There are many specialized glossaries that cover the terms describing the unique details about temperature and moisture sensors and their uses and this page represents an attempt to index most of them in one place.
Many online articles about radiation thermometry and its uses (infrared thermometers, radiation pyrometers) exist including technology articles, PowerPoint slide presentations and .pdf downloads, but they seem to be vanishing as more and more “big businesses” take over these specialized sensors.But few are aimed at being useful glossaries or definition of terms.
There are some exceptions and some well-crafted pieces that have been online for a while and can be found in semi-hidden corners of the Web.
Below is a list of some Thermal Imaging Services or Directories where more lists can be found. It is not complete, we know.
Sorry if you were left out. If you should be listed or know of others who should be listed or if you want to improve your organization’s listing, let us know, please.
Note that the training organizations are listed on a separate page. Some of them provide classified ads for used equipment as do some of the service providers below.
Also, some of the training companies do other things, like practice thermography and run information exchange/training meetings at nice places in the Fall and Winter, like Orlando, New Orleans and Las Vegas.
Tell your new product and application stories at The Temperature Directories website: www.tempsensor.net or feedback to us and we’ll consider adding it here with your byline!
A unique inspection service that has developed a high-tech approach to aerial infrared thermographic scans for large, flat-roofed buildings as well as locating Stormwater pollution sources and more. A most visually and technically rewarding website.
Chemical & Infrared INSPECTIONS, LLC (USA)
Professional Services Assisting Industrial, Commercial and Residential Customers locate potential problems through Infrared Thermography and Structural Drug Detection
Colbert Infrared Services, Inc. (USA)
All of their Infrared Thermographers have completed the ASNT (American society of Non-destructive Testing) requirements for certified Thermographers, are members of the Professional Thermographers Association, and have had extensive training as Certified Thermal Trend Professional Solution Providers. The latter is their own software that they developed, sell and support for data collection, and fault-finding.
Emerson Process Management/CSI (USA)
Reliability Based Maintenance: vibration, tribology, oil lab services, motor monitoring, ir thermography, laser alignment, dynamic balancing, and RBM Services.
InfraredPredictive Surveys, Inc. (USA)
A Maryland Corporation is “The Total Inspection and Survey Service for Architects, Owners and Industry”, that performs infrared inspections of electrical systems, ovens, bearings, gears, condensers, heat exchangers, belt drives, chain drives, refractory insulation, valves, hydraulic systems, pumps, tanks and electrical equipment and more.
Infrared Services, Inc.(USA)
A Colorado Corporation that has been doing electrical, distribution, power system, uninterrupted power systems, mechanical systems, rotating equipment, roof moisture, energy audits, glycol snow melt systems, plumbing leak detection and other nondestructive surveys for over 9 years.
Jersey Infrared Consultants(USA)
Focused on process and predictive maintenance, JerseyIR is known throughout the USA for its expertise in petroleum thermal cracking and petrochemical thermal reformer furnaces-Headquartered in Burlington New Jersey, near Philadelphia PA.
Kleinfeld Technical Services, Inc. . Bronx, New York (USA).
A unique company with IR Thermography, heat transfer analysis, process engineering and FEA consulting services run by Jack Kleinfeld, P.E., a graduate chemical engineer.
Maintenance Reliability Group, Another unique organization, one aimed at the big picture of reliability in maintenance operations-with a strong thermography component. Run by Rich Wurzbach in south central Pennsylvania.
Si Termografia Infraroja . Bueneos Aires, (Argentina),
Services, consulting and products for infrared thermal imaging from Sr. Andrés E. Rozlosnik.
Sierra Pacific Innovations(USA)
SPI infrared thermography services thermal imaging infrared inspections. They have, according to their web site, the largest selection on the internet of new, demo, and previously owned imagers. 251 Waterton Lakes Avenue, Las Vegas, NV 89148.
