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Reader Feedback: On Ceramic Coatings

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Here is what readers are saying about recent posts on Heat Treat Today. As is our policy, we allowed the original author to preview and respond to this reader feedback. See Greg Odenthal’s response at the bottom of this post.

Submit your reader feedback comments to editor@heattreattoday.com.

William (Bill) Jones of Solar Atmospheres Inc. on the Heat Treat Radio podcast interview with Greg Odenthal of ITC Coatings. Click here for the podcast (transcript here):

William R. Jones, FASM, Solar Atmospheres Inc.

Re: Heat Treat Radio: ITC Coatings

This would be a poor selection for a vacuum furnace as it is well known that ceramic coatings and the like are hydroscopic and will absorb water from the atmosphere when opening the furnace to air for work unloading and reloading, with adverse effects on following vacuum pump down, i.e., to pump out the absorbed water vapor.

With respect to ceramic lined refractory insulated atmospheric furnaces: I can respect the coating for sealing an older furnace lining for porosity and lining leaks to the outer furnace wall and for improving re-radiation to the work load with well-known surface emissivity improvement. This is not an easy coating to apply and will require maintenance “man-hours”. So one has to balance the coating time and coating cost compared to furnace out of production cost. Furnaces are like airplanes, when sitting on the ground for any purpose, they lose money.

Now, when looking at furnace hot zone efficiency, one has to review power losses both before and after changes such as coatings. With an electric furnace a totalizing wattmeter or with a gas totalizing gas meter similar to our utility company meters. Such data needs to be presented for both furnace before and after coatings on an exact furnace and production cycle.

William R. Jones, FASM

Solar Atmospheres Inc.

 

We offered Greg Odenthal of ITC Coatings the opportunity to respond:

Greg Odenthal, Director of Engineering & Technical Operations, ITC| International Technical Ceramics, LLC

Mr. Jones,

I cannot agree or disagree with you regarding your opinion that ITC Coatings are a poor selection for vacuum furnaces as we have never tested in nor targeted this industry. It is true that ceramic coatings are hydroscopic; however, I’m not sure just how much water/moisture a layer of ceramic coating only 1 to 2 mils thick will absorb. With that being said, any moisture absorbed would wick away in a very short period of time. Whether or not they are good for the vacuum heat treating industry is still up for discussion.

As for your comment regarding that this is not an easy coating to apply, I must tell you that you are wrong. I have been onsite on just about every installation that we have done and our crew size can be very small. For an average size heat treat or forge furnace — for example, 32’ L x 16’ H x 15’ W with a new ceramic fiber lining — a crew of two men can and have coated the entire square foot surface area in an eight (8) hour shift. The cost of the coatings and labor to install is pennies on the dollar compared to the cost of regularly scheduled downturns every 3 to 4 months to pack joints and cracks with new fiber, trying to prevent heat loss and increasing fuel consumption. We have current customers that have not done any refractory maintenance in four to five years and now only have one outage per year for their yearly furnace inspection. Once installed, the ITC Coatings increase a furnace’s efficiency by reducing refractory maintenance, reducing fuel consumption, improving temperature uniformity, improving product quality, improving turnaround times, along with a host of additional benefits, thus preventing the furnace from costing the customer money, unlike your grounded airplane analogy.

In regard to hot zone efficiency and gas/power reduction, we have been working with the gas supply companies in Canada who are currently monitoring our customers’ fuel usage and see the reductions. They are now beginning to give current and potential customers money for this type of upgrade, upwards of 50% of the cost to install ITC Coatings. We do not just sell ceramic coatings, we provide the customer with a complete engineered solution along with a total Btu savings analysis for each furnace we quote. Each Btu savings analysis is unique to that furnace and based on operational data supplied by the customer. We have also provided before and after thermal imaging of the furnace as proof that the heat transfer/loss through the refractory and to the shell is less, so you do not necessarily need totalizing meters to prove energy savings.

If you would like to learn more about ITC Coatings and our technology, I encourage you to contact me and discuss this topic in greater detail.

Regards,

Greg Odenthal

Director of Engineering & Technical Operations

ITC| International Technical Ceramics, LLC

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Reader Feedback: On TUSs and SATs

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, READER FEEDBACK

Here is what readers are saying about recent posts on Heat Treat Today. Submit your comments to editor@heattreattoday.com.

On Jason Schulze’s article, “AMS2750E: The Importance of Temperature Uniformity” (click here to see original article):

READER QUESTION (from a heat treat supplier across multiple industries):  My vacuum furnace uses a type S thermocouple, and there is no access to perform the SAT. Is there an alternative? (We supply to aerospace and must be in accordance with 2750E.)

Jason Schulze (Conrad Kacsik) for HTT:Jason Schulze, Aerospace Heat Treating
If you do not have access to the hot-junction (measuring tip) of the control thermocouple, an option would be to purchase a dual-element thermocouple.
If you are not familiar with dual-element thermocouples, they have two thermocouples in one small Inconel sheath. You can purchase a Type N and a Type S in a single sheath. The type N can be used as a resident SAT thermocouple. This will give you access to the connection-end of both the control thermocouple and a resident SAT sensor that is in the same sheath.
The only set-back in this situation would be the re-calibration or replacement of the dual element thermocouple every 3 months (per AMS2750E – Resident SAT sensors).

READER QUESTION: [I] just have two questions, one in regards to SAT and one in regards to TUS.

[Question 1] When SAT testing a lead sensor, let’s just say for the purpose of this example this lead sensor is a type “k” base metal thermocouple, is it acceptable to test this sensor against an SAT sensor which is also type “k”? I see that for resident SAT, the sensor should be of a different type, but for non-resident SAT, is this acceptable?

