Hi, looking for advice regarding my dredge jet flare,i wore the old one out,and cant get the proper replacement one,so bought a blank one,which was shorter narrower and put the water a bit higher into the sluice.
So i spent the off season fitting it in ,then have gone to test it out and it starts to cavitate over half revs.
Would the flare be the problem?
Have checked the pump,suction hose ,pressure hose ,and power jet all seem ok.
Thinking of building a alloy flare with the old one as a pattern,is this the best way forward?
Last i heard of the dredge builder he was in Africa and that was 10 year ago so needle in haystack there, its been a great dredge would love to keep it going.
Thanks heaps for any advice!
yeah it sounds like the water isnt flaring enough to put an even flow down your box, id say the cavitating , is caused be uneven pressure on your sluice box, if it didnt do it before , then your new flare is the problem .
Thats great to hear ,its been really bugging me ,and makes alot of sense,
Thanks alot
Can you put some photos up of your powerjet and flare set up. Did you make the jet yourself? Are the jet orifices the correct size for the pump. Maybe the water is restricted. Have you checked the impeller for a stone?
Are your pumps cavitating ?
Id be checking all hoses for birdsnests /stones/ dead rodents
Or the powerjet flow itself is disturbed ?
Throw it away and build an alloy crashbox better for breaking material such as clays and conglomerate materials up
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Hi ,thanks for all your help we have checked everything out and built at flare to original specs test day sunday ,great idea about the crash box,we are thinking of building a dredge to the specs of my gold grabber as its been a awesome machine these last 10 years,but a crash box may be better on a claim i have with blue bottom clay,ill keep you posted how it goes ,thanks again.
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venturi system ? 2 hoses can be a pain at times
Dont agree with this. Flares are alot more efficient and better on fine gold recovery.
If you have lots of clay or conglomerate a good blaster nozzle is needed and you shouldn’t rely on a crash box
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the length of the flare and its angle is most important. The flare should flare at the same angle as your angle of your jet logs. It sounds to me as though your powerjet is too short or the jet logs are not submerged enough in the water. You want them to underwater.
Its important to angle the flare properly so the water wells up into the head of the sluice.
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Thanks for the info,we built a flare same as the old worn out one and it works mint,thank goodness,after 10 years i thought id have to divorce my dredge and buy another,but no ,man im looking forward to jumping in the river now,when it isnt in flood like it is at the moment.
Thanks for everyones advice.
Will try to post some pics when we runnning.
Hope everyone has a golden summer!
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Can you provide some evidence for some of your statements ?
Mainly jetlog angle matching flare angle .
And the powerjet and its hoses needing to be under water ? I can see how it may help it prime faster but its not going to make a difference once its operating unless theres a lot of air leaks
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The flares job is mainly threefold:
- To slow and spread the waterflow as it enters the head of the sluice.
- allow heavy particles to re stratify within the water column
- to extract energy out of the high speed water introduced from the jet logs and helping create laminar flow.
By having the angle of the flare proportional to the angle the jet log enters the powerjet helps achieve (3) above. The other variable is length between the jet log and where the flare starts flaring.
Im not aware of many dredges where the seal between the hose and the powerjet is sealed 100% especially on an oversized powerjet which is the gold standard when it comes to dredging. Getting air into your water column is not good for fine gold recovery or powerjet efficiency
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Cheers for the reply. I’ll leave it at that
If you disagree could you please share your logic for building a dredge where the jetlogs are higher than the waterline, and explain your thoughts around flare angles/design? Cheers