How Dredges Work

So let us now get into how it functions. Let us imagine that the manufacturer of the dredge has made his four-inch nozzle so that it will only accept a three-inch stone so that there is a reduction in clogging of the tube. In other words, the biggest stone that would be able to go in the nozzle would have to be in the shape of a perfectly round circle. A stone like that of granite would weight around 3.7 pounds if it were above the water and 2.3 under the water. However to get it to move up a suction tube that has been inclined at sixty degrees with the surface of the stream would only need around two pounds of force so that it continues to move at the velocity of the water.

There are certain things that have been left out as far as how dredges function such as things like turbulence, vapor pressure, cavitation and a few others. However, be aware that the things previously mentioned (amongst others) are occurring inside the suction tube and pressure box however in learning how a dredge functions they are not as important in comparison to the bigger forces. Even though all these different things are not being highlighted on, they are in fact very important to keeping the dredge working adequately.

All prospectors that have worked with a normal sluice know that in many occasions the material that has gold in it is lightly cemented and on occasions it is clayey while other times it is harder. When a hand operation is taking place this material needs to be broken up and in many occasions it needs to be run through a grizzly. This whole process is done inside the tube where turbulence and cross currents begin the process at the bottom or base end of the jet. In this place sand and cemented materials are crushed up due to the force of the water and bigger pieces of gravel keep on with the process throughout the journey up the tube while they crush into each other. After the force of the jet is squandered in the pressure box under a lot of agitation caused by the turbulence, in most cases even material that is very cemented will break up.

This is when the initial classification normally starts. In most cases almost all dredges have a small grizzly or a screen that sorts that lets a good amount of the little particles to drop through to the bottom while the rocks that are bigger rush out. Due to the sand that normally has the gold particles is directed to the lower part of the sluice stream, the gold becomes more easily separated and held.

Before we get into how to set up and test your new dredge we will first get into describing a few of the different types of dredges that are available and this way you will have some information and so it will help you make a decision on what type you are considering purchasing.

When you are looking into buying a dredge you should keep in mind that after the float, pump and engine combination and sluice have been decided on you will then be able to make a number of decisions on the type of suction nozzle you will need. For instance, if you begin with a fixed ejector, surface sluice, you will possibly be able to include a portable ejector later on for more shallow operations or you can also add on an underwater dredge in order to take care of major overburden.

If you have the idea of adding different suction nozzles later on or in the future, talk about it with the manufacturer before you decide which dredge to purchase. The capacity of the pump and sluice is fundamental and there are a good number of manufacturers that are offering combination dredges as a unit, therefore putting together the pump and sluice to suction nozzles you are planning on getting later on will not be a problem. If you need to buy a pump that is rated higher then the capacity of the first suction nozzle, this can in most cases be slowed down and this is done by lowering the speed of the engine.