Increase Your Dredging Knowledge At The End Of The Discharge Line

Keeping watch at the end of the discharge pipe line
Keeping watch at the end of the discharge pipe line

Solving something at the end of the pipe is usually a less desired approach. However, in dredging, it is the place where the valuable stuff is delivered, it might be a good place to start monitoring your process. Let me explain this to you by going back to latest discussed exhibit at the Damen Dredging Experience1.

Pump power exhibit at the Damen Dredging Experience
Pump power exhibit at the Damen Dredging Experience

You might have observed in the pictures of the pump power exhibit, that the velocity of the water flow is indicated by the parabolas of the trajectory. The arc of water is bound by gravity and obeys this trajectory always; independent of the density of the mixture. The two equations of motion can be combined, where the time parameter falls away and the height for a certain distance is only depending on the initial horizontal velocity2. As such, it is fairly accurate indication of the pipe flow. The calculation is universally applicable on earth and the results can be presented in a very simple graph to take with you. Every parabola is labelled with the corresponding horizontal velocity.

Nomogram to find end of pipe velocity
Nomogram to find end of pipe velocity

The above example is a straightforward method to measure the mixture velocity. The US Geological Survey even extended this approach as a standard method to measure the production of wells3. The resulting nomogram has a slightly different layout, as it is intended for finding the production instead of the velocity. For production planning, this will be useful. For monitoring your dredging process, the velocity might be more important. Both approaches of this elegant method do have the benefit, that there is no obstruction needed as in the case of an orifice measurement4.

Nomogram to find the end of pipe production
Nomogram to find the end of pipe production

There is an unconfirmed anecdote that my old professor de Koning started his career as a velocity measurer. In the old days, when he was working as a twelve year old boy with the dredging company of his father. He was assigned to keep watch at the end of the pipe and monitor the mixture pouring out. He had a simple beam with a plumb bob. The beam was moved along the top of the pipe, until the plumb bob was touching the arc of mixture. On the beam were two markings. When the beam was moved in and passed the first mark, the mixture velocity was too low and a red warning flag had to be displayed. If the beam had to move out and the mixture velocity was too high at the second mark, a green flag had to be flown. There was also another white flag, in case only water came on the reclamation area. With this very simple setup, the dredge master could check through his binoculars what the state of the dredging process was.

Working principle and explanation of end of pipe meter
Working principle and explanation of end of pipe meter

They were clever in those days. But the physics still apply. So, even today, one might have a situation, where there is no electronic velocity measurement available (broken, not supplied, not (yet) purchased) and you have to push the limits of the operating envelope of the dredging process. Then, there is probably always somebody around that might be appointed volunteer to be head of the velocity measurement crew. Who knows, he might have a bright future in the dredging academia.

Professor de Koning of the dredging chair at the TU Delft (1981-1993)
Professor de Koning of the dredging chair at the TU Delft (1981-1993)

References

  1. Presenting Pump Power Peculiarities, Playing With Pumps And Pipes, Discover Dredging
  2. Projectile motion, Wikipedia
  3. Estimating discharge from a pumped well by use of the trajectory free-fall or jet-flow method, US Geological Survey
  4. ISO 5167 Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full, ISO

See also

Book Review: Donald Duck A Muddy Fine Business; Artistic Equipment Design

Front page of Penny Pincher magazine with Donald Duck as dredge master (Credit: Disney)
Front page of Penny Pincher magazine with Donald Duck as dredge master (Credit: Disney)

Donald Duck is a Jack of all trades, that he eventually he would end up on a dredge was inevitable. The story was already published in 1977 in a Donald Duck comic magazine. It is written by Freddy Milton1 and drawn by Daan Jippes2. At that time, I read it and already liked it very much. Later, I had it in a comic album3, but lost it moving to a new house. I wanted to review this story here already for a long time. Eventually, I consulted ‘Bul Super’ in Delft4, he advised me to search for Daan Jippes. That helped to find the story back on the internet.5

Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)
Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)

The story revolves around the endless feud between Donald Duck and Gladstone Gander. This time they have to compete in a success test by operating two different vessels: a ferry, ‘Seagull’ and a dredge ‘Aristoteles’. They have varying degrees of success and the outcome is unexpected.

The best known illustrator of Donald Duck is Carl Barks6. But Daan grew into his footsteps and eventually his stories are at the same level as the original master. He was with the Disney studios in the USA, but was working mostly in the Netherlands. In this edition, Jippes drew one of the most Dutch professions: dredging. Jippes had a keen eye for the elements that make up a dredge, tough the execution lacks some reality. Here I want to highlight some shortcomings that will help to illustrate the tricks that should have made it work and explain how real life dredging equipment functions.

Various details of the ‘Aristoteles’ (Modified from Disney)
Various details of the ‘Aristoteles’ (Modified from Disney)

The ‘Aristoteles’ is a truly multi-functional dredging vessel. It features both a grab and a bucket chain and the sediment can be loaded unto the vessel itself like a hopper or into a barge in tow. It is also self-propelled, although there seems to be a magical power generation as there is no visible exhaust pipe. Maybe Donald is again ahead of his time and running fully electric already?

Than the dredging equipment; the grab is suspended from a gantry, but it does not seem to be able to swing. Loading the tow barge would be difficult, as he has to reposition either the dredge or the barge. Apparently Donald should know about the technology of a rotating crane, as the picture on the front page has such a crane. And how would the material end up in the hopper?

