Student Interviews On Their Projects With Our Dredge Pump Slurry Test Circuit In Damen Nieuws

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

‘What sets men apart from boys is the size of their toys.’ And that wisdom applies to a lot of students that we’ve had at our company and have grown from boy to man working on our dredge pump slurry test circuit for their internship or graduation. As the test circuit has seen some intense activity these last months and yielded us with some very innovative concepts and possible new products, it was the right time to cover this interesting piece of equipment in the internal Damen Nieuws1 of January 2021 to share with all our colleagues. And that occasion in turn is an excellent opportunity to share with you the article and zoom into some of the details of the circuit.

General arrangement of the dredge pump slurry test circuit
General arrangement of the dredge pump slurry test circuit

Already more than ten years ago, we felt the need to have our own testing facility to experiment with the processes in our dredges or check the performance of new products2. After defining the specifications of the circuit, we had Hylke Visscher assisting us in designing the circuit for his internship. Subsequently he could actually supervise the manufacturing of the circuit for his graduation. Hylke worked in close cooperation with Arjan de Vries who in turn did his graduation on the building, outfitting and commissioning of the circuit. Both students from then are now esteemed and valuable colleagues as we have appreciated their performance on their projects.

After those ten years, we have a new generation of students working on the circuit. Arend van Roon recently graduated on his project with the circuit, as covered in my last post3. Currently Wim Kleermaker is preparing his experiments on the dredge pump. Upcoming is Williem Salim, not yet mentioned in the article, but now already starting his internship on the instrumentation of our laboratory. All project on the test circuit are supervised by Pieter van der Kooi as plant manager, Frank Bosman as student coordinator. Depending on the project, Ewout van Duursen, Suman Sapkota and me are supervising the student projects more on a subject level.

Various executions of a U-bend c-meter in the test circuit, for delivery and installed on a dredge
Various executions of a U-bend c-meter in the test circuit, for delivery and installed on a dredge

The odd thing you might notice in the loop of the test circuit is the U-bend directly after the dredge pump. Contrary to most first impressions, it is not to generate resistance, although it does so slightly. It is to measure how much sand has been transported. As the circuit is by nature closed, there is no way to check how much we’ve transported through the dredge pump. Sure, there is a density sensor4, but this will only indicate the so called volumetric density; how much material is there in the cross section. It will not differentiate between fast moving slurry and a slow sliding bed. In the extreme you could have a static bed, indicating a very high concentration. Multiplying this with a very high fluid speed, that is squeezed through the remaining aperture, you would expect an impressive production. Wrong! Not a single particle gets transported.

Enter: the U-bend. It measures the hydrostatic pressure differences over a certain hight in the upstream and downstream branches. This will cancel out the velocity differences but will yield the actual transported mass flow. So, that is how we can claim that we already dredged millions of cubic meters, all on the floor area of a 40 foot container flatbed.

Explanation of the U-bend measuring principle
Explanation of the U-bend measuring principle

References

  1. Testcircuit, Damen
  2. Innovation, Damen
  3. Graduation of Arend van Roon: Detecting Flow Regime And Optimising Transport Efficiency, Discover Dredging
  4. Production management, Damen

See also

A Virtual Tour Through The Dredging Experience In Damen Nieuws

Head line of the virtual tour through the Damen Dredging Experience in Damen Nieuws

One of the things I like about my work is to tell people about it and explain all the delicate details of dredging in a fashion that everybody should be able to comprehend the complexity of moving sand. I am very fortunate to work at Damen as they gave me my own museum to care for: The Damen Dredging Experience1. I’ve discussed several of the exhibits in the Experience on this website already2. Since our last appearance in the internal Damen Nieuws magazine3, the intriguing science of dredging caught the attention of the editorial board. And what better way to share our knowledge on dredging than reporting about it in our Damen Nieuws.

Here on my own website, I already introduced ‘the Experience’ about two years ago, intending to cover the various exhibits regularly. Alas, reality not always behaves as planned. There were so many other interesting items to share, or current CEDA events, or urgent requests from the service department. Well, this publication is a good incentive to continue my coverage of the Damen Dredging Experience.

First exhibit in the entrance hall: a real size DOP pump
First exhibit in the entrance hall: a real size DOP pump (Credit: Judith Korver)

One part of the experience, that does not lend itself for a very detailed explanation is the entrance to the building and the journey to the fourth floor where the experience is located. Immediately after entering the building, you may be overwhelmed by the DOP pump suspended from the ceiling. DOP pumps by themselves are not very large. But, when they are displayed out of place like inside a building, they are still formidable machines. Visitors can be introduced to the general composition of our dredging equipment with this DOP pump: it is basically a small scale dredging machine. It has a suction mouth, a dredge pump and a construction to keep everything together. Same follows for a CSD or even a hopper dredge.

Pictures about the history of The Netherlands and dredging used in the wall illustrations
Pictures about the history of The Netherlands and dredging used in the wall illustrations

Next are four floors with murals depicting topics from the dredging industry. First floor is covering the history of dredging in the Netherlands. How we always had to battle the sea to keep our land dry and tame the rivers for infrastructure. This long history made The Netherlands an excellent breeding ground for knowledge on dredging. The blooming industry is backed up by centers of excellence as the TU Delft, Marin and Deltares. With each of which we as Damen have cooperated to develop our products.

