Ensuring calibration compliance for critical heat treatment process

Peter Sherwin discusses a project that aimed to develop specific software solutions to fully manage the calibration and compliance of the thermal treatment process required for most aircraft components.
Article originally appeared in Control Engineering Europe, July 2016.

Nadcap AMS2750E compliance in regulated aerospace processes

Aircraft engine and safety critical components undergo stringent processing requirements to assure their performance in the field. A key part of the aerospace production process is the thermal treatment cycle these components are subjected to in order to enhance specific material properties. These thermal treatments are often referred to as 'special processes' and they are governed by strict aerospace standards (Nadcap), including the SAE AMS2750E specification for Pyrometry Control.

A significant part of the AMS2750E temperature standard focuses on calibration of the thermal process. In order to ensure accuracy of the process, calibration checks are performed on a regular basis to gauge actual results against known national standards and adjustments are made to minimise errors. AMS2750E dictates calibration requirements for thermocouples as well as control and data management systems.

For engine components subject to Class 1 or Class 2 requirements, each thermal process must be calibrated at a maximum interval of one month. Any out of tolerance results ('as found') will result in the entire prior months production being suspect and it is mandatory to notify the end customer of the issue in order to verify the suitability of these now suspect batches. This situation can lead to cost penalties for the processor, costly quality over-checks and also damages the reputation of the supplier. Thermal processors are therefore keen to minimise the risk of failing any calibration test.

Eurotherm by Schneider Electric and partners have provided solutions to the heat treatment industry and aerospace special processes for over 50 years, designing precision control equipment and secure data management solutions to aid the automation of the thermal process. Building on the strengths and expert knowledge of a European calibration team, Eurotherm undertook a project to develop specific software solutions to fully manage the calibration and compliance process. 

Interviews with a number of customers exposed several key problems with the current calibration standards within industry  – based on both customer internal and third-party calibration service provider experiences:

• Calibration checks were not always on time because of the lack of visibility of the calibration status across the plant (management, quality, maintenance, production, third- party supplier).
• Mistakes/typos have been made when transposing written data from technician visits onto hard copy certificates.
• Variable performance by technicians (not all following the same procedures and processes).
• Certificates were often created days or even weeks after the calibration on-site – leaving short periods where the site did not have specific details about the calibration results.
• Storage strategy of certificates differed between customers but these ad-hoc filing systems resulted in lost certificates and painful audit experiences. Some customers just stored in bulky filing cabinets while others scanned the certificates onto their PC network (but not always consistently as this was an additional administration burden). 

Calibration solution

Based on the input from customers, an internal/service based solution was initially created to create an easy to access plant/equipment view of the calibration and compliance status. The solution also aimed to provide a quicker turnaround of accurate certificates of calibration and to maintain a reliable storage and retrieval system.

Eurotherm Online Services (EOS) was created with the following architecture:
• EOS Advisor; a secure-user web-based portal for calibration and compliance status management/planning and document storage/retrieval.
• eCAT tablet app provides a method of direct entry of calibration data following a strict workflow (to eliminate potential errors) and a certificate engine to automatically create certificates from the data entered.
• A QR code automatically printed on the calibration label provides a quick link to the certificate by scanning with a smartphone - very useful for quick retrieval during external audits.

Next steps

The next release  – Version 2 – will soon be available for customers to use directly and will not just be offered as a service provided by Eurotherm engineers. OEM's, third-party calibration companies or medium to large end users with their own calibration maintenance teams will be able to take advantage of this compliance and calibration management solution.

Version 2 has been built using the Schneider Electric Cloud services which provides limitless scaling of the application across a global customer base. Data analytics and machine learning solutions already in use across other Schneider Electric solutions will soon provide enhancements to these calibration and compliance solutions by providing both insights and predictions to calibration performance in order to provide true drift management of process instrumentation.

Peter Sherwin is global heat treatment BDM at Eurotherm by Schneider Electric.
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