Heat Treat Today’s Technical Tuesday feature means that on just about any given Tuesday, there will be an article that aims to educate our heat treating readers – be it in a process, equipment, metals, analysis, critical parts, or more. Enjoy this sampling of Technical Tuesday articles from the past several months.
Case Study: Heat Treat Equipment Meets the Future Industry Today
Contact us with your Reader Feedback!Construction and schematic furnace cross-section CMe-T6810-25 Source: SECO/WARWICK
How has one heat treat furnace supplier contended with modern challenges of manufacturing? In this case study about a shift away from traditional forms of heat treat, explore how vacuum furnace technology has more technological horizons to bound.
Several key features discussed will be the various challenges that characterize modern industry; the differences between historical heat treat furnaces and vacuum furnaces; furnace features that can meet these obstacles; and a close look at what one equipment option from SECO/WARWICK helps. Additionally, explore the case study of a process that resulted in the following assessment: “all technological requirements have been met, obtaining the following indicators of efficiency and consumption of energy factors calculated for the entire load and per unit net weight of the load (700 kg).”
Eric Yeager of Cleveland Electric explaining the 101 of all things thermocouple Source: Heat Treat Today
How do thermocouples work? How would you tell if you had a bad one? Those ever present temperature monitors are fairly straightforward to use, but when it comes to how it works – and why – things get complicated.
This transcript Q&A article was published in the print edition last year (2022), but there was too much information to fill the pages. Online, read the full-length interview, including the final conversation about how dissimilar metals create EMF. Included in the discussion is proper care of the T/C and knowledge of when it’s time to replace.
Trends in the heat treat industry Source: Unsplash.com/getty images
What’s “hot” for heat treaters in recent months? The trends are pointing towards streamlining upgrading information systems, more efforts to reduce carbon footprint, and ensuring processes in salt quenching and electricity use are as efficient as they can be.
Each of the 6 trends included in the article demonstrates that heat treaters are making thoughtful and responsible decisions and purchases. Considerations include care for the environment and methods to help employees share and receive information needed for each job.
Read more about each of the trends to see what’s happening with equipment purchases and technology decisions and how companies are pushing to make that carbon footprint smaller.
A Quick Guide to Alloys and Their Medical Applications
Sneak peak of this medical alloys resource Source: Heat Treat Today
If you’re pining for a medical heat treat quick resource in our “off-season,” we have a resource for you. Whether you are a seasoned heat treater of medical application parts or not, you know that the alloy composition of a part will greatly determine the type of heat treat application that is suitable. Before you expand your heat treat capabilities of medical devices, check out this graphic to quickly pin-point what alloys are in high-demand within the medical industry and what end-product they relate to.
The alloys addressed in this graphic are: titanium, cobalt chromium, niobium, nitinol, copper, and tantalum.
Resource — Forging, Quenching, and Integrated Heat Treat: DFIQ Final Report
Examples of DFIQ equipment Source: Joe Powell
How much time and energy does it take to bring parts through forging and heat treatment? Have you ever tried to integrating these heat intensive processes? If part design, forging method, and heat treat quenching solutions are considered together, some amazing results can occur. Check out the report findings when the Direct from Forge Intensive Quenching (DFIQTM) was studied.
Forgings were tested, in three different locations, to see if immediate quenching after forging made a difference in a variety of steel samples. The report shares, “The following material mechanical properties were evaluated: tensile strength, yield strength, elongation, reduction in area and impact strength. Data obtained on the mechanical properties of DFIQ forgings were compared to that of forgings after applying a conventional post-forging heat-treating process.”
The days are getting a little longer, you’ve saved up some vacation hours, it’s time for a break this spring!
Make use of some down time to listen in on a couple of Heat Treat Radio series. Putting in some driving miles, relaxing in the sand, or enjoying a staycation all mean some time to peacefully enjoy some heat treat topics. We’ve put together an original content piece that lets you listen in on a 3-part series on thermocouples, and a back-to-basics series on heat treat hardening. It’s nice to know that there is plenty to listen to; you can just click to play each episode!
Thermocouples 101with Ed Valykeo and John Niggle
This series gives the opportunity to learn from an expert all about thermocouples. The first episode digs into thermocouple history, types, vocabulary, and other basics. Hear from Ed Valykeo, as he gives some of his own history and then dives into all things thermocouple.
The second episode covers thermocouple accuracy and classification. Ed Valykeo continues to review and explain necessary information on how thermocouples are calibrated and used.
The final episode in this series gets into discussion with John Niggle about thermocouple insulation types. His review towards the beginning of the episode is helpful, and his discussion of insulation reminds readers that job specifications and requirements are crucial.
Mark Hemsath sits down with Heat Treat Radio to provide an overview of metal hardening basics. In the first part of the series he provides explanation of what it is, what materials can be hardened, why it has to be done, and more.
For the second episode, Mark Hemsath explains five hardening processes: carburizing, nitriding, carbonitriding, ferritic nitrocarburizing, and low pressure carburizing.
In this final episode for the metal hardening series, a discussion is presented on newer advances in metal hardening. A call is even put out for new ideas and engineers willing to experiment with some of these advance.
As you can see above, this resource provides two series — each with three parts — that give a comprehensive look at two fundamental components in the heat treat industry. Both the discussion of thermocouples and the investigation of metal hardening provide educational listening with something for everyone in the form of review as well as maybe some basics that have been neglected or forgotten.
Thermocouples: You can’t accurately heat treat without them. But how can you choose the best one for your needs? What do current regulations require? Read this helpful explanation, by Víctor Zacarías, managing director of Global Thermal Solutions Mexico, to find out how to choose the right thermocouple.
Keywords: Thermocouple, Heat Treatment, Pyrometry, Temperature Measurement and Control, AMS2750, CQI-9
Read the English version of the article below, or find the Spanish translation when you click the flag above right!
This Technical Tuesday article, first published in English and Spanish translations, is found in Heat Treat Today’s February’s Air & Atmosphere Furnace Systems print edition.
If you have any facts of your own about thermocouples, our editors would be interested in sharing them online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own trivia!
Víctor Zacarías Managing director Global Thermal Solutions México
The SAE AMS2750 aerospace standard and the AIAG CQI-9, CQI-11, CQI-12, and CQI-29 automotive assessments are the universally accepted standards for temperature control in thermal processing operations. Among many things, they describe the requirements for the use and control of thermocouples used in process ovens and furnaces. In this article you will find the requirements of these regulations so that you can make a correct decision when choosing a thermocouple, and thus have a repeatable measurement that ensures a reliable process.
1. Application
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For the appropriate selection of a thermocouple for the control and/or recording of temperature, you must first take into account the type of process. In choosing the right thermocouple, consider some factors that could alter its performance, such as:
The temperature range at which it will be in use
The type of atmosphere to which it will be exposed
Possible electrical interference
The accuracy required by the applicable specification, etc.
