Space product assurance - Processing and quality assurance requirements for hard brazing of metallic materials for flight hardware

2021-04-21: This EN is based on ECSS-Q-ST-70-40C

Raumfahrtproduktsicherung - Prozess- und Qualitätssicherungsanforderungen für das Hartlöten von Metallen für Flughardware

This standard will establish the processing and quality assurance requirements for different types of brazing treatment for space flight applications.
This standard will be applicable to all Projects and Programmes where brazing treatments activities are performed. The document is intended to be used by PA Managers, Project Managers, Engineers and those involved with manufacturing.
Few international standards which relate to brazing treatments of metallic materials are readily available. A few of these are dedicated towards aeronautic applications which are currently used for space applications. Moreover, it is common to encounter the use of aircraft manufacturer standards (Boeing, Airbus) in Space Industry. However, experience demonstrates that on a regular basis, there are significant differences among the various standards, which lead to variations in the interpretation of the standards from one to another. At the same, there is a lack of information concerning specific brazing systems: e.g. ceramic/ceramic or ceramic/metals. As a consequence, Space Industries are using their own standards to improve reproducibility of brazing processes. Moreover, because there is no single high level ECSS standard on brazing processes, it has also been discovered on a number of occasions that processes are partially qualified, or if a qualification has been performed, it is not to a known standard. Moreover, during manufacturing, a clear definition and implementation of brazing treatment quality monitoring and control means is often not present.
By developing a single high level ECSS standard which can be tailored in the Project definition phase, it will help all project actors in performing the following functions related to brazing processes which shall be considered as a very critical Special Process:
(i)   select and verify equipment (furnaces, induction, flame, bath), atmosphere, temperature (control & uniformity),
(ii)   Verify the whole brazing treatment sequences including cleaning and etching,
(iii)   determine the acceptance criteria for imperfections in brazed joint
(iv)   define monitoring and control means during production to ensure that brazing processes are reproducible and produced with the required quality,
(v)   define rules for applying Test and Inspection methods
This will significantly reduce the number of partially-verified brazing treatment processes and also reduce the number of occasions when parts are delivered to the customer which do not conform to the required specification.

Assurance produit des projets spatiaux - Exigences de traitement et d'assurance qualité pour le brasage fort de matériaux métalliques pour matériel de vol

La présente norme spécifie les exigences relatives au traitement et à l'assurance qualité des procédés de brasage destinés aux applications de vol spatial. Le brasage s’entend comme l’assemblage et le scellement de matériaux au moyen d’une solidification d’un métal d’apport liquide.
Dans la présente norme, le terme « brasage » est utilisé comme regroupant les notions de « brasage fort » (brazing en anglais) et « brasage tendre » (soldering), pour le cas des matériaux d'apport qui ont des températures de liquidus en dessous de 450 °C.
Le brasage fort et le brasage tendre sont des techniques connexes au soudage (welding) et la présente norme vient en complément de la norme ECSS-Q-ST-70-39 relative au soudage.
La présente norme ne couvre pas les exigences relatives :
• aux procédés d'assemblage par collage adhésif (ECSS-Q-ST-70-16) ;
• au brasage à des fins d’assemblage électronique (ECSS-Q-ST-70-61) ;
• au brasage utilisé dans la fabrication d'hybrides (ESCC 2566000).
La norme couvre, sans toutefois s’y limiter, les procédés de brasage suivants :
• brasage fort aux gaz ;
• brasage fort au four ;
• brasage fort au trempé et brasage fort au bain de sel ;
• brasage fort par induction.
La présente norme ne donne pas de détails sur les phases de définition et de pré-vérification du brasage, y compris les écarts de conception autorisés.
La présente norme peut être adaptée aux caractéristiques et contraintes spécifiques d'un projet spatial conformément à l'ECSS-S-ST-00.

