crab shedding

7/28/2019 Crab Shedding

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FLSGP-G-97-003 C2FLORIDA SEA GKAN'I' C O L L E G E P R O G W I

June 1997

Crab Shedding-System DesignsDon Jac bo n and Don Sweat

The Only Way?There are as many ways to build and arrange crab shedding setups as there are people who m ake them. Thefollowing drawings are suggestion s based on the experiencesof successful shedders. You may find changesthat suit your operation better.

The Simpler - The Better!Tank floors can be 314-inchor 1-inch CD plywood. The sides can be m ade from 12-inch plywood,r 2-by-10-inch boards, or 2-by-12-inch boards. They can be caulked at the seam s and sealed with either fiberglassresin or a product such as G1uvitTM.Tanks can be set on wood frames or concrete blocks. Fiberglass tankswork well, too.All plumbing should be PVC . No m etal should com e in contact with the water, partly because of saltwa tereffects on the metal, but more for the health of the crabs. Size of PVC is important, too. The main feederline from the pum p to the individual spreaders shouldbe 2-inch PVC. This creates less "h e a d than smallerpiping, allowing for a large savings in electricity. Few er bends in the plumbing are better; every elbo w andtee increases friction, creating more head, and costing more m oney for pum ping.The draw ings show two mechanical filters. You only need one. The reason we've shown two is to offer anoption of placing the m echanical filter at the end of the drain line, or to m ount it as an integral part of thebiological filter. Eitherw ay w orks, it's a matter of convenience for cleaning it out regularly. You may notneed one with a headwall if it is mounted above the biological filter- t can drain out the bottom. In thatcase, a plastic "milk" box m ight work aswell.Th e biological filter is the key factor in a closed system . Any building m aterial will do, but concrete isprobably the simplest, and may be cheap est in the long run. The size shown (abo ut 5-by-10-feet) shouldservice any expansion up to 20 tanks, depending on how many crabs are put in each tank.

Don Jackson is the F lorida Sea Grant Blue Crab Project Coordinator and Don Sweatis the Florida Sea Grant Marine Agent for Levy, Citrus, Hemando, Pasco andPinellas counties.Florida


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Crab Shedding Tanks and FiltersClosed System3 tank setup - modular viewMechanical@ and Biological@ filters canbe arranged in several other configurations.Drain system should have shortest runspossible to preserve "fall" for gravitydrains - from first tank in line toBiological filter. This may necessiateburying this filter.Tank spreaders illustrate 3 differentways of distributing water within thetank. All work well.

@ Mechanical Filter0 Biological Filter@ 1 h.p. Pump@ Open Elbow - open flow@ Open Elbow - whose@ Cap wholes drilled


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Machine Bolts

Note: Middle Brace andlegs offset to allow roomfor drain in center of floor.

TI 4'x8' Tank wI10" Sides on 314" Floor 1


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Mechanical Filter

4" PVC Drainfrom Tanks

toBiological

Filter+...........................................12"kiberglass Batt--+ ............................................. .

-V-V-v-v-v-

NOTES:1. Mechanical filter can drain from bottom if biological

filter is below grade. Use of headwall-baffle system preserveshead for gravity flow into biological filter if necessary.

2. Mechanical filter can be separate unit or placed insidetank of biological filter.


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Biological Filter

FromShedding Mechanical

Tanks Filter Concrete orPlywoodHeadwallBiologicalF i t HardwareC l o t h 7preader4

From Mechanical Filter

\ \ Fiberglass Roofingw/slits I I

3500 PSI ConcreteTank Reinforced with#3 Rebar@ 12"O.C.Tank Only Weight=5,452 lbs.


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Shedding TankEnd view

k "PVC Outer Drain - 6"ta\2" PVC Drain - 4" tall\ "PVC Coupler - bedded\ " PVC Piping\ " x ~ " x z "anitary Tee in4" PVC Drain Pipe


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TanWTable ConstructionNailer Strip,Vertical

1" x l "Nailer Strip,Horizontal I 1-114" Flathea d- Wood Screw

Floor: 4'x8' Plywood - 314" preferred - 518" acceptab le- Marine grade preferredSides : 314" or 518" Plywoodor 1"x12" Pine boards (or 1"x10")Nailer Strips: 1" xl" nominally - Pine - bedded w1CaulkFasteners: 1-114" Screws or Nails


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Feed From Supply (Pump) Into Tank

1-1/2"x1-1/2"x3/4" educing Tee1-112" PVC Supply, overhead

314" PVC Ball Valve

Alternative A

314" Tee

AlternativeB

Note: Alternative C is similar to B with vrnnyl!tUt4mWdHi

crab shedding

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