Download - Corin Holmes, Jenike & Johanson: Investigating the Effects of Larger Particles on Proctor/Fagerberg Transportable Moisture Limit Test Method

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


Definitions

IMSBC Code – International Maritime Solid Bulk Cargoes Code

2012 Edition

• Appendix 2 – Defines test procedures to determine TML


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


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


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


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


• 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


Output of the Proctor/Fagerberg Test

Method

Gross Water Content [% by Mass]

Vo

id

R

atio


•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


•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


J & J Study

Study was conducted to explore the effects of particle

size on TML values


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.


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.


J & J Study Part 1

TML determination of each subsample


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


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


J & J Study Part 2

6 Types of Iron Ore

12 mm x 0 mm

TML

5 mm x 0 mm

TML


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


J & J Study Part 2 Results


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.


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.


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.


J & J Study Summary

TML = 8.6%

12mm x 0mm

TML = 8.8%

5mm x 0mm


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


Questions?

Corin Holmes, MSc Eng

Technical Officer

Jenike & Johanson Perth, WA

[email protected]