Pyrometers: Non-contact Temperature Measurement

Pyrometers come in handy for applications
such as heat treating.

Non-contact temperature measurement technology allows process operators and technicians to evaluate the temperature of process materials, machinery, or piping by measuring their electromagnetic radiation. Through inferential calculation and one or more radiation measurements, specialized instruments can determine temperature without contacting the subject material or surface. While the concept of non-contact measurement technology has existed for many years, more recent advancements in non-contact temperature sensing and the evolution of the pyrometer have allowed temperature measurement at a distance to become popular throughout industrial process operations.

Pyrometers can commonly concentrate light from an object onto a temperature sensing element. The sensed elevation in temperature is proportional to the infrared optical energy. Different instruments may have varying arrangements of concentrating lenses and sensors, but the operating principle is the same. The physical law behind the pyrometer's operating principle operates on an exponential mathematical basis that is non-linear. This results in one of the limitations of the pyrometer. A single pyrometer can only, with high accuracy, deliver a comparatively narrow range of target temperature. If the need for accuracy is reduced, the applicable temperature range widens. Innovative manufacturers have developed instruments with technology and features overcoming many of the limitations imposed by the physics, delivering instruments with accuracy and applicable temperature range usable in a wide array of applications.

One of the advantages to using a non-contact pyrometer is that their calibration is independent of the distance between the sensor and the object being evaluated. This phenomenon is due to the fact pyrometers have a field of view and can be filled with the target object in a way independent of distance. While the radiation emanating from the target object may be decreasing, the field of view of the pyrometer is measuring a greater portion of the object which is proportional to the amount of radiation being lost, essentially canceling out the distance and allowing the pyrometer to provide useful output. An example of a practical application of a pyrometer in industry would be its use to check the temperature of a ventilation system in the HVAC field.

Share your temperature measurement requirements and challenges with process instrumentation specialists. Their product application expertise will combine with your own process knowledge and experience to produce an effective solution.

Electric Process Heaters & Controls

Hotfoil specializes in electric surface heating systems for fly ash hoppers on electrostatic precipitators or baghouses, coal and material handling systems, tanks, pipes, etc. in all types of industry.

For more information, visit http://www.hotfoilehs.com or call 609.588.0900.

Fuel Based Furnace Types and Applications

Large furnace in production (Hotfoil-EHS)

With fuel-based systems, heat is generated by the combustion of solid, liquid, or gaseous fuel, and transferred either directly or indirectly to the material. The combustion gases can be either in contact with the material (direct heating), or be con ned and thus be separated from the material (indirect heating, e.g., radiant burner tube, retort, muffle). Examples of fuel-based process heating equipment include furnaces, ovens, kilns, lehrs, and melters.

Fuel-based process heating systems are common in nearly every industry segment, and include furnaces like ovens, heaters, kilns, and melters, but also the surface treatment in ambient air. Typical fuel-based furnaces include the following:

• Atmosphere generators. Used to prepare and/or condition protective atmospheres. Processes include the manufacture of endothermic gas used primarily to protect steel and iron during processing, and exothermic gas used to protect metals, but also to purge oxygen or volatile gases from con ned areas.
• Blast furnaces. Furnaces that burn solid fuel with a blast of air, often used to smelt ore.
• Crucible furnaces. A furnace in which the heated materials are held in a refractory vessel for processes such as melting or calcining.
• Dryer. A device that removes free water, or other volatile components, from materials through direct or indirect heating. Dryers can be grouped into several categories based on factors such as continuous versus batch operation, type of material handling system, or source of heat generation.
• Indirect process heaters. Used to indirectly heat a variety of materials by remotely heating and circulating a heat transfer uid.
• Kilns. A furnace used to bake, dry, and re ceramic ware or wood. Kilns are also used for

  

