Merwede 5 / Sand: wet & dry
Merwede 5 sandpump
The all-rounder machine of Dekker Natural resources, also called the sand dredging/classification installation ‘Merwede 5’, is a multifunctional composition of 3 floating installation elements (Merwede 5 / Rotterdam 31 / Rotterdam 37). This installation has the purpose of mining the present and leftover sand grains in the most efficient manner. This is done in locations where the sand is less coarse or where one of our other sand classification installations has already mined the sand.
The Merwede 5 is designed in such a way that 3 basic types of sand can be produced which are wet filling sand, wet industrial sand and dry industrial sand. The foundation of all these sands are equal; dredged sand from a sand mining location. The big difference is in the adjustments which are done on board and online. For the filling sand, this is a single screening of the wet product which is applied to a static screen. Through this process we get rid of the coarse clay, wood or stones and what is left is a clean, easy to use and densifying product for a wide range of civil applications.
The wet industrial sand is also screened but this is done with very fine mazed screening mats (between 1 and 6 mm). This also gets rid of the dredged clay and wood particles which is dredged together with the usable sand. First of all, we buffer the sand on the Merwede 5 in a large pump container from which we pump it on the Rotterdam 31 for the processing on the Rotterdam 37. By separating flow and return from this pump container we can create an amount of overflow and that overflow we use to get rid of the lightest, floating parts. As an addition, the cradle has 2 seperate water pumps which can be used on two different heights to inject a high volume of extra water into the pump container. This is used for the sand which is used in bitumen roads; there is less demand for the grains between 0,5 and 0,25 mm and we can separate this grain size from the desired grains of sand efficiently and easily in this manner.
From this cradle, we dredge the sand with our pump station Rotterdam 31, located behind the Merwede 5 and we push it towards our processing pontoon Rotterdam 37. Here, with the help of 2 adjustable hydrocyclones, we work further on getting rid of the lightest and finest particles. The output of these cyclones is put on a dewatersift with which the water and sand can be separated and the dry sand (moisture percentage ~15%) can be loaded alongside the Rotterdam 37( a docked sandship) via two transport belts. In this process the filtered and finest sand particles are washed overboard and the sand is mined again at a later time with the installation together with wet filling sand as a most preferred application. Through this efficient process we can use all the grains and optimize sand mining all together!
Dredging proces in detail
The dredging process is done through a suction pipe with a length of 38 metres. With a maximum angle of 45 degrees the installation reaches its maximum dredging depth of 27 metres. For special projects the Merwede 5 has a suction pipe and lifting pontoon, which is a pontoon with an addition of a longer suction pipe so that the maximum mining depth can be reached of 40 metres. Alongside the suction pipe a tube is installed through which the high pressure jet water is pumped downwards.With this water,with a pressure of 8 bar, the sand on the bottom is loosened up and made into a liquid so that the suction pipe can dredge it. The sand pump, that ultimately take care of the dredging and pushing of the sand, is located in the pump room underneath the operation cabin. In order to transport the sand up the pump must have an under pressure or vacuum in the entire suction pipe through which the sand/water mixture will start to stream upwards. This costs a lot of energy and thats why the Merwede 5 has a tool to get the mixture easily through the hose and its called an injector. This injector is created by taking a second waterpump which injects water from downwards to upwards so that there is always a steady flow and speed in the suction pipe.
Equipment on board
In order to dredge the sand and to process on board we have the following pumps, screens and transport belts:
• Sandpump Merwede 5 – diesel driven – 250 kW
• Jetpump 8 bar for loosening sand underwater – diesel driven – 250 kW
• Injectorpump on suction pipe – diesel driven – 160 kW
• Pump ‘Rotterdam 31’ for dry loading – diesel driven – 250 kW
• Generator for electricity dry loading – diesel driven – 130 kW
• Generator for electricity in general – diesel driven – 130 kW
• De-watering screen for dry loading – Electr. driven – 30 kW
• 2 transport belts for dry loading – Electr. driven – 18 kW
Merwede 5: 65 x 6,8 metres (sand dredger + loading wet)
Rotterdam 31: 17,5 x 6 metres (pump Merwede 5 > R’dam 37)
Rotterdam 37: 16 x 36 metres (classification dry sand)
Basic configuration: 27 metres
With suction pipe lifting pontoon: 40 metres
Wet filling sand: max. 750 ton/ hour
Wet industrial sand (grain size 0-1) max. 600 ton/hour
Dry industrial sand (grain size 0-2) max. 400 ton/hour
Dry industrial sand (grain size 0-4) max. 350 ton/hour
1 Skipper / Dredge Master
1 Vlet skipper / Laboratory worker
1 Driver / Deckhand
5 days a week – 51 hours
Build year 1950; modernisation / expansion continually done up to now