Heat Treatment is one of 15 special-process and product programs operating within Nadcap. The Heat Treatment program has seen significant growth since its launch. In fact, in the last 10 years, the number of audits conducted annually has grown by over 400% from 157 audits in 1996 to 655 audits in 2007 at the time of print. The Heat Treatment program accounts for almost 18% of all Nadcap audits conducted in 2007 throughout the world.

Nadcap Heat Treat subscribers

Industry-Wide Involvement

It is not only aerospace suppliers who undergo Nadcap audits. The NUCAP program provides major aerospace companies with the opportunity to strengthen internal quality procedures, assisted by independent technical experts. In this way, they can better appreciate the supplier perspective, and it raises their credibility among suppliers about their commitment to Nadcap. The increasing popularity of the NUCAP program has seen aerospace primes including Alenia Aeronautica SpA, Bombardier Aerospace Inc., EADS-CASA, Honeywell Aerospace, Rolls-Royce plc and Vought Aircraft attain NUCAP heat-treatment approval.

Rossella Andreozzi, Alenia Aeronautica SpA quality special processes manager said, “NUCAP approval is a real huge achievement for our company. Alenia strongly believes in the NUCAP approach as a good opportunity and effective tool for continuous improvement in our processes. Alenia’s goal is to improve our participation in the Nadcap/NUCAP programs – with the involvement of all our sites and our suppliers – in order to better standardize our processes using a cost-effective approach assuring, at the same time, a high-quality product.”

The Audit

During a Heat Treatment audit, the Nadcap auditor – who is on-site for an average of four days – will carry out a number of job audits depending on the scope of the audit. A job audit is a step-by-step review of all processing on actual hardware, evaluating how all customer requirements are met.

For a Heat Treatment audit, a job audit may include verification of:
  • Material, material specification, heat-treatment specification
  • Atmosphere, racking, thermal treatment, quench, temper, load thermocouple, special treatments, stress relieve, testing
  • Requirement, shop paper, actual
  • Operator control and acceptance
  • Release testing
The auditor will review two completed jobs all the way through, including test results and eight in-process jobs, which will be witnessed during the audit. The auditor will also review all pyrometry records and procedures, and if possible, witness a Temperature-Uniformity Survey (TUS) or a Systems-Accuracy Test (SAT).

The level of detail required makes this a true assessment. Nadcap audits are not intended to be easy – they are designed to challenge the aerospace industry to strive for excellence and continual improvement in the quality of their work and procedures.

Nadcap heat-treatment auditor Chee Soon Lum from Singapore explains, “I would recommend becoming a Nadcap auditor to anyone who is dedicated to the aerospace industry. Working as a Nadcap auditor, I am continually learning about new technology in my field, and it also allows me the opportunity to experience different cultures.”

How to deal with repetitive NCRs

How to Succeed

At the January 2007 Nadcap meeting, Mike Navaira of Lockheed Martin and Mitch Nelson of Cessna Aircraft Company reviewed some of the common causes of repetitive non-conformances and how to prevent them. In their words, “There should never be a repeat NCR (non-conformance report) for any major or minor finding. They are an indicator of a quality-system failure, and there’s no excuse for that.”

Data has shown that the two principal causes of non-conformances are job audits and pyrometry. For job audits, the following are most likely to be problematic:
  • Customer flowdown – or more accurately, the lack of it. It is important for suppliers to be sure of the requirements of their customer(s) and to continue this flowdown internally.
  • Lack of documentation/objective evidence. This is key for Nadcap audit success. The auditor is representing the prime stakeholders in the Nadcap program, and they must be satisfied that there is evidence of ongoing compliance with the industry standards and customer requirements.
The top five NCRs related to AMS 2750D Pyrometry are detailed below, with a real example of a supplier’s root-cause corrective-action response to the top NCR (Sidebar, below).

1. The temperature-uniformity survey data and summary reports for all aerospace-approved furnaces did not include the test-instrument calibration correction factors in accordance with AMS 2750D, paragraph 3.5.20.1. (From Nadcap AC7102 Rev C 9.23.10)

2. Supplier’s report of system-accuracy testing reflects only one date and time of testing when three points are being independently tested on the same furnace. The furnace has two control zones and one quench, which are being tested independent from each other. However, the log reflects only the date and time for the first sensor tested and the date and time for the two additional sensors are reported as same. Actual time of test for each sensor should be different since supplier is testing one sensor at a time. (From Nadcap AC7102 Rev C 9.20.1)

3. With the calibration of the data logger used for recording the nine thermocouple readings during the temperature-uniformity surveys and the chart recorder that records up to 10 traces from the thermocouples of all the batch furnaces, only one channel of each recorder is calibrated. It was stated that each channel of the recorders is adjustable, so each channel should be individually calibrated as specified in AMS 2750D 3.2.5.3.3. (From Nadcap AC7102 Rev C 9.18.1)

4. AMS 2750D requires in paragraph 3.4.1 that systems-accuracy tests be performed on load thermocouples used to qualify the furnace to type-B instrumentation – also on load TCs used for acceptance of the load. Supplier is not performing SATs on load TCs. Load TCs are used to qualify the furnace as type B and are used for establishing time of cycle. (From Nadcap AC7102 Rev C 9.20.2)

