Ams2750d Q&A [PDF]

Zitiervorschau

Pyrometry Webinar – Q&A Concerning security temperature, what requirement do we have to apply (± 5, ±10°C) during TUS? There is no requirement for the indicated temperature, unless the overtemperature device is also used as a process monitor. In that case, Section 3.5.17.1 would apply. We would expect the setting to be ‘as for normal production’.

We will close the factory during 3 weeks at the end of the year. Can we deduct these days of stops for the following of our SAT and TUS, knowing that the furnaces are not used during this period? No. The test frequencies take no account of holidays, shutdowns, breakdowns etc. There is no requirement to do tests if the equipment is not in use, but a valid test must be done before processing restarts. This often means that the first job after a vacation is to do SAT on each furnace.

How many decimals must we take into account (SAT, TUS, secondary calibration of standard) The requirement is that equipment is readable to 1F or 1C. The specifications in AMS2750D were defined in whole degrees Fahrenheit. The pyrometry reference guide FAQ26 describes working to fractions of a degree F and rounding to whole numbers before making decisions. IN Europe the requirements, converted from Fahrenheit, are stated to 0.1C and cannot be rounded. If you can work to 0.1C then do so.

What are the requirements for calibration of refrigeration instruments? This is described in the pyrometry reference guide located on the webinar page of eQuaLearn and in the public documents section of www.eAuditNet.com. Calibration of instruments is required at least every six months, usually done at the same time as an SAT. There is no requirement to do TUS on refrigeration equipment.

Where can I find the requirements for calibration of vacuum lines? Not in AMS2750. General vacuum requirements are given in AMS2769, which also includes the frequency of testing. There are no defined accuracy limits for vacuum equipment in either standard. Some customers do make a requirement while most vacuum equipment suppliers work to “0.3x decade”, while some customers

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Point 3.2.6.2 calibrations records: If there was no adjustment what information should be showed on the certificate? The requirement is to give ‘as found’ and ‘as left’ data. If no adjustment is made and the two sets of results are the same then this must be clear on the report. Many companies have spaces for two sets of data and simply over-write one of them with “no adjustments made. ‘As left’ = ‘as found’”

Are SAT tests required for high and low couples? Yes. SAT’s are required on the high and low monitor couples used in Type A & C furnaces. See last sentence of section 3.4.1.

On a circular chart, what data shall be recorded, as a minimum, by the TUS operator? The general requirement is to record data from the furnace instruments at two minute intervals. See section 3.5.13.3.2.a. The type of chart recording makes no difference to this requirement.

Does AMS 2750 D have requirements for cryogenic furnace use? Yes. Cryogenic systems are refrigeration systems. Section 3.3.1.6.1 applies. ‘Time at temperature’ treatments generally means all treatments used to complete transformations in steels. Refrigeration to retard aging in aluminum alloys is not a ‘Time at temperature’ treatment. Instrument calibration and SAT are required at six monthly intervals (see the pyrometry reference guide FAQ).

What is the minimum temperature that a load thermocouple needs to get to for it to count as a cycle? This is not defined, but would reflect the lowest specified treatment temperature. Essentially it would be any excursion above ambient – which can be as high as 45C in some parts of Europe and Asia in the summer. In practice the lowest specified treatment temperature would be about 100C for metal treatments, but could be lower for paint and composite curing ovens.

Do you suggest Interpolation of correction factors? My personal opinion and the Nadcap Heat Treat Task Group recommendation is ‘Yes’, but the use of the nearest known value above or below are also allowed. See the pyrometry reference guide for comments on this. Whatever method is used must be defined in your procedures and applied consistently.

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Should TUS be done with or without loads? This depends on the type and construction of the furnace. Some air circulating furnaces are best tested empty, gas fired furnaces often need a typical load. Vacuum furnaces need something to divide the volume so as to allow determination of the effects of hot spots in the heaters. AMS2750D requires that you choose one method and stick with it, and that any load or rack is defined and described in the TUS report.

What is the relation between the number of thermocouples for dummy load test and TUS? The number of TUS test thermocouples must comply with table 11. The number of load couples during a TUS is the number required by you furnace type usually one load couple per control zone. Note that the load couple used for type A & B furnaces is in addition to the number of TUS couples defined in table 11.