Stockton Infrared Thermographic Services, Inc.(USA) A major service company located in North Carolina. Stockton is dedicated to providing a wide range of quality infrared thermographic services to their clients. They do not manufacture or represent products of any kind and do not provide any services other than infrared. Their site features images, videos and a great deal of information on applications. Stockton is divided into four seperate divisions and provide the following services:
The Aerial Infrared Thermography at Stockton is performed by its AITscan Division: Stormwater and other unplanned and illicit water discharges into Waterways and Lakes can be found more quickly at much lower cost than shoeleather surveys with AITscan’s PollutionFindIR™ Services
The Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational Scientific and Cultural Organization (UNESCO),
The United Nations Environment Programme (UNEP) and
The International Council for Science (ICSU).
Its goal is to provide comprehensive information on the total climate system, involving a multidisciplinary range of physical, chemical and biological properties, and atmospheric, oceanic, hydrological, cryospheric and terrestrial processes.
It is built on the WMO Integrated Global Observing System (WIGOS), the IOC-WMO-UNEP-ICSU Global Ocean Observing System (GOOS), the UN Food and Agriculture Organization (FAO)-UNEP-UNESCO-ICSU Global Terrestrial Observing System (GTOS) and a number of other domain-based and cross-domain research and operational observing systems.
It includes both in situ and remote sensing components, with its space based components coordinated by the Committee on Earth Observation Satellites (CEOS) and the Coordination Group for Meteorological Satellites (CGMS).
GCOS is intended to meet the full range of national and international requirements for climate and climate-related observations.
The Global Observing System is an extremely complex undertaking, and perhaps one of the most ambitious and successful instances of international collaboration of the last 100 years. It consists of a multitude of individual observing systems owned and operated by a plethora of national and international agencies with different funding lines, allegiances, overall priorities and management processes.
We have reviewed these documents and find them to be an excellent summary of this temperature measurement method and have archived them on our site in two formats, mobi, suitable for reading on an E-reader and in Adobe pdf format.
Part 1 provides and Overview, Nomenclature, a bit about what temperature is and the history of measurement methods and delves into the physics underlying Radiation Thermometry.
Part II covers practical radiation thermometers, some detail on measurement techniques and calibration and a brief reference list.
These files are linked below many be freely downloaded as long as we maintain this website.
The NASA description for both article reads as follows:
This document is a two-part course on the theory and practice of radiation thermometry.
Radiation thermometry is the technique for determining the temperature of a surface or a volume by measuring the electromagnetic radiation it emits.
This course covers the theory and practice of radiative thermometry and emphasizes the modern application of the field using commercially available electronic detectors and optical components.
Online — When customers are considering which thermal security camera or system to buy, one of the first questions asked of thermal imager manufacturers is usually: “At what distance can the IR camera detect a target?”.
In other words, what is the camera’s ability to capture very small details at great distances?
When thinking about effective surveillance, it is indeed a good criterion to differentiate one sensor from another.
No matter which manufacturer you are buying from, the answer given to this question will almost always include the “DRI ranges” expression.
DRI refers to the distance at which a target can be Detected, Recognized, or Identified, based on certain universally accepted parameters.
In order to select the right sensor for your defense, security, or surveillance needs, these DRI ranges have to be, first, perfectly defined, but also assessed with regards to globally adopted industrial standards.
Enter: The Origin of Johnson’s Criteria
In 1958, at the first ever “Night Vision Image Intensifier Symposium”, John Johnson, a night vision scientist at the U.S. Army’s “Night Vision and Electronic Sensors Directorate” (NVESD), presented a paper named the “Analysis of Image Forming Systems”.
Johnson’s paper defined a clear system with criteria and methodology for predicting an observer’s ability to find and assess targets using image intensifying equipment (such as thermal cameras), under various conditions. It worked well, and it was the first of its kind.
Johnson’s Criteria Definitions
Johnson’s model provided definitive criteria for calculating the maximum range at which “Detection, Recognition, and Identification (D, R, I)” could take place, with a 50% probability of success. (Orientation was also discussed, but this parameter is not used or recognized today).
