Pyrometric device

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Pyrometric devices gauge heatwork (the combined effect of both time and temperature) when firing materials inside a kiln. Pyrometric devices do not measure temperature, but can report temperature equivalents. In principle, a pyrometric device relates the amount of heat work on ware to a measurable shrinkage or deformation of a regular shape.

Contents

Care should be taken with the interpretation, as some naively assume they are a measure of temperature alone.

Types

Buller Rings that were placed at top and bottom of a kiln Gelang Buller - Buller Ring.jpg
Buller Rings that were placed at top and bottom of a kiln
Rings
Rings are flat, hollow centred discs whose contraction is proportional to the heat work experienced. A micrometer or gauge measures the fired ring, with the difference being an arbitrary number that is used to describe the firing regime experienced. Various grades of ring, each of slightly different compositions, are available to cover all firing conditions and temperature equivalents likely to be encountered. Examples of pyrometric rings include Bullers Rings, [1] PTCR Rings and Thermorings. [2] [3]
Bars
Bars are square sectioned, and mounted horizontally across two fixed distance supports. During firing the softening of the material results in sagging at the centre. Pyrometric Bars have found popularity in Kiln Sitters, which uses the described deformation to act as a triggering element, thus turning off the kiln at a desired point of maturity. Examples of pyrometric Bars include Holdcroft Bars and "Orton Bars".
Four Seger cones after use Segerkegel.jpg
Four Seger cones after use
Cones
Cones are slender, three sided pyramids that are made from a range of compositions, each composition with a reference number corresponding to a certain heat work. Rather than shrink as rings do, a cone's tip will bend forward to the same level as the base at the time of maturity. Other deformations of a cone, such as bloating, cracking or bending backward, can be appropriately interpreted to troubleshoot activity inside the kiln.
Discs
Are calibrated ceramic disc-shaped devices. Examples include Bullers Process Control Discs and TempCHEKS. [4]

History

In 1782, Josiah Wedgwood created an accurately scaled pyrometric device working (see Wedgwood scale for details), with details published in the Philosophical Transactions of the Royal Society of London in 1782 (Vol. LXXII, part 2). This led him to be elected a fellow of the Royal Society. [5] [6] [7] [8] [9]

The modern form of the pyrometric cone was developed by the German ceramics technologist Hermann Seger and first used to control the firing of porcelain wares at the Königliche Porzellanmanufaktur (Royal Porcelain Works) in Berlin, in 1886. Seger cones are still made by a small number of companies and the term is often used as a synonym for pyrometric cones.

Holdcroft Bars were developed in 1898 by Holdcroft & Co. [10]

Bullers rings have been in continuous production for over 80 years, and are currently in use in over 45 countries. Originally developed by the company named Bullers, the current manufacturers, Taylor Tunnicliff Limited, were founded in 1867. [11]

The Standard Pyrometric Cone Company was founded by Edward J. Orton, Jr. in 1896.

PTCR rings (Process Temperature Control Rings) were originally called "Phillips Temperature Control Rings" and developed by Phillips Electronics in Uden, Netherlands. The plant is now owned by Ferro and moved to its current location in St Dizier, France in 2010.

Related Research Articles

<span class="mw-page-title-main">Ceramic</span> An inorganic, nonmetallic solid prepared by the action of heat

A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.

<span class="mw-page-title-main">Kiln</span> Oven for clay products

A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay into pottery, tiles and bricks. Various industries use rotary kilns for pyroprocessing and to transform many other materials.

<span class="mw-page-title-main">Melting point</span> Temperature at which a solid turns liquid

The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.

<span class="mw-page-title-main">Pyrometer</span> Type of thermometer sensing radiation

A pyrometer, or radiation thermometer, is a type of remote sensing thermometer used to measure the temperature of distant objects. Various forms of pyrometers have historically existed. In the modern usage, it is a device that from a distance determines the temperature of a surface from the amount of the thermal radiation it emits, a process known as pyrometry, a type of radiometry.

<span class="mw-page-title-main">Earthenware</span> Nonvitreous pottery

Earthenware is glazed or unglazed nonvitreous pottery that has normally been fired below 1,200 °C (2,190 °F). Basic earthenware, often called terracotta, absorbs liquids such as water. However, earthenware can be made impervious to liquids by coating it with a ceramic glaze, and such a process is used for the great majority of modern domestic earthenware. The main other important types of pottery are porcelain, bone china, and stoneware, all fired at high enough temperatures to vitrify. End applications include tableware and decorative ware such as figurines.

<span class="mw-page-title-main">Refractory</span> Materials resistant to decomposition under high temperatures

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<span class="mw-page-title-main">Pyrometric cone</span> Pyramidal ceramic specimen whose slump is proportional to the temperature reached in the kiln

Pyrometric cones are pyrometric devices that are used to gauge heatwork during the firing of ceramic materials in a kiln. The cones, often used in sets of three, are positioned in a kiln with the wares to be fired and, because the individual cones in a set soften and fall over at different temperatures, they provide a visual indication of when the wares have reached a required state of maturity, a combination of time and temperature.

