Wavelength Matters

Application Note: Aluminum Hot Rolling Mill - Roughing/Reversing Mill

Posted by Thomas Huff on Tue, Apr 25, 2017 @ 08:51 AM

This is part 2 of the 4-part Aluminum Hot Rolling Mill application note series - be sure to check out the rest of the series!

Application Overview:

At the reversing mill, rolling speed, roll bite and coolant flow may be optimized only with a precise real-time knowledge of metal temperature.  The low and highly variable non-greybody emissivity character associated with this complex aluminum process dictates the use of the most sophisticated multi-wavelength infrared pyrometers as the material converts from a coarse ingot to a smooth strip. 

Williamson Wavelength Advantage:Aluminum Reversing Mill.jpg

The Williamson model MWx, designed specifically for the demanding aluminum hot reversing rolling mill application, uses the most advanced Multi-Wavelength Dynamic ESP Technology available for unequalled accuracy under all operating conditions.

Pyrometer Benefits:

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Topics: aluminum, hot rolling, application note

Application Note: Aluminum Hot Rolling Mill - Ingot Measurement

Posted by Thomas Huff on Mon, Apr 24, 2017 @ 08:51 AM

This is part 1 of a 4-part application note that covers the Aluminum Hot Rolling Mill  - stay tuned for more posts.

Application Overview:

Before heading to the rolling stands, a large ingot of aluminum is heated in a furnace for hours to days. Ingots need to be heated for this long of a time so they are completely heated through to the core so that the ingot can be rolled out into a longer strip without being reheated.

Williamson Wavelength Advantage:Aluminum Ingot.jpg

The ingot is soaked for such a long time to assure uniform temperature prior to rolling, and the soaking time is often extended due to process down time. These extended soaking times often alter the emissive character of the aluminum even when the surface texture is reasonably consistent, and this is the primary reason why the Dynamic ESP Technology associated with the MWx pyrometer is required.

Pyrometer Benefits:

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Topics: aluminum, hot rolling, application note

The 3 Most Common SRU Temperature Measurement Issues and How to Solve Them

Posted by Thomas Huff on Sat, Apr 1, 2017 @ 03:23 PM

When natural gas and crude oil is extracted from the ground it contains some percentage of sulfur.  Gas or oil with a high level of sulfur is said to be sour.  Gas or oil with a low level of sulfur is said to be sweet.  This sulfur is removed from the gas stream by a chemical reaction.  After this process, the sulfur is removed from the gas or oil and is instead contained in amine gas and sour water gas.  The sulfur is then removed from the amine gas and sour water gas in a thermal reactor called an SRU (Sulfur Reactor Unit).  This process is known as the Claus process. The Claus reaction that removes these gasses from the process stream is exothermal, meaning that it creates heat once the process has begun.  As a result, there are several reasons to monitor the temperature of the thermal reaction.

sru_thermal_reactor2.jpgThe thermal reaction is more efficient when run at higher temperatures, and the gas stream may be run through more quickly; therefore, there is tremendous incentive to run the process hot.  Many plants inject oxygen in an effort to raise operating temperatures and to increase process capacity.  However, the refractory walls of the vessel degrade at excessive temperatures, making it essential that the process temperature be closely monitored to balance the need to be efficient at extracting the sulfur while at the same time extending the life of the refractory.  These gasses are highly toxic, and the safe operation of the process is highly critical.

So while temperature is a critical process control parameter in the sulfur recovery process, there can be a number of complications when trying to get an accurate measurement. There are two generally accepted methods of measuring temperature inside of a Claus reactor - thermocouples and infrared pyrometers. This article gives a very comprehensive overview of the benefits and drawbacks of each measurement technique. However,  the following are the most common issues and difficulties associated with the SRU temperature measurement and how to address them.

 1. Constant replacement of thermocouples

One of the most common ways to measure the temperature inside the furnace is with a contact thermocouple device.  However, the inside of the reactor is a hot, nasty, and corrosive environment and thermocouples will often fail and need to be replaced. Thermocouples tend to be troublesome because of their unreliability and require a lot of maintenance work to replace them. It can be difficult to consistently run a process to the same temperature off of thermocouples alone and another means of measurement is typically required. Not to mention, that the constant replacement of these thermocouple devices can be expensive over time.

