nes 872 part 4 procedures for first level nickel aluminium bronze castings - category 1

Procedures for First Level NickelAluminium Bronze Castings

Part 4

Inspections outside of Long OverhaulPeriods

Ministry of Defence Defence Standard 02-872 Part 4

Issue 1 Publication Date 02 December 2002

Category 1

AMENDMENTS ISSUED SINCE PUBLICATION

AMD NO DATE OFISSUE

TEXT AFFECTED SIGNATURE &DATE

Revision Note

This Issue of this Standard has been prepared to incorporate changes to text and presentation.The technical content has been updated in line with current practice.

Historical Record

D/DGFS(S)/SM511A/743/20/GEN-T memo Feb 95

1DEFENCE STANDARD 02-872

PROCEDURES FOR FIRST LEVEL NICKEL ALUMINIUM BRONZE CASTINGS

PART 4

ISSUE 1

INSPECTIONS OUTSIDE OF LONG OVERHAUL PERIOD

This Defence Standard

Is authorised for use in MOD contracts

By the Defence Procurement Agency

And the Warship Support Agency

Published By:

Defence Procurement AgencyAn Executive Agency of the Ministry of DefenceUK Defence StandardizationKentigern House65 Brown StGlasgow G2 8EX

2SCOPE

1. This procedure is to be used for in-service inspections carried out outside of the LongOverhaul Period. This process is used to gauge the overall health of all Nickel AluminiumBronze (NAB) contained in the NAB Register of a submarine by detailed examination of asample of NAB castings.

2. Castings are to be chosen for inspection from the assessments carried out usingNABWETLIFE or as requested by the Design Authority.

3. Part 1 of this Defence Standard covers the policy for the recording and updating of NickelAluminium Bronze castings fitted in submarines to meet the First Level Quality Assurancerequirements in accordance with SSP 25.

4. Part 2 of this Defence Standard is to be used for the validation of all Submarine First Levelcastings made of Nickel Aluminium Bronze (NAB) manufactured to Defence Standard 02-747 Part 1, 2 or 4. It is to be used to establish a baseline of data for any weld repairs, wallthickness measurements and the integrity of the casting at manufacture.

5. Part 3 of this Defence Standard is to be used for the revalidation of Submarine First Levelcastings made of Nickel Aluminium Bronze (NAB) manufactured to DGS 8520, DGS 348 orDefence Standard 02-747 Part 1, 2 or 4 which have had service use involving contact with seawater.

FOREWORDSponsorship

1. This Defence Standard is sponsored by the Warship Support Agency, Ministry of Defence(MOD).

2. The complete Defence Standard 02-872 comprises:

Procedures for First Level Nickel Aluminium Bronze castings.

Part 1: Policy

Part 2: Validation

Part 3: Revalidation

Part 4: Inspections Outside of Long Overhaul Period

3. If it is found to be unsuitable for any particular requirement the MOD is to be informed inwriting of the circumstances.

4. Any user of this Defence Standard either within MOD or in industry may propose anamendment to it. Proposals for amendments that are not directly applicable to a particularcontract are to be made to the publishing authority identified on Page 1 and those directlyapplicable to a particular contract are to be dealt with using existing procedures.

5. No alteration is to be made to this Defence Standard except by the issue of an authorizedamendment.

6. Unless otherwise stated, reference in this Defence Standard to approval, approved, authorizedor similar terms, means the MOD in writing.

DEF STAN 02-872 Pt 4 / Issue 1

37. Any significant amendments that may be made to this Defence Standard at a later date will beindicated by a vertical side line. Deletions will be indicated by 000 appearing at the end of theline interval.

8. Extracts from British Standards within this Defence Standard have been included with thepermission of the British Standards Institution.

Conditions of Release

General

9. This Defence Standard has been devised solely for the use of the MOD, and its contractors inthe execution of contracts for the MOD. To the extent permitted by law, the MOD herebyexcludes all liability whatsoever and howsoever arising (including but without limitation,liability resulting from negligence) for any loss or damage however caused when the DefenceStandard is used for any other purpose.

10. This document is Crown Copyright and the information herein may be subject to Crown orthird party rights. It is not to be released, reproduced or published without written permissionof the MOD.

11. The Crown reserves the right to amend or modify the contents of this Defence Standardwithout consulting or informing any holder.

