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Steel
and Metals Applications Index
Each item in the following list will eventually take you to another, in-depth
list of references articles, vendor applications information or a direct download
of a related technical paper. Those items in blue have been so linked, the rest
will follow as we acquire them. Some
of those references are hyperlinked to other web sites. Some of the others are
papers which have been collected and require an authenticated registration before
access to the hyperlink is provided. This is still free, however, and requires
only a valid email address for access when implemented. If
anyone would like to add to this list, let
us know, please and we will do our best to comply.
Applications Resources
- "Review
of noncontact process temperature measurements in steel manufacturing" Includes
a paper presented at the 1999 SPIE Thermosense Meeting, courtesy of the copyright
holder, SPIE: The International Society For Optical Engineering .
- Taconite
temperatures in pelletizing operations
- Sinter
temperature
- Coke
oven temperature measurements and transfer belts protection
- Thermocouples
in Blast Furnace environments
- Stove
Domes and Bustle Pipe Temperatures
- Temperature
Measurement of Liquid Iron, Liquid Steel and other molten metals
- Slag
Detection in Steel pouring streams and detection of Iron in Slag streams
- IR Radiation Thermometers
for oxidized steel objects in cooler surroundings (e.g. Continuous Casting, Hot
Rolling, Cold Rolling)
- Non-Contact
measurement of steel surface temperatures in Reheat Furnaces
- IR
Radiation Thermometers used in Continuous Anneal Furnaces
- Non-contact
temperature measurement on Coating Lines, e.g. Tin, Zinc, plastic film
- Measuring steel sheet
surface temperatures in the Galvanneal process
- Verifying
IR Radiation Thermometers measurements on-line
- Thermocouples
for Reheat Furnaces
- Thermocouples
in Batch Anneal Furnaces
- Cold
Reduction temperature measurements
- Thermocouples
in Continuous Anneal Furnaces
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Commentary
The Steel Industry was one of the first to use
temperature sensors for automatic process control and QA measurements. The extent
of temperature sensor use in steel mills and process plants is quite large. Virtually
all kinds are used, ranging from liquid-in-glass thermometers in the testing and
QA labs to networked infrared line-measuring sensors called "line scanners"
and computer-linked thermal imaging versions of area-measuring infrared thermometers
for detecting slag on the stream of liquid steel poured from a melting vessel
into a transfer ladle. By and large, the
majority of the temperatures sensor applications that get the most attention are
those involved in monitoring or controlling a process. That's where the money
is made. That's where productivity, acceptable quality tons, or parts per unit
time, are produced. A vital part of productivity is the yield, that fraction of
production that is within acceptable quality limits.
Three examples
on yield in USA steel plants and temperature sensor technology from first hand
observations by the author of this page: 1.
It is most interesting to note that in USA hot rolling operations of sheet steel,
for instance, the vast majority of produced tons are monitored by a spot IR Radiation
thermometer measuring the centerline temperature of the product at the roughing,
finishing and cooling section exits. Yet,
the line-measuring IR radiation thermometer (line-scanner) was introduced to the
steel industry in the 1980's by Japanese steel makers Nippon Steel and N.K.K
Steel. These devices were shown to be capable of monitoring the temperature
across the entire strip width and several instrument
companies have produced commercial instruments. The
fact that one could determine whether an off-centerline portion of the strip did
or did not not acheive desired temperatures seems, even today, not to interest
many US steel makers based on the number of line-scanners installed. Yet these
temperatures are key process variables in a yield analysis program and remain
unquantified in most hot mills in 2002, nearly 20 years after the introduction
of the technology! It's
a sorry state in those mills where line-scanner equipment has been installed with
all good intentions and effectively are not used by operations. 2.
The lack of adoption of even old technology in US Steel plants exists in other
temperature measurement areas as well. It is often interesting to look around
the iron and steel making areas and ask what thermocouple calibration tables are
used,not the type of thermocouple. One
gets a quick answer on the latter score. No, the really interesting 'technical'
question is: "What year is the calibration of your thermocouple table based
upon?" This, of course, refers to the year of the International Temperatature
Scale, ITS, or International Practical Temperature Scale, IPTS, upon which the
thermocouple table is based. The present standard is ITS-90,
the Scale introduced in 1990. It
is not surprising to hear, or even see, the tables referred to as 1948 or 1960.
This, in and of itself, does not make a huge difference in the actual measurements
made, but can make it a bit difficult for one to claim that their ISO-9000 or
QS-9000 compliant quality system includes all measurement control devices, especially
thermocouples, that are "traceable to the appropriate fundamental or national
standard". The
last time anyone looked, most national standard agencies, like NIST in the USA,
were not certifying thermocouple standards to IPTS-68, or some earlier, out-of-date
reference, but rather were certifying everything to the ITS-90 scale. What's
it take to get all areas of steel mill plant temperature sensor measurement devices
up to snuff? Not much. Awareness is the first step. We all know that measurment
without traceable calibration is a very poor quality approach, but why is it tolerated
at the higest levels of steel company management? Could
it be that no one is really aware? 3.
