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Conditions for approval required by: Philippe Canteau
Certification of Aerospace Products to international quality Standards
Certification of Aerospace Products to international quality Standards
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Conditions for initial qualification of EN2910-070 nuts under EN3004 technical specification:
• Axial load at 650°C temperature: EN3004 technical specification states that the test bolt has to be in the same material as the nut (stainless steel 1100 MPa) during baking to 650°C. QTR states that an Inconel test bolt 1550 MPa has been used. Please clarify this point.
• Axial load at 650 °C: Has a new test bolt been used for each tested nut? Please provide ASD-CERT with this evidence as stated in EN3004 technical specification.
• Self-locking torque at ambient temperature after baking to 650°C. How the 517 MPa stress stated in EN3004 technical specification in the nut has been achieved? Has a spacer been used with the test bolt when baking to 650°C as stated in EN3004? The QTR does not precise.
• Material: a statement that material spec used to procure material is equivalent to EN material mentioned in EN2910 product standard.
Conditions for initial qualification of EN2910-070 nuts under EN3004 technical specification:
Correct the EN3004:1997 has been used for this initial qualification, see QTP and QTR.
• Axial load at 650°C temperature: EN3004 technical specification states that the test bolt has to be in the same material as the nut (stainless steel 1100 MPa) during baking to 650°C. QTR states that an Inconel test bolt 1550 MPa has been used. Please clarify this point.
Because it is axial load and if we use a test bolt with the same material (1100 MPa) as the nut we cannot achieve the axial strength required we have a failure of the bolt so the test is invalid.
It is the reason why we use a bolt with a strength higher than the nut. The behavior of a Inconel bolt is better after baking than a stainless steel bolt.
• Axial load at 650 °C: Has a new test bolt been used for each tested nut?
Yes of course.
Please provide ASD-CERT with this evidence as stated in EN3004 technical specification.
The 4 nuts as mentioned in clause 5.4.1.2 for the qualification will be in the oven at the same time. The use of “old” already used bolts jeopardizes the test. The use of 4 new bolts therefore provides more certainty and is much cheaper than having a failed test with the need to repeat this test. So it is a good practice (and prescribed in the standard) to use always new bolts for the test as mentioned in the EN3004.
• Self-locking torque at ambient temperature after baking to 650°C.
How the 517 MPa stress stated in EN3004 technical specification in the nut has been achieved?
By measuring the elongation of the bolt, method as described in the paragraph of 5.4.5.2 of EN3004 standard.
Has a spacer been used with the test bolt when baking to 650°C as stated in EN3004? The QTR does not precise.
Yes of course the complete assembly was submitted to 650°C.
• Material: a statement that material spec used to procure material is equivalent to EN material mentioned in EN2910 product standard.
The EN2910:1994 calls out on page 3 two types of material EN2399 or EN3629. In the “Additional Documents” of this ASD-Cert report a document is uploaded, called SAM0013 (Supplying of EZ6NCT25 (A286)) this documents gives a translation from EZ6NCT25 to EN2399.