MoD Tender or Contract Process

12. This Defence Standard is the property of the Crown. Unless otherwise authorized in writingby the MOD, it must be returned on completion of the contract, or submission of the tender, inconnection with which it is issued.

13. When this Defence Standard is used in connection with a MOD tender or contract, the user isto ensure that they are in possession of the appropriate version of each document, includingrelated documents, relevant to each particular tender or contract. Enquiries in this connectionmay be made to the Authority named in the tender or contract.

14. When Defence Standards are incorporated into MOD contracts, users are responsible for theircorrect application and for complying with contractual and other statutory requirements.Compliance with an Defence Standards does not of itself confer immunity from legalobligations.

Categories of Naval Defence Standard

15. The Category of the Naval Defence Standards has been determined using the followingcriteria:

a) Category 1. If not applied may have a Critical affect on the following:Safety of the Vessel, its complement or third partiesOperational performance of the vessel, its systems or equipment.

b) Category 2. If not applied may have a Significant affect on the following;Safety of the Vessel, its complement or third partiesOperational performance of the vessel, its systems or equipment.Through life costs and support.


4c) Category 3. If not applied may have a Minor affect on the following.MOD best practice and fleet commonality.Corporate experience and knowledge.Current support practice.

Related Documents

16. In the tender and procurement processes the related documents in each Section and Annex Acan be obtained as follows:

a) British Standards British Standards Institution, 389 Chiswick High Road, London, W4 4AL b) Defence Standards Defence Procurement Agency

An Executive Agency of the MoDUK Defence Standardization,Kentigern House, 65 Brown Street,Glasgow G2 8EX

c) Other documents Tender or Contract Sponsor to advise.

17. All applications to Ministry Establishments for related documents are to quote the relevantMOD Invitation to Tender or Contract Number and date, together with the sponsoringDirectorate and the Tender or Contract Sponsor.

18. Prime Contractors are responsible for supplying their subcontractors with relevantdocumentation, including specifications, standards and drawings.

Health and Safety

Warning

19. This Defence Standards may call for the use of processes, substances and procedures that maybe injurious to health if adequate precautions are not taken. It refers only to technicalsuitability and in no way absolves either the supplier or the user from statutory obligationsrelating to health and safety at any stage of manufacture or use. Where attention is drawn tohazards, those quoted may not necessarily be exhaustive.

20. This Defence Standards has been written and is to be used taking into account the policystipulated in JSP430: MOD Ship Safety Management System Handbook.


5

Use of ARDROX 160 and silver nitrate solution

21. Before using this Defence Standards in connection with Ardrox 160 and the silver nitratesolution, users should make themselves familiar with the precautionary measures set out inthis Section.

22. Care is to be taken to ensure that the silver nitrate etching solution does not come into contactwith the skin or eyes, eg a face mask and rubber gloves must be worn.

23. Protective clothing should be worn and other measures taken as necessary in handling thematerials referred to in this Defence Standards.

24. Ardrox 160 is a proprietary product and the manufacturers health and safety instructions mustbe followed.

Additional information.

(There is no relevant information)


6CONTENTS

Page No

TITLE PAGE 1

SCOPE 2

FOREWORD 2

Sponsorship 2

Conditions of Release 3

Categories of Naval Defence Standard 3

Related Documents 4

Health and Safety 4

CONTENTS 6

SECTION 1. GENERAL REQUIREMENTS 81.1 NABWETLIFE Code 81.2 Selection of Castings for Inspection 81.3 Identification 81.4 Pre-requisites 8

SECTION 2. CLEANING OF CASTINGS 92.1 General 92.2 Shore Based Cleaning and General Etching 92.2.1 Cleaning Method 1 102.2.2 Cleaning Method 2 102.2.3 General Etching Method 102.3 In Situ Cleaning 112.3.1 In Situ Cleaning Method 11

SECTION 3. SHORE BASED EXAMINATION FOR CORROSION 113.1 General 113.2 Visual Examination 113.3 Thickness Check 123.4 Detection of Corrosion 123.4.1 Detailed Etching Method 123.4.2 Ultrasonic Corrosion Detection 123.5 Removal of Corrosion 133.6 Post Dressing Thickness Gauging 133.7 Recording of Examination Results 133.8 Corrosion Limits 14


