INFORMATION FROM WEB SOURCES AND FROM THE WEBSITE OF UK PNI
CLUB
Improvements in iron extraction processes have made steel producers take a second look at what they do with Mill Scale
which is the by product of the steel making process. Mill Scale is not a common commodity to carriers and while is
may not be covered by any steel industry code of practice it is covered by the marine industry IMSBC Code requirements.
It should however be no surprise that as a commodity much likened to iron ore fines it is liable to liquefaction.
Mill Scale is formed during the steel making process as a means of providing a protective coating on hot rolled steel.
During further processing the scale has to be removed and this process creates flakes of iron oxide.
It is these flakes of Mill Scale that are being increasingly traded as a bulk cargo. While Mill Scale is deliberately
formed in steel mills, it is treated as a waste product once it has been flaked off. Recycling this product has become
possible due to changes in iron production methods as it can be mixed with other iron sources in smelters as well as with
lower grade ores prior to shipping. Mill Scale is traded effectively in the same manner as primary mined iron ore fines.
The nature of the production methods are such that Mill Scale flakes form in a variety of particle sizes. In addition,
in order to accumulate sufficient cargo for transport many shippers will stockpile the Mill Scale flakes from various
sources, and this along with the low mechanical strength of the flakes so they easily break, means that such stockpiles
are likely to be made up from varied particle sizes. If the hot steel is made into cast ingots (smaller than plates or sheets),
or if Mill Scale is ground to reduce the size for industrial processing, the flakes are smaller hence the term Mill Scale fines
is used. Mill Scale fines are largely used interchangeably with iron ore fines in steel processing.
However, the cargo is not listed in the IMSBC Code. Section 1.3 of the IMSBC Code specifies that unlisted cargoes, such as Mill Scale, should only be accepted for loading provided it is accompanied by a certificate issued by the national competent authority, stating the commodities suitability for seagoing carriage, of the country of the port of loading.
The physical nature of Mill Scale is similar to primary mined iron fines. IMO Circular DSC.1/Circ.63 of 12 October 2010
states that iron ore fines are a cargo that may liquefy (and are therefore a Group A cargo), and the terms of this circular
should also be applied to Mill Scale. The Circular goes on to invite Member Governments to submit relevant information
regarding the safe handling and carriage of this cargo, at their earliest convenience, to the IMO.
The IMSBC Code also warns about the potential liquefaction hazard of all fine-grained mineral cargoes shipped with inherent
moisture content, regardless of whether or not the cargo is specifically identified as a Group A cargo in the Code.
Appendix 3, para 2.1 of the Code states;
“Many fine-particled cargoes if possessing a sufficiently high moisture content are liable to flow. Thus any damp or
wet cargo containing a proportion of fine particles should be tested for flow characteristics prior to loading”.
Mill Scale and Mill Scale Fines do have fine particle sizes with a significant inherent moisture content, and fall therefore
within the scope of this provision. Therefore, Mill Scale cargoes should be treated as cargoes that may liquefy unless
testing shows otherwise. For Group A cargoes, SOLAS and the IMSBC Code require shippers to provide the Master with a
certificate of the moisture content and the transportable moisture limit (TML) prior to loading.
Improvements in iron extraction processes have made steel producers take a second look at what they do with Mill Scale
which is the by product of the steel making process. Mill Scale is not a common commodity to carriers and while is
may not be covered by any steel industry code of practice it is covered by the marine industry IMSBC Code requirements.
It should however be no surprise that as a commodity much likened to iron ore fines it is liable to liquefaction.
Mill Scale is formed during the steel making process as a means of providing a protective coating on hot rolled steel.
During further processing the scale has to be removed and this process creates flakes of iron oxide.
It is these flakes of Mill Scale that are being increasingly traded as a bulk cargo. While Mill Scale is deliberately
formed in steel mills, it is treated as a waste product once it has been flaked off. Recycling this product has become
possible due to changes in iron production methods as it can be mixed with other iron sources in smelters as well as with
lower grade ores prior to shipping. Mill Scale is traded effectively in the same manner as primary mined iron ore fines.
The nature of the production methods are such that Mill Scale flakes form in a variety of particle sizes. In addition,
in order to accumulate sufficient cargo for transport many shippers will stockpile the Mill Scale flakes from various
sources, and this along with the low mechanical strength of the flakes so they easily break, means that such stockpiles
are likely to be made up from varied particle sizes. If the hot steel is made into cast ingots (smaller than plates or sheets),
or if Mill Scale is ground to reduce the size for industrial processing, the flakes are smaller hence the term Mill Scale fines
is used. Mill Scale fines are largely used interchangeably with iron ore fines in steel processing.
However, the cargo is not listed in the IMSBC Code. Section 1.3 of the IMSBC Code specifies that unlisted cargoes, such as Mill Scale, should only be accepted for loading provided it is accompanied by a certificate issued by the national competent authority, stating the commodities suitability for seagoing carriage, of the country of the port of loading.
The physical nature of Mill Scale is similar to primary mined iron fines. IMO Circular DSC.1/Circ.63 of 12 October 2010
states that iron ore fines are a cargo that may liquefy (and are therefore a Group A cargo), and the terms of this circular
should also be applied to Mill Scale. The Circular goes on to invite Member Governments to submit relevant information
regarding the safe handling and carriage of this cargo, at their earliest convenience, to the IMO.
The IMSBC Code also warns about the potential liquefaction hazard of all fine-grained mineral cargoes shipped with inherent
moisture content, regardless of whether or not the cargo is specifically identified as a Group A cargo in the Code.
Appendix 3, para 2.1 of the Code states;
“Many fine-particled cargoes if possessing a sufficiently high moisture content are liable to flow. Thus any damp or
wet cargo containing a proportion of fine particles should be tested for flow characteristics prior to loading”.
Mill Scale and Mill Scale Fines do have fine particle sizes with a significant inherent moisture content, and fall therefore
within the scope of this provision. Therefore, Mill Scale cargoes should be treated as cargoes that may liquefy unless
testing shows otherwise. For Group A cargoes, SOLAS and the IMSBC Code require shippers to provide the Master with a
certificate of the moisture content and the transportable moisture limit (TML) prior to loading.
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