Developing Inspection Procedures from ASTM LPI and MPI Standard Practices

Transcription

1 Dr Gary Mar<n, Paul Grosser and Malcolm Oakey Aircra& Inspec-on and Maintenance- Higher Standards, Be9er Compliance October, Coogee, NSW

2 NDT Procedures are a set of detailed instructions that enable an NDT technician to complete inspection of critical aircraft components. Often these Procedures are produced by Original Equipment Manufacturers (OEM s), maintenance organisations and sometimes the Civil Aviation Safety Authority (CASA). What is an NDT Procedure? Is it just a list of operations to followed during an inspection? NO!!! Developing Inspection Procedures It s a document that, if followed ensure not only the safety of the aircrak and NDT technician but permits traceability of results.

3 Recently CASA published Airworthiness Bulletin AWB Issue 1 18 September 2017, NDT data - The use of during the course of maintenance. This AWB applies to all aircraft and aeronautical products maintained in accordance with the 1988 Civil Aviation Regulations (CAR). The purpose of the AWB is to clarify: approval of Non Destructive Testing (NDT) data, the different ways NDT data can be presented, the precedence of different NDT data approvals, and how to control NDT data to ensure its proper use. Importantly CASA requires all non OEM NDT Procedures to have Civil Aviation Regulation (CAR), specifically CAR 2A, approval before they can become Approved Data.

4 Under the more recent 1998 Civil Aviation Safety Regulations (CASR) a Part 42 organisation, i.e. a Continuing Airworthiness Management Organisation (CAMO) is responsible for the airworthiness of the aircraft and it has the responsibility to ensure the Part 145 maintenance organisation, i.e. the Approved Maintenance Organisation (AMO) has the correct maintenance instructions. The Part 145 AMO must ensure it has the correct maintenance instructions, in this case NDT Procedures. Either organisation can produce maintenance data as long as it is produced and approved as described in the respective Manual of Standards (MOS). This is a legal requirement under the regulations (CASR).

5 Where OEM Procedures are provided they must be used for the inspection. OEM s often include the following in their Inspection Manuals: 3. References Magnetic Particle Inspection shall be carried out in accordance with Standard Practice for Magnetic Particle Examination ASTM E1444. ASTM-E-1417 is referenced when LPI is required. There are also examples where inspection procedures are not available or may be inappropriate for some components. Under the CAR 1988 CASA has approved a number of General Inspection Procedures for Liquid Penetrant Inspection and Magnetic Particle Inspection - attached to draft Civil Aviation Advisory Publication (CAAP) These procedures may be considered approved maintenance data

6 Use of this maintenance data is subject to the following conditions : the maintenance data mentioned in paragraph 2A(2)(a), (b), (c) or (d) of CAR is inadequate for the purpose the person carrying out the maintenance on the aircraft, aircraft component or aircraft material first determines that the instructions are: o appropriate to the aircraft, aircraft component or aircraft material to be maintained o directly applicable to the maintenance that is to be carried out o not contrary to, or inconsistent with the manufacturer s data; or any other applicable approved maintenance data mentioned in regulation 2A of CAR. Some of the procedures in the CAAP may be used in place of: Australian Standard (AS) 2062 American Society for Testing and Materials (ASTM)-E-1417 or a European equivalent a generic European Standard for penetrant testing a Department of Defence standard for penetrant testing

7 These procedures could also provide the basis for maintenance data developed under the 1988 CASR. Material contained in the Draft CAAP only covers the inspection portion of the inspection procedure. More material will be required to create a complete Inspection Procedure and this will be outlined later. Procedures developed for any components need to refer back to the requirements of the ASTM Standards upon which it must be based, either ASTM E 1417 or ASTM E Procedures may be drafted by an NDT Level 3 or by an NDT Level 2 Technician approved in the relevant method. Procedures should follow a consistent format and after drafting need to be reviewed by a Level 3 NDT Technician who may make amendments before approving the procedure. Under the 1988 CAR once the Level 3 has approved the Procedure it must be forwarded to CASA for CAR 2A (4) approval or to an authorised delegate for approval prior to use.