7SECTION 4. INSPECTION ACCEPTANCE CRITERIA 144.1 Cleaning 144.2 Removal of Corrosion 154.3 Wall Thickness 154.4 Re-installation 154.5 Re-Stamping 154.6 Certification 154.7 Records 16

SECTION 5. IN SITU EXAMINATIONS 165.1 In situ Cleaning 165.2 Ultrasonic Thickness Checks 165.3 In Situ Etching Method 165.4 Ultrasonic Corrosion Measurements 175.5 Records 175.6 Acceptance Criteria 17

ANNEX A. RELATED DOCUMENTS 18

ANNEX B. DEFINITIONS AND ABBREVIATIONS 19

ANNEX C. PROCUREMENT CHECK LIST 20

ANNEX D CASTING RECORD OF REVALIDATION INSPECTION 21

ANNEX E REVALIDATION CERTIFICATE FOR NAB CASTINGS 22

ANNEX F CHECK LIST FOR DOCUMENTS TO BE INCLUDEDIN THE QA PACK FOR REVALIDATED CASTINGS 23

ALPHABETICAL INDEX 24


81. GENERAL REQUIREMENTS

Related Documents: DGS 8520, see also Annex A

a. Extensive examinations have shown that the Nickel Aluminium Bronze (NAB)castings used since the early 1960s are, to varying degrees, susceptible to normaland selective phase attack by sea water. The selective phase corrosion occursunder crevices and in the Heat Affected Zones (HAZ) of weld repairs. Thisdestroys the mechanical properties of the material without any obvious change inthe appearance of the materials surface.

b. To limit the effect of this corrosion problem, it is necessary to examine NABcastings prior to fitting in critical positions, and to carry out periodic examinationsduring their life. These examinations are termed Validation and Revalidationrespectively.

c. Outside of Long Overhaul Period, examination of individual castings may berequired by Design Authority, for example high risk castings predicted by theNABWETLIFE code, or to provide information to assist in the commissionextension safety justification and life extension safety justification.

1.1 NABWETLIFE Code

a. NABWETLIFE is a computer code, written by MOD, which has been devised toaddress the problem of how NAB corrosion affects the safe diving periods ofsubmarines. The aim of the program is to recommend when castings should beremoved/replaced outside of Long Overhaul Period to achieve the maximum safewetted life for a submarine. The high risk castings recommended byNABWETLIFE are removed from the submarine at a suitable Upkeep Period egRAMP, and examined to the requirements of this specification.

1.2 Selection of Castings for Inspection

a. Castings for inspection are to be selected by the Design Authority.

1.3 Identification

a. Previously validated/revalidated castings should be stamped with a code whichuniquely identifies them. The code consists of the radiographic number which maybe preceded by the letters H or HA. The letters H and A indicate that the castinghas been heat treated and weld repaired respectively. Castings manufactured tospecifications subsequent to DGS 8520 will have their specification indicated,followed by letters VAL and the date. The letters VAL and the date show that thecasting has been previously validated/revalidated on the date shown.

1.4 Pre-Requisites

a. A casting examination control facility is required at the repair source, togetherwith a register of properly trained personnel who have the necessary experience tocarry out the procedures described in this Defence Standard. The Design Authoritywill define what level of training and experience is necessary.


9b. The Examination Contractor is to demonstrate to the Design Authority that theprocedures necessary to control and document the application of this DefenceStandard are in place before work is carried out.

c. The following documentation on each casting is to be made available to theexamination personnel prior to commencement of the examination:-

(1) Drawings with dimensions and wall thicknesses

(2) Casting radiographic interpretation sheets

(3) Weld repair details

If the documentation is not available, advice is to be sought from the DesignAuthority.

d. Examination Contractors who find information on the castings which does notcorrespond to that on the QA documentation should refer to the Design Authorityfor advice on further action.