Based on the above, existing regulations refer to a specific classification for thermocouples based on their manufacture and final application. These classifications are:
a) Base thermocouples and noble thermocouples
b) Expendable and non-expendable thermocouples
2. Types of Thermocouples and Their Insulation
2.1 Base Thermocouple or Noble Thermocouple
A base thermocouple is made of basic alloys such as iron, chrome, nickel, copper, etc., and they are the most common types in the industry due to their versatility and cost. Base thermocouples are types K, E, J, N, and T. A good supplier of sensors will recommend a thermocouple based on the application, the temperature range, and your budget (see Table 1).
Table 1: Temperature range and application of most common thermocouples Source: GTS México
On the other hand, a noble thermocouple is made from metals such as platinum and rhodium: types R, S, and B thermocouples. These thermocouples are more stable at high temperatures and maintain their accuracy for a longer time. However, they have the highest cost since they are made from precious metals. Due to this nature, noble thermocouples are the preferred choice for vacuum heat treatment applications and high temperature processes.
2.2 Expendable or Non-expendable Thermocouples
The second criteria from the regulations are the material which protects the elements of the thermocouple.
Expendable thermocouples are those whose elements are covered by materials such as fiberglass, ceramic fabric, or polymeric coating and are generally provided in the form of a spool. This form allows the user to cut the cable to size and manufacture the thermocouple by joining the two wires by twisting or welding, making them ideal for single use applications such as a TUS test or charging thermocouples, for example (see Figure 1).
Figure 1: TUS using type K expendable thermocouple insulated in ceramic fiber Source: Trucal, Inc.
In contrast, a nonexpendable thermocouple is normally protected with ceramic or mineral insulation and covered on the outside by a metallic sheath (the elements are not exposed in this configuration), which gives it a longer useful life. Therefore, it is preferred for use as a control or recording thermocouple (see Figure 2).
Figure 2: Non-expendable type N and K mineral insulated thermocouples Source: GTS México
Whatever the application, when wiring interconnections are required for sensor installation, these connections must be made using standard connectors and terminals such as those shown in Figure 3, as both AMS2750 and CQI-9 prohibit the wiring splice.
Figure 3: Standard type K connectors Source: GTS México
3. Calibration
According to regulations, all thermocouples used in the heat treatment operation must have been calibrated before being used for the first time. The user of the thermocouple must ensure that they have calibrations traceable to a national laboratory such as the NIST in the United States or its equivalent in Mexico (CENAM).
Pyrometry standards defi ne the acceptable error ranges for thermocouples depending on their final application. These categories for final application include: standard thermocouples, test thermocouples (SAT and TUS), control and recording thermocouples, and load thermocouples (see Table 2). Table 2 describes the maximum errors allowed to be selected depending on the use of the sensor.
Table 2: Accuracy required for temperature sensors according to AMS2750 and CQI-9 Source: GTS México
Once the thermocouple is installed, the person responsible for the heat treatment operation must document the date on which it comes into service, since the regulations establish the life of a sensor based on its application.
When receiving the report/certificate of the thermocouple, the user must review the content of the document, since the standards specifically define the minimum information that shall appear in a calibration report, which includes but is not limited to:
1. Test readings
2. Actual readings
3. Correction factors
4. Data source
5. Laboratory accreditation
6. Calibration method used
The calibration certificate can cover individual thermocouples or a group of thermocouples manufactured from the same lot (spool).
It is very important to note that both AMS2750 and CQI-9 require all calibrations to be conducted by ISO/IEC 17025 accredited organizations, so ensure that you review the accreditation certificate before selecting your supplier.
4. In Summary
If you’ve ever bought the wrong thermocouple, you know how annoying it can be. Therefore, here is a quick guide to select the right sensor for your application in five easy steps:
1. Define the type of thermocouple: base (K, T, J, E, N, and M) or noble (S, R, and B)
2. Define the type of insulation you require: textile fiber, polymer, ceramic, metallic, etc.
3. Specify the exact temperature range in which the sensor will operate
4. Specify the use of the sensor: standard thermocouple, SAT/TUS thermocouple, control/load thermocouple
5. Request the calibration certificate in accordance with the applicable regulations (AMS2750 or CQI-9)
References
ASTM International. ASTM E230, Standard Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples, Rev. 2017.
Automotive Industry Action Group. CQI-9 Special Process: Heat Treat System Assessment, 4th Edition. June 2020.
International Organization for Standardization. ISO/IEC 17025, General Requirements for the Competence of Testing and Calibration Laboratories, 3rd Edition. 2017.
Nadcap AC7102/8 Audit Criteria for Pyrometry, Rev. A, 2021
About the Author: Víctor Zacarías is a metallurgical engineer from the University of Queretaro with studies in Strategic Management from Tec de Monterrey. With over 15 years of experience in Heat Treatment Management, he is currently the managing director of Global Thermal Solutions México. He has conducted numerous courses, workshops, and assessments in México, the United States, Brazil, Argentina, and Costa Rica. He has been a member of the AIAG Heat Treat Work Group (CQI-9 committee) and the SAE Aerospace Materials Engineering Committee.
Thermocouples are ubiquitous. Whether you are 20 days or 20 years into the industry, you know the essential role they play in making sure heat treat processes are running efficiently, accurately, and dependably. This quick trivia questionnaire will test your thermocouple knowledge on a dozen either obscure or obvious facts about thermocouples.
Los termopares son ubicuos. Sin importar que tu experiencia en la industria sea de 20 días o 20 años, conoces bien el papel esencial que juegan en asegurar que los procesos de tratamiento térmico avancen de manera eficiente, precisa y confiable…
Take the English version of the quiz below, or find the Spanish translation when you click the flag above right!
If you have any facts of your own about thermocouples, our editors would be interested in sharing them online at www.heattreattoday.com. Email Bethany Leone at bethany@heattreattoday.com with your own trivia!
This Technical Tuesday article, first published in English and Spanish translations, is found in Heat Treat Today’s November 2022 Vacuum print edition.