Although newer methodologies for D,R,I exist today, such as NVESD’s “Night Vision Image Performance Model” (NV-IPM), the “Johnson’s Criteria” system was groundbreaking for its time, was the accepted standard in the defense industry for many years, and is still widely used in the security industry today.
Johnson defined “Detection” as the ability to subtend 1 TV line pair (+/- 0.25 line pairs) across the critical dimension of the subject (this translates to 2 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect that a subject was in the field of view, 50% of the time. Today, many security camera companies loosely follow Johnson’s Criteria and define their camera’s “Detection” performance range as the ability to subtend either 1.5 or 2 pixels on the target, using various target sizes.
Johnson defined “Recognition” as the ability to subtend 4 TV line pairs (+/- 0.8 line pairs) across the critical dimension of the subject (this translates to 8 +/- 1 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer determines the type of subject, a human or a car for example, 50% of the time. Today many security camera companies typically define their cameras “Recognition” performance range as the ability to subtend 6 pixels on the target, using various target sizes.
Johnson defined “Identification” as the ability to subtend 6.4 TV line pairs (+/- 1.5 line pairs) across the critical dimension of the subject (this translates to 12 +/- 3 pixels when using an LCD monitor). At the range that this occurs, regardless of target type, the observer could detect the subject.
Today many security camera companies loosely follow Johnson’s Criteria and define their cameras “Identification” performance range as the ability to subtend 12 pixels on the target, using various target sizes.
Johnson’s Criteria in the Security Industry
DRI ranges, expressed in kilometers (or miles), can usually be found in the specification table of infrared camera brochures, or in a description of the cameras features. While a very helpful jumping off point for narrowing down the options and homing in on the best systems, customers would be doing themselves a disservice to only look at DRI.
This is because today the application of Johnson’s criteria varies somewhat across the security industry. In most instances, documentation uses simplified or modified versions of the criteria, but they do all generally follow similar rules.
Typically, most companies use twelve pixels on the target for identification, six for recognition, and two for detection (sometimes 1.5). However, the target size can vary greatly. Normally the defense industry “NATO” target size (2.3×2.3 meters) is used for calculating the performance range for detecting vehicles, but for a human target, various target sizes can be found.
It is important when selecting your thermal infrared camera to keep in mind that in any given document, the target size for a human can range from 1.7-1.83 meters tall and from 0.3- 0.75 meters wide, and factor this into your decision-making process.
The Need to look at the Bigger Picture
Because end-users often place a high value on the written specifications of the camera, marketing departments are under pressure to use performance calculations that make their cameras look better than the competitors. However, since these calculations typically do not take environmental factors into account, customers should ask their thermal camera providers to explain the other elements and benefits of each camera they are offering, and how they will perform in a variety of conditions.
An Update on the Handheld IR Thermometer line that took over from DFPs*
The NEW Land Cyclops L family of high quality portable non-contact thermal infrared radiation thermometers provides spot temperature measurement with incredible accuracy and reliability.
The Cyclops product line is still going strong after nearly 30 years! (Note that the terms ‘radiation thermometer’ and ‘infrared thermometer” no longer appear on the Ametek-Land webpage that describes these measurement instruments! Clearly that’s an effort to simplify the terminology of these devices.)
Features such as a precision view of the measurement target spot with simultaneous digital display of temperature in the viewfinder, choice of operating and calculating modes, digital output and out of range alarms are provided as standard.
The Cyclops L family of non-contact portable thermometers introduce several new features to this instrument “dynasty”.
*With the introduction of the Minolta-Land Cyclops 52 in the 1980s, Land Instruments basically replaced the widely used Optical Pyrometer, AKA Disappearing Filament Pyrometer (DFP), sold world-wide by Leeds & Northrup Corporation (now defunct).
(ED NOTE: Land took over the full line when Minolta Camera Company merged with Konica and then withdrew from the camera business in the early 2000s.)
