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KEENE ENGINEERING’S 5" EDUC-TION DREDGE EQUIPPED WITHNEW OVER/UNDER DOUBLESLUICE BOX.. MODEL 5109H.

This report is based upon datadeveloped on tests conducted in theEast Fork of the San Gabriel River,San Gabriel Mountain Range, Stateof California. The site of the test wasapproximately one-half mile south ofthe confluence point of the East Forkof the San Gabriel River with CattleCreek in the Angeles National Forest.The test area was of typical placergeology for the area.

EQUIPMENT:The equipment used to conduct

the test was a new KeeneEngineering 5" Eduction Dredgeequipped with the prototype versionof the over/under double sluice box,as fed by a standard productionmodel 5" Marlex Jet

Flare fitted with a 5" jet poweredby a 3" singlelog inlet with 20 feet of5" Tigerflex suction hose. The engineand pump assembly consisted of afactory-new Honda GX270 9H.P.overhead valve engine fitted to aKeene Engineering P350 pump witha 4" intake and 3" discharge outlet.The engine was also equipped with adirectmounted belt driven T h o m a smodel T80 low pressure compressorfitted to a Keene Engineering RT1reserve tank and 20 feet of air line.

The factory supplied Hondamuffler and spark arrestor assemblywas removed and replaced with a sin-gle diver Stapp Mining Companywater heater equipped with a stockBriggs & Stratton muffler and sparkarrestor assembly. The water heaterwas supplied with feed water directlyfrom the P350 pump via the integrallyfitted factory hose connection. A l lclamps, hose connectors and the jet

were pre equipped with quick discon-nect style couplings.

It should be noted that the fol-lowing test was conducted after theequipment was subjected to a 20hour break in period where initialengine operation, gaskets, seals andhose and tube connections werechecked for leakage and proper con-nections. An initial factory specifiedoil change was performed on theengine after the break in trial period,but before the commencement of thetest period.

ASSEMBLY AND SETUPPREPARATION:

After the initial break in period,the equipment was disassembled intotransportable component parts andchecked for defects while basic facto-ry recommended engine mainte-nance was performed. No defectswere noted in the factory manufacthe

5 inch Dredge Model 5109H

By CAESAR J. MILCH

Produc tReport

ture or assembly of the componentparts.

On the first day of the test peri-od, all equipment was checked foroperational readiness and transport-ed to the site of the test. The entiredredge was assembled by two per-sons without the use of tools inapproximately 15 minutes and floatedinto a preselected position in moder-ate water flow. Fuel and oil levelswere confirmed and initial operationwas commenced.

Adjustment of the sluice boxangle, jet flare and jet depth wasdetermined based upon the depth ofdredging operation and type of mate-rial being educted and sluiced. Attimes during the test it was necessaryto drop the jet position using the pro-vided holes in the jet hanger supportstrap to increase the eductive powerbased upon the depth of the materialbeing transported up to the surface.Other times it was necessary toadjust the angle of the Marlex flarewhere it met the head end of thesluice box so that a better flow ofwater was more evenly distributedover the leading portion of the sluicebox in order to prevent the first sec-tion of riffles (as covered by the firstgrizzly) from being clogged with loosematerial that was not compacted inthe stream bed, and which thus had atendency to be educted faster thatharder packed materials.

Lastly, it was also necessary toadjust the angle of the sluice box onthe dredge frame several times inorder to achieve a satisfactory aver-age angle. This was noted to be nec-essary due to the change in weight ofthe sluice box as the heavier materi-als began collecting in thelower/under sub sluice. Once a medi-an position was determined, thesluice box was left in this position andoperated without incident for theremainder of the test period.

NOTED DIFFICULTIES:The only problem of concern

was found approximately seven daysinto the test when the T80 compres-sor pulley rotation was periodicallystopping and starting while the

engine was running at constantspeed. It was determined that the pul-ley would begin slipping when thedemand on the air supply was low, orthe engine R.P.M. was slow enoughto decrease the friction on the drivebelt. Operations were immediatelystopped and the problem was deter-mined to be caused by the compres-sor not being held in a secure manneron the mounting plate. A furtherexamination revealed that the flatwashers on the compressor mountingbolts did not have enough purchaseagainst the underside of the alu-minum compressor bracket to holdthe compressor in position without it“walking" up the adjustment holes inthe mounting plate. This problemwas corrected that day by removingthe compressor mounting bolts andinstalling stellated style lock washersunderneath the supplied flat washers,and re tightening the bolts after a cor-rect belt tension was obtained andthe compressor blocked into positionthrough field expedient means whilethe dredge was still afloat. No furtherproblems of this nature were found tooccur throughout the test.

SLUICE BOX OPERATIONALPERFORMANCE:

After approximately two days ofrunning time, it was determined thatthe secondary grizzly needed to beremoved frequently in order for the rif-fles to adequately clear out. Theheight of the grizzly was varied in anattempt to remediate this problem,but it was found that a satisfactorylevel could not be achieved withoutconstantly changing the jet flareangle or angle of the sluice box onthe dredge frame. It was eventuallydecided to remove this secondarygrizzly. The continued operation ofsluice box went unhampered with thisremoval as there was more thanenough water flow through the box toremove the heavier cobblets out andover the riffles after they dropped offof the first grizzly.