Zagotavljanje kakovosti proizvodov v vesoljski tehniki - Zahteve za obdelavo in zagotavljanje kakovosti za trdo spajkanje kovinskih materialov za letalsko strojno opremo

General Information

Status
Not Published
Publication Date
27-Jun-2023
Technical Committee
Current Stage
6055 - CEN Ratification completed (DOR) - Publishing
Start Date
28-Nov-2022
Due Date
26-Jul-2023
Completion Date
28-Nov-2022

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Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 16602-70-40:2022
01-februar-2022
Zagotavljanje kakovosti proizvodov v vesoljski tehniki - Zahteve za obdelavo in

zagotavljanje kakovosti za trdo spajkanje kovinskih materialov za letalsko strojno

opremo
Space product assurance - Processing and quality assurance requirements for hard
brazing of metallic materials for flight hardware
Raumfahrtproduktsicherung - Metallschweißen in Flug-Hardware
Ta slovenski standard je istoveten z: prEN 16602-70-40
ICS:
03.120.99 Drugi standardi v zvezi s Other standards related to
kakovostjo quality
25.160.50 Trdo in mehko lotanje Brazing and soldering
49.140 Vesoljski sistemi in operacije Space systems and
operations
oSIST prEN 16602-70-40:2022 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 16602-70-40:2022
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oSIST prEN 16602-70-40:2022
EUROPEAN STANDARD DRAFT
prEN 16602-70-40
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2021
ICS 25.160.50; 49.140
English version
Space product assurance - Processing and quality
assurance requirements for hard brazing of metallic
materials for flight hardware
Raumfahrtproduktsicherung - Metallschweißen in
Flug-Hardware

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/CLC/JTC 5.

If this draft becomes a European Standard, CEN and CENELEC members are bound to comply with the CEN/CENELEC Internal

Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any

alteration.

This draft European Standard was established by CEN and CENELEC in three official versions (English, French, German). A

version in any other language made by translation under the responsibility of a CEN and CENELEC member into its own language

and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,

Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,

Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,

Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.Recipients of this draft are invited to submit, with their comments, notification

of any relevant patent rights of which they are aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
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Table of contents

European Foreword ................................................................................................... 5

1 Scope ....................................................................................................................... 6

2 Normative references ............................................................................................. 7

3 Terms, definitions and abbreviated terms ............................................................ 8

3.1 Terms from other standards ...................................................................................... 8

3.2 Terms specific to the present standard ..................................................................... 8

3.3 Abbreviated terms................................................................................................... 10

3.4 Conventions............................................................................................................ 10

3.5 Nomenclature ......................................................................................................... 10

3.6 Schematic of brazed assembly ............................................................................... 11

4 Principles .............................................................................................................. 12

4.1 General ................................................................................................................... 12

4.2 Classification of safety classes and quality levels ................................................... 15

4.2.1 Overview ................................................................................................... 15

4.2.2 Safety classes ........................................................................................... 15

4.2.3 Quality levels ............................................................................................. 15

4.3 Tailoring of the brazing acceptance criteria ............................................................. 15

5 Brazing Design ..................................................................................................... 16

5.1 Design for brazed connections................................................................................ 16

5.2 Design for inspection .............................................................................................. 16

6 Brazing and inspection personnel ...................................................................... 17

6.1 Overview ................................................................................................................ 17

6.2 Brazer and brazing operator training ....................................................................... 17

6.3 Brazing inspector training ....................................................................................... 17

7 Equipment and facilities ...................................................................................... 18

7.1 Equipment .............................................................................................................. 18

7.2 Materials and consumables .................................................................................... 18

7.2.1 Filler material ............................................................................................ 18

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7.2.2 Flux ........................................................................................................... 18

7.2.3 Tooling and fixtures ................................................................................... 18

8 Brazing procedure specification (BPS) .............................................................. 19

8.1 General ................................................................................................................... 19

8.2 Drawing .................................................................................................................. 19

8.3 Process description ................................................................................................ 19

8.4 Cleanliness aspects of Brazing ............................................................................... 19

8.4.1 Overview ................................................................................................... 19

8.4.2 Requirements ............................................................................................ 20

9 Brazing inspection ............................................................................................... 21

9.1 Non-destructive testing ........................................................................................... 21

