|New Optical Pyrometer
|New Optical Pyrometer for Measuring the Temperature
of Aluminum Alloys
|Dr. E. Glassman
3T – True temperature Technologies
Theradion Industrial Park, Misgav, Israel
Improvement in the effectiveness and quality in the modern technological processes employed in the manufacture of aluminum and its alloys cannot be achieved unless the temperature can be measured to an accuracy of ± 0.5 – 1%.
In static processes, where there is a calm object surface, measurements of errors to this order of magnitude have been achieved by contact means using a thermocouple.
In dynamic processes, such as casting, rolling, extrusion etc., accurate continuous temperature control is possible using non-contact, in particular optical, methods. The advanced characteristics of the instruments used in this type of pyrometry (such as high speed, sensitivity, etc.), make it possible to measure relatively low temperatures.
The use of optical pyrometry methods in the aluminum industry is, however, associated with a number of fundamental difficulties, such as:
The harsh operating environment of the optical pyrometer – the wide temperature changes, dust and humidity, and the action of variable and permanent electro-magnetic fields – introduces secondary destabilizing factors that need to be corrected by various technical solutions.
- the variable emissivity and transmission of intermediate media intervening between the pyrometer and the measured object in the course of measurements;
- the influence of the light reflected from external radiation sources; and
- the fluctuation of objects within the field of view of the optical pyrometer allowing only partial object sighting.
All this makes modern optical pyrometry more complicated and therefore more expensive.
|New Optical Pyrometer for Measuring the Temperature
|Overview of AST / 3T Technology
|AST \ 3T development is oriented for a product, which can be the new step in the quite tight market of Infrared non –contact optical thermometers (pyrometers). And the main goal, achieved by our team was development of the system which is able to reach high accuracy temperature measurement of objects with various optical properties.
Optical properties variations of target are the fundamental problem for all non-contact temperature measurements. Different technologies have different approaches to resolve this problem.
Thus, one wavelength pyrometers are able to supply good result in case when the target Emissivity is absolutely constant and pyrometer need recalibration for each change.
Two wavelength (color) pyrometers can work with variable Emissivity without calibrations, but under very strong condition – the target should be Black or Grey physical body. As well known – it is not the most frequent case in industry, as well as in the all nature.
3T technology has started as multi wavelength, and because of original physical algorithms, the pyrometer, being initially calibrated for different target situations, after that can automatically recognize the type of the target and to use the most compatible calibration.
By this way we achieved 1% measurements accuracy. But each unit required being initially on line calibrated.
With rising of 3T sales and acquiring more and more experience in industrial applications we have developed Standard Calibration Databases for typical applications. This Database, being saved in pyrometer memory while production stage, allowed to customer to use our device as Plug & Play and avoid necessity in initial on site calibrations. We have developed Application SW, and by means of it customer got the possibility to install Database by his own, record data loggers of measurements, build Real temperature and Real Emissivity trends.
In the next stage we have found clear mathematical dependence between optical signals for different wavelength and objects optical properties, thus arise possibility to use pyrometer not only working in Discrete mode with Database, but also in Analytic Mode by using Analytic coefficients, specified for each application. It makes results more consistent, stable and allows performing of fine tuning by coefficients modification.
Now typical 3T Pyrometer measurements procedure may be described by follow:
a) For known applications – instrument working in Analytic mode Plug & Play with standard coefficients, without any customer’s intervention.
b) For unknown applications – initially started in Discrete mode for new Calibration Database acquisition. After that system calculates new Analytic coefficients, which can be used as typical coefficients for this application.
High sensitivity, high accuracy and target properties independence allowed us to take a step into very difficult measurements branch of non-ferrous metallurgy – Aluminum industry, where most of the objects are very bright, low temperature and have very variable optical properties.
Further development showed us the way how on the base of existing algorithms to minimize the number of required wavelength, simplify the design, and reduce the cost of the device.