Thermocouple Trivia
1. What thermocouple type potentially has the longest life (but is also the most expensive)?
(a) Type K (Chromel-Alumel)
(b) Type N (Nicrosil-Nisil)
(c) Type R (Platinum-13% Rhodium)
(d) Type J (Iron-Constantan)
2. What is something you might find at home that uses a thermocouple to control its temperature?
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(a) Your oven
(b) Your toaster
(c) Your water heater
(d) All of the above
3. What do you need to know when purchasing thermocouples for your heat treat furnace or oven?
(a) The length of the thermocouple
(b) The process application you are running
(c) The type of thermocouple best suited for the
(d) All of the above
4. Who was Thomas Johann Seebeck?
(a) The person credited with describing the scientific theory behind thermocouples
(b) An advocate for the elimination of thermocouples in furnaces and ovens
(c) A German physicist who was responsible for helping develop rockets for the United States
(d) None of the above
5. What would be the best thermocouple to use to control the temperature of an oil quench tank?
(a) Type R (platinum – 13% rhodium)
(b) Type S (platinum – 10% rhodium)
(c) Type K (chromel-alumel)
(d) Type J (iron-constantan)
6. Why use an over temperature (aka “excess temperature”) device on your furnace or oven?
(a) For better process control, it is always helpful to have more than one thermocouple in the furnace/oven
(b) To prevent the furnace temperature from running away and damaging the equipment
(c) An obsolete device no longer required by NFPA 86
(d) A method of ensuring the process being run in the furnace stays close to the set point temperature
7. How are thermocouples used in the heat treat industry?
(a)temperature control devices
(b) As part of a safety system designed to prevent the furnace/oven from running away and damaging itself
(c) To ensure that temperature, the most important process parameter, is maintained within limits necessary to successfully run a heat treat process
(d) All of the above
8. Why use type K versus type N thermocouples?
(a) Because type K has better accuracy
(b) Because type K has better temperature limits
(c) Because type K is more expensive
(d) None of the above
9. Thermocouples produce what type of voltage?
(a) PPM (parts per million)
(b) EMF (electromotive force)
(c) EMP (electromagnetic pulse)
(d) mV (millivolt)
10. What are some of the most common reasons why a thermocouple “drifts” or fails in a heat treat furnace or oven?
(a) Age
(b) Running at temperatures higher than its rated use temperature
(c) The wrong thermocouple type is used
(d) All of the above
11. What is a common problem seen in thermocouples that fail in service?
(a) Green rot (oxidation of chromium)
(b) Metal dusting (aka “catastrophic carburization”)
(c) Grain growth
(d) All of the above
12. Complete the sentence: Types S, R, and B noble metal thermocouples are generally specified for use . . .
(a) . . . when temperatures exceed the upper recommended operating temperatures of base metal thermocouples.
(b) . . . after failing compliance on three SATs .
(c) . . . if the furnace only processes automotive parts.
(d) . . . to safeguard against low temperature readings in large loads.
Trivia Key
Compare your answers with the key on page 26 . How did you stack up in thermocouple knowledge? See where your skills measure up in the scale below.
Learn more about thermocouples in the interview between Doug Glenn and Eric Yeager on page 16 or check out the reference list below.
Heat Treat Today would also like to thank the following for their expert input: Dan Herring, The Heat Treat Doctor® at The HERRING GROUP, Inc.; Hank Prusinski, Summit Aerospace Products Corp.; and Andrew Bassett, Aerospace Testing and Pyrometry.
Find heat treating products and services when you search on Heat Treat Buyers Guide.com
Readers are checking out recent AMS2750 Rev. G changes and want some more information from Heat Treat Today about a specific clarification. Read the correspondence about the implications of AMS2750 Rev. G paragraph 3.1.1.5 about how to measure junction construction.
Douglas Shuler, lead auditor at Pyro Consulting, has written numerous articles with Heat Treat Today about AMS2750 standards. Check them out by searching “Doug Shuler” at www.heattreattoday.com.
READER QUESTION: After combing the new AMS2750 Rev. G, I found that paragraph 3.1.1.5 no longer allows thermocouples to be tack welded directly to parts, OR to representative dummy parts. This has been standard practice for decades. So I dug into it further with the folks from PRI and it turns out to be true. They’re now expecting load thermocouples to be either placed inside of a part (ends twisted and inserted), or inside the hole of a dummy block.
I’d done some searching online and there isn’t a single source talking about this major change. This could lead to a lot of failed upcoming Nadcap audits.
Doug Shuler Lead Auditor Pyro Consulting
Douglas (Doug) Shuler (Pyro Consulting) for Heat Treat Today: Historically (i.e. prior to Rev. F), AMS2750 was silent on measuring junction construction. In Rev. F, the construction of the measuring junction was as follows:
Measuring junctions shall be made by any combination of twisting and/or welding the thermal elements provided there is no addition of filler metal.
This raised concerns about both the use of quick tips and spot welding to make the measuring junction. The AMEC AMS2750 revision team engaged with Cleveland Electric Laboratories to perform testing on these measuring junctions as compared to the twisting/welding combinations.
The conclusion of the tests were that both quick tips and spot welding to a part/heat sink became unstable at temperatures above 2000°F. The quick tip crimping point and the spot welds showed rapid oxidation and increased errors in a short period of time. Based on the results of these tests the AMEC AMS2750 revision team put forth the following update in Rev. G:
Measuring junctions shall be made by either of the following methods:
Any combination of twisting and/or welding the thermoelements provided there is no addition of filler metal (including ungrounded and grounded MIMS).
Spot welding the thermoelements directly to a part, simulated part, or heat sink is permitted for temperatures ≤2000°F or 1100°C.
This allows spot welding measuring junctions for process temperatures at or lower than 2000°F. The team and AMEC members decided that quick tips were to unstable to permit their use going forward.
READER FOLLOW-UP: Our current method that we’re using is to twist the thermocouple using a set of Twister Pliers, then tack-weld that twist onto the part (first photo below). We’ve been doing this for parts up through brazing temperatures (~2150°F) without issue. We recently ran a furnace run around 2100°F with parts tack-welded as I’ve described AND had T/Cs that were just twisted with no tack weld. We noticed there was no significant difference in the temperature the TCs were reading. This was also our technique that we used at my previous company.
The way I read AMS2750 Rev. G was: You may twist and weld thermocouples to a part, but only for temperatures less than or equal to 2000°F.
To comply with Rev. G, we have gone ahead and made heatsink blocks to make sure we’re in compliance. Our new method of temperature measurement is twisting the wires and sticking the twisted end down inside of a block of solid metal (like the one I’ve shown below).
Source: Heat TreatToday ReaderWe welcome your inquiries to and feedback on Heat Treat Today articles. Submit your questions/comments to editor@heattreattoday.com.
Solar Atmospheres of Western PA received delivery of their vacuum oil quench (VOQ) furnace last week.
This 36” x 36″ x 48” furnace from Solar Manufacturing will be fully installed, tested and operational in early April. See the largest component, a 40,000 pound vestibule/oil quench tank, being transferred and inverted into its pit. This will be the first vacuum oil quench furnace to employ work thermocouples in the actual load!
Solar Atmospheres indicates that they will be releasing updates on this furnace in the future.
We’ve assembled some of the top 101 Heat TreatTips that heat treating professionals submitted over the last three years into todays original content. If you want more, search for “101 heat treat tips” on the website! Today’s tips are all things temperature: thermocouples, how to keep temperatures in check, TUS, and more.
By the way, Heat TreatToday introduced Heat TreatResources this year; this is a feature you can use when you’re at the plant or on the road. Check out the digital edition of the September Tradeshow magazine to check it out yourself!
