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Tunnels, Reclaims, & Soil Borings
Grain Entrapment & Other Safety Areas
Presented By: Rodney Carpenter, P.E.
TUNNELS & RECLAIMS
The purpose of reclaims in tunnels is to give better access for operation, maintenance, & cleaning to both the gates & reclaim along with protecting the area from the elements
Center Unloading
Unloading Conditions
Clean
Dry
Free Flowing
In Condition
Unloading Not a Simple Process When:
• Gates plug• Grain develops clumps• Foreign items end up in the conveyors• Grain goes out of condition & becomes
non-free flowing
Off Center Unloading
Grain Facilities Today
• Grain facilities have evolved to a highly complex operation compared to the past. Today there is more automation for high volume incoming & outbound grain.
• The increase has taxed the present state of practical design. The new direction is to give a higher level of consideration to operations, safety, cleanliness, & maintenance.
History
• Facilities that handled over 2 million bushels used to be concrete clusters
• Grain bin storage was maxing out at 750k bushels per bin
• Conveying at 40k bph was high speed• Filling large dia. bins took days to weeks • Soil loads at 4000psf allowable were great
to build on.
Today
• Facilities can have over 2 million bushels in 2 corrugated bins
• A single grain bin is capable of storing 1.3 million bushels
• Conveying has moved toward 100k bph• Now able to fill large diameter bins in
hours, not days.• Geopiers, pilings, soil additives, & soil with
5000psf is being required.
Larger Grain Facility
Tunnels, Reclaims, & Soil Borings
• Tunnels– Type of tunnels– Dimensional design– Safety– Access
Types of Tunnels– No trench or tunnel
• Equipment on top of ground or floor• Conveying under aeration floors
– Equipment trench• Just wide enough for equipment• Top of equipment at surface or floor (usually)
– Equipment only tunnel• Room for equipment • No real access for operations or maintenance
– Equipment tunnel with access
No Tunnels
No Tunnels
• Floor access but below aeration floors
• Limited access to flighting, drag, or belt
• No gate access when filled with grain
• Grating over gates
Pros & Cons
Benefits• Low expense• Minimum planning• Can patch if need to
move
Drawbacks• No gate access• Not always sure gate is
closed• No access to blocked
gates• Can reach conveyor from
bin floor
Trench Only
Trench
• At top edge of concrete
• No gate access when filled with grain
• Trench should run all the way through bin
Trench
• Inside bin access by removing cover
• Flighting, chain close to the surface
• Maintenance when bin is empty
• No gate access• Grating of gates
Pros & Cons
Benefits• Low expense• Requires planning• Fixed location
Drawbacks• No gate access• Not always sure gate is
closed• Blocked gates• Can reach conveyor from
bin floor
Tunnel Equipment Only
Tunnel Equipment Only
• No access for people• Equipment takes up
the space in tunnel• Treated as a confined
space• No access to flighting,
chain, or belt from bin floor
Pros & Cons
Benefits• Requires planning• Blocked gates• Usually can not reach
conveyor from bin floor
Drawbacks• Expense• Fixed location• Poor gate access• Maintenance is difficult• Clean out is difficult• Confined space
Tunnel With Access
• Room to walk & access gates
• Room to maintenance equipment
• Easy to clean
Pros & Cons
Benefits• Requires planning• Maintenance• Clean out• Gate access• Allows for access to clean
out a blocked gate
Drawbacks• Expense• Fixed location
Location of Tunnels
• Above grade• Below grade• Part in grade &
part out
Dimension For Tunnels
• Min height of tunnel– 6’ 8” min (Nebraska)– Min height to transition
to conveyor• Width of tunnel
– Belt conveyor width add 5ft
– Chain conveyor width add 3.5ft
Nebraska
• NFPA 101 requires that above ground tunnels also be minimum 6’8” high
• Also minimum 36” clear width through the entire length of the tunnel.