Today 3T Pyrometer working with our original technology on the base of 2 wavelength and can be used as set composed from different elements: Camera only + PC; Camera assembled with scanner; Camera + Display; Camera communicated with PLC through Analog Output or Serial output and also as the number of cameras Serial communication with one registering device..
Instrument can be accomplished with few different types of application SW.
The main amount of our pyrometers is being used as Plug & Play devices in Aluminium industry for Extrusion of profiles, Hot Rolling, Forging, casting of aluminium, Continuous casting. But our applications for brass, steel, grey iron, titanium are also successful. Technological potential of our team allowed us to participate in development of Silicon wafers processing machine, in cooperation with another Israeli companies.
We designed Reflectometer –Pyrometer for current monitoring of the Silicon wafer temperature with high accuracy. Unfortunately, the recession which has a place in Hi-Tech during early 2000 does not allow us to transform this project to the serial industrial application.
In present time we have the number of models, which are covering Temperaturbereich from 200° C to 3000°C, with measurement spot size from 2.5mm for high temperature to 20mm for low temperature (diameters mentioned for 1m distance).
The Temperaturbereich of each model is quite flexible and, by optics modification we can find the optimal model and optimal conditions for the range, required by customer.
|Real Temperature Parameters For Isothermal Extrusion
|Real Temperature Parameters For Isothermal Extrusion
|Prepared By Boris Shtarker, Eduard Hodos, Ofer Yoely,
3t True Temperature Technologies, Misgav, Israel.
Abstract — The Main Parameters That Must Be Controlled For Isothermal Extrusion, And To Achieve The Optimum Metallurgical Properties In The Profile, Are The Taper Heating Of The Billet, The Die Exit Temperature, And The Temperature Of The Profile During Cooling.
This Paper Discusses Different Ways To Achieve Isothermal Extrusion, Including System Requirements And Different Methods Of Temperature Measurement.
In The Last Few Years, Several Different Closed Loop Isothermal Extrusion Systems Have Appeared On The Market. Systems Differ In The Hardware Used And The Algorithms, With User Opinions Varying Regarding The Performance Of Each System.
Many Tests Have Come To The Same Conclusion. The Most Important Parameter To Achieve Isothermal Extrusion Is Accurate Temperature Measurement. The Most Common Reason For Failure In Many Systems Was Inaccurate Pyrometers.
Accuracy Problems Arise In Profile Measurements When The Profile Exhibits Temperature Variations Across Complex Sections, Or Differences In Temperature Between Small Profiles From Multi-Cavity Dies. This Effect Occurs Most Often When The Pyrometer Used Has A Large Spot Size And Gives Averaged Measurements. In Order To Avoid This, An Effort Should Be Made To Concentrate On Measurements Using A Small Spot Size With The Possibility Of Automatic Targeting Of The Pyrometer On The Hottest Point.
Effective Billet Taper Heating Control Requires An Accuracy Of +/- 5° C (10° F) And Several Measurements Along The Billet Axis.
The Best Way To Achieve The Required Parameters For Billets, Is When The Remote Pyrometer Is Several Meters Away, With The Billet Area Free From Obstructions. This Also Avoids The Danger Of The Pyrometer Being Affected By Heat From The Billet.
The Dilemma Of Repeatability Or Accuracy
Examination Of The Performance Of Some Of The Isothermal Systems And Pyrometers Used, Shows That Due To The Inadequate Accuracy Of The Pyrometers, Manufacturers Often Promote The Theory That Repeatable Temperature Measurement Is Good Enough
Key Arguments And Recorded Experiences That Counter This Theory Are Discussed Below:
When Looking On (Figure 1.) One May Ask If Repeatability Is Good Enough, But If There Is Always A Discrepancy Of 15-30°C See (Figure 3.) Is It Possible To Reach The Peak? Will You Always Be Somewhere Below Or In The Range Where Quality And Metallurgical Properties Of Profile Are Impaired?