9.2 Destructive testing .................................................................................................. 21

10 Brazing acceptance criteria ............................................................................... 22

10.1 General ................................................................................................................... 22

10.2 Classification of Imperfections ................................................................................ 22

10.3 Brazing Imperfections Acceptance Criteria ............................................................. 22

10.4 Selection of quality levels........................................................................................ 23

11 Brazing process verification .............................................................................. 28

11.1 General ................................................................................................................... 28

11.2 Brazing Verification Test Plan ................................................................................. 28

11.3 Completion of verification ........................................................................................ 29

11.4 Delta verification ..................................................................................................... 29

11.5 Re-brazing, in-process correction ........................................................................... 29

11.6 Repair-brazing ........................................................................................................ 30

11.7 Documentation ....................................................................................................... 30

12 Flight hardware production ............................................................................... 31

12.1 Documentation ....................................................................................................... 31

12.2 Requirements for flight hardware brazing ............................................................... 31

12.2.1 General ..................................................................................................... 31

12.2.2 Extent of testing to support flight hardware production .............................. 31

13 Quality assurance ............................................................................................... 33

13.1 Maintenance of BPS ............................................................................................... 33

13.2 Quality control ......................................................................................................... 33

13.2.1 Documentation of brazing parameters....................................................... 33

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13.2.2 Anomalies and nonconformances occurring during the brazing

process ..................................................................................................... 33

13.2.3 Inspection and test methods ..................................................................... 34

Annex A (normative) Brazing Procedure Specification (BPS) - DRD .................. 35

A.1 DRD identification ................................................................................................... 35

A.1.1 Requirement identification and source document ......................................... 35

A.1.2 Purpose and objective ............................................................................... 35

A.2 Expected response ................................................................................................. 35

A.2.1 Scope and content .................................................................................... 35

A.2.2 Special remarks ........................................................................................ 36

Annex B (normative) Brazing Verification Test Plan (BVTP) - DRD .................... 37

B.1 DRD identification ................................................................................................... 37

B.1.1 Purpose and scope .................................................................................... 37

B.2 Expected response ................................................................................................. 37

B.2.1 Scope and content ..................................................................................... 37

B.2.2 Special remarks ......................................................................................... 37

Bibliography ............................................................................................................. 38

Figures

Figure 3-1: Schematic of a brazed and soldered joint (taken from EN ISO 18279:2004) ...... 11

Figure 4-1: Steps for brazing process verification and flight hardware production ................ 14

Tables

Table 10-1: Classification of imperfections in Brazing joints (the classification of

imperfections is derived from EN ISO 18279:2004) ............................................ 24

Table 11-1: Test Matrix for standard test .............................................................................. 29

Table 12-1: Tests to be performed on parts performed during production of flight

hardware ............................................................................................................ 32

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European Foreword
This document (prEN 16602-70-40:2021) has been prepared by Technical
Committee CEN/CLC/TC 5 “Space”, the secretariat of which is held by DIN
(Germany).
This document (prEN 16602-70-40:2021) originates from ECSS-Q-ST-70-40C
DIR1.
This document is currently submitted to the ENQUIRY.
This document has been developed to cover specifically space systems and will
therefore have precedence over any EN covering the same scope but with a
wider do-main of applicability (e.g. : aerospace).
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Scope
This Standard specifies the processing and quality assurance requirements for
brazing processes for space flight application. Brazing is understood as the
joining and sealing of materials by means of a solidification of a liquid filler
metal.
The term brazing in this standard s is used as equivalent to soldering, in cases
that the filler materials have liquidus temperatures below 450 °C.
Brazing and soldering are allied process to welding and this standard is
supplementing the standard for welding ECSS-Q-ST-70-39.
This standard does not cover requirements for:
• Joining processes by adhesive bonding (ECSS-Q-ST-70-16),
• Soldering for electronic assembly purposes (ECSS-Q-ST-70-61),
• Soldering used in hybrid manufacturing (ESCC 2566000).
The standard covers but is not limited to the following brazing processes:
• Torch brazing,
• Furnace brazing,
• Dip Brazing and Salt-bath brazing,
• Induction Brazing.
This Standard does not detail the brazing definition phase and brazing pre-
verification phase, including the derivation of design allowables.