  Heat treating furnace (Hotfoil-EHS)

  calcining ores.
• Lehrs. An enclosed oven or furnace used for annealing, or other forms of heat treatment, particularly in glass manufacturing. Lehrs may be the open type (in which the flame comes in contact with the ware), or the muffle type.
• Muffle furnaces. A furnace in which heat is applied to the outside of a refractory chamber or another enclosure containing the heated material that is enveloped by the hot gases. The heat must reach the charge by flowing through the walls of the container.
• Ovens. A furnace-like chamber in which substances are heated for purposes, such as baking, annealing, curing, and drying. Heated systems can use forced convection or infrared.
• Radiant-tube heat-treating furnaces. Used for processing iron, steel, and aluminum under a controlled atmosphere. The flame is contained within tubes that radiate heat to the work. Processes include carburizing, hardening, carbo-nitriding, and austempering. The atmosphere may be inert, reducing, or oxidizing.
• Reverberatory furnaces. Furnaces in which open flames heat the upper portion of a chamber (crown). Heat is transferred to the material mainly by radiation ( flame, reflection of the flame by the crown) and convection (combustion gases).
• Salt bath furnaces. Metal pot furnaces filled with molten salt where heat is applied to the outside of the pot or inside of the pot by radiant tube. Salt bath furnaces are used for processes such as heat treating metals and curing plastics and rubber.
• Solid waste incinerators. Used to dispose of solid waste material through burning.
• Thermal oxidizers. Used to oxidize volatile organic compounds (VOC) in various industrial waste streams. Processes include paint and polymer curing and/or drying.

Induction Heating Basics

Induction heating coils
around large pipe for
pre-weld heat treatment.

Induction heating occurs when passing alternating magnetic fields through conductive materials. This is accomplished by placing an alternating current carrying coil around or in close proximity to the materials. The alternating fields generate eddy currents in the materials. These currents interact with the resistance of the material to produce heat. There is a secondary heating process called hysteresis. This disappears at the temperature at which the material loses its magnetic properties.

Direct Induction

Direct induction heating occurs when the material to be heated is in the direct alternating magnetic field. The frequency of the electromagnetic field and the electric properties of the material determine the penetration depth of the field, thus enabling the localized, near-surface heating of the material. 

Comparably high power densities and high heating rates can be achieved. Direct induction heating is primarily used in the metals industry for melting, heating, and heat treatment (hardening, tempering, and annealing).

Indirect Induction

With indirect induction heating, a strong electromagnetic field generated by a water- cooled coil induces an eddy current into an electrically conducting material (susceptor), which is in contact with the material to be treated. Indirect induction heating is often used to melt optical glasses in platinum crucibles, to sinter ceramic powders in graphite crucibles, and to melt materials in crucibles prior to drawing crystals. Indirect induction is also used to heat susceptors used for joining operations.

Welding Heat Treatment Products from Hotfoil-EHS

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Quick Facts About Welding as a Profession

Reprinted from the Bureau of Labor Statistics  "Welders, Cutters, Solderers, and Brazers"

Welding is the most common way of permanently joining metal parts. In this process, heat is applied to metal pieces, melting and fusing them to form a permanent bond. Because of its strength, welding is used in shipbuilding, automobile manufacturing and repair, aerospace applications, and thousands of other manufacturing activities. Welding also is used to join steel beams in the construction of buildings, bridges, and other structures and to join pipes in pipelines, power plants, and refineries.

Welders work in a wide variety of industries, from car racing to manufacturing. The work that welders do and the equipment they use vary with the industry. Arc welding, the most common type of welding today, uses electrical currents to create heat and bond metals together—but there are more than 100 different processes that a welder can use. The type of weld normally is determined by the types of metals being joined and the conditions under which the welding is to take place.

Welders, cutters, solderers, and brazers typically do the following:

• Study blueprints, sketches, or specifications
• Calculate dimensions to be welded
• Inspect structures or materials to be welded
• Ignite torches or start power supplies
• Monitor the welding process to avoid overheating
• Maintain equipment and machinery

PAY

The median annual wage for welders, cutters, solderers, and brazers was $39,390 in May 2016. The median wage is the wage at which half the workers in an occupation earned more than that amount and half earned less. The lowest 10 percent earned less than $26,800, and the highest 10 percent earned more than $62,100.

In May 2016, the median annual wages for welders, cutters, solderers, and brazers in the top industries in which they worked were as follows:

• Specialty trade contractors - $42,900
• Repair and maintenance - $39,340
• Manufacturing - $38,200
• Merchant wholesalers, durable goods - $37,790

Wages for welders, cutters, solderers, and brazers vary with the worker’s experience and skill level, the industry, and the size of the company.

Most welders, cutters, solderers, and brazers work full time, and overtime is common. Many manufacturing firms have two or three 8- to 12-hour shifts each day, allowing the firm to continue production around the clock if needed. As a result, welders, cutters, solderers, and brazers may work evenings and weekends.