When The Method Is Solely Based On The Repeatability Of The System, Any Changes Within The Press Environment Will Affect All The Saved Data, And Tests Will Have To Be Repeated To Ensure The Correct Process Control.
Profile Positioning (See Figure 4.), This Is The Most Common Change That Will Happen Between Extrusions From The Same Die Each Time It Is Extruded. Different Locations Will Give Different Temperature Readings. All Of The Data Base Will Be Invalid, As It Was Based On Different Temperature Readings.
The Profile Quality Will Have To Be Re Verified, As It May Be That The Measured Temperature Is Now 30°C Higher Than The Last Time (See Figure 3.). All The Quality Process Parameters (Speed, Pressure, Billet Temperature) Must Be Changed.
With Multi Cavity Dies, There Is Frequently A Difference In Temperature Between Profiles Coming From The Die.
A Number Of Different Methods And Equipment Are Available In The Market For Temperature Measurement In The Aluminum Extrusion Process.
The Basic Question To Be Asked Is What We Are Targeting? Are We Targeting The 80 % Of Extruded Profiles, Which We Can Already Extrude At The Optimum Parameters, Or The 20% More Complex Ones? We All Probably Agree That It Is A Waste Of Money To Invest In Something That Does Not Contribute To Our Aim. We Need To Focus On The 20% Difficult Profiles Where Accurate Measurements Are Needed For Maximum Production.
Practical Experience, Aluminum Profile. – At The Exit Of The Press And Downstream.
Two Different Approaches Have Been Tested In The Field, Wide And Narrow Spot Measurement.
With Wide Spot Size Measurement Pyrometers Use A 50-90 Mm Spot Size From 1 Meter. The Camera Collects Energy From A Wide Area, Therefore The Measurement Is Less Affected By Profile Location The Parameters Within The Processor Are Set To Correctly Measure The 80% Mentioned Above, And Probably Will Have Errors Of Up To 50°C.
This Occurs Because Of Differences In Temperature Between Different Profiles In Multi-Cavity Extrusion (Figure 3.), Temperature Variations Across The Profile (Figure 4.), Different Alloys Within The Common 6000 Series, Or, When The Profile Is Smaller Than The Pyrometer’s Field Of View. (Figure 5.) – In This Case There Is Often A Location Error.
With A Narrow Spot Size Sensor, Accurate Measurements Result Only If The Profile Is In The Field Of View. Data Collected During A Benchmark Test Last Year Demonstrate The Error Of Using Wide Spot Size Pyrometers (Figure 3).
Figure 3. Comparison Test
In Recent Years Most Customers Reported That Even Today When Level Of Accuracy Of Measured Temperature Has Jumped, The Main Obstacle To Having Their System Running Well Is The Accuracy And Repeatability Of Pyrometers.
Figure 6. Shows Field Data Of A Simple Profile At The Press Exit. Temperature Was Measured By Small Spot Size Pyrometer. This Provided Excellent Accuracy. A Sensor Was Connected To A Scanning System.
On Figure 6 Data Difference In Temperature Between Highest Temperature And Lowest Temperature Exceeds 20°C (68°F).
Data May Explain Why In Some Closed Loop Systems Installed In Europe, Extruders Noted That On 10-15% Of Profiles They Couldn’t Run The System Due To Pyrometer Inaccuracy.
Figure 6 Profile Temperature At The Press Exit
Practical Experience Aluminum Billet
For This Application It Is Impossible To Achieve Good Results Using Simple Pyrometers Because Of Large Variations In Emissivity And Surface Spectral Properties Between Billets.
Two Different Approaches Have Been Introduced To The Market. The First Uses An Emissivity Transformer And Therefore The Sensor Is Located A Few Millimeters From The Hot Billet. The Second Locates The Sensor 1-4 Meter From The Billet – Similar To Profile Measurement.
