SAE AMS2750H RATIONALE
AMS2750H results from a Two-Year Review and update of this specification with changes to Definitions (see 2.4.21, 2.4.25, 2.4.36, 2.4.47, and 2.4.84); General Sensor Requirements (see Table 3); Sensor Calibration (see 3.1.4.6 and Table 5); SAT and TUS Sensor Reuse (see 3.1.7.4 and 3.1.7.5); Base Metal Load Sensors (see 3.1.10.3); General Instrumentation Requirements (see 3.2.1.4.1, 3.2.1.5, and Table 7); Control, Recording, and Over-Temperature Instruments (see 3.2.3.4, 3.2.3.5, 3.2.3.16, and 3.2.3.18); Instrumentation Calibration Results and Records (see 3.2.5.1); General Instrument Correction and Modification Offset Requirements (see 3.2.6.1.2 and 3.2.6.1.8); Thermal Processing Equipment (see 3.3.7); General SAT Requirements (see Table 11, Table 12, and 3.4.1.2.1); Performing an SAT (see 3.4.2.2); Alternate SAT Frequency (see 3.4.8.3); SAT Waiver (see 3.4.9.6.3); SAT Difference Pass/Fail Requirements (see 3.4.10.4); Comparison SAT (see 3.4.11.1.e); Parts furnace class, instrument type, and TUS internal (see Table 15); Raw material furnace class, instrument type, and TUS internal (see Table 16); Initial TUS Temperatures (see 3.5.2.4); TUS Requirements for Batch Furnaces, Salt Baths, Controlled Temperature Liquid Baths, and Fluidized Bed Furnaces (Excluding Controlled Temperature Quench Baths) (see Table 17); TUS Data Collection (see 3.5.10.1 and 3.5.10.2); Relocation of Hot or Cold Recording Sensors for Type A and C Instrumentation (see 3.5.15.2); Radiation Survey (see 3.5.17, 3.5.17.1, and 3.5.17.2); TUS Interval Deviations (see 3.5.18); Rounding (see 3.8); and Quality Assurance Provisions (see 4.2, 4.4, and Table 22). Deleted Zener Voltage Reference (was 3.5.87).
- SCOPE
1.1 This specification covers pyrometric requirements for equipment used for the thermal processing of metallic materials. Specifically, it covers temperature sensors, instrumentation, thermal processing equipment, correction factors and instrument offsets, system accuracy tests, and temperature uniformity surveys. These are necessary to ensure that parts or raw materials are heat treated in accordance with the applicable specification(s).
1.2 This specification may be used in other non-heat-treating applications when specified.
1.3 This specification is not applicable to heating or to intermediate thermal processing unless otherwise specified.
1.4 This specification applies to laboratory furnaces to the extent specified in 3.6. - APPLICABLE DOCUMENTS
The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is specified. When the referenced document has been cancelled and no superseding document has been specified, the last published issue of that document shall apply.
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2.1 SAE Publications
Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org.
AS7766 Terms Used in Aerospace Metals Specifications
2.2 ASTM Publications
Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org.
ASTM E29 Using Significant Digits in Test Data to Determine Conformance with Specifications
ASTM E207 Standard Test Method for Thermal EMF Test of Single Thermoelement Materials by Comparison with a Reference Thermoelement of Similar EMF-Temperature Properties
ASTM E220 Calibration of Thermocouples by Comparison Techniques
ASTM E230 Temperature-Electromotive Force (EMF) Tables for Standardized Thermocouples
ASTM E608 Mineral-Insulated, Metal-Sheathed Base Metal Thermocouples
ASTM E1137 Industrial Platinum Resistance Thermometers
ASTM E1751 Standard Guide for Temperature Electromotive Force (emf) Tables for Non-Letter Designated Thermocouple Combinations
ASTM MNL7 Presentation of Data and Control Chart Analysis
ASTM MNL12 Use of Thermocouples in Temperature Measurement
2.3 IEC Publications
Available from IEC Central Office, 3, rue de Varembe, P.O. Box 131, CH-1211 Geneva 20, Switzerland, Tel: +41 22 919 02 11, www.iec.ch.
IEC 60751 Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors
ISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories
2.4 Definitions
Terms used in AMS2750 are defined in AS7766 and as follows:
2.4.1 ACCURACY
The maximum deviation of the instrument or sensor being tested from the values of a traceable standard.
2.4.2 ADJUSTMENT
Any change to an instrument’s parameters.
2.4.3 AUTOCLAVE
An oven capable of operating at pressures higher than atmospheric pressure (nominally 760 mm Hg), commonly used in the processing of materials. It may be pressurized with steam, compressed air, or inert gas.
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2.4.4 BASE METAL SENSOR
Sensor whose thermoelements are composed primarily of base metals and their alloys. Examples of base metal sensors include Types E, J, K, N, M, and T.
2.4.5 BATCH FURNACE
A furnace where parts or raw material are stationary during the soak.
NOTE: Some batch furnaces may oscillate material within a stationary work zone.
2.4.6 BIAS or INPUT SHIFT
The act of making an adjustment to an instrument to add, remove, or alter an offset.
2.4.7 BIMONTHLY
See FREQUENCY.
2.4.8 BIWEEKLY
See FREQUENCY.
2.4.9 CALIBRATION
An assessment of the accuracy of a sensor or an instrument to a traceable standard sensor and/or field test or standard instrument, based on one or more measurements, and potentially adjusting an instrument and/or compiling a deviation chart for a sensor or instrument in order to ensure compliance with requirements.
2.4.10 CONTINUOUS FURNACE
A furnace where parts or raw material are conveyed continuously or semi-continuously from the charge area to the discharge area. Examples include: bump furnace, shaker furnace, belt furnace, roller furnace, and rotary hearth furnace.
2.4.11 CONTROL INSTRUMENT
An instrument connected to a control sensor used to control the temperature of thermal processing equipment. The instrument may or may not also record temperature data.
2.4.12 CONTROL SENSOR
A sensor connected to a control instrument on thermal processing equipment, the temperature of which may or may not be recorded.
2.4.13 CONTROL ZONE
A portion of the working zone in thermal processing equipment having a separate sensor, instrument, and heating or cooling system to control its temperature. This portion of the thermal processing equipment is independently controlled.
2.4.14 CONTROLLED TEMPERATURE LIQUID BATH
A furnace containing a liquid that is heated to the desired heat-treat temperature. Parts and raw material are normally immersed in the liquid.
2.4.15 CONTROLLER
A digital or mechanical device that controls the temperature of thermal processing equipment (e.g., furnace control instruments, quench mechanical thermostat, freezer pressure controls, etc.).
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2.4.16 CORRECTION FACTOR
The number of degrees, determined from the most recent calibration, that must be added to, or subtracted from, the temperature reading of a sensor, or an instrument, or a combination thereof (system) to obtain true temperature. The correction factors of sensors and instruments are usually kept separately and added together algebraically when a combination is used. Correction factor is the algebraic opposite of deviation (error).
2.4.17 DATA ACQUISITION SYSTEM
An instrument system used to automatically collect and store process data as an electronic record; for example, a Programmable Logic Controller (PLC).
2.4.18 DEVIATION/ERROR
In the context of this specification, the difference between the uncorrected indicated temperature and the true temperature (Indicated Temperature – True Temperature = Deviation/Error).
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