8 Procedure Format standard formats should be followed to ensure no steps are overlooked nor important material omitted. a typical standard format for surface method NDT procedures is: 1. Procedure designation - A unique identifier for a stand-alone document. Including aircraft type, Inspection Method, inspection by name or number, issue number and date. eg: ATTAR/B200/ LPI/wing spars 1 issue 1 dated 13 October Provision for revision must be made. 2. Procedure title - A clear concise statement, including aircraft type, inspection method and approximate location of the inspection. The title should be in bold type larger than normal text. 3.Approval authority A table including Author, Position of the Author and signature, Date of Issue, Regulatory Authority Approval, Number, Name and Signature. 4. Introduction a paragraph briefly outlining reason for inspection linking it to an Airworthiness Directive (AD) or similar. Use photographs or diagrams showing inspection location within the aircraft or component

9 5. Scope a paragraph indicating what the procedure is applicable to, what type of defects, and minimum detectable defects sought. Detection reliability should be included here. 6. Personnel qualification and level - Refers to the NAS 410 level; Trainee, Level 1 Limited, Level 1, 2 or 3 classification of the NDI Technician eligible to carry out the Procedure. 7. References Include all relevant references, e.g. ASTM E 1444, here. 8. Safety - All safety requirements covering equipment, consumables and site must be included. 9. Equipment - A list of equipment required to carry out the inspection, covers both plant and consumables, including lighting requirements and sensitivity levels where applicable. General equipment such as rags and marking pens etc need not be listed. 10. Pre-inspection requirements - A list of what has to be done to the aircraft or component prior to the commencement of the Inspection. Any process that may cause deformation of the surface must be avoided.

10 11. Inspection - This is a set of detailed instructions on how to perform the inspection. The use of photographs and diagrams is encouraged where possible. 12. Acceptance/Rejection Criteria - A clear statement of what discontinuities are acceptable and or unacceptable. 13. Post Inspection Requirements - This is generally a short statement to ensure all equipment used to carry out the inspection is removed from the aircraft. Post cleaning requirements are included here. 14. Reporting Requirements for recording and reporting of the inspection results are detailed here. 15. Annexes - Annexes are used to include supporting information from another source or defect logging diagrams etc. if appropriate.

11 ASTM Standard Practice and Draft CAAP The ASTM Standard Practices contain information that may not be relevant to every inspection which is why a Level 3 is required to review and approve Procedures before they are sent for regulatory authority approval. The following is a interpreta<on guide of some of the specific statements in the ASTM which we hope will enable the produc<on of workable procedures from those statements, giving due considera<on to the part to be inspected and the defects sought. It is not exhaustive and further assistance may be required.

12 ASTM E Standard Practice for Magnetic Particle Examination. This covers all magnetic particle inspections and is therefore going to contain much more information than required in any one inspection procedure. Head shot on bench Camshaft cracking Coil shot on bench In the aircraft industry most magnetic particle inspection is done on a bench with a head, central conductor or coil. Though the draft CAAP does permit the use of electromagnetic yokes.

13 Magne<c par<cle carrier may be water but it does require the addi<on of both surfactants and corrosion inhibitors - Safer Hydrocarbon based carrier is easier to work with and does not have foaming or corrosion issues. Magnetic particle concentration is critical care needed to ensure it is always within the specified range - regular concentration checks. When working with electromagne<c yokes the consumables normally come in Cer<ficated aerosol cans - par<cle concentra<on checks are not required. Any procedure using them must include a reminder to adequately shake the cans to ensure appropriate par<cle distribu<on.

14 Clause To ensure the detection of discontinuities in any direction, each part must be magnetized in a minimum of two directions at approximately right angles to each other. Depending on part geometry, this may be circular magnetization in two or more directions, multiple circular and longitudinal magnetization, or longitudinal magnetization in two or more directions. If the discontinuity sought is known then magnetisation only needs to be at right angles to the known orientation. If a part is being checked for any discontinuities then the need to magnetise in 2 directions at right angles remains.

15 The same clause indicates that the pie gauge or flexible laminated strips shall not be used to determine field strength. i.e. Castrol, Burmah or Ely strips may not be used to indicate field strength, only orientation. Exceptions necessitated by part geometry, size, or other factors require specific approval of the Cognizant Engineering Organization. Clause tells us that prods may not be used on aircraft components.

16 Clause indicates the field strength in unidirec<onal, or mul<direc<onal magne<zing applica<ons, is best assessed for adequacy by examining parts having known or ar<ficial discon<nui<es of the type, size, and loca<on specified in the acceptance requirements or by using the notched shims as detailed may also be used. In unidirec<onal magne<sa<on a Hall Effect probe gaussmeter may be used to measure the peak values of the tangen<al field provided its strength is minimum of 30 Gauss ( Tesla [T]).

17 All inspections should be done using the wet continuous method. Magnetizing current shall be applied for a duration of at least 0.5 second for each application, with a minimum of two shots being used. The second shot shall follow the first while the particles are still mobile on the surface of the part. When evaluating indications using fluorescent materials, personnel shall not wear eye glasses that are photochromic or that have permanently darkened lenses. This is not intended to prohibit the use of eyeglasses with lenses treated to absorb ultraviolet light as the light from the indication is not UV. Black lights have changed significantly over the last couple of decades with LED units now becoming very popular. When used all UV lights still need to produce a minimum of 1000µWatt/cm 2 at the surface of the part.