With The First Method We Have Again The 20%-80% Question. If The Billet Is Scalped And Very Shiny, The Accuracy Drops Immediately With Up To 40-°C Deviations. This Is Just The Application Where Accuracy Is Needed For Our High Quality And Expensive Product!.
With The Second Method, Its Big Advantage Is The Location – Far Away From Hazards. Simple To Install, Easy To Maintain. It Covers The Full Range Of Billet Surfaces (Emissivity) From Dark Black To Shiny Scalped Billet – Covering The Full 100% And Particularly The Most Important 20% Of Production.
All Existing Optical Measurements Give The Result Of Billet Heating After The Procedure Has Been Completed, On The Exit From The Furnace, And In The Best Case This Information Is Available For Modifying The Next Heating Cycle. Control Of The Heating By The Pyrometer Allows Direct Involvement In The Heating Process Without Having To Take Into Consideration The Reliability Of The Measurements, As Is The Case With Contact Thermocouples.
Billet Test Field Figure 7 And 8, Explains The Need For Accurate Measurements Of Billet Temperature.
Measurement Of Temperature Along The Billet Helps The Extruder In Two Ways – First To Monitor Billet Furnace Performance And Control It, Second And Most Important, Data May Be Transmitted To A Closed Loop System, And Will Immediately Correct Pressure And Speed For The Current Billet.
Aluminum 1000 Inductive heater
Figure 7. Billet Temperature Measurements
Figure 8. Billet Temperature
Isothermal Extrusion Systems Must Use An Accurate Pyrometer, The Method Of Repeatable Sensors Is Not Always Repeatable In Practice Nor Applicable In Practice For The Most Important Profiles.
Comment From Extruders That Are Using These Systems Are Usually, “Yes It Working, But . . . “Analyzing The “But” Shows That It Ranges On 10-20 % Of Production.
Achieving Accurate Temperature Measurements Is A Hard Task. Some Of The Companies In The Field, Have Chosen To Make A Detour.
At The Very End There Are No Detours. One May Manipulate Numbers, Explain In Detail Why Repeatability Is Best, You May See Improvement Of Productivity, But It May Be That Quality As Been Reduced – At The End Of Day, Your Production And Quality Are On The Table.
The Choice Is Between Compromising With The 80% Or Become One Of The 20% Market Leaders.
1. Measuring The Temperature Of Aluminum Alloys
Dr. E. Glazman
2. Closed Loop Isothermal Extrusion
Jan Ingvorsen, Alu Mac
3. The 80%: 20% Question
Accurate Temperature Measurement
Boris Shtarker & Ofer Yoely, 3t True Temperature Technologies, Misgav Israel
The Authors Wish To Acknowledge Klil Industries And Mr. Hilel Frenkel For Their Assistance During Tests.
|Real Temperature Parameters For Isothermal Extrusion
|Continuous Control of Thermodynamic Temperature
|Continuous Control of Thermodynamic Temperature in Extrusion, Rolling and Forging of Aluminum Alloys
|Prepared by—Dr. E.D. Glazman, Chief Scientist, R. Goshen, T. Kornfeld, S. Levy,
ABSTRACT - Dynamic nature of particles behavior in extrusion, rolling and forging of aluminum and its alloys almost totally rules out the possibility for contact thermometry under continuous control of thermodynamic temperature. The authors examined the basic potentialities of non-contact passive optical pyrometry for these processes. Method of optical pyrometry which provides for thermodynamic temperature measurement at unknown and varying emissivity in the range of 200-1000ºC with maximal tolerance of approximately 1% are presented in the report. Results of industrial use of designed pyrometry systems obtained over a period of years for aluminum and its alloys in extrusion in a number of large companies in the USA, Europe, Canada, Australia etc. are discussed
|Continuous Control of Thermodynamic Temperature
|Aluminum Extrusion Measurement
|Accurate Temperature Measurement In Aluminum Extrusion For Increases Productivity, Quality And Energy Savings
|By Tuvia Kornfeld - Former Managing Director of 3T - True Temperature Technologies Ltd.
