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Monday, October 01 2018

A highbanker, sometimes called a power sluice, is a very flexible and efficient piece of equipment when you’re gold mining in areas with a good amount of water. Their main use is to allow you to pump the water to the gravels rather than carrying heavy buckets of gravel to the water. The optimal place to use a high banker is a location along a river where there are lots of bench gravels that have been lefthighbanker high and dry by erosion. Just shovel material directly into a high banker and let the equipment do the rest of the work! As long as there is sufficient water close by so the hose can reach it, you’ll be good to go. High bankers are available in various sizes. The bigger the unit, the more gravel it will handle in a day. That also means it will likely be heavier and less portable. High bankers are fairly simple to set up and operate. They have three main components: a hopper feed box, and sluice box, and a pump.

Hopper: The feed box contains a grizzly screen with a water spray bar. The water is normally sprayed from simple plastic pipes with a series of small holes drilled into them. A water valve located ahead of the spray pipe controls the amount of water flow going into the feed box sprays. A series of rods are arranged to make a slat-type screen (called a grizzly) that allows water and smaller material to fall through and go down into the sluice box. The large rocks that are caught by the grizzly are washed with the spray and then rejected. The slats should be set on an angle so that most of the larger gravel will slide off the slats by the pull of gravity without you needing to push them off by hand. Some rocks may hang up, but for the most part, they will slide off on their own. The spray water comes out under a lot of pressure and washes any loose sand or clay into the sluice and also provides part of the water needed to move material through the sluicebox area.

Sluice: High bankers utilize a normal sluice to recover the gold from the gravels, and the operation of the sluice box portion of a high banker is basically the same as that of a hand or stream sluice. With a highbanker, the water is supplied by a pump rather than the flowing water of a stream. The matting and miners moss underneath the sluice’s riffles are the same. Gold flakes get caught in the riffles and moss the very same way as it does in a hand sluice.  A nice back-saving bonus on a high banker is that it will be on legs, so you can operate it on any terrain. A normal hand sluice lays on the bottom of a streambed.

Pump: The centrifugal type pump should be set near the water as it is more efficient to pump water uphill to the sluice than to suck it up to the pump. This is only important where there is a lot of vertical distance between the pump and the sluice. If there is less than 10 feet of vertical distance, it does not matter much. Pumps can be set up quite a distance away horizontally from the sluice. It will work so long as there is sufficient water at the source where the pump is located. Vertical distance is more of a problem than horizontal distance; 30-40 feet is the maximum vertical climb for most pumps. The standard lay flat type of hose is used to carry the water up to the feed hopper. Be sure to have enough hose and some extra in case you spring a leak! Remember to position the pump so that you aren’t breathing motor exhaust fumes all day!

The big advantage of a highbanker is working materials that are found in a location away from a river, like benches and other isolated patches of gravel. Moving the water to the sluice with a pump saves you from carrying the material down to the stream.  The only disadvantage to highbanking for gold might be that it’s more equipment to pack around than just your usual digging equipment. It would be wise to test your ground before hauling in your high banker. Testing will indicate if there is enough gold in the gravels to warrant bringing in more than a hand sluice. If you have at least an amount of gravel that represents a full day of digging and sluicing, bring in a highbanker.

The adjustment of a high banker is much less than the steep slope you usually would use with a hand sluice. Adjust the water flow to the minimum flow rate that it takes to get all the rocks that fall through the screen to keep moving down the sluice box section. If rocks or gravel hang up and bury the sluice, you need more water and perhaps a steeper box angle to wash that stuff away. The height of the feed box is another important adjustment. You want it low to allow you an ease of feeding in the material. If too high, you will hurt your back lifting heavy shovels full of gravel. Too low and you may be constantly sweeping away tailings at the back of the sluice.

The feed box itself should be adjusted to ensure the angle of the slat screen rods (the grizzly) allow the gravel to be well washed before it moves out as waste. This is because a lot of small gold adheres too the larger cobbles. If rocks and cobbles just roll through without getting a thorough washing, you will be losing gold. The rejection of the large oversize rocks is important as it lets your sluice to a better job. If those bigger rocks make it into the sluice, you’ll be getting much worse recovery of fine gold.

Be sure the foot valve or strainer on the intake hose is clear and able to deliver a full water flow. Sometimes the foot valve can get clogged with leaves or other debris. A blocked or partially obstructed foot-valve won’t allow the high banker to operate properly. For environmental reasons, it is a good idea to have your water drain into a pond or pit that is not directly connected to the stream. This is so that the clay and mud can settle out, otherwise make sure there are no legal issues of putting that mud back into a flowing stream.

Some models of highbankers can also be run as a dredge. These highbanker/dredge combos can save you money, offer flexibility, but are also a bit of a compromise since the dredge portion is generally small. Combo units will be equipped with a suction nozzle type of intake. This design is best for working small shallow streams and tributaries.  These systems are designed to be set up alongside the stream edge and have adjustable legs rather than float systems that you’d normally see on a larger suction dredge. With a suction nozzle and more hoses, the combo unit will operate as a suction dredge, picking up material from underwater crevices  and delivering it to the sluice. Highbanker/dredge combos also can be ideal for working in and around ponds in old hydraulic mining pits.

The next time you are out in the field, consider if a highbanker or power sluice can help you get more gold. To determine if the answer is yes, ask yourself these questions:  Where is the nearest water? Can I shovel directly from the diggings into the feed hopper? Can I set it up to allow gravity to do a lot of the tailings clearing work? Where will the pump go? With a little thought and planning, you’ll be able to decide if highbanking for gold will increase your productivity. In most cases it will. Move more dirt, get more gold!  Good luck!

Posted by: Denise AT 01:00 am   |  Permalink   |  Email
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