This standard may be tailored for the specific characteristic and constraints of a

space project in conformance with ECSS-S-ST-00.
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Normative references
The following normative documents contain provisions which, through
reference in this text, constitute provisions of this ECSS Standard. For dated
references, subsequent amendments to, or revision of any of these publications
do not apply. However, parties to agreements based on this ECSS Standard are

encouraged to investigate the possibility of applying the more recent editions of

the normative documents indicated below. For undated references, the latest
edition of the publication referred to applies.
EN reference Reference in text Title
EN 16601-00-01 ECSS-S-ST-00-01 ECSS system – Glossary of terms
EN 16601-40 ECSS-M-ST-40 Space management – Configuration and information
management
EN 16603-10-02 ECSS-E-ST-10-02 Space engineering – Verification
EN 16603-32-01 ECSS-E-ST-32-01 Space engineering – Fracture control
EN 16602-10-09 ECSS-Q-ST-10-09 Space product assurance – Nonconformance control
system
EN 16602-70 ECSS-Q-ST-70 Space product assurance – Materials, mechanical
parts and processes
EN 16602-70-01 ECSS-Q-ST-70-01 Cleanliness and contamination control
EN ISO 18279:2004 Imperfections in brazed joints
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Terms, definitions and abbreviated terms
3.1 Terms from other standards
a. For the purpose of this Standard, the terms and definitions from ECSS-S-
ST-00-01 apply and in particular the following:
1. critical
b. For the purpose of this Standard, the terms and definitions from ECSS-E-
ST-32-01 apply.
1. fail-safe
3.2 Terms specific to the present standard
3.2.1 alpha sample
sample brazed prior to the start of a production run, used to verify selected
aspects of the quality of the brazing joint to be produced during production
3.2.2 beta sample
sample brazed at the end of a production run, used to verify selected aspects of
the quality of the brazing joint to be produced during production
3.2.3 braze metal
see “filler metal”
3.2.4 brazer
person who performs brazing in a manual operation, guides the heating means,
ensures the introduction of the brazing filler material and verifies the braze
joint configuration specified by the design
3.2.5 brazing
joining and sealing of parent materials by means of a solidification of a liquid
filler metal
NOTE Terms brazing and soldering are synonymous
independent from the liquidus temperature or
the filler material. For more details see clause 4.
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3.2.6 brazing inspector

person with the responsibility and ability to judge the quality of brazed joints in