[Question 2] My other question is in regards to TUS, specifically para 3.5.18 of AMS2750E. I see that in this paragraph two options are addressed. I have a decent understanding of the first requirement, the second option is where I’m getting a bit confused which states ” . . . or if the difference between the measured temperature at the current recording locations and the actual respective hottest and coldest measured areas is less than the SAT tolerance for the applicable furnace class.” How does one calculate this difference?

Jason Schulze for HTT:

[To question 1] As long as the SAT thermocouple is not a resident SAT thermocouple, you are permitted to use the same type (i.e., K, J, T, etc.) as the thermocouple being tested.

[To question 2] I’ll use an example to work the next question. We will assume the furnace is a Class 2 (±3°F SAT difference). Let’s say a previous TUS had a hot location at #5 and it was +6°F. On a new TUS,  the location changed to #9 and is now +2°F. The difference between the previous location and the current one is 4°F. This 4°F difference is more than the applicable SAT tolerance of ±3°F, therefore, the location would need to be moved from #5 to #6.

READER REPLY:  In regards to the TUS requirement, I’m assuming the actual M.P. Reading(s) from the current hottest and coldest locations don’t get compared to the respective hottest and coldest locations on the TUS report? For example, I have a furnace that’s classified as class 1 (±5) surveyed at 385°F. The TUS report is stating that the lowest T/C location was 382°F T/C 8. I have now exceeded half the maximum temperature uniformity tolerance (2.5°F), therefore I must relocate unless the difference between the “current recording location” and the actual respective coldest location per the TUS is less the SAT tolerance. I was under the impression that as long as the cold location per the report T/C 8 382°F, when compared to the furnace low multipoint reading during the survey – being less than 2°F, it would not require relocation as my “current recording location” when compared to the actual respective cold location is less than the SAT tolerance. My understanding now is that the process control sensors are not used for this difference calculation but rather the TUS sensor representing the low location? I believe that the “current recording location” statement is where I’m getting thrown off a bit.

Jason Schulze:

You are correct in stating that the comparison is made between the previous and current hot or cold (respectively) locations and not the control thermocouple. AMS2750E is not that easy to follow in some instances so any confusion is understandable.

READER QUESTION (from a metals castings provider for aerospace and defense):  For 1020°F SAT, if test instrument/thermocouple reads 1015°F and temperature controller reads 1020°F, it is acceptable to program -5°F bias/offset in controller so temp controller reads 1015°F, matching test instrument/thermocouple, correct?

Jason Schulze for HTT:

You are able to utilize offsets to the limits of AMS2750E table 6 or 7 to correct both TUSs and SATs. Instrument calibration is a bit different. AMS2750E does not invoke limitations regarding an offset due to instrument calibration.

Your comment regarding the application of a -5°F offset to correct the SAT would, in fact, be permitted according to AMS2750E. One thing that would be required is, if the SAT failed and that is why the offset is needed, there would need to be an internal corrective action and product impact investigation.

We welcome your inquiries to and feedback on Heat Treat Today articles. Submit your questions/comments to editor@heattreattoday.com.

Reader Feedback: On TUSs and SATs Read More »

Reader Feedback: On TUS

/ MANUFACTURING HEAT TREAT, READER FEEDBACK

Here is what readers are saying about recent posts on Heat Treat Today. Submit your comments to editor@heattreattoday.com.

Jason Schulze, Aerospace Heat Treating
Jason Schulze, contributing editor to Heat Treat Today, author of "AMS2750E: The Importance of Temperature Uniformity"

Joe Powell, President, Intensive Quench Technologies, on Jason Schulze's article, "AMS2750E: The Importance of Temperature Uniformity" (click here to see original article):

Interesting to me how big a deal specs make on temperature uniformity in the hot zones, and how little attention is paid to quantifying the uniformity of the quench cooling process!  But we all know predictable distortion and uniformity of mechanical properties can only happen when the quench cooling is uniform!

Bill Jones, CEO Solar Atmosphere, on Jason Schulze's article, "AMS2750E: The Importance of Temperature Uniformity" (click here to see original article):

Let us assume a standard box furnace air atmosphere operating at 1650f with a plus-minus 25f delta T. What first areas would you recommend to look for improvement.

Jason Schulze (Conrad Kacsik) for HTT:

When I had issues achieving uniformity, I typically focus on the position of the control thermocouple 1st, then work my way to other items.

From the article "Jason Schulze on AMS2750E: The Importance of Temperature Uniformity"

Bill Jones:

AMS 2750, etc, is fine for setting specification and procedure. In some cases unreasonable and meaningless in operation, for example, a 1-degree overshoot on ramp rate by a control TC can result in a major NADCAP finding even though work TC's are well below set point. Okay, so we do a TUS and it fails, so now you have to locate and solve the furnace problem or very possibly mis-survey TC placement. Now, I don't recommend changing control TC placement away from factory location or position at all. The OEM is supposed to run a full TUS survey prior to shipment in his plant. In other words, go back to those locations before introducing new problems. Now, a furnace may be 5 or 10 years in service with many HZ "aging" problems. These issues must be located and addressed. Another major fault is TC survey plugs, jacks, and deteriorated wiring all leading to measurement error and survey failure. This entire TUS subject is an art with many pitfalls with not too many really experienced technicians.

Jason Schulze for HTT:

I do agree that there are aspects of some requirements that do not actually affect production processing. Since my experience is metallurgical, that is where my examples would reside.

 

 

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