5. AMS 2750D (3.5.20.1) requires the use of calibrated, independent test instrumentation for TUS. Process instruments of thermal-processing equipment shall not be used to record TUS sensor data. The sup*plier is not in compliance with this requirement on the TUS for their vacuum furnaces (VF1 and VF2). The same chart recorder for the furnace is used for TUS surveys. (From Nadcap AC7102 Rev C 9.15.1)

Excellence Through Education

The Deming Study on Errors showed that 94% of errors are process-related, while only 6% are people-related. PRI offers a “Root Cause Corrective Action (RCCA)” training seminar to counter these. This seminar is based on the flow chart used by Nadcap, and it provides a method for participants to use to improve root-cause analysis and prevent the same mistakes from occurring again. On average, data has shown that course participants perform 30% better on their audits than those who do not participate. After participating in a RCCA course, suppliers close out their audits on average 25% faster than before they participated in this training.

In response to the fact that non-compliance to AMS 2750D has been highlighted as a major cause of Nadcap audit NCRs, there is also an “Introduction to Pyrometry” training seminar. The objectives of this training course are to ensure that participants gain a thorough understanding of how to implement the requirements of AMS 2750D within their facilities. Topics include temperature sensors, instrumentation, classification of furnaces, system-accuracy tests and temperature-uniformity tests. David Smith of Rolls-Royce plc commented, “I was pleased with the organization and overall quality of this course. I would recommend this training to anyone who uses AMS 2750D in their operations.” IH

For more information on training: Contact Jennifer Gallagher at jgall@sae.org. Visit www.pri-network.org to learn more about Nadcap or www.eAuditStaff.com to find out about becoming a Nadcap auditor.

Additional related information may be found by searching for these (and other) key words/terms via BNP Media SEARCH at www.industrialheating.com: Nadcap, AMS 2750, pyrometry, temperature uniformity, systems accuracy test

SIDEBAR: Top NCR with Corrective-Action Response

The temperature uniformity survey data and summary reports for all aerospace approved furnaces did not include the test instrument calibration correction factors in accordance with AMS 2750D paragraph 3.5.20.1

Initial Response From Supplier
Immediate Corrective Action Taken (Containment Actions): The datalogger instrument correction factors were compiled into a spreadsheet. We then looked at all TUS performed using this instrument using the highest and lowest thermocouple readings taken during the TUS. We applied the instrument correction factors to those readings and listed the new spread and matched it against the furnace tolerance. Because of the small amount of correction factor applied none of the furnace TUS were shifted out of the furnace tolerance band. See attached excel spreadsheet.

Root Cause of Nonconformance: This was not addressed specifically enough in our procedure. However when the new datalogger was purchased in September 2006 which was suppose to be AMS 2750 D compliant it only had one space to use for thermocouple correction. This would be fine if you were using thermocouples made from wire rolls with only one correction factor, but we use the nonexpendable that have individual correction factors. There was another area that was used for instrument corrections, which allowed you to enter correction factors for each channel (this instrument has 20 channels.) We decided to use the area for the individual channel correction to enter the thermocouple correction factors and inadvertently forgot about combining the thermocouple correction together with the instrument correction factors.

Impact of all Identified Causes and the Root Cause: No impact - the instrument correction values were small and when we reviewed the TUSs that were done using this instrument (which is listed on the attached spreadsheet) there were no TUS that were shifted out of the uniformity tolerance.

Action Taken to Prevent Recurrence: I have contacted the company that makes the datalogger and informed them about the nonconformance they are investigating this and may make changes to the instrument and update the software. In the mean time we will mathematically combine the correction factors for the instrument and the thermocouples and enter that into the area for the instrument corrections for the individual channels. This is now stated in the procedure. See attached corrected procedure.

Initial Response From Nadcap Staff Engineer
Please readdress the root cause. The wire and instrument correction factors can be added to the actual uncorrected temperature values from the data logger after the survey has been completed. It is not a requirement to have these factor entered into the data logger. Why was this requirement not identified during the review of AMS2750 Rev D and flowed down to the procedure as a requirement? What is being changed in the specification review process to ensure that all requirements are identified an flowed down to the procedures in the future?Please provide an future of a TUS which shows the proper application of the T/C and the wire correction factors to the highest and lowest uncorrected temperatures within the 30 minute survey.

Second Response From Supplier
Root Cause: As it was stated in the original root cause statement the requirement was flowed down in the procedure (see attached copy of old procedure). The root cause of this NCR is a training issue and procedural problem. The statement in the old revision of the procedure was too ambiguous and did not state specifically enough where and how to apply the correction factors. Since we were operating with a new datalogger at this time we were not sure how the correction factors were going to be added. The procedure has been changed to state and the technician has been retrained as to were and how to make the TC and instrument correction factors. See attached training record. We are not using a wire correction factor, we are using individual non-expendable thermocouples and each one has it’s own correction factor. The correction factors for the TC’s and the instrument are combined (see page 4 of survey attached) and are continuously added during the entire survey run.

Second Response From Nadcap Staff Engineer
Accepted based on response and submitted documents.