Solution: Non-contact temperature devices are often used instead or in addition to thermocouple measurements. Non-contact measurement

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Topics: Petrochemical

Troubleshooting for the Initializing Error

Posted by Kam Olaogun on Wed, Mar 29, 2017 @ 08:44 AM

Have you tried installing a new Williamson Pyrometer and Interface Module (IM) only to find the sensor to be stuck in "Initializing" mode? Or maybe you have moved your sensor from one location to another and now it is stuck in "Initializing." Please follow the below guide so that we can get your pyrometer back up and running.

Under normal conditions the LEDs on the IM's display should be all dashes during start-up and should display the following messages as it establishes communications and synchronizes with the pyrometer.

 IM establishing communications  IM Synchronizing  

Once communication has been established the sensor and IM should display either "LO", "HI" or an actual temperature value as shown below. If it isn't displaying any of these after one minute of startup then there is a problem with the sensor. Open up the back hatch of the sensor and verify that the LCD display is working by using the buttons to scroll through and activate the menu items. If these work, then the problem lies in the connection to the IM.

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Topics: pyrometer, maintenance, troubleshooting, initializing, digital mode, IM, interface module

Installation Guide and Overview for Williamson Flare Monitors

Posted by Jonathan Stronach on Tue, Mar 28, 2017 @ 01:30 PM

Williamson offers three optical non-contact sensors for the petrochemical industry and flare monitoring. This post covers the mounting and installation guidelines to ensure peak performance and accurate readings. 

The Williamson Pilot Monitor (PM): Uses dual-wavelength technology to sense the presence of small, wandering, and distant pilot flames. This unique technology allows for the sensor to be mounted at considerable distances while effectively detecting the presence of a flame despite severe weather conditions caused by wind, snow, sleet, fog, and rain. 

The Williamson Flare Monitor (FM): Also uses dual-wavelength technology and is used to adjust the flow of air or steam to a smokeless stack by monitoring the combustion efficiency. This ensures smoke free operation as well as maximum combustion efficiency. 

The Williamson Flame Intensity Monitor (FI): This single-wavelength device is used to sense the presence and intensity of flames of all types. This lower cost option is commonly used as a pilot monitoring device for ground flares and land fills where the mounting distance is less than 300ft. 

These three petrochemical products are optical devices that can be mounted up to 2000ft. The mounting distance allows for easy access to the sensor and can help prevent costly shutdowns from faulty thermocouples. Because the sensor is an optical device, the unit should be mounted in a location where the flare is within the sensors field of view. The below installation/mounting guidelines will ensure that the Williamson flare product can properly view the flare and provide an accurate reading. 

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Temperature Control of Flame Fired Processes

Posted by Kam Olaogun on Thu, Mar 9, 2017 @ 03:37 PM

What is a flame fired process?

Every flame fired process is dictated by the reaction of a fuel in the presence of oxygen or an oxidized environment; this reaction is more commonly known as combustion or more simply burning. Fuels used may be solid, liquid or gaseous and common examples include wood, coal, natural gas and other hydrocarbon variations, biodegradable waste and used tires.

The most common example of a combustion process occurs in the engine of your car. When gasoline (fuel) is ignited by a flame within a very small area of a car's engine it releases a great deal of gas which then pushes the car's pistons, which then rotates the car's crankshaft, and ultimately this will then turn the car's wheels. Another common example is a coal power boiler. The stored energy in coal is released by combustion and converted into electricity. When coal is burned in air the carbon in the coal and the oxygen in the air react to produce CO2 and heat. The heat is then used to convert the water within the boiler into steam. The high pressure steam is used to turn a turbine and a generator converts this mechanical energy into electrical energy. About half of the world's electricity is created this way. Waste treatment is another example of a flame fired process. Hazardous waste is fed into into a rotating combustion chamber of an inclined rotary kiln. The combustion of these waste materials creates heat, ash, and flue gas which is then treated before being released into the atmosphere.

As you can see the presence of a burning flame is the catalyst in these kinds of processes. Therefore close temperature control of the flame is absolutely essential to ensure that these processes are occurring efficiently. 



