hoog and Joep Goeree, Basel Yousef and Jeroen van Stappen, and if you really want to get academic: Janek Gundlach, Ebi Shahmirzadi and Arno Talmon. You can just add to your own list and see who also joins in in the audience. Other interesting sessions will be the student ‘Flash Talks’5 and the ‘Young CEDA ask a CEO’ session6 with Peter Berdovski and Kees van de Graaf. And I am very curious what the other working groups and commissions of CEDA have to present about their work.

Thursday evening is the big get together of the dredging community; meet you there! (Credit: CEDA)
Dredging Days as a they used to be: personal interaction (Credit: CEDA)

References

  1. CEDA Dredging Days 2021, CEDA
  2. CEDA Dredging Days 2021, Outsourced Events
  3. Session 5: Latest in dredging equipment and technology
  4. Session 2: Developments in modelling and measuring hydraulic transport, CEDA
  5. Session 8: Young CEDA Flash Talks
  6. Session 7: Young CEDA ask a CEO

See also

Graduation Of Wim Kleermaker: Measuring And Predicting Wear In Impellers

Wim Kleermaker during the practical phase of his graduation in dredging
Wim Kleermaker during the practical phase of his graduation in dredging

Yesterday, Wim Kleermaker graduated at the TU Delft on a research project he conducted on our slurry test circuit at Damen Dredging Equipment. Specifically, he was investigating the wear behaviour in our dredge pumps. The noteworthy aspect of this project, was that Wim was supervised by our colleague Suman Sapkota. As long time readers in the audience might remember Suman was my own pupil some years ago1.

Example of a worn impeller at the Damen Dredging Experience
Example of a worn impeller at the Damen Dredging Experience

Wear is a very common process in the dredging industry and one of the main cost factors in a project2. It is beneficial to know the amount of wear to expect in a certain condition and be able to predict the budget to reserve for this nuisance. This is only possible when we as a manufacturer will be able to predict the wear rate and pattern can provide the information to the operator for his estimates. We do have historical data that will allow us to provide a ball park figure, but a more analytical approach might assist us in particular unusual cases. Furthermore, it will also provide us insight in the impact of certain design decisions for the wear performance of a certain pump design. For Wim’s graduation, he had to approach this academically: come up with a simulation model and verify this with measurements.

Damen dredge pump slurry test circuit on the outfitting quay in Nijkerk
Damen dredge pump slurry test circuit on the outfitting quay in Nijkerk

The measurements were done in our slurry pump test circuit. This circuit has been highlighted a couple of posts back3. For Wim’s experiments, he used an impeller under a certain operating condition and mixture properties. Before and after a representative period, the condition of the impeller was measured and the difference is a measure of the wear experienced.

CFD result for the wear experiments
CFD result for the wear experiments

Wear (or scientifically: erosion) is related to the impact of the particles on the material surface. In order to know the kinetic energy of the particles, the flow field has to be known. As the flow fleild cannot be measured directly at the test circuit, we have to resort to Computation Fluid Dynamics. We already know of Suman’s graduation, to look for patterns in the flow lines, but Wim has extended the procedure to also quantitively estimate the related erosion.

Comparing CFD results (l) with measured erosion (r)
Comparing CFD results (l) with measured erosion (r)

Although there is only a limited amount of data available, comparing the results of the CFD estimation and the measured erosion are looking promising. This is certainly a workflow that will provide us the unique tools for engineering better pumps and assisting customers in their specific projects.
Although Wim will not join our ranks in the dredging community and pursue a different career in another interesting industry, we are sure he will be constructive and dedicated colleague at Marin.

