Space product assurance
Control of limited shelf-life materials
Foreword
This Standard is one of the series of ECSS Standards intended to be applied together for the management, engineering and product assurance in space projects and applications. ECSS is a cooperative effort of the European Space Agency, national space agencies and European industry associations for the purpose of developing and maintaining common standards. Requirements in this Standard are defined in terms of what shall be accomplished, rather than in terms of how to organize and perform the necessary work. This allows existing organizational structures and methods to be applied where they are effective, and for the structures and methods to evolve as necessary without rewriting the standards.
This Standard has been prepared by the ECSS Executive Secretariat, endorsed by the Document and Discipline Focal points, and approved by the ECSS Technical Authority.
Disclaimer
ECSS does not provide any warranty whatsoever, whether expressed, implied, or statutory, including, but not limited to, any warranty of merchantability or fitness for a particular purpose or any warranty that the contents of the item are error-free. In no respect shall ECSS incur any liability for any damages, including, but not limited to, direct, indirect, special, or consequential damages arising out of, resulting from, or in any way connected to the use of this Standard, whether or not based upon warranty, business agreement, tort, or otherwise; whether or not injury was sustained by persons or property or otherwise; and whether or not loss was sustained from, or arose out of, the results of, the item, or any services that may be provided by ECSS.
Published by: ESA Requirements and Standards Division
ESTEC, ,
2200 AG Noordwijk
The
Copyright: 2008 © by the European Space Agency for the members of ECSS
Change log
|
ECSS-Q-70-22A
|
First issue
|
|
ECSS-Q-70-22B
|
Never issued
|
|
ECSS-Q-ST-70-22C
|
Second issue
|
Scope
Several classes of materials depend on a chemical reaction for their application and their final properties are sensitive to the exact composition of the reactants. The final properties vary with the reactants’ age and storage condition.
This Standard defines the requirements for the identification, handling, storage and control of limited shelflife materials employed in the fabrication of spacecraft and associated equipment.
This standard may be tailored for the specific characteristic and constrains of a space project in conformance with ECSS-S-ST-00.
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.
|
ECSS-S-ST-00-01
|
ECSS system – Glossary of terms
|
|
ECSSQST10-09
|
Space product assurance – Nonconformance control system
|
|
ECSSQST40
|
Space product assurance Safety
|
|
ECSSQST70
|
Space product assurance Materials, mechanical parts and processes
|
Terms, definitions and abbreviated terms
Terms defined in other standards
For the purpose of this Standard, the terms and definitions from ECSSSST0001 and ECSSQST70 apply.
Terms specific to the present standard
batch
quantity produced at one operation
One batch can be subdivided into several lots.
shelflife
period of time during which a material can be processed to produce final properties with consistently stable parameters
Abbreviated terms
For the purpose of this Standard, the abbreviated terms from ECSS-S-ST-00-01 and the following apply:
|
Abbreviation
|
Meaning
|
|
RH
|
relative humidity
|
Requirements
Control of material life
Hazards, health and safety precautions
Materials and parts with hazardous characteristics shall be identified and manage in conformance with the “Safety programme plan” specified in ECSSQST40.
Procedures to control hazards, health and safety to personnel, equipment or materials shall be defined and implemented.
Material control
Procurement document
For procurement specifications and purchase orders, the date of manufacture, storage conditions and shelflife of the products shall be declared.
Identification
Materials shall be labelled with the shelflife and the date of the beginning of life or the date of manufacture (see clause 4.1.3).
In some critical applications, the project can reduce the shelflife as originally stated by the manufacturer or supplier in order to meet particularly stringent product assurance requirements.
For quantities which are split from a batch, it shall be ensured that materials are fully traceable to it and bear the same date and life indications.
Storage
Materials shall be stored in a nominally clean area at (22 3) C with a relative humidity of (55 10) % unless specified otherwise by the manufacturer or supplier.
A wide range of preimpregnated composites, adhesives and related materials which are used in the fabrication of spacecraft structures at lower temperatures to preserve their shelflives. Refer to clause 4.1.3.
Storage areas shall be organized and controlled in such a way that limited shelflife items are identified.
The reason is to avoid the possibility of overaged material being used.
Handling
Materials shall be handled with clean lintfree or nylon gloves unless their use is precluded for reasons of safety.
For example, when handling corrosive, toxic and oxidizing substances.
Assessment of shelflife
If the shelflife cannot be obtained, the following steps shall be performed:
- Certify the material at incoming inspection.