Temperature Monitoring When the Pressure is On!
Increasing in popularity in the carburizing market is the use of batch or semi-continuous batch low pressure carburizing furnaces. Following the diffusion, the product is transferred to a high-pressure gas quench chamber where the product is rapidly gas cooled using typically N2 or Helium at up to 20 bar pressure.
In such processes, the technical challenge for thru-process temperature monitoring is twofold. The thermal barrier must be capable of protecting against not only heat during the carburizing, but also very rapid pressure and temperature changes inflicted by the gas quench. From a data collection perspective, to efficiently perform temperature uniformity surveys at different temperature levels in the furnace it is important that temperature readings can be reviewed live from the process but without need for trailing thermocouples.
During the gas quench, the barrier needs to be protected from Nitrogen N2(g) or Helium He(g) gas pressures up to 20 bar. Such pressures on the flat top of the barrier would create excessive stress to the metal work and internal insulation / logger. To protect the barrier therefore a separate gas quench deflector is used. The tapered top plate deflects the gas away from the barrier. The unique Phoenix design means the plate is supported on either four or six support legs. As it is not in contact with the barrier no force is applied directly to the barrier and the force is shared between the support legs. The quench shield in addition to protecting against pressure, also acts as an additional reflective IR shield reducing the rate if IR absorption by the barrier in the vacuum heating chamber.
(PhoenixTM)
3 Tips to Meet Temperature Uniformity Surveys
Adjust the burners with some excess air to improve convection.
Make sure that the low fire adjustment is as small as possible. Since low fire will provide very little energy, it will make the furnace pulse more frequently and this will improve heat transfer by convection and radiation.
Increase internal pressure. This will “push” heat to dead zones allowing you to increase your coldest thermocouples (typically near the floor and in the corners of the furnace).
(Nutec Bickley)
Ways to Increase Temperature Uniformity in Heat Treat Furnaces
A (sometimes) simple way to increase uniformity in a furnace is to add a circulation fan. Circulation fans can be a quick way to add an additional 5°F tighter uniformity on a batch furnace application.
Be sure that the furnace is tuned optimally to reduce/eliminate any overshoot and oscillation around setpoint.
Eliminate any thermal lag by making sure that the control thermocouple and TUS thermocouples have similar sensitivity. If not, the control thermocouples can fall behind and cause the TUS thermocouples to overshoot and fail.
(L & L Special Furnace Co., Inc.)
Pack Your Thermocouples
When a thermocouple is used with an open-ended protection tube, pack rope or fiber between the thermocouple and the protection tube to prevent cold air infiltration from influencing the reading.
(Super Systems, Inc.)
A Good Fit
If a thermocouple fits loosely in a protection tube, avoid errors by ensuring that the tip maintains good contact with the tube.
(Super Systems, Inc.)
Introducing Your Common Thermocouple Types
What are the common thermocouple types?
Thermocouple material is available in types K, J, E, N, T, R, S, and B. These thermocouple types can be separated into two categories: Base and Noble Metals.
Types K, J, E, N, and T are Base Metals. They are made from common materials such as Nickel, Copper, Iron, Chromium, and Aluminum. Each base metal thermocouple has preferred usage conditions.
Types S, R, and B thermocouples are Noble Metals because they are made of one or more of the noble metals, such as Ruthenium, Rhodium, Palladium, Silver, Osmium, Iridium, Platinum, and Gold. Noble metals resist oxidation and corrosion in moist air. Noble metals are not easily attacked by acids. Some Noble metal thermocouples can be used as high as 3100°F.
(Pelican Wire)
Culprits of a Stable Thermocouple
Factors affecting the stability of a thermocouple:
The EMF output of any thermocouple will change slightly with time in service and at elevated temperatures. The rate and change are influenced by metallurgical and environmental factors. The four factors that can induce EMF drift are: Evaporation, Diffusion, Oxidation, and Contamination.
(Pelican Wire)
Does Length Matter?
Does the length of a thermocouple wire matter?
In a word, “Yes.” There are several factors when considering the maximum length of a thermocouple assembly. Total loop resistance and electrical noise. Total loop resistance should be kept under 100 ohms for any given thermocouple assembly. Remember, the total loop resistance would include any extension wire used to complete the circuit. Motors and power wires can create noise that could affect the EMF output.
(Pelican Wire)
Type N Thermocouple (Nicrosil/Nisil)
Type N Thermocouple (Nicrosil/Nisil): The Type N shares the same accuracy and temperature limits as the Type K. Type N is slightly more expensive and has better repeatability between 572°F to 932°F (300°C to 500°C) compared to type K.
(Pelican Wire)
Know Your Thermocouple Wire Insulations
Know your thermocouple wire insulations. When is Teflon® not Teflon®? Teflon® is a brand name for PTFE or Polytetrafluoroethylene owned by Chemours, a spin-off from Dupont. FEP is Fluorinated Ethylene Propylene. PFA is Perfluoroalkoxy Polymer. All three are part of the Fluoropolymer family but have different properties. Of the three compounds, PTFE has the highest heat resistance, PFA second highest and FEP third. The higher the heat resistance the more expensive the insulation. Keep that in mind when specifying the insulation and only pay for what you need.
(Pelican Wire)
Check out these magazines to see where these tips were first featured:
Welcome to another Technical Tuesday for 18 hard-hitting resources to use at your heat treat shop. These include quick tables, data sets, and videos/downloadable reports covering a range of heat treat topics from case hardening and thermocouples to HIPing and powder metallurgy.
Defining Terms: Tables and Lists
Table #3 Suggested Tests and Frequencies for a Polymer Quench Solution (in article here)
Case Hardening Process Equipment Considerations (bottom of the article here)
Two simulations of a moving billet through heating systems (in article here)
Fourier’s Law of Heat Conduction (in article here)
Webinar on Parts Washing (link to full webinar at the top of the review article here)
Materials 101 Series from Mega Mechatronics, Part 4, Heat Treatment/Hardening here
Heat Treat TV: Press-and-Sinter Powder Metallurgy here
BONUS: 39 Top Heat Treat Resources
Heat Treat Today is always on the hunt for cutting-edge heat treat technology, trends, and resources that will help our audience become better informed. To find the top resources being used in the industry, we asked your colleagues. Discover their go-to resources that help them to hone their skills in the 39 Top Heat Treat Resources on this page of the September print magazine.
Measuring temperatures inside a furnace can present a number of challenges: temperature cycling, high temperatures and hostile atmospheres exceeding the limits of several measurement devices while others have significantly reduced lifetimes and poor accuracy. This article discusses some of the challenges associated with temperature measurement in furnaces where oxidizing and reducing atmospheres are employed in microelectronics fabrication.