Another master and student fighting evil forces (Credit: Star Wars)
Another master and student fighting evil forces (Credit: Star Wars)

References

  1. Graduation Suman Sapkota: Where wear parts were worn down, Discover Dredging
  2. Wear parts, Discover Dredging
  3. Student Interviews On Their Projects With Our Dredge Pump Slurry Test Circuit In Damen Nieuws, Discover Dredging

See also

Graduation of Arend van Roon: Detecting Flow Regime And Optimising Transport Efficiency

Arend van Roon defending his graduation thesis
Arend van Roon defending his graduation thesis

Our first happy event this year is the graduation of Arend van Roon. He recently graduated on a project in the slurry test circuit at our Research and Development department at Damen Dredging Equipment1. His research was an interesting investigation in the detection of flow regimes. It gives some insight in the processes involved in the transport of water-solids mixtures. Let me share some details from the background with you, as I think this might be helpful for your own operation also.

Overview of the Damen Dredging Equipment slurry pumping test circuit
Overview of the Damen Dredging Equipment slurry pumping test circuit

At first sight, it is hard to imagine, how something heavier than water, the grains, can be lifted when the fluid is moving. Sape Miedema has written the standard on mixture transport in his book ‘Slurry Transport’, explaining his approach with the ‘Delft Head Loss & Limit Deposit Velocity Framework2’. Without going into the academic details, I will try to help you grasp the gist of the phenomena.

DHLLDV book (Credit: Sape Miedema)
Slurry Transport text book cover (Credit: Sape Miedema)

First the grains have to be picked up. When they are lying on the bottom of the pipe, they are fully immersed, surrounded by the fluid on all sides. The free fluid on top and the pore water between the grains under and on the side of the grains. Now comes Bernoulli’s trick. When the fluid in the pipe starts moving, he says that the local dynamic pressure decreases, while the static fluid in the pores remains at the same pressure. The pressure difference between the pressure in the pores and in the moving fluid, pushes the grains out of the bed into the fluid.

Grain pickup and suspension process explained
Grain pickup and suspension process explained

Once the particles are in the fluid are in the fluid, they should stay suspended, or they fall back into the bed. The driving force here is the turbulence in the fluid. Usually dredging slurry mixtures are turbulent. This turbulence causes the fluid to flow in eddies. These are little vortices that generally move in the direction of the flow, but in a moving frame of reference tumble in all directions. Mmh, as they rotate in all directions, why don’t they cancel each other out? Now, imagine being a particle yourself, surfing on those eddies. When it is in a fluid, it tends to sink with a certain settling velocity. Independent of the local movement of the fluid. This means, that on the downward side of the eddy, the particle has a higher total velocity than on the upward side. As the eddy is sort of symmetric, the particle dwells longer in the upward draft than on the downward fall. In this infinitesimal time difference, the eddy transfers some extra kinetic energy from the fluid to the potential energy of the particle. As this loss of kinetic energy is compensated by an increase in pressure (remember Bernoulli) carrying grains in a fluid increases the pressure loss in the slurry transport.

Flow regimes and excess hydraulic gradient requirements in dredging slurry transport (Credit: Sape Miedema)
Flow regimes and excess hydraulic gradient requirements in dredging slurry transport (Credit: Sape Miedema)

This turbulence is in short the background of suspension in the slurry transport process. Depending on al the various governing parameters: densities, viscosity, diameters, velocities etc, the equilibrium of forces result in several different regimes in the slurry flow. Ranging from homogeneous, through stratified to ultimately a static bed. Each with their own particular pressure losses. And that is what we are interested in. On our dredges, we want to transport as much material to the least amount of energy3. We are constantly looking for improvements in our equipment and sensors to assist the operator in visualising and controlling the actual state of his process4. Thanks to Arend’s project and the promising results, we can set the next step in our product development.

Explanation on slurry flow conditions, critical speed and specific power consumption
Explanation on slurry flow conditions, critical speed and specific power consumption

References

  1. Innovation, Damen
  2. Slurry Transport: Fundamentals, A Historical Overview & The Delft Head Loss & Limit Deposit Velocity Framework 2nd Edition, TU Delft
  3. Innovations In The New MAD Series To Increase Uptime And Reduce Fuel Consumption, Discover Dredging
  4. Dredging Instrumentation, Damen

See also