When you have a short during the TUS, can you just repair the short and continue the survey, or should you restart your 30 minute cycle? Normally, you can continue the survey. The Pyrometry Reference Guide on P25 says: “A temporary condition such as a short or loose connection where normal temperature readout is restored shall not be considered a failed survey thermocouple.” The only time this might be a problem is if the interruption occurs during the initial transient, when it might hide an unacceptable over-shoot.

Can you round your calculated SAT result? Yes, but you should not round it by more than 0.1C because that is the accuracy to which the SAT difference is specified in Table 6.

Can you clarify bullet 14 section 3.5.21.1 of AMS2750D regarding summary of final plus or minus readings at each temperature? This means the max and min variation from the set point. It could be a +/+ or -/result. For example a TUS at 900c gave instantaneous max = 905C and min=897C. The TUS result is +5/-3C

Part one of my question is fairly simple, does para 3.5.13.3.3 allow for oscillations in temperatures recorded during a TUS, so longs as those oscillations remain within the tolerances applicable for that furnace class/type? say +/-5°C Yes. Any oscillation must stay within the applicable tolerance.

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We need to work to 0.1 but if we read 0.01 which should we do? If you can read to 0.01C then do so, and calculate the correction factors to the best possible resolution, but round the final values to 0.1C before making any decisions. This should be described in your procedures. Must we do SAT on thermocouple in oil bath used for quench? Yes. Every six months to an accuracy of +/-5F/ 3C. See FAQ 28 on page 37-38 of the Pyrometry Reference Guide.

A paper chart recorder sometimes prints the temperatures every 1 minute... does this print out constitute a digital output? Prints out the numeric digits In such a case you would have an instrument with an attached printer. This would be digital and could be calibrated in accordance with the ‘digital’ requirements of note 5 to table 3. However, you must also ensure that the process can be verified from this data – that means the “one data set per minute” must allow determination of the start and end of soak and of any specified heating or cooling rates.

What kind of products (different from sodium fluoborate) can I use to protect from HTO ? This is outside the scope of this training and presentation. However, Fluoborate (Ammonium or Sodium) is the normal protection. Depending on your customers and their requirements, it is possible to run without this if you can prove (by initial and regular testing) that no hydrogen induced porosity occurs.

About U rule §3.1.1.10 : for thermocouple in salt bath, how to know the number of used cycle ? The bath is always at the same T° Section 3.1.1.10 applies only to expendable load couples. I have never seen these used in association with salt baths, so I suspect that this question applies to control monitoring and recording couple rather than load couples. U factor does not apply to these thermocouples. For U factor for load couples used in a salt bath, a cycle would be once from ambient up to furnace temperature and back again.

For type D furnaces, only 2 thermocouples are necessary:1 for over T° security and 1 for the regulation who is recording ? Correct. One thermocouple is connected to the controller (regulator) and is also recorded. The second one must be attached to an over-temperature instrument.

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Can you explain how to calculate correctly the furnaces offsets? Both via SAT and TUS This is beyond the scope of this brief presentation and typically occupies 20-30 minutes during the full Pyrometry training course.

According to the AMS WE CAN NOT USE sensors type E and K but I don't know why? Over than 260°C This is incorrect. There is no rule in AMS2750D that says E & K cannot be used over 260C. There are limits on their re-use and recalibration for load and test (SAT & TUS) thermocouples (see sections 3.1.1.8 and 3.1.1.11), but they can be used at any temperature within the range recommended by the manufacturer..

Does the load thermocouple have to actually touch the product or can it be very close? See section 8.2.25. Load sensors must be attached to the production material or a representation of the production material.

Furnace oscillations are not accounted for in the SAT methodology, this was highlighted during our recent audit. This is a matter for your detailed procedures. If the furnaces oscillate then you should defined how to take measurements. SAT is defined as an instantaneous check, so you should usually track the oscillations for couple of cycles and then take readings at the top or bottom of the cycle. At these moments the rate of change is lowest and there is usually a period of 10-30 seconds when comparative readings can be made. If initial TUS working range is 500 - 1200 deg.(we TUS at 500 - 750 - 1000 1200) are periodic TUS at 800 & 1000 degrees ok as they capture +-335 deg. We currently do periodics the same as initial This question is under discussion and a full response will be supplied in a week or so.

Do you need an SAT thermocouple to check the cold spot thermocouple? See above and the pyrometry reference guide. If the cold spot thermocouple is used to control the process (as in Type A & C furnaces) then SAT is required.

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