Other Flame fired processes include:

  • Power Boilers
  • Incinerators
  • Industrial Furnaces & Kilns
  • Thermal Reactors



The Nature of Flames

Temperature control of a flame fired process is tricky because of the elevated temperatures along with the presence of a burning voluminous flame. A non-contact infrared pyrometer is recommended because of the harsh conditions found in these areas. Thermocouples have proven to be inaccurate and constant replacement of these contact devices become costly. To better understand the challenges of making temperature measurements of flame fired processes we must understand the nature of flames.

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Topics: pyrometer, temperature control, flame

How to Improve Temperature Measurement Accuracy and Repeatability for Aluminum Rolling Mills

Posted by Thomas Huff on Thu, Feb 16, 2017 @ 02:05 PM

Temperature Control in the Hot Rolling Mill

Aluminum sheet and plate products are used for a wide range of applications, including can stock, brazing, automotive and aerospace.   These industries demand exacting tolerances and precise mechanical properties, particularly for new, technically challenging high-strength alloys.   As a result, the modern aluminum hot rolling mill demands previously unobtainable levels of temperature measurement accuracy for the control of rolling mill bite, pressure, speed, and coolant.  To meet this need, Williamson offers two multi-wavelength infrared technologies able to provide the unprecedented accuracy this industry now demands for temperature readings throughout the hot rolling process.

Aluminum Rolling Mill Diagram2.png

Current Measurement Technologies and Limitations


Some plants use and thermocouple probes to get a temperature measurement throughout the process and make adjustments based on these contact measurement points. Thermocouples - while a contact measurement, are never really accurate and repeatable - the temperature output can change depending on how hard they are pressed onto the metal, they often read lower than the true temperature as they are influenced by air temperature, and need to be sharpened and checked against a calibration device often to be trusted (which pretty much never happens).  

Multi-Wavelength Pyrometers

Pyrometers are non-contact temperature sensors that measure the infrared energy that is emitted from a target.  Aluminum is a notoriously difficult material to measure because it is a non-greybody material, which means that it has a low and varying emissivity that varies at different wavelengths. For these type of non-greybody materials a multi-wavelength pyrometer is the recommended option (see point 1 in this blog post for more information). However, the aluminum undergoes such a dramatic change during the roughing/reversing mill process (from ingot, to slab, to strip) that traditional multi-wavelength pyrometers often need to have an adjustment to the reading so that they can be more accurate in their reading. The needed adjustments are different for different alloys, and also vary by the thickness (pass number) of the aluminum strip.

While the multi-wavelength technology is highly repeatable and accurate under very specific process conditions, any time these conditions vary (and they do), there will be a measurement error. As a result, many plants will have very detailed matrices, models, or recipe systems that will adjust the offset for each pyrometer based on individual alloy, strip thickness, and position (if the algorithms worked for all conditions, they wouldn't need the offsets!). These model and/or recipe systems are extremely complicated and difficult to manage if anything in the process changes or if the pyrometer is not functioning properly, which makes them difficult to rely upon.

A New Approach - MWx

With the increasing demand for tighter temperature tolerances from the automotive and aerospace industries, the existing pyrometer technologies were not cutting it and we set out to develop a new approach

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Topics: aluminum

Compensating for Optical Obstructions and Emissivity Variation with Single-Wavelength Sensors

Posted by Jonathan Stronach on Wed, Jan 18, 2017 @ 08:42 AM


Williamson Short-Wavelength Advantage

Infrared pyrometers rely on making a reading based on the amount of energy collected. The amount of energy collected can be affected by emissivity variance and optical obstructions. Selecting the shortest possible wavelength helps to eliminate variables such as emissivity variation and optical obstruction. Being less sensitive to these variables ensures for a more accurate reading compared to a general purpose long-wavelength sensor.

Emissivity Variance

Every object emits infrared energy proportional to its temperature. Infrared pyrometers collect the infrared energy emitted by an object and convert it into a temperature value. Emissivity is the percent of energy emitted by an object compared to the theoretical amount of infrared energy emitted by a perfect emitter at the same temperature. The amount of energy emitted is a function of both temperature and emissivity.


Therefore, the emissivity of a measured target has a direct correlation to the energy reading of a pyrometer. Emissivity varies due to changes in material, surface texture, degree of oxidation, micro structure or surface contamination. The emissivity of a material can also vary at different wavelengths. The graph to the right shows that selecting the shortest possible wavelength will result in smaller errors due to emissivity variance. In fact, short-wavelength sensors can be 4-20 times less sensitive to emissivity variation compared to long-wavelength sensors. By reducing the errors caused by emissivity variation short wavelength sensors produce a more accurate and repeatable reading.