2. CLEANING OF CASTINGS

Related Documents: Def Stan 68-188, Def Stan 80-20, see also Annex A

2.1 General

a. The sea water wetted surface of the castings will be covered with varying degreesof bio fouling, calcareous deposits and redeposited copper which can be difficultto remove.

b. Any cleaning process must use methods which are not detrimental to the casting.Special care should be taken to protect machined surfaces. Approved methods ofcleaning NAB castings include hydrojetting with or without entrained abrasives,dry blasting with alumina grit and Chemical Dip. Metal will be removed with anyblasting process and care will be required to prevent damage to the casting. Thenozzle must be kept moving at all times i.e. castings should be swept blast andmachined surfaces must be masked.

c. Suitable methods of cleaning are described in Clauses 2.2.1 and 2.2.2. Thecontractors cleaning procedure and the training of operators must have DesignAuthority written approval.

d. Cleaning of castings must be carried out by staff who are suitably experienced.

e. Where examination of castings is required outside of a Long Overhaul Period, it ispreferable for the casting to be removed from the submarine so that the examinationcan be carried out at a suitably equipped shore based facility. However, wherecastings are too large to remove from the submarine without a hull cut, in-situinspection may be required. Procedures to be followed for shore based inspectionare described in Clause 2.2 and Section 3. Procedures for in situ inspection aredescribed in Clause 2.3 and Section 5.

2.2 Shore Based Cleaning and General Etching

a. The surfaces of the casting that have been in contact with sea water are to becleaned by an approved method, as described below. Cleaning Method 1 should be


10

used to remove all marine growth and surface corrosion products. This should befollowed by Cleaning Method 2 to provide clean, degreased surfaces for etching.

2.2.1 Cleaning Method 1

a. Approved methods of mechanically cleaning NAB castings include hydrojettingwith or without entrained abrasives and dry blasting with alumina grit.

b. Blasted surfaces are then to be lightly abraded with an emery disc or flap wheel toremove all surface redeposited copper where present. Note that the etchingsolution used to detect selective phase corrosion will give a false indication ifsurface redeposited copper is still present.

2.2.2 Cleaning Method 2

a. The casting is to be degreased either in a hot water detergent or in a cold agitatedsolvent to Def Stan 68-188 or similar approved alternative for between 30 minutesand 1 hour, or as advised by the manufacturers instructions.

b. After degreasing, the casting is to be washed in hot fresh water i.a.w.manufacturers instructions, until the degreasing solvent is removed.

c. Paint can be removed by an additional dip in a chemical cleaner to Def Stan 80-20or similar approved alternative for up to 8 hours after which the casting mustagain be washed, this time in cold water.

2.2.3 General Etching Method

a. On completion of cleaning, the casting is to be dipped for between 1 and 10minutes in an approved brightening solution e.g. Ardrox 160 (available underNSN 99 220 1162) or similar approved alternative. This process will etch thesurface of the casting, highlighting areas of weld repair, and selective phasecorrosion should these exist. The solution must be sufficiently fresh not tocontaminate the casting surface with redeposited copper. After removal from thedip bath, the casting is to be thoroughly washed in cold fresh water to remove alltraces of the brightening solution.

b. In general, the appearance of the various exposed surfaces of the casting followingdipping in Ardrox 160 will be roughly as follows:

Weld metal - Dark Grey or BlackParent Metal - Mid GreyHAZ Corrosion - Greyish GreenPlug/Crevice Corrosion - Copper Colour or Greyish Green

c. A suitably experienced person (see Clause 1.4a) is to check that the casting is freefrom surface redeposited copper before the examination for corrosion described inSection 3 is carried out. The suitably experienced person is to advise when thebrightening solution requires changing, e.g. if it causes re-deposition of copper.

NOTE: Due to the toxicity of Ardrox 160, contractors may prefer to use an alternativegeneral etching chemical, e.g. ferric chloride. Where such a change is proposed, priorapproval should be obtained from the Design Authority.


11

2.3 In Situ Cleaning

a. In situ cleaning of castings will require procedures to identify the access restrictions,the requirements for casting relocation, the proposed method of cleaning and therequired training / qualifications of staff. Particular attention will be required toprotect the surrounding components and the arrangements to be made for theremoval of debris.

b. Written procedures are to be prepared and approved by the Design Authority tocover the following.

(1) Prerequisite requirements in accordance with Clause 1.4.

(2) Work in way to prepare the casting for cleaning.

(3) Protection of surrounding equipment such as heat exchangers tubes, electricaland electronic equipment by suitable screening.

(4) Containment and disposal of waste fluids / abrasive particles.