It was also found that the sluicebox operated at peak performance (interms of keeping itself clean) whenthe water flow was kept about 1/2"

below the top edge of the box at thedischarge end. This only requiredthat the engine be operated atapproximately 60% throttle for mostsituations, even when the depth ofthe dredging reached 12 feet belowthe water surface.

Some packing of material wasfound to occur under the first grizzlywhen the dredged material was in astate of heavy saltation and suspen-sion, and thus was more readilyeducted in higher quantities muchfaster. A field expedient fix was effect-ed which raised the rear of the grizzlyapproximately one half inch abovethe tops of the last set of “V" barsattached to the riffles below the tailend of the grizzly. This did not impedethe rearward movement of cobbletsoff the grizzly and out of the sluicebox, and also did not require the fur-ther adjustment of the jet flare orsluice box on the dredge frame.

SUBSLUICE OPERATION:I n i t i a l l y, the sub sluice was

cleanedout on a daily basis to seehow it was operating and what type ofmaterial was being collected and heldthroughout its length. It was laterdetermined that a daily clean out wasunnecessary, and actually took moretime than necessary on a daily basisto conclude the day's operations.Once it was determined that therewas not going to a problem with thesub sluice “loading up" it was left inplace for up to three days at a time,depending upon the type of materialencountered during dredging opera-tions. (The added weight of the subsluice material helped keep thedredge platform stable and obviatedthe need to constantly change thesluice box angle on the frame to com-pensate for the lighter box weightwhen it was empty. Once the subsluice was emptied and the dischargeend of the dredge was felt to be toohigh, a spare diving weight belt wasset on the discharge end pontoonsuntil the sub sluice had accumulatedenough weight to achieve a satisfac-tory angle of operation). Although notemptied and cleaned on a daily basis,the sub sluice was examined on a

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daily basis for distribution of valuesand to make sure it was not clogged.This was easy to do based on thedesign of the large removable topplate which allowed the riffle tray toremain undisturbed.

It should be noted that such aninspection should only be done whenthe box has been allowed to drain ofwater and the material allowed to set-tle, so that the removal of the topcover does not allow the sub sluiceriffle tray to become raised and thematerial allowed to flow underneaththe riffle bases, which then makereassembly impossible without a totalclean out being performed.

The sub sluice was found to trapand hold a great deal of fine material,and was responsible for the recoveryof the bulk of the minus 20 screenvalues recovered during the test peri-od. It did not pack up when a lot offine material was being dredged, asthe punch plate entry to the subsluice would only admit a meteredamount of material, with the excessbeing allowed to travel forward aninto the top sluice where it wassluiced, and discharged normally,with the values being held in the firstfew sections of the upper box riffles.

One anomaly was found in thesub sluice: an inordinate amount ofrocks that were approximately the

size of a dime, and very flat in thick-ness. It is postulated that these rocksentered into the sub sluice eitherthrough the sides of the punch plate,or under the back lip of the punchplate when material would build up infront of the punch plate lip at the dis-charge end of the Marlex flare. Thiswould have the effect of raising therear of the punch plate slightly, allow-ing a vacuum like effect to suck theserocks into the lower sluice. Theirpresence was not detrimental to thesub sluice operation, and the majoritywould most often wash out the dis-charge end of the box in time. Onlythe flattest and biggest such stoneswould remain in the riffles.

Their out flow from the box dur-ing operations could be detected byplacing one's hand under the dis-charge end of the sub sluice and feel-ing them drop out along with thelighter sands and materials. This wasquite evident even when the dis-charge end of the sub sluice wasunder water as the pressure of thewater at the head end of the sluicewas sufficient to push the water downinto and through the sub sluice onaccount of its own weight and theadditional pressure created by thedampening flap trailing over the jetflare discharge flow.

OBSTRUCTIONS:Operational obstructions were

infrequent and mainly consisted offlat “skipping style" stones that wouldorient themselves in such a was asthey traveled up the suction hose tobecome lodged in the log opening inthe jet. These stones would thencause a fairly large jam which usuallycould be freed with a rod afterdecreasing engine speed to an idle.Very infrequently was it necessary toremove the suction hose from the jetquick release and manipulate the jamfrom both sides in order to clear it.

Hose jams were virtually nonexistent and were always able to becleared by manipulating the hose inthe water. The flexibility and ductilenature of the hose made jam clearingeasy and undoubtedly prevented amajority of jams in the hose itself. Nojams were noted to have occurred inthe Marlex jet flare and only a fewjams occurred in the swivel nozzle.These were almost exclusively trian-gular shaped rocks with a slow taperwhich lent themselves to stickingfirmly in the nozzle. Breaking suctionby raising the nozzle out of the watermomentarily would usually free thistype of rock without the need for fur-ther tools or shutting down thedredge.