Pictures about the historical relation between Damen and dredging on the second floor
Pictures about the historical relation between Damen and dredging on the second floor

Within the Dutch dredging industry Kommer Damen played a pivotal role in the supply of auxiliary equipment to the big dredging contractors. Eventually, the company De Groot Nijkerk was acquired to also deliver dredging equipment directly.

Pictures with Damen products used in projects around the world
Pictures with Damen products used in projects around the world

Our products have been applied world wide on small and large projects. Everywhere where some wet infrastructure was developed, Damen has supplied some or more equipment. It always makes me proud to see the result of a big project and know that in some (remote indirect) way I have contributed to it.

Pictures illustrating the future of dredging industry
Pictures illustrating the future of dredging industry

The last mural is about the future of the dredging industry. One example is the increasing demand of raw materials. Beginning with the most basic of all: sand for the concrete industry. Increasingly, we see more demand for more exotic materials that are even harder to get: sea floor minerals from the abyss of the ocean. The other example is the ever increasing environmental awareness of society and the attention of cleaning up contamination and creating value for nature. Each of which our DOP pumps form the beginning is excellently purposed.

The Damen Dredging Experience is available for anyone who wants to visit, although it is best to request an appointment with one of our staff4.

Overview of the exhibits in the ‘Damen Dredging Experience’
Overview of the exhibits in the ‘Damen Dredging Experience’

References

  1. Damen Dredging Equipment in Nijkerk Officially Open, DredgingToday
  2. Dredging Experience, Discover Dredging
  3. Our Interview About New Pump Designs In The Latest Damen Nieuws
  4. Contact, Damen Dredging Equipment

See also

Our Interview About New Pump Designs In The Latest Damen Nieuws

Headline of our interview in ‘Damen Nieuws’
Headline of our interview in ‘Damen Nieuws’

Another magazine dropped on my doormat, albeit a digital edition of ‘Damen Nieuws’1. The internal magazine for Damen colleagues. It featured an article with Suman Sapkota and me. Suman is our pump design specialist2 and at a Damen wide R&D convention he presented a poster on his pump design workflow within Damen Dredging Equipment. This caught the attention of the editorial board and we were interviewed on what we actually do for a living. Although we can’t share the exact details of the article or the poster, it is still an interesting message that we can highlight here.

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

The design of a dredge pump is based on the required specifications(1). The most important properties of the pump are: efficiency, NPSH, wear and ball passage. The first important property we try to fix is the ball passage3. We do use our own geometry generator(2) that assist us in creating a pump with a big ball passage. Unlike normal pumps, dredge pumps have to cope with debris and boulders that have to pass the impeller. The bigger chunks that can pass, the more uptime the dredge will have. Once we are satisfied with the geometry, we feed this through a file format converter(3). The resulting 3D file can be used on several platforms. This will enable us to create the digital solid for the engineering4, but it also gives us the negative volume, also known as fluid. Then to do mathematical operations on the digital fluid, we have to divide the volume into tiny cells. This process is called meshing.(4) When the mesh is available, the fluid flow through the mesh can be simulated with computational fluid dynamics.(5) All the fluid properties of every cell are calculated and the results are shared with the adjoining cells. This can be repeated until all properties of the cells don’t change very much anymore, a stable solution. Integrating all the properties of the cells give the resulting performance of the pump.

Balancing the four dredge pump performance properties
Balancing the four dredge pump performance properties

The estimated performance can be evaluated against the four properties.(6) The head times the capacity divided by the power required will give the efficiency. That is one of the items we wanted to know, as it relates to how much fuel will be consumed. The other parameter obtained from the CFD is the NPSH, or roughly: the suction performance. Wear cannot be estimated yet, but we are working on that2. Although the calculated turbulence might give a clue what wear to expect. If the properties are not satisfying our requirements we make an iteration in the geometry for improving the performance. However, changing the geometry will usually result in a smaller ball passage. If the parameters are OK to our requirements we have a pump design.(7) Manufacturing it is a completely different game.5

The design process of the dredge pump takes quite some effort and we are continually looking to improve the workflow6. Eventually we would like to be able to cater for all special requirements each individual customer might have.

Working for a dredge manufacturer, I am happy we design and produce our own pumps. It gives us the confidence, that when we supply dredges, they are as we like them to be. Another benefit is in discussions with the customer. It is easier when we can sit at the table as experts on their equipment assit them in finding a solution for their dredge.

Pump experts immersing themselves in checking the design of their pumps
Pump experts immersing themselves in checking the design of their pumps

References

  1. Damen Nieuws, Juni 2020, Damen
  2. Graduation Suman Sapkota: Where wear parts were worn down, Discover Dredging
  3. On The Relation Of Maximum Ball Passage And Recirculation Losses In Dredge Pumps, WODA
  4. Graduation Of Carsten Markus: Designing And Casting Of Impellers
  5. Don’t Play Games With Your Wear Part Planning
  6. Innovation, Damen

See also