Corin Holmes, Jenike & Johanson: Investigating the Effects of Larger Particles on Proctor/Fagerberg...
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Transcript of Corin Holmes, Jenike & Johanson: Investigating the Effects of Larger Particles on Proctor/Fagerberg...
Bulk Solids: Science / Engineering / Design
Jenike & Johanson
Investigation into the Effects of Larger
Particles on Proctor/Fagerberg
Transportable Moisture Limit Test
Method
By:
Corin Holmes, MSc Eng.
Technical Officer
Bulk Solids: Science / Engineering / Design
Definitions
IMSBC Code – International Maritime Solid Bulk Cargoes Code
2012 Edition
• Appendix 2 – Defines test procedures to determine TML
Bulk Solids: Science / Engineering / Design
Definitions
Transportable Moisture Limit (TML):
The TML value is the moisture content of a bulk material above
which it is considered unsafe to transport in a bulk carrier as it may
liquefy
Bulk Solids: Science / Engineering / Design
Definitions
Liquefaction:
Occurs when the volume of spaces between particles reduces,
causing pore water pressure to rise, reducing the shear strength of
the particles.[2]
[2] Bulk Cargo Liquefaction (Iron Ore Fines and Nickel Ore), Standard Cargo,
February 2011, pp. 2
Material in a liquid-like flow state
Bulk Solids: Science / Engineering / Design
How to Determine TML
• Flow Table Test
• Penetration Test
• Proctor/Fagerberg Test
• Procedures for each test method are given in Appendix 2 of the
IMSBC Code
• We will focus on Proctor/Fagerberg test method
Bulk Solids: Science / Engineering / Design
Importance of TML
• There is clear need to accurately determine a maximum
moisture content of a bulk material for safe transport in bulk
cargoes.
• In 2009 two ships, the Asian Forest and the Black Rose
capsized and sank following liquefaction of iron ore cargoes
after being loaded in Indian ports during the monsoon
season.[3]
• In 2010 there was a further loss of three bulk carriers
carrying nickel ore loaded in Indonesia.[4]
[3] Bilbrough, A., et al., Circular: India – Safe Shipment of Iron Ore Fines from Indian Ports, The
London P&I Club, Dec 13, 2010 pp. 1
[4] Bulk Cargo Liquefaction (Iron Ore Fines and Nickel Ore), Standard Cargo, February 2011, pp. 2
Bulk Solids: Science / Engineering / Design
• Cell Volume = 1000 cm3
• Minimum of 5 test points (from dry to almost saturated)
• Material is dried prior to test
• Material filled into cell in 5 equal amounts
• Tamper mass, drop height, number of tamps
• Intersection of void ratio curve and 70% of saturation = TML
value
• Maximum particle size of 5 mm
Summary of Proctor/Fagerberg Test
Method
Bulk Solids: Science / Engineering / Design
Output of the Proctor/Fagerberg Test
Method
Gross Water Content [% by Mass]
Vo
id
R
atio
Bulk Solids: Science / Engineering / Design
•Particle Density – Heavy reliance on this figure but nowhere in
the code does it clearly define how this value is measured
•Consolidation Pressure – Does tamping the material surface 25
times over five layers equate to a compacted density like that
which would be seen by a material in a bulk vessel?
•Segregation & Whipping – Does liquefaction by whipping really
occur in a ships hold? Does segregation? Do they play a role in
potential liquefaction?
Proctor/Fagerberg Method Questioned
Bulk Solids: Science / Engineering / Design
•Starting Moisture Content – Does drying out the material fully alter
the material properties?
•Conservatism – Why is the TML value determined to be at the
intersection of void ratio curve and 70% of saturation as the test
method outlines? Perhaps 80 - 85% is still conservative enough?
•What about particle size? Why was 5mm chosen?
Proctor/Fagerberg Method Questioned
Bulk Solids: Science / Engineering / Design
J & J Study
Study was conducted to explore the effects of particle
size on TML values
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
Jenike & Johanson (J&J) investigated the effects of including >5
mm particles in the Proctor/Fagerberg test procedure, and the
resultant determination of TML values.
•The inter-particle void space in a material compacted per the
Proctor/Fagerberg TML test procedure will vary depending on the
sample’s particle size distribution (PSD).
•The finer fraction of a bulk material tends to carry a higher
proportion of the moisture than the coarser fraction.
•Determining the TML value on coarser particle distributions may
result in a different TML value than that determined for the minus
5mm fraction alone.
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
Determine TML values for a single sample of Australian Iron Ore
which was divided into four subsamples; separated by their
respective size distributions.
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
TML determination of each subsample
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
• To examine the sensitivity of moisture content to PSD, Sample 3 was
adjusted to its average TML value of 9.6% moisture
• It was then quartered and sieved to produce three subsamples with
maximum particle size to match those of Samples 1, 2, and 3
• The moisture contents (wet basis) for each of these subsamples
were determined
Bulk Solids: Science / Engineering / Design
J & J Study Part 1 Summary
• Coarser samples often yield lower TML values
• The finer fractions of the ore have higher moisture contents
than the coarser or full size distributions
Bulk Solids: Science / Engineering / Design
J & J Study Part 2
6 Types of Iron Ore
12 mm x 0 mm
TML
5 mm x 0 mm
TML
Bulk Solids: Science / Engineering / Design
J & J Study Part 2
5 mm x 0 mm
Samples Adjusted to TML
MC %
12 mm x 0 mm
MC % MC %
12 mm x 5 mm
Split
Bulk Solids: Science / Engineering / Design
J & J Study Part 2 Results
Bulk Solids: Science / Engineering / Design
J & J Study Part 2 Results
In five of the six samples tested the moisture content of
the -5 mm fractions were higher than the TML values
determined for the -5 mm subsamples.
The -5 mm fraction is ~78% of the sample.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
•The moisture content varied as a function of the sample’s
particle size distribution.
•The fine fraction of an ore will tend to have a higher
moisture content than the full size distribution, since the
finer fractions of a bulk material tend to carry a higher
proportion of moisture than the coarser fractions do.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
• Measured TML values may either increase or decrease
as materials become coarser,
• If the TML value is measured using >5 mm top size:
• overall moisture content of the whole material is
below the TML value determined for 12mm x 0mm
• moisture content of the <5 mm could be above the
TML value determined for 12mm x 0mm
• May even be above the 5mm x 0mm determined
TML value.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
TML = 8.6%
12mm x 0mm
TML = 8.8%
5mm x 0mm
Bulk Solids: Science / Engineering / Design
J & J Study Conclusion
• Iron ores shipped in other locations around the globe at
>TML values measured.
• If the standard is changed to include, as an example,
TML determination at 80% or 85% of saturation, then
care must be taken.
• The fines present in the sample might be even closer to
their liquefaction value especially if >5 mm are included
in the determination of the TML value
More research needs to be done to investigate this issue
Bulk Solids: Science / Engineering / Design
Questions?
Corin Holmes, MSc Eng
Technical Officer
Jenike & Johanson Perth, WA