An excerpt:
“The Type K is low-priced and can be used across a temperature range from -200 to 1250 °C (-328 to 2282 °F). However, metallurgical changes at temperatures more than 1000 °C (1832 °F) decrease accuracy, and cycling via this temperature induces hysteresis effects, further reducing accuracy. Type K thermocouples are also vulnerable to corrosion in an oxidizing atmosphere.”
Heat Treat Radio host, Doug Glenn, begins a 4-part series with Justin Rydzewski about Revision 4 of CQI-9. Having served on the 4th revision of CQI-9, this expert is full of interesting information and practical advice on how to understand and comply with CQI-9 Rev.4.
Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): Today, we’re beginning a new four-part series on the latest revisions to the CQI-9 specification. If you want to learn more about this series or related content, stick around ‘til the end of this episode.
We’re here with Justin Rydzewski who is the director of sales and marketing at Controls Service, Inc. in lovely Livonia, Michigan. At least, this time of year it’s still lovely, right?
Justin Rydzewski (JR): Yes, we’ve got a few weeks left, I think.
DG: Justin is involved with the new revision of CQI-9. First off, I want to welcome you. Thank you so much for joining us on Heat Treat Radio. If you wouldn’t mind, let’s give listeners/readers just a sense of who you are and what your qualifications are to talk about CQI-9 and a little bit about Controls Service.
JR: I am the director of sales and market development for Controls Service. I got my start with this company around 2009/2010 working just as a sales rep, making phone calls and quoting work. Around 2010, the then president of the company was making a presentation to the AIAG, the Automotive Industry Action Group, the organization that publishes CQI-9, regarding their standard CQI-9. We had some questions and concerns, and so they allowed us an audience. After our presentation, they inquired whether or not we’d be interested in assisting them with drafting the third edition. We obviously said yes. I indirectly helped support at that point, and then when the third edition was released, we started working on the next one almost right away. After the third was rolled out, it wasn’t too long before the fourth edition meetings started, and then I began participating in a support role, and finally as a full blown participant at the end. The fourth edition took about 8 or 9 years to complete. It’s was an involved process, but it was fun. I learned a lot, and I’m proud of what we’ve been able to kick out.
As far as Controls Service is concerned, we’re an accredited calibration laboratory. We provide various on-site calibration and pyrometry testing services within the metro Detroit area, northern Illinois, Indiana, and Ohio.
DG: According to your website, the company is an ISO/IEC 17025 accredited provider of process control systems, calibration, maintenance, and services. Just to be clear, you were, in fact, fully engaged in this Revision 4. It wasn’t that you were standing on the sidelines; you were on the committee doing the work.
CQI-9 4th Edition vs. CQI-9 3rd edition (photo source: Control Services Inc.)
JR: Yes, I, myself. The president of the company was heavily involved with the third edition, so he was firsthand in the trenches on that one. My participation was directly hands-on with the fourth edition.
DG: The point is, you can speak with a good bit of authority, and that’s great. You’ve hit on it, but give us information again on CQI-9. Give us a brief history. When did it start? Who owns it? Maintains its update? To whom does it apply? And what’s its scope?
JR: The best way I know to describe it, because perhaps the most widely known pyrometry specification is AMS2750, is CQI-9 is the automotive equivalent of AMS2750. There are obviously some differences between the two documents, but, in a nutshell, that’s the comparison. It is a document supported by the AIAG, the Automotive Industry Action Group. They oversee the publication of it, the drafting of it, and supervise the whole thing through that process. CQI-9 is the number. Officially, I think it’s called the Special Process Heat Treat System Assessment and that kind of gets the nomenclature of CQI-9 that applies to automotive heat treaters, or any performing heat treat work within the automotive industry; and several processes fall into that category. It can be from commercial heat to in-house heat treat, to organizations like mine that support. It applies to anyone participating in that effort of heat treat.
DG: Let’s talk about Rev 4. You said as soon as “3” was out, you started on “4” and it took 8 – 9 years to get done with “4.” What was the main reason why you needed to abandon “3,” if you will?
JR: They schedule these things out to be rewritten on a routine basis. Like most specifications, they are reviewed on some established interval of time. When the third edition came out, the biggest difference between the second edition of CQI-9 and the third edition was that the third edition removed all references to AMS2750. When 2750 was in the document, it created a world of confusion, and the guidance and errata sheets that followed were just so numerous that they made it a somewhat difficult document to adhere to. One of the ideas we brought to the table was that maybe we should just remove all reference to it [2750] and write our own specification. So, the third edition removed the 2750 references. In doing so, it ended up being a very well written document. It was effective. The OEMs – your GMs, Fords, FCAs – were happy with the results of the document. The prolonged active interval of that document allowed us to collect a lot of really good data about what was working, what wasn’t, what was confusing, and where additional clarity was needed. The more data we collected, the more confident we were that the fourth edition would truly make a stride toward being a more effective document. It was longer than what we would have probably prepared for – in terms of that interval of review – but I think, all in all, the result shows for itself that it is better than it was.
Click here to read the Expert Analysis Article to hear more voices on this CQI-9 Revision 4.
DG: You would say this Rev 4 is a major revision? Or is it just minor?
JR: The way the drafting process works is that you get all this feedback from the industry and review it. Everyone who participates in that work group brings their notes about things they noticed or things that they would like to see different; then we compile all of those notes together, review it, and establish a charter that drives every effort thereafter. The major items on our charter was to increase clarity and guidance, simplify, and make it easier for the end user to adapt. Largely, the changes within the fourth edition are towards that primary focus of our charter.
There are a lot of things in there that are different, but the difference there was merely to try to make it more clear: adjust syntax of a sentence, use a different choice of words, etc. One of the things I’ve learned in this process is that this document, while it might be clear as day in English, when it translates to German, it’s not. Or, when it translates to a different language, whatever the language, it’s not as clear; so, when you find out what it says in the other language, you say, “Hey, that’s not what we meant to say. We’ve got to think of another way to say it.” Largely, the changes are to increase clarity, but there are some real big changes in that effort. Like the heat treat assessment questions. The formatting was completely revamped, we changed that up dramatically, expanded it in some instances, and removed some that were redundant in terms of requirements.
So, there are some big changes, but, for the most part, it was an effort to enhance the clarity. It’s not a complete rewrite, but it is a different document.
DG: Substantial enough that people need to pay attention. You and I have talked in the past about the addition of a number of process tables. Wasn’t there a lot added there?
JR: There was one process table added to the primary document and it was Process Table I, which is regarding hot stamping. Process Table I technically existed in the third edition of the document. It was issued as an errata sheet in 2014, three years after the third edition, but it was never part of the primary document, so issuing it as an errata sheet had its complications. Not only did you have to make sure that the end user was aware of the document requirements, they had to be aware that there was an errata sheet also available to them, and this complicated things. It was very frequent for me to be out in my travels and talk to customers that were performing hot stamping that would say, “Well, it’s tough to tell what requirements in CQI-9 apply to us because we don’t have a process table.” Well, yes you do, actually; it’s an errata sheet. That caused frustration because, again, most people want to adhere to the requirements– they just want to know what the requirements are. When they don’t, it’s frustrating.
