AMS2750, CQI-9 and NADCAP Explained

Three terms, three different things

The confusion is common but has practical consequences: AMS2750 and CQI-9 affect the furnace design, NADCAP affects your organisation. A furnace can be instrumented to AMS2750; what gets accredited is not the furnace but the operation.

AMS2750 – Pyrometry in aerospace

AMS2750 governs the entire temperature measurement chain in heat treatment:

• Thermocouples: types, usage limits, service lives, replacement intervals
• Calibration: traceability and intervals for all measuring equipment
• Furnace classification: by demonstrated temperature uniformity
• Instrumentation types: scope of control, recording and load measurement
• Recurring checks: TUS and SAT at defined intervals

Furnace classes by temperature uniformity

The class follows from the deviation demonstrated in the TUS across the qualified working space. The usual breakdown:

The tighter the class, the more demanding the control zones, air routing and instrumentation become – and the more expensive the furnace. Binding values and inspection intervals are set out in the current revision of the specification; the table above is for orientation, not for evidence.

In practice: aluminium heat treatment to T5/T6 is frequently run in Class 2 – see aluminium foundry. The NTH Therm air-circulation ranges ICO and IWO achieve uniformity below ±5 °C.

Instrumentation types

AMS2750 distinguishes instrumentation types (usually A through E) by how comprehensively temperature is measured and recorded – from monitoring the control thermocouple alone through to additionally recording load thermocouples. Which type applies follows from the process and from your customer’s specification.

CQI-9 – System assessment in automotive

AIAG’s CQI-9 assesses not individual furnaces but the entire heat treatment system. Its scope reaches well beyond pyrometry:

• Process management and process documentation
• Equipment condition and preventive maintenance
• Qualification and training of operating personnel
• Measuring equipment and calibration
• Process tables with requirements specific to each process – hardening, tempering, carburising and others

CQI-9 also requires TUS and SAT. The assessment is normally an annual self-assessment and is demanded by customers as part of supplier approval.

NADCAP – Accreditation, not a standard

NADCAP accredits operations for special processes whose results cannot be fully verified non-destructively – heat treatment among them. The audit checks whether the applicable specifications, AMS2750 included, are genuinely being met.

For procurement this means: you do not buy a “NADCAP-certified furnace”. You buy a furnace whose instrumentation, documentation and uniformity evidence will survive a NADCAP audit.

TUS and SAT compared

Both are part of the recurring overhead of a qualified plant. NTH Therm performs temperature calibration as part of maintenance contracts and during commissioning.

What this means for your enquiry

A furnace with a qualification requirement is, in design terms, a different product from the same furnace without one. So settle the following before the design is fixed:

1. Which specification applies – AMS2750, CQI-9, both?
2. Which furnace class does your customer require?
3. Which instrumentation type is demanded?
4. Is NADCAP accreditation being sought?
5. What recording and archiving obligations apply?

These five points feed directly into control zones, thermocouple positions, recording equipment and acceptance scope – and therefore into the price. Why it pays to settle them early is covered under What does an industrial furnace cost.

The current revisions of the standards and your customer’s specification are always the binding sources. This page explains how they relate and does not replace a normative reference.