FUEL CONSUMPTION:The total running time for the

test period consisted of 100 hoursover 20 working days. Intermittentdays off were taken for rest and main-tenance purposes, as well as supplytrips and the like. A total of 42 gallonsof 87 octane gasoline was consumedby the 9 H.P. engine during these 100hours. Fuel consumption was there-fore .42 gallons per hour of runningtime. The average price per gallon forfuel during the test period was $1.35per gallon. Accordingly, the fuel costper hour of running time equates to56.7 cents per hour.

One oil change was performedduring the test period for the purpos-es of determining the engine break inprocess and to ensure that no metal-lic fragments were left in the engine

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as a result of the assembly process atthe factory. This added $2.40 to theoperational costs and when factoredinto the fuel cost perhour, raised theoperational costs to 59.1 cents perhour.

VOLUME OF MATERIAL MOVED:An estimate of the hole dredged

during the test period indicated that itwas an average of 10 feet wide at alltimes, and extended for a distance ofapproximately 65 feet. The depthranged from 8 feet at the shallow end,to a depth of 12 feet at the forwardend. The 8 foot depth continued for adistance of 20 feet, and then droppedto a depth of 10 feet for an additionaldistance of 25 feet. At this point thedepth dropped to 12 feet for the final20 feet to the forward end of the hole.

A conversion of the above fig-ures into cubic yards indicates that atotal approximate amount of 241cubic yards of material was moved.(It should be noted that not all of thismaterial processed through thedredge. A significant amount was ofa size larger than the nozzle intake,and therefore was moved by hand, orwinched out of the hole). It shouldlalsobe noted that much of the mater-ial being dredged was also heavilyimpacted with clay. This ‘hardpacked” conditon as well as the larg-er cobbles unable ot pass through thesuction intake, can significantly effectthe “yard per hour rating” indicated bythe manufacturer.

Dividing the amount of materialmoved by hours run, provides a figureof 2.41 cubic yards of material beingmoved per hour. If one furtherassumes that only 4 hours of actualdredging time occurred over the 20work days (leaving 1 hour per day ofrunning time for water heater warmup and clean out time) this wouldrevise the material moved figure to3.01 cubic yards moved per hour(241 cu. yd. divided by 80 hours ofactual dredging time), or 12.05 cubicyards of material flow through thedredge in a 4 hour period.

COST TO MOVE MATERIALAs previously indicated, it cost 59.1

cents per hour to operate the dredgeduring the test period. If we thenassume the previous figure of 3.01cu. Ds. being moved per hour, it canbe calculated that it cost 19.63 centsper cubic yard of material moved, atthe average price of gasoline listedabove.

REQUIRED VALUES PRESENT INMATERIAL MOVED:

Given the forgoing figures, it canthen be calculated how much valuesmust be present in the materialsbeing moved for the operational costsof the dredge to make a break-evenpoint.

The average price per cwt. goldduring the time of the test was $19.50per dwt at a fineness of .999, and$17.55 per cwt. at a fineness of only.900. Dividing the cost per cubic yardof material movement, the materialmust contain at least .0100 cwt. ofvalue per cubic yard at .999 fineness,and at least .0111 cwt. per cubic yardat a fineness level of .900. (This isdetermined by dividing the cost ofmovement of each cubic yard by theprice of value per cwt.)

However, it must be understoodthat even though the material maycontain the above required levels ofvalues (at the listed prices and duringthe times when gasoline is at the testperiod levels per gallon), this may notbe the level of efficient recovery oneexperiences with the equipment test-ed. Accordingly, if no assay of thevalue. content of the materials movedis performed, and one does notexceed the break even recovery levelof values, it cannot conclusively beknown at what recovery efficiencylevel the equipment is functioning.

CONCLUSION:Depending upon the price of valuesrecovered and the operational costsencountered, the equipment present-ed itself as a very reliable, easilytransportable and economical meansto conduct values extraction. Most of

the test time was conducted by oneperson running and maintaining theequipment once it was brought to thetest site, thereby indicating that theaddition of more personnel to anoperating crew would certainlyincrease the amount of materialcapable of being moved, and therebytheoretically increase the amount ofvalues recovered.

ADDENDUM TABLE OF VALUES RECOVERED DURING TEST PERIOD:

A total of 20.2 dwt of valueswere recovered from the materialmoved during the test period. (A peri-odic check of the tailings was madewith several recovery methods, and itwas determined that no identifiableloss of values was occurring duringthe times the tailings were beingmonitored on a daily basis).1.8 cwt. in + 4 screen size nuggets7.7 cwt. in 20 screen size flake andpieces4.0 cwt. in 16 screen size flake andpieces3.3 cwt. in 12 screen size smallnuggets1.7 cwt. in 8 screen size smallnuggets0.9 cwt. in 4 screen size nuggets0.8 cwt. in dust

It should be noted that the 0.8cwt. recovered and listed as “dust" isindeed just that. This material wascaught and washed out of the upperand lower sluice carpeting after thefinal clean out on the last day of thetest period. It appears so fine that itstays in suspension in water whenagitated. This would tend to substan-tiate the above referenced minimalloss of values experienced in the test-ing of the tailings, and also indicatesthat the surface tension of the waterexiting the jet flare is adequatelybeing broken, so that this material isgiven the opportunity to settleout andbe entrapped in both sulice boxes.