Below are some of the features of the latest models
On-board Data Storage – Up to 9,999 measurement points, stored inside the thermometer
Unique Route Manager – Ideal tool for plants with multiple locations, which you need to monitor on a regular basis. This includes pre-configured location settings for emissivity and window correction – no requirement to make a change to a Cyclops at different locations.
UKAS Calibration (option) – Full UKAS calibration in the Land on-site labs
New Logger Software – allows users to connect a Land Cyclops Portable thermometer to a personal computer or mobile device and view, analyse and record live temperature readings.
Added Protection – industrial rubber casing to withstand harsh environments for extended periods
The new Cyclops 055L Meltmaster is a dedicated high precision, portable non-contact thermometer, designed for accurate temperature measurement of liquid metal in foundries and steel plants.
The new Cyclops 100L is a general purpose, high temperature, portable non-contact thermometer, designed for accurate measurement of temperatures in the range 550 to 3000 °C/ 1022 to 5432 °F, in applications such steel, glass plus other high temperature applications.
The new Cyclops 160L is a general purpose, medium temperature, portable non-contact thermometer, designed for accurate measurement of temperatures in the range 200 to 1400 °C/ 392 to 2552 °F, in applications such steel, glass plus other medium temperature applications.
The unique features of the ruggedized Cyclops 390L portable non-contact thermometer make it the ideal instrument for accurate non contact temperature measurements in hydrocarbon-fuelled furnaces.
See if you can spot when the actual name changed from “Minolta-Land Cyclops” to just plain “Land Cyclops”. Given the fact that Land products are presently a part of the AMETEK product mix, it’s reasonable to expect a further designation change in the near future. (Hmmmm…“AMETEK Land Cyclops” sounds right)
In 2006 we wrote:
A “new” Cyclops™ Infrared Thermometer has been born..er…hached..er.. created (that sounds best).
The Cyclops™ Model C100 from Land Instruments International has appeared on the scientific and industrial instrument marketplace without much ballyhoo and glitter.
Yet, its understated presence belies some remarkable things about it and its forebears.
Simply stated: it is the latest in a long family of Cyclopses*, the replacements for the venerable Optical Pyrometer.(It doesn’t sound quite right, but the root word is Greek, not Latin)
In its earliest incarnations in the 1980s as the Minolta-Land Cyclops were breakthrough devices, very innovative and actually more accurate in most uses than the century-plus, much venerated, old Disappearing Filament Optical Pyrometers.
The latest Cyclops, Model C100, is no less innovative in its own quiet way. It is the first portable IR thermometer, of which we are aware, to incorporate Bluetooth RS-232 communications capability.
A brief walk through Cyclops™ Past
When the first Cyclops Model 51 was sold, by the Land companies, then Land Pyrometers Ltd. in the UK and Land Instruments Inc. in North America, it was also understated, but powerful in the market.
In a few short years it and the even more capable Cyclops Model 52, displaced the Optical Pyrometer in all but a few uses.
Going back, first…in the beginning, in the late 1970s, Land Pyrometers, Infrared Division in the UK was developing their own high-temperature handheld IR thermometer to compete with the Leeds & Northrup (L&N) Optical Pyrometer which held a significant portion of the portable, noncontact temperature sensor market around the world.
(ED NOTE:Optical Pyrometers are also known familiarly as “Opticals” and “DFPs”. Some even called them “Paperweights”, they were so heavy.)
When, at around the same time, the Minolta Camera Company of Japan produced a prototype handheld, automatic thermometer that covered the most important portions of the industrial high temperature range.
In comparison with the Land planned unit, the Minolta design was compact, light, sleek and had SLR optics that were adjustable focus and gave a wide view of the observed area.
Then the two companies met.
Minolta had a great, well-designed instrument but no experience in the industrial markets. Whereas, Land had years of experience in the metals, glass and ceramics markets and their first prototype was already getting known as “The Meat Tenderizer” by most of the people charged with marketing it.
The “Meat Tenderizer” was basically rugged and very ugly. Add to that the difference in experience in blackbody calibration and traceability (Land~100%, Minolta~50%) and it was a match destined to be made.