Discharging buckets with reception carriage on a bucket ladder dredge
Discharging buckets with reception carriage on a bucket ladder dredge

Maybe with the other dredging tool: the obvious bucket chain? Though it is not supported on a ladder. Maybe that makes sense, as the buckets seem to be positioned on port or starboard in various panels. The material falling from the buckets might end up in the hopper. The vertical orientation presents some difficulty, as the material will fall onto the previous bucket and eventually through the well. In a normal operation, this is controlled by moving a carriage receiving the load and bringing it to the chutes. With a real vertical orientation, this would not be helpful anymore.

I once saw a solution for working with a vertical bucket chain on an exhibit in the National Dredging Museum7. A manual operated drawer-like slide was moved between every passing bucket to catch the load. It seems very labour intensive and prone to accidents.

Even after breaking down these operational details in the design of the ‘Aristoteles’, the vessel serves its purpose in the story: it is a really useful dredge for dredge master Donald. Well done Daan.

Exhibit with vertical ladder at the national dredging museum
Exhibit with vertical ladder at the national dredging museum

Call to the audience

The exhibit is still there, but unfortunately, it is broken. The mechanism has to be repaired, any model building fanatics are invited to help the museum restore it. There is a special event for new volunteers, now!

References

  1. Freddy Milton, Wikipedia
  2. Daan Jippes, Wikipedia
  3. Oom Dagobert En De Ondergrondse Kluis, nr34, Disney
  4. Stripboekhandel Bul Super
  5. Read online Walt Disney’s Comics Penny Pincher comic – Issue #4, ZipComic
  6. Carl Barks, Wikipedia
  7. Nationaal Baggermuesum

See also

Graduation Omar Karam: Rock Cutting The Egyptian Way

Graduation presentation of Omar Karam
Graduation presentation of Omar Karam

Egypt is a great nation when it comes to ancient engineering. No other country has such a concentration of impressive monuments and such an interesting history as over there. If you are not convinced that modern Egyptians are not capable of great engineering feats you are wrong. Last Monday, Omar Karam graduated at our R&D department of Damen Dredging Equipment1 on his thesis about ‘CSD Rock Cutting.’

Cutting processes have been extensively described by Sape Miedema in ‘The Delft Sand, Clay & Rock Cutting Model’2. Omar has been using the frame work of Miedema to make some useful tools for the estimation of the production of our dredging equipment in rock. In due time, you will find the results of his thesis in the online dredge selection tool ‘Sandy’. Omar’s curiosity and ingenuity does not end here. He will continue studying at a university, but I do hope to meet him again, as he would be a valuable asset for our dredging community. Keep an eye out for him.

Program structure diagram of cutting force calculations
Program structure diagram of cutting force calculations

His graduation brings me back to my first lessons in dredging technology at the Delft University of Technology by the illustrious professor de Koning. In a sense he was an old school engineer, who hammered it in to us that thinking is done by doing it with your hands3. Back than the Polytechnic School was just rebranded to University and he was mocking that as a university, we had to set the topics in a broader perspective. So, he started his introduction on cutting technology with some slides of the unfinished obelisk at Aswan4 as every aspect of the cutting process could be illustrated.

Phases of chip forming in rock cutting
Phases of chip forming in rock cutting

The story according to de Koning is: ‘Around the quarry of the obelisk, they have found diorites5. These are some sort of volcanic balls of rock. In combination with the marks and scratches all around the obelisk, archaeologists believe these stones have been used to pound the granite. The impact compresses the bedrock and the resulting stresses fracture the contact surface(1). For every hit a whiff of dust is created. Eventually the dust is collected and scooped away for the next layer. Next, trees would be planted in the trench on one side of the obelisk. The growing root system displaces volume and create shear stress underneath the obelisk that would sever the obelisk from the bed rock(2). At last the trees are removed and dry wooden dowels would have been inserted in the shear cracks. Saturating the wooden dowels will make them grow. The last strands of rock will now be broken due to tensile stresses(3). Repeated insertion of new dry dowels and saturating them will lift the whole obelisk enough to pull some ropes under and carry the obelisk away to the building site.’

Although the diorites and the scratch marks are a smoking gun, current archaeologists argue about the feasibility of this process as experiments yield a very low production and it is doubted that the obelisk could be finished in the lifetime of the client6. Even if disputed, de Koning told a story that conveys the message; I vividly remember it and makes me understand the rock cutting process.

These mysterious monolithic ornamental spires have been an inspiration for many legends and stories. When we have solved the riddle of the rock cutting with diorite balls, it may inspire the development of new rock cutting technology for the dredging community and we can put the story of the obelisks to an end.7

End of the story on the cutting of obelisks (Credit: Uderzo)
End of the story on the cutting of obelisks (Credit: Uderzo)

References

  1. Innovation, Damen
  2. The Delft Sand, Clay & Rock Cutting Model, TU Delft
  3. De Koning (1978), Denken met de handen’, TU Delft
  4. Unfinished obelisk, Wikipedia
  5. Diorite, Wikipedia
  6. The Unfinished Obelisk, NOVA
  7. Asterix and Cleopatra, Goscinny-Uderzo

See also