• Max travel distance 50ft. for dead end or single exit
• Max travel distance in tunnels is 200ft. with 2 exits
• Max travel distance in tunnels is 400ft. if sprinkled
Dimensions for Tunnels– Keep conveyor off floor 12in no less than 6in– Keep drives outside of tunnel when possible
Access To Tunnels
• Personnel access• Equipment hatches
4-6ft. X 10ft.• Personnel access per
OSHA, Fire Marshal• Access every 100ft. • Check Nebraska
Lack of Maintenance Space
Cleaning & Maintenance
• Tunnel with lights (emergency)
• Add compressed air lines and/or water lines
• Portable vac system to pick up grain and/or dust
• Electric outlets (110V)
Cleaning Difficult
Tunnel Drainage
• Sumps in all below grade tunnels
• Crown tunnel based on soil report, usually 2-4in
• Drain outside water away from tunnel
Reclaims• Drags 5k to 40k bph
– Shorter runs– Multiple discharges– Less height to load a drag
• Enclosed Belts 20k to 80k bph– Longer runs– Single discharge– Height to load – Low horsepower
• Screws 1.5k to 10k bph– Shorter runs – Lower capacity
Loading a Reclaim
Tunnels
Walkway
Room for maintenance
Keep reclaim off the floor
Access to gates
Gates, Wells, & Sumps
Gates, Wells, & Sumps
• Location of grain sumps– Spread
• Approximately 10ft. apart• Have at least 2 sumps less than ¼ of the radius of
the bin– Sweep wheels should miss all sumps– Types
• Primary• Intermediate grain sumps
– Last sump within 3ft. to 5ft. of the bin wall
Grain Sump Capacity
• 50 to 90 bu/sq inch rule of thumb for spouting (We use 70 bu/sq inch)
• Sumps use 50 bu/sq inch when possible• Keep sumps as large as realistic for the
application
Flow Rates (bph)
Gate Size Area Max bu Normal Conservativeinches^2 90 70 50
10 by 10 120 10,800 8,400 6,000 12 by 12 144 12,960 10,080 7,200 14 by 14 196 17,640 13,720 9,800 16 by 16 256 23,040 17,920 12,800 18 by 18 324 29,160 22,680 16,200 20 by 20 400 36,000 28,000 20,000 22 by 22 484 43,560 33,880 24,200 24 by 24 576 51,840 40,320 28,800 30 by 30 900 81,000 63,000 45,000 36 by 36 1,296 116,640 90,720 64,800
Larger is better for sumps in grain bin floors
Typical Sump
Grating vs. No Grating of Sumps
• Grate sumps when flighting, chain, or belts can be reached from the bin floor
• Grate sumps next to bin entry doors• Grating will cause more blockage for grain• We recommend Grating all gates
? Which is safer: grating or dealing with sumps that will not flow…
Gates & Transitions
• Keep flow angles at 45° or greater • Access opening for probing in transition
above the gates• Keep gates easy to access• Use a key lock system on all intermediate
gates
Gate Control
Procedure • Unload center gate to bin
floor• Unlock intermediate
gates• Then unload intermediate
gates from the center out
Gate With Wheel Control
Gate Control
Gate Control
Tunnel & Reclaim Design Process
• Design equipment• Allow access left & right of reclaim• Locate sumps • Transition to gates• Transition to reclaim• Build tunnel around equipment• Crown floor keeping minimum head room
required• Add in lights, electrical, air, and/or water
Layout Sumps
Center Sump Intermediate Sump
Layout Sumps
Sumps, Transitions, & Gates
• Sump size center – 50% larger than normal flow– Sweeps will limit flow
• Gate– Center gate(s) proportional– Intermediate gates rack & pinion – Gate size, keep close to flow rate– Gates slow moving; do not slam shut!
Transitions
Transitions• Widen sumps• Place pipe connection for
probing• Transition at 45°
Gate
Clearance under conveyor
Pipeconnection
Gates & Sumps
Large
Alternate center
Probe access
Lock policy
Soil Borings
Yes!! You need them & not necessarily from the
lowest bidder!
Information Geotech’s Need
• Proposed layout • Loads of major structures
(grain bins, towers, etc.)• Allowable, piling, soil
improvement
Information DesignEngineer Needs
• Allowable soil pressure • Settlement: uniform & differential• Excavation & removal• Backfill & soil improvement options• Modulus of subgrade reaction
Information Design Engineer Needs
• Seismic site classification• Lateral earth pressures• Equivalent fluid pressure• K active• K passive• Friction coefficient for the soil
Information DesignEngineer Needs
• Water level & possible dewatering• Ram aggregate piers• Piling recommendations
Borings
• 90ft. & above– Borings: 3 equally spaced & one in center
• 80 to 54ft. – Borings: 2 equally spaced & one in center
• 48 ft. dia. – Borings: 1 in the center
Depth of Boring
• Min 40ft.• Should be about dia. of the bin• Geotech on site should make the final
determination