With sales in Europe, the United States and the Far East, 3T - True Temperature Technologies, Ltd. enjoys a worldwide reputation for its unique pyrometers. The Company has introduced a unique line of proprietary pyrometers that use a totally new approach for remote temperature measurement. These proprietary pyrometers provide highly accurate, non-contact measurement of true target temperatures, regardless of target emissivity and intermediate conditions.
Unlike other pyrometers, these products are not sensitive to changes in emissivity or other target parameters and are not affected by the intermediate conditions between the pyrometer and the target. As a result, 3T’s pyrometers are the only products available today capable of handling the unstable targets and intermediate conditions commonly found in the aluminum, steel and other metals industries while still indicating the target temperature to a high degree of accuracy.
Advantages Of Using 3T Systems For Measuring Precise Temperatures In Aluminum Extrusion Lines
1. Productivity – Allows for increased extrusion speed;
2. Quality – Better profiles reduce amount of scrap produced;
3. Energy – Saves gas or electricity at the die furnace, billet furnace and container electrical element.
Installation Locations For 3T Pyrometers On Aluminum Extrusion Lines
There are three locations where the 3T pyrometer can be placed:
A. Press Exit
B. Billet Furnace Exit OR before the Billet Loader
C. On the Extrusion Cooling Table
By measuring the temperature of aluminum profiles at the press exit the following advantages can be achieved:
INCREASED PRESS SPEED – As extrusion speed is increased productivity is increased. For example, if aluminum profiles are usually extruded at a low temperature of 520°C and the extrusion temperature is increased to 560°C, the extrusion press speed can be dramatically increased.
Some 3T customers report increased productivity rates of 5 - 10% .
QUALITY – Emissivity is a surface parameter with a value between 0 to 1. Low emissivity leads to a mirror profile surface. When low emissivity is maintained, the surface quality is higher. 3T’s systems provide a display showing the emissivity of each profile, resulting in better profiles.
When profiles are extruded at very high temperatures, for example between 580°C to 600°C, product may be damaged. 3T pyrometers can prevent this damage.
IDEAL EXTRUSION – is accomplished by using the maximum temperature, the optimal pressing speed and minimum emissivity.
a. To achieve Ideal Extrusion collect following data from each extrusion:
1) Press speed
4) Quantity per hour
b. Data can be collected:
1) Manually: from 3T’s controller display
2) By chart recorder: 0 - 10V from 3T’s controller;
3) By computer: from 3T’s controller (RS 232 or RS 485 compatible).
c. The data is analyzed and, based on this information, instructions regarding the optimal press speed are given to the press operator.
Using 3T pyrometers, a press operator can use the information obtained, along with his experience, to achieve the best extrusion process possible.
COMBINED CLOSED LOOP CONTROL – 3T’s controller signals can be combined with a closed loop control system allowing for the automatic control of press speed.
B. BILLET FURNACE EXIT
By measuring the temperature of aluminum profiles at the billet furnace exit or positioned before the billet loader the following advantages can be achieved:
Prevents A Hot Or Cold Billet From Entering The Press:
A hot billet damages the profile resulting in a low quality.
A cold billet causes maintenance problems.
Better control of the billet furnace temperature allows for improved control of the furnace.
QUALITY – The emissivity measurement provides the user with a parameter for controlling the quality of the billet.
PRODUCTIVITY – Control of the profile temperature assists in increasing productivity.
ENERGY – Billet temperature control can result in energy savings at the billet furnace.
C. AT THE COOLING TABLE
By measuring the temperature of aluminum profiles at the cooling table where profile temperatures range between 200°C - 230°C the following advantages can be achieved:
IMPROVED MECHANICAL PROPERTIES RESULT IN BETTER QUALITY. Profiles must be cooled with precise timing.