DG: For those who might not know, or have not been baptized into CQI-9 in the past, what are the major sections? Can you break it down into the three or four major sections and a very, very brief description of those sections?
JR: It is structured very similar to the way of AMS2750 in that regard. You have four sections that divvy up a pyrometry section: thermocouples, instrumentation, system accuracy testing and temperature uniformity survey. But, unlike AMS2750, CQI-9 is a system assessment, it is a process, it is a heat treat management system. It encompasses more than just pyrometry. Where AMS2750 is a pyrometry specification, CQI-9 is a process specification; it encompasses everything. It also includes your heat treat system assessment, which is three sections of questions regarding your heat treat operation, then you have your pyrometry which is those four sections I mentioned. Then you have your process tables. Your process tables drive all of your requirements for your particular operation, in terms of frequencies and tolerances.
Process tables from Rollout Webinar (Source: Rollout Webinar PowerPoint)
DG: Let’s jump into the section that, I think, you would probably say you’re most comfortable with- the pyrometry section. You mentioned in that section there are four subsections. Let’s run down through those. I’d like to do two things. First, let’s just talk about, very briefly, what are the major changes in each of those four sections and then let’s come back and revisit each of those sections with maybe some very practical advice. Let’s talk thermocouples first; that’s the first section.
JR: The thermocouple section had a fair amount of changes made to that portion of the document, but again, they were mostly for the clarity aspect of things. I would say, from a significant standpoint, one of the things that we had in the third edition that was rather confusing was in regards to grace periods. The only area in which a grace period was stated within the third edition was within the thermocouple section, which is funny because it doesn’t apply to thermocouples, in terms of CQI-9. It applies to instrumentation and system accuracy tests, and so that portion was removed and placed into a more appropriate area within the document.
Another aspect of it was the requirement for the calibration report to include an accreditation symbol. It was already a requirement that if the thermocouples were calibrated by an outside provider or third party, that they had to be accredited. But one of the areas that that doesn’t address is that if I am an accredited calibration laboratory, and my scope includes instrument calibration, whether it be for measure or source, it doesn’t necessarily mean that I’m accredited to perform a thermocouple calibration. So, instead of trying to overcomplicate the document and write something that says that the calibration that I’m performing on the thermocouple has to be included on my scope and create something more difficult than it has to be, we decided to just establish that the accreditation symbol needed to be included on the report. Also, as an accredited lab, I can’t place that symbol on a report for calibrations that aren’t part of my scope. It kind of allows that portion of the industry to self-police a little bit. That was one of the more significant changes.
Another one was that we made some adjustments to the usage side of things. There was a requirement – in lieu of tracking uses of nonexpendable thermocouples – which allowed you could to put a nonexpendable thermocouple in use for a duration of time, and you could have unlimited uses essentially for that duration, and then you could remove it from service at that point. However, that duration of time was absent of some critical information, that being, for usage of the elevated temperatures. In the usage table, it was 90 uses for over 1800 degrees and 180 for under 1800 degrees, and you had 6 months for a placement interval. That didn’t necessarily convey what we were trying to do, so we added some usage in there for the nonexpendable for over that 1800 degree mark.
We also included RTDs. I come across them, but just because of the temperature range that most of the processes within the automotive heat treat world are operating RTDs are necessarily applicable. But, they exist and a common approach that I would come across at least, was “well, they’re not included, so I don’t have to do anything.” So, we just included them to wipe that off the board, and now we know that any sort of temperature sensor is critical to address, if that portion of the process is temperature critical.
We added some caveats around resident thermocouples and their usage, which, in the previous one, were only allowed for comparative method SAT. We added some caveats for requirements when they’re used for probe methods within the realm of CQI-9.
DG: Before we go on to the next section which will be calibration, let’s back up just for a half a second. You and your team actually did a rollout webinar. Can you briefly tell the listeners where they can find a little more thorough description of the rollout on this thing, because we’re not going to cover all the details here, obviously.
Rollout Webinar PowerPoint Cover Image. Get the webinar here.
JR: Yes. It would be really tough to dive into everything; some of the changes are so insignificant, that it’s not worthy of discussion, really. The AIG’s website has a page assigned to automotive heat treat and on that page they have some links to different content that we produced for that rollout presentation back in mid-September. There is also a page 3 of the document itself which outlines the majority of the changes, (at least the significant ones), made within the fourth edition. So there is a list, 3 ½ pages long, of the different changes made. There are summaries of those changes that exist in several different places, but one of them being the document itself.
DG: Did you not do a webinar? Is there a webinar? Can people actually see the webinar?
JR: I’ve not seen the webinar posted yet, I’ve not checked in a little while, but the intent was to post a version of that webinar.
DG: In our transcript of this podcast, we will look for it first off, and if we find it, we will put a link to it when we put this online. So if you’re listening and you want to see that webinar, if it’s out there, we’ll put the link in.
OK, let’s move on then, Justin, to the second of the four pyrometry sections which is calibration. What were the major changes?
JR: Again with reporting, the reporting requirements for calibration are updated; they are different. There are some minor revisions to the requirements for the calibration report. Those sort of things can be easily overlooked, so I wouldn’t ignore that. They are different. The biggest, perhaps most significant difference within the instrumentation section is that in June 2023, all control monitoring recording instrumentation must be digital. It is very similar to the approach taken by 2750 in removal of analog instrumentation, CQI-9 as well, is going to follow suit there, as well. [Listen to the AMS2750F episode with this update here.]
DG: I think AMS is by 2022, so you guys are an extra year, but nonetheless, you’ve got to start getting away from analog over to digital.
JR: For the most part, that’s the biggest change within the instrumentation section.
DG: Let’s move on to system accuracy tests.
JR: Within system accuracy tests, again reporting requirements are updated. They include some new requirements there. The illustrations within the system accuracy test section have all been updated and revamped. I believe the old ones, that were in the third edition, were very similar in nature to the illustrations that were included in AMS2750 C, so they were well overdue for an update. We cleaned those up. We removed nonessential information just to make it clear what it is we’re actually discussing there.
Also, we established grace periods that are specific to each method of system accuracy test. There are three different accepted methods for SAT within CQI-9- probe method A, probe method B, and a comparative method, and we established grace periods for each of those individually so that it’s clear and not an assumed grace period.
DG: And grace periods being, for example, “Well, the due date falls on a holiday, how many days afterwards do I have?” That type of thing?
JR: Yes. If my system accuracy tests were due on a Friday, let’s say they’re due on the 1st, technically. I don’t lose my compliance on that system from a system accuracy test standpoint for x period of days after the fact. It’s to allow for, like you said, a weekend coming up, a holiday coming up. You can still maintain your compliance interval without having to shut everything down and start fresh. A practical application would be, say you order some test thermocouples and they’re delayed. So now, all of a sudden, you don’t have the test materials that you need to perform the task, or your instrument that you sent out for calibration got delayed and it’s not back yet. Those uncontrollable sort of events don’t prevent you from operating.