Most steel coil batch anneal (BA) furnace operations were originally controlled
by Type J, 8-gauge wire thermocouples. That was prior to the development of the
stainless steel swaged or mineral-insulated metal sheathed (MIMS) construction.
Most BA operations switched to the new thermocouple style but never updated their
know-how on these latter thermocouples. They
are not without their faults and ASTM recommendations for the maximum temperature
use of MIMS Type J Thermocouples is well below the temperatures they experience
in BA typical operations (Ref:ASTM E-608). The
use of ASTM Standard E-1380 for testing such thermocouples
does not seem to be widely used either. This is a blatent misuse of technology
and most likely a significant contributor to uncontrolled variability on the operation
of a BA shop.
It is also very difficult to imagine a quality system auditor failing to find
such inconsistancies, but the rules are changing and it is no doubt they, too,
will begin to check for such mistakes. The facts are that both the Type K and
Type N thermocouples in MIMS configuration are priced nearly the same as the Type
J and they have recommended use limits well within the ASTM specs and, further,
the Type N were demonstrated in a 1992 paper by another Japanese steel company,
Sumitomo Metals, to be a superior thermocouple for this application. This
writer knows of only one USA steel plant that has adopted the Type N MIMS thermocouple
in BA operations, the formerLTV Steel Indiana Harbor plant-Kudos to the plant
electronics and instrument system engineers for acheiving improvements using current
measurement technology!
If anyone knows of other plant examples of measurement inprovements with modern
temperature sensor technology, we'd be happy to recognize them here, too. Several
of the classic, near-impossible measurements for radiation thermometers can be
found in Steel Mill uses, e.g., the hotter background problem (the surroundings
are hotter than the object of measurement) exists in hot strip and bar mill
reheat furnaces; the hotter background combined with uncertain emissivity
problem exists in continuous anneal furnaces. Fortunately,
there are solutions or work-arounds for both these problems, although they are
not widely known and even less well understood by those normally charged with
specifiying and/or maintaining the requisite measuring devices. Similar
problems in the Aluminum and Brass Industries plague many operations such as hot
rolling, extruding and cold drawing. Yes,
infrared radiation thermometers, those unstandardized, frustrating temperature
sensors, are widely used in metal processing operations simply because nothing
else will work. If automation engineers could accurately model all their processes,
they would do away with those "pyrometers" (as they are called), because
they are also perceived to be a maintenance pain in the neck.
Yet, over the years of successful use, many such devices and their supportive
suppliers have earned, in some plants, a good reputation for accuracy and reliability.
Their maintenance requirements are not all that intensive and, like many other
measuring devices, they are much more reliable if checked and adjusted on a regular
and not too infrequent basis. That is not
to say that radiation thermometers of the spot, line and area measuring types
are all excellently made devices. There is only one clear standard in the USA
for characterizing them and, to this writer's knowledge, no metal industry company
in the USA has yet adopted that standard (ASTM E1256)
as a qualification for their sensors. So,
the industry has learned, not by staying current with the technicnology, but by
the notoriously expensive techniques of trial and error to find reliable vendors
with good products and services. The situation is made worse by the economics
of the industries. For instance, in the
USA, very few, if any, organizations even have incoming inspection or calibration
verification on new or repaired equipment. It's not that they don't know how.
Most don't have time or manpower to do it. Others have lost the skills to do it
in-house through force reduction measures focused on short term survival. The
recent dire economic straits of many steel companies in the USA has not changed
the fact that most still make steel and still use lots of temperature sensors
as critical components of the processes. We hope these application repositories
can help existing and future engineers to save some time by not reinventing existing
successes and providing guides to sources of technical abilities. Listed
below are a series of topics that we expect to cover and fill out soon. Most of
the information about each of these topics is available in the open, published
literature. We shall summarize each of them, in turn, and provide hypertext links
to those resources that exist on the Web rather than copy existing information.
Those papers that are not as easily obtained will hopefully be available here
by permission of the various copyright holders. Time
and feedback will govern our priorities. An
additional feature, to help save time, will be a listing with each topic of the
suppliers of equipment for these applications that we have uncovered. These are
not de facto recommendations. Someone other
than this organization must still make a quality judgement on the equipment sold
by each organization listed. We're just shortening the list (or perhaps lengthening
it-depending how extensive one's view has been) by listing those who offer equipment
in these specific areas.
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