VENTILATION UNITS CAN BE CONTROLLED WITH THE 3T PYROMETER.
Fig. No. 1 - Block Diagram of Temperature Factors.
3T – True Temperature Technologies Ltd. recommends to adopt all three applications in order to achieve temperature control and an isothermal extrusion process.
Remember if you wish to join the superextruders, who always have time enough to make profit, begin by concentrating on three things:
First - Temperature
Second - Temperature
Third - Temperature
1. Robbins, , Who are the Superextruders?; Light Metal Age Magazine, April 1997.
2. Glazman, Dr. E. D., Measurement of Thermodynamic Temperature in the Extrusion Process of Aluminum and Aluminum Alloys, Light Metal Age Magazine, April 1998.
3. Glazman, Dr. E. D., New Optical Pyrometer for Measuring the Temperature of Aluminum Alloys, Aluminum Extrusion Magazine, No. 5 1998.
Accurate Temperature Measurement In Aluminum Extrusion For Increases Productivity, Quality And Energy Savings
|Accurate Temperature Measurement In Aluminum Extrusion
|Billet And Bar In Forging Process
|Temperature Measurement Of Aluminium Billet And Bar In Forging Process
|Prepared by: Boris Shtarker and Ofer Yoely
Temperature control plays an important role in any hot-working operation. Contact methods of measurement are often difficult as the probes tends to wear and maintenance of the probes can be time consuming and expensive. Non-contact measurement using infrared sensors has been tried many times but with only limited success on aluminum because of the low and variable emissivity. The 3T company in Israel has successfully developed an infra-red temperature measurement system that uses several different wavelengths and complex algorithms to accurately measure the temperature in the extrusion, forging, hot-rolling and casting of aluminum alloys.
The P3000 pyrometer joins the family of innovative products that have been developed by 3T - True Temperature Technologies for use in the aluminum forging industry.
Accurate measurement of aluminum parts during forging process is vital to ensure quality product. It is well established that even minor changes in the billet temperature can cause deterioration in the mechanical properties of the forged part, by creating internal stresses and deformations.
For that reason, AUTOMOTIVE PARTS MANUFACTURERS demand accurate measurement of each forged billet coming in and out the press.
Due to long response time of contact probe, and frequent probe tip maintenance, measurement with thermocouple is not applicable - a few seconds for each measurement will be very expensive in mass production.
Unlike contact probe 3Ts non-contact optical pyrometer, will measure temperature within less than a second, and therefore is the most suitable instrument for forging application.
Furthermore 3Ts optical non-contact pyrometer enables automatic, continuous, maintenance free temperature measurement.
Non-contact temperature measurement provides accurate consistent reliable reading, which can be recorded (via RS232 communication or analog 4-20mA), for quality assurance purposes.
Measurement Range: 300°C - 1000°C (572°F - 1832°F).
Emissivity range: 0.1 (300°C) to 1.0 (1000°C)
High sensitivity and accuracy: ±1%
Locating the P3000:
There are a few possible locations for 3T-pyrometer model P3000:
On the exit from the heating furnace
On the entry to forging press
On the exit from forging press (for temperature control of forged parts).
The pyrometer can be installed also on a linear motion scanning motor in order to measure and improve the temperature distribution uniformity of the billet. Data can be collected and analyzed through analog or digital outputs.
The measurement of the temperature of the aluminum billet in the forging process is an important parameter affecting the physical and mechanical properties of the product. Therefore, when safety involved measurement of the temperature of each piece is necessary and mandatory.
3T – True Temperature Technologies Ltd. specializes in non-contact true temperature measurement, offering pyrometers that show the exact temperature in different locations of aluminum forging and extrusion process, and significantly improving product quality while increasing productivity.
Comparison between 3T P3000 and contact probe (thermocouple)
|No of reading
||Contact Probe °C
||3T P3000 °C
|Billet And Bar In Forging Process