18 Draft CAAP 33-02, requires the following minimum ancillary equipment for magnetic particle testing using a fixed bench : black and white light meter 100 ml pear-shaped centrifuge tool steel ring (Ketos ring) or known cracked specimen flexible Type II laminated strips field indicator (Gauss meter) shunt meter for ammeter verification black light (capable of 1,000µW/cm² minimum at 38cm) fluorescent particle mixture conforming to AMS 3046 Developing Inspection Procedures inspection lights, mirrors and magnifiers. Marking media which won t damage the part

19 For testing with electromagnetic yokes it requires: black and white light meter black light (capable of 1,000µW/cm² minimum at 38cm) light restricting cloak of an appropriate size marking media which will not damage the part, mirror and rule hand-held AC/HWAC magnetic yoke type II laminated strips (or equivalent) AMS 3046 fluorescent particle mixture field indicator (Gauss meter). More information may be found in ASTM E Standard Guide for Magnetic Particle Testing which is intended as a reference to aid in the preparation of specifications/standards, procedures and techniques.

20 ASTM-E Standard Practice for Liquid Penetrant Testing. In Australia penetrant inspection on aircraft and components is supposed to be restricted to the use of Fluorescent penetrants because of the fluorescence quenching effects of residual colour contrast penetrants on subsequent fluorescent penetrants and because fluorescent penetrants have higher sensitivity levels. Not sure everyone is aware of this! The Standard practice covers all penetrant types, all penetrant remover types and all developer types. Most commonly used inspection systems in Australia are: Solvent removable, Water washable and Hydrophilic remover.

21 Draft CAAP requires the following basic equipment for Penetrant testing : Developing Inspection Procedures dip tanks or spray equipment black light (capable of 1,000 µw/cm² minimum at 38 cm) light restricting cloak of an appropriate size marking media which won t damage the part, mirror and rule UV and white light meter process performance test pieces (testing and monitoring panels or similar) for systems other than pressure pack materials.

22 For specific procedures ASTM has specific Standard Practice documents as follows: E Standard Practice for Fluorescent Liquid Penetrant Testing Using the Water Washable Process E Standard Practice for Fluorescent Liquid Penetrant Testing Using the Hydrophilic Post-Emulsification Process E Standard Practice for Fluorescent Liquid Penetrant Testing Using the Solvent Removable Process The inspection process for all of these methods is similar with the variation being the removal of excess penetrant. Prepare the surface avoiding mechanical damage Mask any internal cavities avoids excessive bleed out Apply Penetrant by spray, immersion or brush Drain for dwell time. Penetrant collected may be re-used. Do not exceed as penetrant in the discontinuities may dry out.

23 Excess penetrant is to be removed from the surface by one of the three following methods: E , solvent removal - removed by wiping with clean, lintfree material - done under UV light. Finish using lint-free material lightly moistened with the solvent remover. Spraying or dipping the surface with solvent to remove the excess penetrant is prohibited. E , water wash - avoid overwashing. Developing Inspection Procedures water temperature and pressure requirements as well as wash technique must be adhered to - also under UV light. When examining single components it is better to wipe clean in the same manner as for solvent removable penetrant.

24 E , hydrophilic remover - used when processing larger numbers of components. Developing Inspection Procedures requires intial pre-rinse of the developer, unless spraying the emulsifier, followed by immersion in an air agitated bath for a specified time. Effective post-rinsing can be accomplished using either manual, semiautomatic, or automatic water spray or immersion equipment or combinations thereof. After washing, parts must be dried prior to developer application. Best in an air recirculating oven that does not exceed 70 o C. Parts should be removed from the oven once dry as excessive dwell time will dry penetrant in discontinuities. Other techniques such as air blast may be used.

25 Developer may be applied by spraying, immersion dusting, immersing, flooding, or spraying. T size, configuration, surface condition, number of parts to be processed, etc., controls choice of developer and application technique. Single components are best coated with a solvent based developer. Developer time commences when the developer is completely dry on the part. Multiple components are best done with dry powder in cloud chamber or The longer developer is left on the part the more diffuse the indication so if indications are to be measured for evaluation it must be done within the stipulated time frame. After inspection parts should be cleaned so that any penetrant or developer is removed by washing with warm water. Blow out passages and cavities with dry air to prevent contamination or corrosion of the part.

26 Conclusion: Inspec<on procedures cover more than the inspec<on itself and an outline of the requirements of such a document has been provided. It will be necessary to consult a number of documents in order to develop the procedure for par<cular inspec<ons. The DraK CAAP provides a good star<ng point for the basic inspec<on procedure but more informa<ve detail may be found in the ASTM Standard Prac<ce documents.