DG: The final section under pyrometry would be temperature uniformity surveys. Any major changes there?
JR: There were a few. First, the reporting requirements are now different; they’ve been updated. They include some new things. Perhaps most notable is the requirement for when you perform a test on a semi-continuous or continuous system to indicate the soak time required versus soak time achieved. That has to be included on the report. Technically, it probably should have been there for the third edition as well, since one of the requirements is that you have to have obtained your desired soak time. This just calls it out to the forefront and makes it a bit clear. That information of the report makes assessing that aspect of things a bit more simple.
We added a specific grace period for temperature uniformity surveys so that it’s clear, it’s not assumptive. Where I’ve seen it most often is within the hot stamping world. You have a single stack furnace with multiple individually controlled chambers that are all separated by insulation or wall or some sort of means of differentiating them, so that they’re all essentially individual furnace cavities. We added in some clarity to say that it’s not good enough just to test one of those chambers, you need to test all of them, because they all can be different.
[blockquote author=”Justin Rydzewski ” style=”1″]Perhaps the most significant change within the temperature uniformity survey section is to the alternative temperature uniformity survey testing methods.[/blockquote]
Perhaps the most significant change within the temperature uniformity survey section is to the alternative temperature uniformity survey testing methods. In instances when I can’t perform a survey with sensors being trailed in, or I can’t send a data pack sort of unit or a PhoenixTM unit through that furnace system itself to collect the data, for systems like that, in the third edition, there were three or four paragraphs of information about what you could do. It was not entirely clear what other aspects of the section applied, what reporting was required, what sort of procedures needed to exist, and so you found a lot of variance in that testing practice. A lot of times, I’d have customers that say, “I don’t know how to perform a TUS on it, or I don’t think that I can, or it’s not practical, so I guess I don’t have to do anything.” And that’s not proper. It wasn’t clear that these surveys applied in instances where you couldn’t do the other, like a traditional TUS. So that whole entire section got rewritten from ground up to include a structure that is very similar to the other aspects of that TUS section, structured in the same way, in terms of data collection, when you need to perform the tests, these alternative tests like property surveys and whatnot, the procedure that needs to exist, what needs to be included in the procedure, and what needs to be included in the reporting. Basically, just more clear guidance so that in those instances where a survey can’t be performed, the heat treater at least has a degree of confidence that what it is they are going to be doing is going to be up to snuff, that it’s going to pass muster with their auditor.
DG: I want to go back and go all through those four sections again and ask you the same basic question for each of those four sections. When your company, or companies like yours, walk into a prep for an audit situation, what are the things that you’re seeing, practically, on the thermocouple end of things, the calibration end of things, the SAT and the TUS? Let’s start with the thermocouple: When you walk in, what do you most often see and what do you tell people?
JR: When I first walk into a facility, one of the first things I’m looking for is how the flow down of information is conducted. How are they approaching the flow down of information? Because, in order for me to assess whether or not you’re compliant with the document, I need certain bits of information. And it’s not just me, anyone would need it. As I go through a plant, and I’m looking for information on thermocouples, I want to know when the thermocouple was installed, I want to know if it was calibrated, what’s the number of the calibration certificate that it ties back into, what’s the location of that thermocouple and where it’s installed, what’s its purpose? I can tell you that often it happens where I ask, “What’s this thermocouple?” “Well, that’s my control thermocouple.” “Are you sure?” “Yes, I’m sure.” Then, when you go to remove it, it turns out to be the high limit. There are these little things where people ask, “Well, what’s it matter if one is a control or one is the high limit?” Especially if they’re both in the same well and it’s a dual element sort of thermocouple. It’s important for a multitude of reasons. If you don’t know that basic sort of information, or you don’t find that information to be important, what other information won’t you find important? It becomes like a mentality aspect of things. I like seeing that sort of information available and ready, that you don’t have to go digging for it. So, that’s the first thing I look for any time I walk in a plant. More often than not, I find that aspect of things can be lacking, from a documentation standpoint, from an availability of documentation standpoint, or “Can I see the calibration certificate for this specific thermocouple?” and I get, “Well, here are all of my certificates.” “Well, which one applies to that thermocouple?”
Justin Rydzewski explains the importance in knowing your thermocouple system inside and out from an auditing perspective. (Photo source: Pelican Wire)
What I also try to convey is that the more difficult that you make this for me – for someone who’s coming out to audit you or to perform this assessment to check on you – the more difficult you make it, the harder they’re going to start scratching. You want this to be easy. You want to convey confidence. You want to convey the repeatability of things. I can’t stress enough strong documentation and great documentation systems for easy recall, like availability of information at the actual thermocouple itself is such a nice convenience, and when someone sees that, it conveys confidence. Outside of just a basic compliance issue, it’s that support system for thermocouples, because everything starts there. All of it starts there. Even from the basic things like knowing what it is you have there, from a thermocouple aspect.
With one of my closer customers in our first interaction together, he called and asked for a 30” long thermocouple and to just make sure that it’s type K. “Well, I need just a little bit more information than that. What else can you tell me about it?” “That’s all I have. Just get me one.” “Well, I have a binder on my desk that’s an inch and a half thick and every thermocouple in there just about matches your description. I need more. Should I just flip a page and pick one?” There are a lot of variants that can exist there and when you introduce variants, you have an opportunity to introduce variance in your performance of that system.
So, consistency, repeatability, and assuring those things on a perpetual basis is critical. Things like insertion depth, length, diameter, type, calibration, where you have it calibrated. All of those things should be documented and standardized and that documentation should be readily available to anyone who needs it so that you can ensure that you’re replacing like with like, what was there before, if it was compliant, and what you replace it with is also compliant. The performance that you had on that system on day 1 versus day 180, you want to be able to assess that variance in performance, not based on the variables that have changed, like are they new thermocouples, are they in new locations; you want to assess it in terms of those other exterior factors. That’s why you call out thermocouples instrumentation and the like within pyrometry and CQI-9. Those things, to me, are really important, and they’re the first things that give that indicator of what things are going to be like as I go through a job site initially.
DG: Anything else under thermocouples, or should we move on to calibration?
JR: That pretty much covers it. From a thermocouple standpoint, just ensuring that you have solid documentation surrounding those things. It can be an overlooked piece of equipment, but they are so incredibly critical.
[blockquote author=”Justin Rydzewski ” style=”1″]From a thermocouple standpoint, just ensuring that you have solid documentation surrounding those things. It can be an overlooked piece of equipment, but they are so incredibly critical.[/blockquote]
DG: Right. And be able to easily access it and instill confidence in the auditor so that they know you know what’s going on.