A deal was struck and Land began selling the Minolta-made instruments around the world except for the Japanese home market; Minolta retained that.
The Cyclops 51 and 51F and their successors and variants, the Cyclops 52, 152, 41, 241, 252 etc. were smaller, faster, lighter, less expensive than Optical Pyrometers and didn’t require as much user judgment or training.
They produced results that were just as accurate, if not better than an optical pyrometer measurement, and often did better even in the hands of a new user.
The Cyclops had six other significant features that distinguished them mightily from “Opticals”.
First, they had a precision emissivity adjustment, something DPFs lacked. That meant immediate correction for an object’s emissivity, assuming it was known. No look-up tables needed.
Second, they had an electrical signal output that could be recorded by a portable or fixed chart recorder and/or datalogger, or actually used as an input to a control system. Opticals never had a recordable output. They depended on the operator to manually write down a reading.
Third, they were, and still are (in the higher temperature models), orders of magnitude faster than Opticals. They could follow rapidly changing temperature readily and with the output feature, record them reliably.
Fourth, the temperature reading was digital and could be “peak-picked” to capture high temperature transients. Opticals could never be adjusted rapidly enough to catch a rapid change or spike in temperature.
Fifth, a Cyclops 51 or 51F took only one 9-volt transistor-radio battery, available almost everywhere, to power it. Even today, the latest models use only a few small, common batteries. Plus there is an auxiliary line-power supply for use in semi-continuous datalogging situations. The DFPs used extra-heavy dry cell batteries that added to their 11 pound weight.
Sixth, and most useful, the Cyclops had the wonderfully crisp, clear adjustable-focus Minolta optics with the measurement spot defined by a small graticle in the field of view, and, the field of view included the temperature display. The newer models incorporate an auxiliary digital readout on the side of the case, too. The DFP had a red-filtered view of the object being measured and it was oftern difficult to view the surrounding area.
Cyclops combined innovative features, especially its short response time of 0.08 seconds, have yet to be fully matched by any price-competetive Infrared Radiation Thermometer in the last 20+years.
No wonder the Optical Pyrometer has effectively vanished! (The evaporation of Leeds and Northrup under General Signal Corporation’s watch did help speed things along a lot, too).
Other companies, notably Ircon, Inc, Chino Instruments and Mikron Infrared (formerly Mikron Instrument Company, Inc. – now a part of LumaSense Technologies) produced competitive devices. They helped hasten the slide of the Optical Pyrometer into the realm of instrument antiquity.
We know of only two companies that make or sell Disappearing Filament Optical Pyrometers, ostensibly on the basis of “better accuracy” because of the short wavelength of 0.6 microns.
If the users don’t yet know, there has been a special Cyclops model around for several years called the “Meltmaster” (C228) with an effective wavelength of 0.55 microns.
Ircon (now part of Raytek Corporation, subsidiary of Fluke, Corporation, in turn a subsidiary of Danaher Corporation) and Mikron Infrared (now part of LumaSense Technologies, Inc.) have similar models, too. Plus Mikron makes two color, ratio thermometers in a portable configuration.
The Cyclops Family Picture Album:
First there was one Cyclops, the Model 51, then very shortly thereafter there were two, the 51 and 51F.
Yes, there were initially two different models because they were mostly analog instruments and used different linearizer circuits.You know when there’s two of anything what can happen next.
You got it, a family was born! These (above) are however, the “proud parents”.
(Images courtesy ebay.com, where we found a few on sale)
The first all digital Minolta-LandCyclops, Model C52. appeared a few years later and it really smacked down the Optical Pyrometers in the marketplace!
The Model 52 was a revolution in silver-gray plastic. With switchable temperature scale, a, extremely wide temperature range, built-in math functions, super-fast and much more. All for a very reasonable price.
There are rumors of many, and this author knows of a few industry calibration labs, that began to have their Cyclops 52s certified at NIST as used in their own labs as Reference Standards for Radiation Temperature sources.
