SILO FAILURES

1
SILO FAILURES

• By
• Manduri Pramodh (CH05B017)
• Yogesh K S (CH05B050)
• Arjun S Bhadouria (CH05B052)

2
WHAT IS SILO?

• A structure typically cylindrical, in which
  fodder or forage is kept

3
TYPES OF SILOS

• TOWER SILO
• BUNKER SILO
• BAG SILO

4
TOWER SILO

• Storage silos are cylindrical structures,
  typically 4 to 8m in diameter and 10 to 84m in
  height.
• They are made of Wood staves, concrete staves,
  cast concrete, and steel panels.
• Silos storing grain, cement and woodchips are
  typically unloaded with air slides or augers.
• Tower silos containing silage are usually
  unloaded from the top of the pile using
  mechanical unloaders.

5
BUNKER SILO

• Bunker silos are trenches, usually with concrete
  walls, that are filled and packed with tractors
  and loaders .
• The filled trench is covered with a plastic tarp
  to make it airtight.

6
BAG SILO

• Bag silos are heavyweight plastic bags, usually
  around 6 to 8 ft in diameter, and of variable
  length as required for the amount of material to
  be stored.
• They are packed using a machine made for the
  purpose, and sealed on both ends. They are
  unloaded using a tractor and loader or skid-steer
  loader.

7

• WE ARE MAINLY GOING TO DICUSS ABOUT THE
  FAILURE OF TOWER SILOS.

8
REASONS OF SILO FAILURE
9
Failure due to design error

• Bending of circular walls caused by eccentric
  withdrawal..
• Large or non-symmetric pressure developed by
  inserts..
• Ignoring flow patterns material properties
• Special consideration concerning temperature and
  moisture
• Special consideration with bolted tanks
  reinforced concrete construction..

10
Failure due to construction errors

• Incorrect material..
• Uneven foundation settlement.
• Design changes during construction.

11
Failure due to usage

• Dynamic load due to collapsing arches or
  ratholes, self induced vibration or explosion.
• Changes in flow patterns.
• Buckling of unsupported wall.

12
(No Transcript)
13
Failure due to improper maintenance

• Corrosion and erosion.
• Lack of routine inspection.
• Improper reaction to sign of distress.

14
Pressure Distributions
15

• Due to eccentric discharge the pressure in the
  silo is not uniform.
• The pressure
• varies along T as
• Well as along height
• H.
• There is also random
• Pressure variations
• The pressure P is
• PP0 P1CosT P2Cos2T P1SinT Pr
• This empirical relation was derived from
  experiments done by jenike and johanson

16
CASE STUDIES
17
South Western USA, Ash Silo
18

• This silo stored 9000 tons of fly ash from the
  adjacent coal fired power generation station.
• Calculations showed that the silo did not account
  for thermal ratcheting.
• Investigation revealed some cost cutting measures
  taken by supplier during construction
• Material inside silo was not discharged for
  several days so a condition of accumulated
  stresses precipitated the collapse

19
(No Transcript)
20
Johor Flour Mills, Malaysiasilo failure
21

• Silo 20 of johor bahru flour mill collapsed
• The investigation showed that design and actual
  silo had several discrepancies.
• The failure had occurred due to different loading
  conditions as specified for the silo.
• The wall between silo 20 and 35 bent overcoming
  the structural arching causing the failure.

22
Thermal Ratcheting

• The walls of outward metal silos expand during
  the day and contract at night
• During expansion material settles down
• However it cannot be pushed back when walls
  contract
• This increases tensile stress in the wall
• back

23
Bibliography

• Unit Operations of Chemical Engineers-
  McCabe,Smith, Harriot
• www.Engineeringvillage.com
• Chemical engineering progress
• www.Sciencedirect.com
• www.Silo.org/index
• www.jenike.com
• www.wikipedia.org/en

24
THANK YOU