Category: History

How DOP Pumps Developed and Entered the Digital Age

First application of a DOP pump

Recently, my daughter asked me: ‘Dad, what good is it to know your history?’ And I answered: ‘Dear, if you don’t know your past, you will not understand the world around you.’ And the world around us is changing rapidly. The most recent change in our dredging world is the launch of the DOP web shop1. The ultimate entrance into the digital age of a well proven pump. For those young people that only know how to order online (or others interested in dredging history): long before webshops were around, customers and suppliers had a direct relationship with each other.

In the early ‘90s, when Ballast Nedam received the contract to build the railway tunnel near Schiphol Airport2, they had a real tough challenge. The ground water level near Schiphol is very high. Any hole there, fills up rapidly. Using sump pumps to remove the water from a building pit would be useless. To prevent collapse of the sides, there was already sheet piling in place, supported by braces to carry the side load. The space between the braces was too small for a long reach excavator. And the area under the braces too low to work from pontoons. Moreover, the foundation pilings where already in place and they should not get damaged by the excavation with a crab crane.

Construction site of the railway tunnel at Schiphol Airport

At this point, Ballast Nedam contacted their supplier De Groot Nijkerk for a smart solution. Ballast Nedam wanted a small self-contained dredging machine, that would fit between the braces and remove the sediment hydraulically. In a real Gyro Gearloose fashion, De Groot Nijkerk managed to patch together a contraption to prove the concept: ‘the first DOP pump’ (of some sort). It consisted of a normal dredge pump and a submerged jet pump in the same frame.

Proof of concept for a DOP

The tests were successful and the prototype was turned into a production model. The main difference being that the bearing and the dredge pump were designed with a mechanical seal to remove the gland water installation. This mechanical seal required some development on itself, as standard mechanical seals were too fragile. The newly developed seal was of real dredging proof quality. The product was successfully used and word spread around the Dutch contractors about this nifty little dredging machine. As a result, the new DOP was introduced in 1991 and started a career of its own.

Introduction of the first standard DOP on the market

As customers were very original in creating their own solutions for their specific problems, this single product slowly evolved in a whole line of products and options3. For as long as I remember, there was this picture in the product leaflets, that the customer could use to configure their own tool. Hence the slogan: ‘Your job, our tools.’

Typical selection diagram of DOP options

Over time, the range has been reengineered and thoroughly standardised. Due to this standardisation, the sales could also be standardised. Thus, the natural consequence: the webshop. Here you can experience online convenience with personal service.

Real DOP’s on display. Buy them at https://dopshop.damen.com/

References

  1. Damen DOP shop
  2. Schiphol Airport expansion, Wikipedia (Dutch)
  3. The DOP® submersible dredge pump and the possibilities for the contractor, DPC December 1998

See also

 

 

Memorable Moments of the Bucket Ladder Dredge ‘Karimata’

Model of the tin bucket ladder dredge ‘Karimata’ in the National Dredging Museum

This weekend, I took my family out for a day at the National Dredging Museum. A great place to experience the history, the physics, the industry and the interesting stories from the people who made the Netherlands the great dredging nation of today. As museums go, they also have a lot of models of old, new and important dredging equipment. One particular model had my interest: the tin bucket ladder dredge ‘Karimata’ form the mining company Biliton.

This particular model used to be part of the collection of the Delft University of Technology. It was standing in the hall between the dredging laboratory, where we received our lectures from professor ‘de Koning’ and the coffee room where we drank hot chocolate in the coffee break. Passing this exhibit, sometimes he would pause and tell an interesting story, or explain how nice the specific kinematics of a bucket ladder dredge is able to cut cohesive clay, or remind us of the difficulty of keeping the ladder correctly oriented in the bank. During a rationalisation of the available floor area and the ‘required educational space’, the model moved to museum.1

Professor de Koning (Credit: CEDA)

The ‘Karimata’ was designed as a floating mining factory. The front side of the dredge was the normal bucket ladder dredge to remove the tin containing sediment or overburden from the mining pit. Usually the dredge started at the shoreline, creating its own pool. Overburden and tailings were discharged behind the dredge through those long chutes at the back. Valuable ore was separated in the refinery at the second half of the pontoon. Cyclones and jigs densified the ore2 and removed the tailings. Eventually, the ore could be loaded on barges alongside the dredge.

