While the sand-gravel mixture is loosened with the help of powerful water jets, the slurry is transported into the hopper by means of large dredge pumps. A 160 kW Etanorm unit serves as a water jet pump providing the draghead nozzles with high-pressure water during the dredging operation. The pumps handle slurry with a density of up to 1.3 t/m³, dredging almost 2 500 t of solid material per hour from a water depth of up to 20 metres. The casings and impellers are made of highly wear-resistant white cast iron. The two biggest units have a weight of 5 500 kg each and are designed with three-vane impellers sized 835 mm in diameter. Five pump sets are slurry pumps manufactured by KSB’s US subsidiary GIW. The first ship ordered by a Belgian customer is a so-called trailing suction hopper dredger which will be fitted with six pumps. I made a removable restriction nozzle so I could get my hand in to clear blockages, and for easy replacement as it wears out.Two dredgers built at a Dutch shipyard will be equipped with specialised pumps by the KSB Group (Fig.). The water was only 2 feet deep where I was working, but the old venturi did not have had that sort of power. The result was great, power increase was such that the water and gravel came up the hose with such velocity at high rpm, that it shot right over the sluice box and landed back in the creek 2 feet beyond it! I had to slow it right down to be able to wash the gravel. I will try to load 2 photos showing what I came up with. I used alloy for weight reasons, but also because it was what I had on hand. I lined up the new 3/4 inch jet to be slightly pointing downward but up the center of the pipe - so the water jet would hit the bottom of the pipe about 3 or 4 feet up. Mostly because my hand wouldn't fit up past the nozzle restriction. The old shop bought venturi had worn totally out and was very hard to get jammed rocks out of. My pump is a 5 hp Honda driving an Onga pump - a factory built pump/motor unit available here in NZ. The last one was four inch and I used a 3/4 inch jet with a flare out to the 1 1/2 inch supply. Hi there, I have made a few suction venturi nozzles over the years, as I couldn't find or couldn't afford store bought.
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