AEROSPACE

Furnaces and ovens 

Furnaces and ovens According to AMS2750E Norm:

The AMS2750E standard, issued by SAE International, specifies the requirements for pyrometry in thermal processing equipment, including the calibration and maintenance of temperature sensors, instrumentation, and thermal processing equipment used in heat treatment. It is widely used in the aerospace industry to ensure uniformity and accuracy in heat treatment processes. Below is an overview of furnaces according to the AMS2750E norm:

Aeronautics

HCV AC (Forced air circulation)

Forced air circulation industrial furnace up to 1150ºC (According to AMS2750E regulations) Aerospace and automitive applications

HCV Series 

Industrial furnaces up to 1400ºC  from 56 litres to 2000 litres for heat treatment applications

HCV CCH Series 

Retort furnaces up to 1150ºC under modified atmosphere 

Vacuum furnace PR-V

Retort furnaces to work under vacuum and modified atmosphere up to 1150ºC for sintering applications

CRN Series

Muffle furnace up to 1900ºC, pantograph side door (SiC and MoSi2) Large series 

XG Series

Muffle furnace up to 1900ºC, vertical lift door (MoSi2 heating elements)

JM Series

Muffle furnace up to 1600ºC, vertical lift door (SiC heating elements)

HOB Series

Bottom loading furnace up to 1900ºC under air, modified atmosphere and vacuum

Industrial and laboratory ovens

Laboratory ovens up to 300ºC and 500ºC

MF Series

Muffle furnace up to 1400ºC, vertical lift door, 4 heated sides

PR Series

Muffle furnace up to 1400ºC, pantograph side door

MF TGA

Muffle furnace with balance for thermogravimetry tests

ST SP Series 

Split tube furnaces up to 1300ºC, horizontal operation

ST Series 

High temperature tube furnaces from 1600ºC (SiC) up to 1900 (MoSi2) Horizontal Operation

ST VC Series

High temperature tube furnaces from 1600ºC (SiC) up to 1900 (MoSi2) Vertical  Operation

ST Series 

Universal tube furnaces up to 1300ºC, horizontal operation

TR Series

Vertical and split tube furnaces up to 1300ºC, vertical operation

HTF Series

Split or universal tube furnaces to work under modified atmosphere or vacuum, great uniformity, different tube diameters and heating zones up to 1600ºC (Horizontal or Vertical Operation)

Furnaces According to AMS2750E Norm: 

The AMS2750E standard, issued by SAE International, specifies the requirements for pyrometry in thermal processing equipment, including the calibration and maintenance of temperature sensors, instrumentation, and thermal processing equipment used in heat treatment. It is widely used in the aerospace industry to ensure uniformity and accuracy in heat treatment processes. Below is an overview of furnaces according to the AMS2750E norm:

Key Requirements of AMS2750E

  1. Temperature Uniformity Surveys (TUS):
    • Frequency: The frequency of TUS depends on the class of the furnace and the heat treatment process. Surveys must be conducted at specified intervals to ensure the furnace meets uniformity requirements.
    • Procedure: The TUS involves placing thermocouples throughout the furnace workspace to measure temperature variations. The furnace must maintain temperature within specified limits for its class.
  2. System Accuracy Tests (SAT):
    • Frequency: SATs are conducted to ensure the accuracy of the entire thermal processing system, including temperature sensors and controllers. The frequency of these tests is determined by the type of instrumentation and the criticality of the process.
    • Procedure: SAT compares readings from the furnace’s control and recording systems with a calibrated standard to verify accuracy.
  3. Instrumentation Requirements:
    • Types: Instrumentation is categorized into Types A, B, C, D, and E based on their accuracy and application. The selection depends on the criticality of the heat treatment process.
    • Calibration: All instruments must be calibrated regularly against standards traceable to the National Institute of Standards and Technology (NIST) or equivalent.
  4. Thermocouples:
    • Types: The standard specifies different types of thermocouples (e.g., Type K, Type N) and their acceptable tolerances.
    • Calibration: Thermocouples must be calibrated periodically and replaced or recalibrated if they exceed specified drift limits.

Furnace Classes According to AMS2750E

AMS2750E defines furnace classes based on temperature uniformity requirements:

  1. Class 1: ±5°F (±3°C) uniformity
  2. Class 2: ±10°F (±6°C) uniformity
  3. Class 3: ±15°F (±8°C) uniformity
  4. Class 4: ±20°F (±10°C) uniformity
  5. Class 5: ±25°F (±14°C) uniformity
  6. Class 6: ±50°F (±28°C) uniformity

Types of Furnaces and Their Compliance

  1. Batch Furnaces:
    • Application: Used for processing individual loads with specific heat treatment cycles.
    • Compliance: Must undergo regular TUS and SAT to ensure temperature uniformity and accuracy.
  2. Continuous Furnaces:
    • Application: Used for high-volume production with continuous loading and unloading.
    • Compliance: Requires consistent monitoring and periodic surveys to meet AMS2750E standards.
  3. Vacuum Furnaces:
    • Application: Used for processes requiring an oxygen-free environment, such as brazing and sintering.
    • Compliance: Must meet stringent temperature and atmosphere control requirements, verified through TUS and SAT.
  4. Atmosphere Furnaces:
    • Application: Used for heat treatments in controlled atmospheres (e.g., inert gases).
    • Compliance: Requires regular verification of both temperature uniformity and atmosphere composition.
  5. Salt Bath Furnaces:
    • Application: Used for processes like quenching, where the workpiece is immersed in molten salt.
    • Compliance: Must ensure accurate temperature control and uniform heating.

Documentation and Record Keeping

  • Calibration Records: Detailed records of all calibrations performed on instruments and thermocouples must be maintained.
  • Survey Records: Results of TUS and SAT must be documented, including the locations of thermocouples, temperature readings, and any corrective actions taken.
  • Maintenance Logs: Documentation of maintenance activities, repairs, and modifications to the furnace must be kept to ensure ongoing compliance.

Summary

Furnaces compliant with AMS2750E are essential for achieving consistent and reliable heat treatment results in the aerospace industry. The standard ensures that all aspects of temperature measurement and control are rigorously monitored and maintained, contributing to the quality and safety of aerospace components.