relation to the specification
3.2.7 brazing operator
person who prepares the joint and sets up brazing equipment and thereby has
direct influence on the brazed joint quality
3.2.8 brazing responsible
person who is nominated by the company to follow and organise brazing
processes, establish the BPS, be responsible for training and realisation of
acceptable brazing for production
3.2.9 design and engineering authority
organization that has the responsibility for the structural integrity and
maintenance of flightworthiness of the hardware and compliance with all
relevant documents related to brazing and soldering
3.2.10 filler metal
material required for soldered/brazed joints
NOTE The term “braze metal” is synonymous
3.2.11 flux
material which promotes wetting of the parent material by the filler metal
3.2.12 parent material
material being brazed and soldered
3.2.13 soldering
see “brazing”
NOTE Terms soldering and brazing are used
synonymously in this standard. For more
details see clause 4.
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3.3 Abbreviated terms
For the purpose of this Standard, the abbreviated terms and symbols from
ECSS-S-ST-00-01 and the following apply:
Abbreviation Meaning
brazing procedure specification
BPS
brazing verification test plan
BVTP
brazing verification test report
BVTR
coefficient of thermal expansion
CTE
European Cooperation for Space Standardization
ECSS
heat affected zone
HAZ
nonconformance report
NCR
non-destructive test
NDT
request for approval
RfA
3.4 Conventions
For the purpose of this Standard, the following conventions apply:
Convention Meaning
qualification In this ECSS-Q-ST-70-40 the term is synonymous
with the term "verification" used in ECSS
documentation.
qualification test plan used in common brazing documentation is
(QTP) synonymous with the term "Brazing verification
test plan (BVTP)" from this ECSS-Q-ST-70-40
qualification test report used in common brazing documentation is
(QTR) synonymous with the term "Brazing verification
test report (BVTR)" from this ECSS-Q-ST-70-40
3.5 Nomenclature
The following nomenclature applies throughout this document:
a. The word “shall” is used in this Standard to express requirements.
All the requirements are expressed with the word “shall”.
b. The word “should” is used in this Standard to express
recommendations. All the recommendations are expressed with
the word “should”.
NOTE It is expected that, during tailoring,
recommendations in this document are either
converted into requirements or tailored out.
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c. The words “may” and “need not” are used in this Standard to
express positive and negative permissions, respectively. All the
positive permissions are expressed with the word “may”. All the
negative permissions are expressed with the words “need not”.
d. The word “can” is used in this Standard to express capabilities or
possibilities, and therefore, if not accompanied by one of the
previous words, it implies descriptive text.
NOTE In ECSS “may” and “can” have completely
different meanings: “may” is normative
(permission), and “can” is descriptive.
e. The present and past tenses are used in this Standard to express
statements of fact, and therefore they imply descriptive text.
3.6 Schematic of brazed assembly
Figure 3-1 shows a typical joint made by brazing and soldering.
Figure 3-1: Schematic of a brazed and soldered joint (taken from EN ISO
18279:2004)
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Principles
4.1 General

Brazing is the joining of two materials by the introduction of a liquid metal filler

that on solidification holds the two materials together. The parent materials can

react with the braze alloy but remain solid during the process. This differs from

welding where the parent materials partially melt during the joining operation.
The process of brazing has been in use for several millennia, pictures of
craftsmen carrying out brazing operations have been found in an Egyptian
tomb from around 1475 BCE. This long history and development as an artisanal
skill has resulted in a wide imprecise vocabulary with similar terms having
different meanings in multiple languages. For example, by convention, English
differentiates between brazing and soldering when the liquidus temperature of
the filler is above or below 450°C respectively.
In this standard the term brazing is meant to cover also “soldering” processes
with filler materials melting at temperatures lower than 450°C. When the term

brazing is used, then this is meant equivalent to soldering in case that the filler

materials have liquidus temperature below 450°C.
Not all languages make the same distinction. To add to the confusion the filler

metal referred to as ‘silver solder’ is in fact a braze alloy and translations of

terms such as ‘soft brazing’ and ‘hard brazing’ are also freely used in several
languages.
The 450°C boundary in the past was convenient in that it allowed a
differentiation between the:
a. Higher temperature process producing strong structural joints
and,
b. Lower temperature processes used for sealing and joining
plumbing joints and now electronic systems.
Although this boundary is still used it is less relevant in modern brazing
systems where many lower temperature alloys, for example based on tin or
indium, have provided good structural joints in space systems. Soldering for
exclusively electronic applications has already been extensively covered by its
own standards and will not be covered by this standard.

A significant advantage of brazing is that with the correct selection of process,

flux system, braze alloy and joint design, reliable structural joints can be made

between almost any combination of parent materials. Within the space industry
we have successfully used brazing to make structural joints between metals,
ceramics, glasses, ceramic matrix composites (CMCs) and reinforced plastics.
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Often a brazing process is selected when a joint between complex material
combinations is required in difficult environments. As an example, outgassing
of brazed systems can be very low simplifying cleanliness aspects.
This standard specifies the necessary requirements to perform brazing for space
applications, and is comprised of the following clauses:
1. Brazing design,
2. Brazing and inspection personnel,
3. Equipment and facilities,
4. Brazing Procedure Specification (BPS),
5. Brazing inspection,
6. Joint acceptance criteria,
7. Brazing process verification,
8. Flight hardware production,
9. Quality assurance.