This was a major step forward in simplifying the traceability of radiation thermometer calibrations!
Land in the UK also offered traceable calibration certificates to the UK’s national calibration system at the time. (They did this in addition to offering a special line of secondary, traceable radiation thermometers and a set of primary fixed point reference cells at some key points on the ITS-90.)
Here’s an incomplete gallery of images and tidbits about the different Cyclops family members over the last twenty or so years.
Cyclops 390B Furnace Pro Infrared spot thermometer
From left to right, recent Cyclops Models are the New C100;
the unit it replaces, the C153; the Meltmaster, C228;
The Medium Temperature C241 and
the low temperature workhorse, the C300.
The mini Cyclops was part of the response of Minolta-Land to the popularity of very low cost general purpose instruments like the Raytek Mini in the 1990s, but they couldn’t compete effectively on price and appear to have been discontinued. (Note: The Raytek Mini appears to have been discontinued since Fluke took over, but the Fluke 62 Max seems to be its decedent in a market dominated by very low cost handheld IR Thermometers, many with a built-in laser pointer.)
There was an earlier low temperature Cyclops called the Compac 3. These can still be found regularly on ebay.com.
The Cyclops Family of the 1990s before the very low cost IR Temperature gun market heated up, included a wide range of products such as the Tele, with its very large mirror optical system for measuring near ambient temperatures at relatively long distance, shown in the background here and two special waveband units, one at 3,9 microns for looking through hot combustion gases and one at 3.4 microns for measuring thin plastics.
The high-performance C300 has survived nearly without change since the early 1990s. It, and the unique, but discontinued C300AF, an autofocus model that used the technology of Minolta’s autofocusing 35 mm cameras, were priced relatively high at the time and the latter didn’t last in the marketplace despite its incredible features and specifications.
Cyclops 152 with carrying case
On the left is a side view of the Cyclops Model C152, the real workhorse of the family. For nearly 10 years, from the late 1980s to the late 1990s this was the unit used in many high-temperature places like metals processing plants, glass factories etc. The one pictured here was shown on ebay in December 2017 for the price of $1800!
It came with a sturdy carrying case, but its big innovation was the fully sealed body to resist the ingress of dust and moisture that were the biggest sources of instrument problems used in industrial plants.
Minolta engineered a complex, but reliable, inner-adjustable lens system that had no external screw threads.
Dirt didn’t “screw up” the threads anymore. It just made the best device on the market even more superior.
We are also still seeking a photo of the all-digital Cyclops 52 to add to this page to complete it. The case color and style of the Cyclops 52 was very much like the Cyclops 241 (shown above.)
Check back to see when we’ve found them.
Note: Cyclops is a Trademark of Land Instruments International Ltd.
Footnote: Why do I care about all this stuff?
Chalk it up to a combination of personal involvement and a misguided, possibly compulsive sense of history about temperature measurement devices, infrared ones in particular. I had a big hand in the introduction of the Cyclops to North America as the General Manager and then VP of Engineering of Land Instruments in the USA during Cyclops’s first, second and third generations.
I like to think that I helped make it a big part of the Land organization’s product portfolio by insisting on having it to sell in North America when the first prototypes were offered to Land by Minolta in the late 1970s.
Then, I actually got to use and see first-hand the remarkable accuracy, reliability and stability of the devices, especially the Cyclops 152, 241 and 300 Models, during the 1990s as the Senior Staff Engineer for Temperature Measurement at the now-closed LTV Steel Company’s Technology Center and the corporate manufacturing plants where we used them under some rough, industrial conditions.
At LTV Steel we not only recommended and/or actually equipped several in-house Calibration Laboratories with Cyclops models as certified traceable reference standards, but used them for process investigations and trouble-shooting on many hot-strip mills, taconite pellet process lines, reheat furnaces, annealing lines and process simulation devices.
They never failed in my experience of more than twelve years duration. I published several technical papers based in large part on field measurements in operating steel plants made with Cyclops family models.