Optical Obstructions:

The other variables that alter the amount of energy collected by a sensor are the optical obstructions

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3 Infrared Technologies to Use in the World of Competitive Annealing

Posted by Kam Olaogun on Thu, Aug 18, 2016 @ 11:30 AM

3 Infrared Technologies to Use in the World of Competitive Annealing

Not all annealing lines have the same accuracy requirements. Some alloys require tighter temperature control than others. Plants that run high-strength steel or dual/complex-phase steel require precise control of steel temperature. Plants that run low-alloy steels for non-transportation and non-appliance applications often can produce a high-quality product with looser control of the steel temperature; however, these plants also benefit from the improved speed and energy efficiency associated with precise control of steel temperature. Regardless of alloy, effective temperature control of steel dictates the use of an accurate infrared pyrometer. Better temperature control allows plants to perfect their recipes which improves efficiency and lowers operating costs. Moreover, precise temperature control ensures final product quality and repeatability. Infrared pyrometers are the best solution for continuous annealing lines because of their ability to make accurate non-contact temperature measurements. However not all pyrometers offer the same level of performance and different wavelength technologies further validates this.    


Pyrometers are typically installed on a continuous annealing furnace using one of two mounting techniques.

1.) Roller Wedge

Roller_wedge.jpgThe roller wedge measurement technique, also known as the nip measurement technique or as the low-angle multi-reflective measurement technique, relies on the unique geometry associated with the roller nip combined with a low-angle of alignment to artificially enhance the apparent emissivity of the strip and to eliminate the influence of hot background reflections. Roller wedge measurement conditions are valid and the technique is appropriate only when certain conditions are met: (1) the roll and the strip are the same temperature and (2) the pyrometer must be mounted at the sweet spot—an appropriate shallow angle to produce a significant number of reflections.(*)


2.) Direct View

The direct view measurement technique is used when the roller wedge measurement technique is not

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Topics: wavelength, pyrometer, steel, annealing, wedge, temperature control

Billet Temperature Measurement: Typical Practices vs. Best Practices

Posted by Jonathan Stronach on Mon, Aug 8, 2016 @ 10:30 AM

Billet Temperature Measurement: Typical Practices vs. Best Practices

For the forging and extrusion industries there are two temperature measurements that should be made. The first is the temperature of the billet as it is being heated – to make sure that the heating system heats it to the correct temperature value, and the second is the confirmation of the billet temperature just before it enters the forging or extrusion press. In practice, most plants use only one pyrometer to make both temperature readings, but in reality these are two different measurements.

 Why Billet Temperature Matters

Billet Heating: Most plants measure the billet temperature after it exits the billet furnace. However, the temperature of each billet varies making this measurement too late for real time, precise feedback control. In order to actually control the temperature of each billet during the heating process, it is necessary to measure the billet while it is still inside the furnace. This technique is the only way to bblog.jpgcontrol the temperature of each billet to reach the exact process temperature.

Billet Confirmation: Process upsets and delays can result in a billet sitting and waiting before being loaded into the forging or extrusion press. If the delay is long and variable then the billet temperature can be low and variable. The lower temperature caused by the billet sitting can result in poor quality, excessive wear, process upsets, and in some cases damaged equipment.  

Typical Practice

The typical practice is to measure the billet temperature immediately after it exits the furnace. However, the corners of the billet typically heat faster and hotter than the bulk metal temperature. These hot corners can introduce a variable offset in pyrometer readings. But, if the temperature reading is taken 20-30 seconds after the billet exits the furnace, the corners have enough time to cool and the interference is eliminated. This typical practice for billet measurement is too late for feedback control and too early for billet confirmation. Moreover, the point of measurement coincides with the period at which the billet surface temperature is least uniform and most variable.

Best Practices

Billet Heating: Measure the billet while it is still inside the furnace. For the induction
heating process, the best configuration is a fiber-optic pyrometer that can view between the coil windings away from the end of the billet.

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Topics: pyrometer, aluminum, steel, Forging