Figure 4-1 identifies the steps to be taken in order to produce a verified process

which can then be used to produce flight hardware.
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Brazing definition phase
Information relating to design (Clause 5):
Criticality of brazIng:
• Proposed application
• Safety class and quality levels (Clause 4.2)
• Design for brazed connection
• Acceptance criteria for Imperfections
• Design for Inspection: Inspectability,
(Clause 10)
Detectable limits
Definition of properties of brazed joints and assembly:
• Leak, Burst
• Mechanical properties
• Structural analysis
Optimum BRAZING DESIGN:
• Issue Engineering drawings
Brazing pre-verification phase

Equipement and facilities (Clause 7): Brazing and Inspection personnel (Clause 6):

• Equipment • Brazer and Brazing Operator training
• Material & consumables • Brazing Inspector training
Development of brazing parameters:
• Results from test samples
• Variation of brazing parameters
Brazing Inspection (Clause 9):
• Typical defects: Pores, Cracks, etc
• Suitable NDI&DI technique(s) that can detect
defects
Establish working process window
• Actual joints, Window limits
• Joint properties evaluation (can meet
requirements)
• Cleanliness (Clause 8.4)
Optimum BRAZING PROCESS:
• Issue preliminary BPS (Clause 8)
Brazing verification
• Issue BRAZING VERIFICATON TEST PLAN
phase
(BVTP) (Clause 11.2)
Production of samples with pBPS
Production of re-brazing samples (Clause 11.5)
Production of repair brazing samples (Clause 11.6)
Test campaign
• Visual inspection
Delta verification, if change of
• NDT inspection
BPS parameters (Clause 11.4)
• Metallographic inspection Acceptance criteria
not met
• Property evaluation
Acceptance criteria met
VERIFIED BRAZING PROCESS:
• Issue BPS (Clause 8)
• Issue BVTR (Clause 11.7)
Brazing and Inspection personnel (Clause 6):
• Brazer and Brazing Operator certification
• Brazing Inspector certification
Production of
Tests in production (Clause 12.2):
flight hardware
• Production of α / β samples (pre- and post test)
or other approach if agreed with customer
• NDT inspection (RX, US, etc.)
• Visual and dimensional inspection
If needed:
• Re-brazing (Maximum two
attempts) (Clause 11.5)
• Repair brazing (Clause 11.6)
Service

Figure 4-1: Steps for brazing process verification and flight hardware production

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4.2 Classification of safety classes and quality levels
4.2.1 Overview
Brazed joints follow the same definition as welded joints for the classification
related to safety classes depending on their function. Furthermore, the
acceptance criteria for imperfections are by definition of three quality levels.
4.2.2 Safety classes

Class 1 joints are considered critical and structural. Failure of a Class 1 joint

results in a loss of spacecraft, major components, loss of life, or loss of control of

the spacecraft. Class 1 joints have the highest level of scrutiny in terms of
acceptance, which is appropriate to the criticality of performance including
internal and external brazing joint integrity verification.
Class 2 joints are non-critical but structural; their failure can reduce the

efficiency of the system but not cause the loss of the spacecraft. Class 2 joints

require brazing joint integrity verification (either external, internal, or both)

appropriate for the intended application.
Class 3 joints are non-critical and non-structural and are contained so that
failure does not affect other flight elements. These joints require minimal
brazing joint integrity verification, the controls are mainly visual.
For all classes the design and engineering authority has the responsibility to
declare a part structural or not.
4.2.3 Quality levels

In brazing joints it is inevitable that some defects and features can be present.

The acceptability of such defects or features differ by their nature and size and

are assigned for the purpose of quality inspection to three quality acceptance
levels (A, B or C) according to the compliance with the component requirement.
Level A represents the more stringent requirements and Level C the least
stringent requirements and B is in between A and C.
For the selection of the Quality levels see clause 10.4.
4.3 Tailoring of the brazing acceptance criteria
Verification of brazed products takes into account the requirements and
acceptance criteria of thi
...

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