Picture of the ‘Karimata’ (Credit: Nationaal Baggermuseum)

Before the ‘Karimata’ was transported to the customer, the dredge had to be commissioned and tested. Normally, such an operation is usually done in a well-defined environment like the ‘Haringvliet’ or ‘Hollands Diep’. This time, however, a more challenging job was proposed. In 1799, the ‘HMS Lutine’ was sailing north of Terschelling. The ship was used for an enormous gold transport in bullion and coins. Unfortunately, the severe storm sank the vessel and only one crew member survived. The gold treasure was still there. Over time, several attempts were made to recover the gold. In 1938, most of it was still not recovered3. The ‘Karimata’ was set on a mission to recover the rest. Eventually, the commissioning was successful4, but only one bar of gold was found and the endeavour was called off. ‘Karimata’ was sent to her customer and used until her end5 in 1953.

And the remaining treasure of ‘HMS Lutine’? Well I think, the villains in the adventure comic of ‘Captain Rob and the Seven Star Stones’ seized it and none is left.

Captain Rob and the Seven Star Stones (Credit: Erven J.P. Kuhn)

These bucket ladder dredges were successfully used to mine and process tin. Even in the seventies(?) several of these vessels were ordered by a Malaysian company. During a visit in 1995, they were still operating there in a tin mining pit. For the commissioning of those dredges, a consultant was hired to perform some specific measurements on the vessel. As a token of gratitude, he received a big poster of the dredge. After cleaning out his office at his retirement, I received this poster and it has decorated my office ever since.

Poster of an unknown Malaysian tin bucket ladder dredge

References

  1. Deed of donation, National Dredging Museum
  2. The problem of jigging tin ore, Ports and Dredging nr.47
  3. HMS Lutine
  4. Strain Measurements on Gold-Seeking Tin Dredge Established Basis for Scientific Solution of Dredging Problems, Ports and Dredging nr.10
  5. E.B. 22 Karimata, DredgePoint

See also

The Ancient History of the Cutter Suction Dredge ‘10th of Ramadan’

Cutter Suction Dredge ‘10th of Ramadan’

Last week I was away to Egypt. I have some emotional ties with Egypt. It took me the better part of seven years, to deliver the cutter suction dredge ‘10th of Ramadan’1, to the Suez Canal Authority. This all started from the qualification tender, building it at the Port Side Shipyard in cooperation with DTC, eventually all the way through the guarantee period. At a certain moment, I was so occupied with this dredge, I even prepared a paper model of the vessel in my own spare time.

Presentation of the paper model of ‘10th of Ramadan’

This nerdy pastime served a practical purpose. The specifications of the construction and the requirements for the installed equipment, were very complicated and it helped me to understand the problems in the hull construction before they arose in reality. The environment of the Suez Canal demands some specific requirements concerning tank and space division. Furthermore, the SCA is very aware of the capabilities of the crew and demands corresponding considerations on equipment and systems. To fit this all in the prescribed box, was quite a puzzle. The normal operational environment of the dredge is maintenance on the shallow shelves of the Suez Canal.

Example cross section of the Suez Canal

The maximum box size, that made the design so tricky was determined by a certain lock to access the irrigation system along the Suez Canal. On the west side of the canal, water from the River Nile is diverted to the fertile land over there. Already in ancient Egypt, this was a much treasured area. Joseph gave this area than called Land of Goshen to his family to live there2. Senausert III, Pharaoh of Egypt (1874 B.C.) also saw the potential of this area and used it to established a connection, between the Mediterranean and the Red Sea by linking branches of the Nile to the Bitter Lakes3. Subsequent kings renovated and expanded the canal, that eventually became known as the ‘Canal of the Pharaos’4. Unlike the international importance of the current Suez Canal, the Canal of the Pharaos was mainly used for local transport of produce of the irrigated land and construction stones from quarries on the Red Sea coast to the monuments along the Nile.

Canal of the Pharaos (Credit: Wikipedia)

In fact, the ancient Egyptians might be called the inventors of dredging canals for transportation, preceding the Chinese by about 1000 years5. Parts of the canal are still there. They are now incorporated into the irrigation system, that the Suez Canal Authority has to maintain, next to the big Suez Canal. In a way, I feel honoured, that the dredge that was once only a figment of my imagination and became a reality, will one day keep this ancient piece of Egyptian history alive and preserve it for future generations. Well, that may be a bit presumptuous, but I still feel proud over this dredge and have fond memories of the people from the Suez Canal Authority I have worked with.

OK, I may have pestered my colleagues so much with my stories about Egypt and my little dredge, they even prepared a cover for a book for me to write about it on my work anniversary.

Cover page ‘Mark Winkelman as Egyptian’ (Artwork: Gert Kraaij)

References

  1. ‘10th of Ramadan’, DredgePoint.org
  2. Genesis 45:10
  3. Canal History, Suez Canal Authority
  4. Canal of the Pharaos, Wikipedia
  5. History of Canals in China, Wikipedia

See also