Perform tests relevant to the application of the material to ensure that the properties are within those values either specified within the procurement specification or in the manufacturer’s data sheet (where no procurement specification exists).
- Where satisfactory results are obtained, state that the material has spent half its shelflife at the time of delivery.
- If the results are not satisfactory, reject the material.
- Put the date of manufacture and shelflife on the label attached to limited shelflife material in conformance with clause 4.1.2.2. The quantity in each container shall be compatible with the planned short term usage.
The reason is that the number of container openings is kept to the minimum possible.
Materials shall be decanted from larger into smaller containers if there is large air space above the material.
For materials which are stored at temperature below zero, a system shall be defined and implemented to record the time exposed to room temperature and the consequent reduction in shelflife when returned to low temperature storage.
For materials normally stored at low temperature (below zero), exposure to room temperature can dramatically reduce the shelflife.
It shall be ensured that all materials stored at temperatures below room temperature are allowed to attain room temperature prior to use.
Extension of shelflife (recertification)
To extend the shelf-life of a material that has exceeded its shelflife, the following activities shall be performed:
- Recertify the material for the first time by using the relevant tests in conformance with clause 4.1.6;
- If the first re-certification is successful, extend the shelflife equal to half the initial shelflife;
- Recertify the material for the second time on a casebycase basis depending on product, application, storage and user experience;
- If the second re-certification is successful, extend the shelflife to half of the first extension.
If a fully traceable, nonoveraged batch is suspect, for any reason, the user shall submit it for recertification.
Batches awaiting results of a recertification process separately and shall be labelled as “suspended”.
Disposal of materials
In case further recertification is not permitted or traceability has been lost for a batch, or part of a batch, the user shall dispose the material in conformance with the product assurance rules applicable to the project.
Acceptance criteria, recertification testing
Recertification of material shelflife shall be achieved by retesting the material to verify that its properties are still within their specified limits.
Retesting shall include those properties specified in the procurement specification or performed during incoming inspection.
The choice of properties to be measured is based on a combination of the final application of the material and its processing.
The choice of properties to be measured and test methods to be used shall be subject to the approval of product assurance.
For examples of properties to be measured see Annex B.
Quality assurance
Data
Quality records shall be retained for ten years or in conformance with project business agreement requirements.
E.g. logbooks.
The quality records shall be in conformance with Annex A.
Calibration
Any measuring equipment shall be calibrated to traceable reference standards.
Any suspected or actual equipment failure shall be recorded as a project nonconformance report according to the NCR DRD in ECSSQST10-09.
This is to ensure that previous results are examined to ascertain whether or not reinspection and retesting is necessary.
ANNEX(normative)Shelf-life material evaluation report - DRD
DRD identification
Requirement identification and source document
This DRD is called from ECSSQST70-22, requirement 4.2.1b.
Purpose and objective
The purpose of the document is to describe the contents of the evaluation report for the control of limited shelf-life materials.
Expected response
Scope and content
The evaluation report shall contain the supplier’s certification and definition of storage conditions.
The evaluation report shall contain the copy of incoming inspection documentation.
The evaluation report shall contain the nonconformance reports and corrective action (if applicable).
The evaluation report shall contain the record of storage conditions and recertification testing.
Special remarks
None.
ANNEX(informative)Examples of properties to be measured
Properties which can be measured in order to gain recertification are:
Properties related to the individual components and the cure process that are particularly sensitive to the effects of ageing:
molecular weight distribution as determined by gel permeation chromatography;
molecular structure as determined by infrared spectroscopy;
degree of cure, cure exotherm and glass transition temperature as determined by differential scanning calorimetry;
measurement of pot life;
measurement of resin flow characteristics, such as gel time (particularly important in the case of fibre reinforced materials);
measurement of the degree of tackiness in the case of preimpregnated materials.
Properties related to the materials application are measured on cured samples:
adhesives - adhesive strength as determined by lap shear testing;
coatings (paints and varnishes) - adhesion to the relevant substrate using measurements of peel and pulloff strength (see ECSSQST7013);
conformal coatings - hardness, adhesion properties;
potting compounds - hardness, electrical or thermal characteristics;
fibrereinforced materials - resin/fibre/void content using chemical digestion techniques. Measurement of relevant mechanical properties such as tensile strength or flexural strength.
Bibliography
|
ECSS-S-ST-00
|
ECSS system – Description, implementation and general requirements
|
|
ECSSQST7013
|
Space product assurance Measurement of the peel and pulloff strength of coatings and finishes using pressuresensitive tapes
|