Some of those very same devices may be still in use even though LTV Steel has evaporated as a corporation and most of its USA manufacturing plants are now part of the Acelor-Mittal organization.
P. S. Interested in a product listing or doing a sensor review? Check our vendor directories.
They are free and self service at TempSensor.net and reviews are accepted.
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(From the IRInformIR.blogspot.com, September 27, 2017 with format altered for easier reading online – all text and images from IRInformIR)
“One of the more challenging applications of infrared thermography is in the measurement of process heater and furnace tubes. In fact we get dozens of inquiries each year from our clients on this very subject.
“Since this is a very complex subject it is probably appropriate to start from the beginning.”
“There are as many uses for process heaters as there are designs. The basic configuration consists of a shell (outer casing), tubes (where the process fluid flows) and a heat source.
“These units are both thermodynamically and hydraulically complex.”
“In the simple drawing above we illustrate convective gas flow, which is turbulent, and radiant heat from the flame, refractory and other tubes – all non-uniform and time varying. When you view tube from an access port typically you can only see a portion of the tube or the tube at an oblique angle.
“Therefore, the odds are stacked against you from the start!”
“Why are heater tubes of interest anyway?” “There are several reasons for inspecting tubes. Qualitatively slag (scale) buildup on the outside of the tube can be readily identified.
“Buildup on the inside of the tube (coking) is a bit more difficult but commonly performed.
“In both cases the slag or coke prevents the transfer of heat into the process fluid. In the case of slag buildup, the process fluid may not be sufficiently heated, affecting downstream processing.
“The case of coking on the inside of the tube is more serious. Since the coke has an increased resistance to heat transfer, the tube surface temperature increases.
“After all it is the flow of the process fluid that is keeping the tube “cool” in the first place.
“In fossil boilers this is called “DNB” – Departure from Nucleate Boiling and is usually caused by flame impingement, which initiates a layer of steam on the inside of the tube. The external tube surface, unable to conduct its heat to the water, increases dramatically, causing a failure (opening) in the tube.”
ED NOTE: The SPIE has published a very useful and detailed book in its Tutorial Text Series entitled Radiation Thermometry: Fundamentals and Applications in the Petrochemical Industry
Author(s): Peter Saunders (August 2007) that deals with this topic in depth from the point of view of non-contact temperature measurement (radiation thermometry). It contains a wealth of detail about the issues of slag and reflected thermal radiation as well as a useful tutorial on infrared temperature measurement.
It is available online at the SPIE bookstore at a modest price as both a softcover book and a pdf download.
Here’s some details from the (above) linked SPIE web page:
This tutorial text provides an introduction to the subject of radiation thermometry, focusing on sources of measurement error and giving advice on methods for minimizing or eliminating these errors. Topics covered include: blackbody radiation, emissivity, reflection errors, and atmospheric absorption and emission; commonly used radiation thermometer types; uncertainty calculation; and procedures for in-house calibration of radiation thermometers. Included is a chapter containing detailed measurement examples for a variety of furnace types and operating conditions found in the methanol, ammonia, and refining industries.
Date Published: 3 August 2007
With this Handbook for industrial temperature measurements we are attempting to provide the technician with solutions to his wide variety of responsibilities. At the same time, it provides for those new to the field, insight into the basics of the most important measurement principles and their application limits in a clear and descriptive manner.
The basic themes include material science and measurement technology, applications, signal processing and fieldbus communication.
A practice oriented selection of appropriate temperature sensor designs for the process field is presented as well as therequired communication capability of the meter locations.
The factory at Alzenau, Germany, a part of ABB, is the Global Center of Competencefor Temperature, with numerous local experts on hand in the most important industrialsectors, is responsible for activities worldwide in this sector.
125 years of temperature measurement technology equates to experience and competence. At the same time, it forms an important basis for continued innovation.
In close cooperation with our customers and users, our application engineers create conceptsto meet the measurement requirements.
Our Sector-Teams support the customer, planner and user in the preparation of professional solutions.