<span class="mw-page-title-main">Mandrel</span> Gently tapered cylinder against which material can be forged or shaped

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<span class="mw-page-title-main">Infrared thermometer</span> Thermometer which infers temperature by measuring infrared energy emission

An infrared thermometer is a thermometer which infers temperature from a portion of the thermal radiation sometimes called black-body radiation emitted by the object being measured. They are sometimes called laser thermometers as a laser is used to help aim the thermometer, or non-contact thermometers or temperature guns, to describe the device's ability to measure temperature from a distance. By knowing the amount of infrared energy emitted by the object and its emissivity, the object's temperature can often be determined within a certain range of its actual temperature. Infrared thermometers are a subset of devices known as "thermal radiation thermometers".

Slumping is a technique in which items are made in a kiln by means of shaping glass over molds at high temperatures. The slumping of a pyrometric cone is often used to measure temperature in a kiln.

<span class="mw-page-title-main">Ceramic engineering</span> Science and technology of creating objects from inorganic, non-metallic materials

Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.

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<span class="mw-page-title-main">Gladstone Pottery Museum</span> Industrial museum in Staffordshire, England

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<span class="mw-page-title-main">Glaze defects</span> Flaws in a ceramic glaze

Glaze defects are any flaws in the surface quality of a ceramic glaze, its physical structure or its interaction with the body.

<span class="mw-page-title-main">Disappearing-filament pyrometer</span>

The disappearing-filament pyrometer is an optical pyrometer, in which the temperature of a glowing incandescent object is measured by comparing it to the light of a heated filament. Invented independently in 1901 by Ludwig Holborn and Ferdinand Kurlbaum in Germany and Everett Fleet Morse in the United States, it was the first device which could measure temperatures above 1000 °C. Disappearing filament pyrometers have been used to measure temperatures between about 600 °C and 3000 °C. Like other optical pyrometers they are used to measure the temperature of objects too hot for contact thermometers, such as molten metals. Widely used in the steel and ceramics industries as well as for research, they have been almost totally superseded by electronic spectral-band pyrometers.

This is a list of pottery and ceramic terms.

<span class="mw-page-title-main">Warm glass</span>

Warm glass or kiln-formed glass is the working of glass, usually for artistic purposes, by heating it in a kiln. The processes used depend on the temperature reached and range from fusing and slumping to casting.

<span class="mw-page-title-main">Wedgwood scale</span> Unit of temperature

The Wedgwood scale (°W) is an obsolete temperature scale, which was used to measure temperatures above the boiling point of mercury of 356 °C (673 °F). The scale and associated measurement technique were proposed by the English potter Josiah Wedgwood in the 18th century. The measurement was based on the shrinking of clay when heated above red heat, and the shrinking was evaluated by comparing heated and unheated clay cylinders. It was the first standardised pyrometric device. The scale started at 1,077.5 °F (580.8 °C) being 0 °W and had 240 steps of 130 °F (72 °C). Both the origin and the step were later found inaccurate.

<span class="mw-page-title-main">Kiln furniture</span>

Kiln furniture are devices and implements inside furnaces used during the heating of manufactured individual pieces, such as pottery or other ceramic or metal components. Kiln furniture is made of refractory materials, i.e., materials that withstand high temperatures without deformation. Kiln furniture can account for up to 80% of the mass of a kiln charge.

<span class="mw-page-title-main">Hermann Seger</span> German ceramicist (1832–1893)


Hermann Seger (1832–1893) was a German ceramicist who is widely credited with pioneering the development of the pyrometric cone, which enabled the rapid growth of the ceramic industry around the turn of the century.

References

  1. Webster, John G (1999). The measurement, instrumentation, and sensors handbook. ISBN   978-3-540-64830-7.
  2. "Schwendler & Co. KG / Technische Keramik / Meß- und Regeltechnik". www.schwendler.de. Archived from the original on 2002-07-24.
  3. "Archived copy" (PDF). Archived from the original (PDF) on 2014-08-19. Retrieved 2014-08-17.{{cite web}}: CS1 maint: archived copy as title (link)
  4. "Measure your Heat Work with Bullers™ Process Control Discs | Mantec Technical Ceramics". www.mantectechnicalceramics.com. Archived from the original on 2014-08-19.
  5. "Wedgwood Pyrometer by J. Newman, 1827-56 | Science Museum Group Collection".
  6. https://catalogue.museogalileo.it/object/WedgwoodsPyrometer.html
  7. "Image of wedgwood pyrometer, 1786. By Science & Society Picture Library".
  8. "Wedgwood's pyrometer".
  9. "Philosophical Transactions of the Royal Society of London. Vol. LXXII. For the Year 1782. Part II". The London Medical Journal. 4 (3): 225–235. 1783. PMC   5545481 .
  10. A.Dodd, D.Murfin (ed.)Dictionary Of Ceramics. 3rd edition. Institute of Materials. 1994. ISBN   0-901716-56-1.
  11. "Archived copy" (PDF). Archived from the original (PDF) on 2011-07-16. Retrieved 2010-05-02.{{cite web}}: CS1 maint: archived copy as title (link)

Further reading