Profiling Glossary of Terms
Conveyorized oven
Any oven with a mechanism to transfer product or material through the oven. Popular types include mesh belt, roller hearth, rotary hearth and walking beam. Reflow soldering and paint curing ovens also fall into this category.
Batch oven
The product is typically stationary for the duration of the process, loading and unloading through the same door. They vary in size depending on product being processed from table top to room sized.
Heat treatment
Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, normalizing and quenching.
Convection heat transfer
Heat transfer due to bulk movement of molecules within fluids such as gases and liquids. Many low temperature processes will used forced air to increase convection and so transfer heat faster to the product
Line Speed
Defines the speed at which product or material is passing through a conveyorized oven. Units of measure vary depending on process.
AMS2750
The AMS2750 standard was created to provide a consistent specification for temperature control throughout the aerospace supply chain. The standard covers pyrometric requirements for thermal processing equipment used for heat treatment. It covers temperature sensors, instrumentation, thermal processing equipment, system accuracy tests, and temperature uniformity surveys. These are necessary to ensure that parts or raw materials are heat treated in accordance with the applicable specifications.
Temperature Uniformity Survey (TUS)
A TUS is a test undertaken to determine the range of temperatures present at different locations in the furnace under normal operating conditions. This involves determining temperature variations by surveying at the maximum and minimum operating temperatures and at a series of intermediate temperatures. The location of the measurement points define the ‘working zone’ of the furnace.
System Accuracy Test (SAT)
The SAT is performed by monitoring and recording data at a stable temperature and comparing the readings generated by the furnace control system and a reference system. The purpose of the test is to detect and quantify any deviation in furnace instrumentation accuracy and determine if the deviations are within acceptable limits.
Thermal/temperature profile
A set of time-temperature data points typically associated with the measurement of temperature in an oven, furnace or kiln. Temperature profiles can be taken from the product being processed or the ambient temperature in the process.
Thermal barrier
A product designed to reduce thermal energy flow to a minimum; typically to protect temperature sensitive items from temperature extremes. Thermal barriers usually incorporate a combination of insulation and phase change materials.
Heatsink
A device that absorbs heat while remaining at a steady temperature. Typically a sealed solid to liquid system based on phase change materials.
PCM Phase Change Material
At temperatures above its transition temperature, phase change material begins to soften and flow. This phase change requires energy and so a PCM absorbs the heat energy during the phase change with an increase in temperature.
Insulation
Insulation is the process of keeping heat, sound, or electricity from spreading. It's also the material used to do so.
Microporous insulation
Microporous materials are very efficient insulation products. These products actually have thermal conductivity values lower than still air. This performance is based on the ability of microporous insulation to block the three modes of heat transfer (i.e., conduction, convection, and radiation).
Thermal mass
Thermal mass is the ability of a material to absorb and store heat energy. A lot of heat energy is required to change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to have high thermal mass. Lightweight materials such as timber have low thermal mass.
Thermal conductivity
Defined as the time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. Normally measured in units of W/mK. Insulating products will have very low values of thermal conductivity.
Nimh cell
NiMH stands for Nickel-Metal Hydride. Unlike other cells NiMH cells do not use heavy metals that may have toxic effects. In addition, they can store up to 50% more power than NiCad batteries and do not suffer from memory effects.
Lithium Ion cell
A type of secondary or rechargeable cell in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging. They have limited ability to work at temperature and are limited to applications at less than 55C. man use in prtable electronic equipment such as phones and computers
Lithium cell
A type of primary or non-rechargeable cell with a very high energy density. Lithium cells have very low self-discharge and find application in devices where battery life can be measured in years. Some lithium cells can be used at high temperatures so they are often used to power thermal data loggers.
Seebeck
The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference. The voltage measured is composed of two parts one generated at the junction of the conductors and the other along the part of the conductor where the temperature gradient exists. This effect is the method by which thermocouples work and each thermocouple type will have a different Seebeck voltage vs temperature curve.
Hot junction
The pit at which eth two wires of a thermocouple are joined together. This is typically a welded junction free of impurities the size of which is kept small to enable a point measurement to be taken.
Base metal thermocouple
A thermocouple constructed from low cost materials typically copper, nickel and iron. Examples of base metals thermocouples are K type, N type, T type J type and E Type.
Type K thermocouple
Type K is the most commonly used thermocouple it is comprised of one conductor of Alumel and the other of Chromel. Used over temperature range of 0C to 1370C. IEC color coded green and ANSI Yellow
Type N thermocouple
A thermocouple created from the junction of Nicrosil and Nisil conductors. It was developed to tackle the problem of accuracy drift seen in type K thermocouples exposed to high temperatures for long duration. It is often used in aerospace industry when conducting temperature uniformity surveys. IEC color coded orange and ANSI pink
Type T thermocouple
A thermocouple created from the junction of copper and constantan conductors, it is very stable and repeatable. Typically used at cryogenic temperatures it finds wide use in the food processing industry. IEC color coded blue and ANSI blue.
Type J thermocouple
A thermocouple created from the junction of iron and constantan and widely used it has a smaller temperature range than the Type k but similar costs. Care is needed when using in oxidizing environments as the iron leg will corrode. IEC color coded white and ANSI black
Type E thermocouple
A thermocouple created from eth junction of nickel/chrome and constantan. It is very stable but upper temperature is lower than type K and N so use is not as widespread. IEC color coded violet and ANSI violet.
Nobel metal thermocouple
A thermocouple constructed from precious metals typically platinum and rhodium. There are three types in common use Type B type R and Type S.
Type R thermocouple
A thermocouple created from the junction of platinum and platinum/rhodium conductors. The rhodium content is 13%. It is very stable and used at very high temperatures often protected in a ceramic tube the high level of rhodium makes this an expensive thermocouple.
Type S thermocouple
A thermocouple created from the junction of platinum and platinum/rhodium conductors. The rhodium content is 10%. It is very stable and used at very high temperatures often protected in a ceramic tube marginally lower cost than type R.
Type B thermocouple
A thermocouple created from the junction of platinum rhodium 30% and platinum rhodium 6% conductors. This thermocouple has been developed for use at very high temperature. It is very stable and used protected in a ceramic tube.
Thermocouple extension wire
A lower grade and lower cost thermocouple wire that is used to connect the thermocouple grade wire to eth the measuring instrument. It is used in lower temperature environment where lower grade will not adversely affect system accuracy.
Relative humidity
Relative humidity (RH) is a measure of the amount of water vapour present in the atmosphere compared to the amount required to saturate that atmosphere at the same temperature; normally expressed as a percentage.
Process file
A term use in the thermal profiling industry to describe a file containing information related to the oven or furnace and product produced but not the temperature data. It provides a template to superimpose on the data and relates position in the process to temperature measured.
Tolerance curve
A graphical representation of the acceptable limits within which the temperature profile must fall.
Target profile
The ideal temperature profile for a given process and product. This will depend on metallurgical requirements in the metals heat treatment industry and cure schedule provided by the coating manufacturer in eth coatings industry.
Cure schedule
Cure schedule is the time and temperatures specified to complete either a chemical linking or evaporation resulting in a tighter linkage and hence tougher coating.
Statistical Process Control (SPC)
Is a standard methodology for measuring process stability and capability in manufacturing industry. Process or product measurements are taken in time during the manufacturing process and plotted on a graph along with control limits. This provides graphical and numerical indication of the process capability.
Lethality
As used in the food industry the term refers to the calculation used to determine the number of times the population of a target micro-organism has been reduced. The F0 calculation is commonly used in sterilisation processes carried out at 121C