Let’s move on to calibration then. When you walk into some place and you’re going to check their calibration processes and whatnot, what do you see usually?
JR: Especially when a new edition comes out, or a newer revision of a pyrometry specification, the first thing that I typically go there with is – again, similar to the thermocouple side of things – I want to look at documentation. If I have a new Rev, the first thing I’m going to ask is what are the new requirements for reporting? I want to know what was on the report yesterday and what needs to be different tomorrow, so that I can make sure from a documentation standpoint, I’m going to be covered, because that’s what I’m going to put in front of someone. That’s the thing they’re going to evaluate initially. And so, I want to make sure that this first impression is solid and that it checks every box that it’s supposed to. I’ll review all of the reporting requirements initially, just to make sure my reporting is going to pass muster with an audit. And I will scrutinize that thing up and down to the Nth degree, just to make sure that I’ve got it to a point where I’m comfortable with it. That’s where I typically start.
Again, similar to thermocouples, I want to make sure that I have a solid support system for my facility in terms of instrumentation. I know what instruments I have there, I know what’s required of all of them, I know where I want them calibrated, I know how I want them calibrated, I know where they operate, all of those sorts of things. I find often, especially on new job sites, an instrument and they’ll have offset in there. “Well, what’s this offset for?” “I don’t know.” “OK. What was it the last time you had calibrations? Has this changed? Is this a value that changes?” “I couldn’t tell you.” And sometimes, the level of offset there, it’s possible for it to be at a level that is not compliant with the document without that documentation to support it, without something calling out what it’s there for, what the intended purpose is of it. Anytime you have that “I don’t know” answer, or “It’s in someone else’s hands,” let’s say the provider of pyrometry services that are out there perform the calibration, they’re not aware that they have to go through some sort of approval process to change offset, pay the instruments out, I’m going to pump in some offset, and there you go. In the worlds of CQI-9, and especially within AMS, you can’t do that.
There is a right way to go about doing things, and a ladder of things to climb before you can just go ahead and jump. Having a solid foundation of understanding of your instruments, documenting the details of those instruments, and having that readily available. If you have that, the likelihood that you’re going to be compliant and have a favorable audit in terms of your instrumentation, is going to be so much higher than if you don’t. So, strong support system. Strong documentation as well.
DG: Let’s move on to the system accuracy tests.
JR: The system accuracy test is often something that we encourage our customers to take on themselves because it’s not an overly complicated process, by and large. From a third edition to fourth edition, again my first stop is at reporting. I want to make sure whatever it is the data I need to collect is going to be there at the end of the day and is going to be presented in a manner where anyone can understand at glance. I don’t have to have a training session on how to understand my reporting. I want it to be very clear, very forthright in terms of information that it’s clear. And then understanding the differences between the acceptable methods.
Probe method A in CQI-9 is most like the comparison method within AMS2750 where you have a test instrument system alongside your process instrument system and doing a comparative in terms of the calculated difference there. Understanding the math and the order of operations out there is essential. It is so easy to mess that up or forget how to do it properly. One of the benefits of the illustration within the fourth edition is that we made a very concerted effort to make sure that the means in which that math is performed is clear, and how it’s reported is clear, so that there’s no too much confusion. The goal here isn’t, “Aha, gotcha! You don’t know how to do an SAT.” The goal is that you do an SAT and that you do it in a manner that produces you with a level of confidence that you’re okay and that everything is going to have the best likelihood or repeatability and coming out as expected.
Understanding the math is also critical. The only real thing of note in the third edition that wasn’t explicitly called out, that in the fourth edition is explicitly called out, is that the SATs only apply to the control and monitoring and recording thermocouples; it does not apply to thermocouples that are dedicated to the purpose of over-temp protection. That can be a nice break for most users who were thinking that they had to do it in the previous edition.
For the most part I see that the act of actually performing it— again, that flow down of information becomes critical. If I know how long my thermocouple is, the process thermocouple is at that process thermocouple. Say, for instance, it’s identified on a tag at the thermocouple and it says it’s 40”. If I go insert my test thermocouple and it goes in 20” and I feel like I’ve bottomed out, the only indicator that I would have that I’ve not bottomed out my thermocouple and I’ve lined my measuring junctions, would be that measurement at the thermocouple, would be an indication of how long it’s supposed to be or an awareness of how long it’s supposed to be. If I don’t have that, and I drop my test thermocouple in and it feels like it bottomed out. Cool, they’re lined up. They could be dramatically different. In that case, I would go ahead and guess that you would notice that instantly as you’re failing that SAT, but an inch or two inches can make a significant difference in misalignment of junctions. Having an awareness of insertion depth of your process thermocouple, length of process thermocouple, and what’s required for insertion depth on your test thermocouple is critical to perform in that test and it’s something I see lacking often when I’m out in the field assessing how my customers are performing the tests in-house.
DG: And finally, let’s talk about what you’re seeing when you walk into a shop for temperature uniformity surveys.
JR: Uniformity surveys, again, the first thing I’m doing is assessing the reporting requirements to make sure everything is up to snuff, because that’s your first impression you’re going to convey to everyone. The requirements within the fourth edition are of note, that would require something to be done differently, for the most part, you’re going to be find them to be very similar. The thing that I’m looking for most is the repeatability of that test. How like is one test to the next one? What is your means of collecting data and what is your response plan when that data is unfavorable? Having that predetermined, so that you’re not doing in on the fly, can be incredibly helpful and it adds to expedite that process of getting good tests out of there.
[blockquote author=”Justin Rydzewski” style=”1″]How like is one test to the next one? What is your means of collecting data and what is your response plan when that data is unfavorable? Having that predetermined, so that you’re not doing in on the fly, can be incredibly helpful.[/blockquote]
One of things I’ve always recommended my customers doing is that before you perform that survey, have some sort of pre-survey list that you go through of tasks that you want to verify before that test is run, just to make sure that you’re collecting all the data that you need to collect before you perform it. In an instance where that test data is unfavorable, you can go back and take a look at it and compare it against previous tests performed and not have to be concerned about whether or not this test was performed differently than the one prior.
Consistency is the key. And again, strong documentation systems. Understanding what the operating temperature ranges are for each system, where your sensors are placed, how they’re traversed, where they’re installed at if it’s a continuous furnace. There are so many variables to performing that test, having a handle on them is incredibly important. Otherwise, the test data performed on day X compared to on day Y is a meaningless comparison, and you want that value to be there, to be able to compare them, so that you can see where performance has varied or where it’s different, and have something pointing at where you need to go investigate.
DG: Justin Rydzewski of Controls Service up in Livonia, MI, thank you very much. I think this is going to be our first. We’re going to have either three or four of these podcasts. I think next time, we’ll either deal with heat treat assessments or we’ll talk about the process tables some.
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Learn more about thermocouples in the interview between Doug Glenn and Eric Yeager on 
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