2.3.1 In Situ Cleaning Method

a. The biofouling and surface redeposited copper is to be removed by a combination ofabrasive blasting, emery disc and flap wheels, as appropriate depending on accessrestrictions and safe operation.

b. Remote Visual Inspection (RVI) equipment may be necessary to aid cleaning and todemonstrate the condition of the casting internal surfaces and to ensure freedomfrom surface redeposited copper.

3. SHORE BASED ETCHING AND EXAMINATION FOR CORROSION

Related Documents: Def Stan 02-872 Part 2, see also Annex A

3.1 General

a. The main corrosion mechanism causing concern with NAB castings is selectivephase corrosion which occurs under crevices and biofouling (plug corrosion) oraround weld repairs in the heat affected zone (HAZ corrosion). Selective phasecorrosion can penetrate the thickness of the casting at up to 1.1mm per year withno apparent surface loss of metal. The purpose of the procedures described in thisSection is to detect and establish the depth of selective phase corrosion.

b. Castings are to be removed from the vessel, then cleaned and etched as per Clause2.2.

3.2 Visual Examination

a. The detailed visual examination of the casting after the etching described inClauses 2.2.3 and 3.4.1 is to be carried out by staff meeting the prerequisite inClause 1.4a. The location of selective phase corrosion will be around weld repairsand under biofouling and crevices. It is imperative that all welds on sea waterwetted and non wetted surfaces are identified after general etching, referring toClause 2.2.3b. Previous QA documentation should be consulted to locate theseweld repairs which should be identified on the casting. Areas of plug corrosionshall also be identified.


12

b. Corrosion areas can be identified with the aid of 10% non-acidified silver nitrateetch where necessary as per Clause 3.4.1.

3.3 Thickness Check

a. Spot thickness checks are to be made over the casting body by an ultrasonicmethod or calipers. Those regions where the wall thickness is found to be lessthan 90% of the drawing wall thickness are to be logged on radiograph sketchesand reported to the Design Authority. These regions are to be inspected inaccordance with Clause 3.4.2c. All other regions are to be inspected in accordancewith Clause 3.4.2b.

b. Where casting drawings are not available, NDE thickness readings are to beforwarded to the Design Authority for advice.

3.4 Detection of Corrosion

a. HAZ corrosion is typified by a narrow band of corrosion around weld repairs.Areas of plug corrosion are visible following general etching (see Clause 2.2.3)and can be seen as dimpling on polished surfaces (typically after 80 grit flapwheel).

b. To prepare the surface for detailed etching, the surface must be freshly abradedtypically with a flap wheel (80 grit) just prior (i.e. within one hour) to etching.

3.4.1 Detailed Etching Method

a. Areas of selective phase corrosion can be identified by etching with fresh 10%silver nitrate solution stored in a dark bottle to prevent deterioration by light. Theetch is preferably to be applied using a fine spray to moisten the metal surface.Alternatively a soft brush may be used. Swabs may be used provided care is takento avoid contamination which can cause spurious results, (this usually means thatswabs are used only once on a single wipe).

b. The silver nitrate etch will reveal regions of selective phase corrosion which turnblack. This is caused by silver depositing on any redeposited copper within theregions of selective phase corrosion. Note that care is required to ensure that allgeneral surface redeposited copper is removed as this will also turn black and canbe confused with selective phase corrosion.

c. Wash the etched areas thoroughly with fresh water to remove the etchingchemicals.

3.4.2 Ultrasonic Corrosion Detection

a. Corroded areas are to be examined by a ZIPSCAN method, that has been agreedwith the Design Authority, to determine the depth of corrosion and remainingsound wall thickness.

b. All HAZ corrosion is to be examined 100%. Other corrosion patches extendingmore than 10mm along the surface in any direction are to be examined 100%.

c. In those regions which are identified as thinner than 90% of design wall thickness,all corrosion is to be examined 100%.


13

d. Corrosion penetration and casting wall thickness are to be recorded. Corrosionlocation is to be logged on casting sketches with reference to the depth ofcorrosion penetration.

e. Any areas where the remaining uncorroded wall thickness is less than 90% of thedrawing wall thickness are to be reported to the Design Authority at the earliestopportunity to enable further action to be determined.

WARNING: Ultrasonic NDE methods, have been used with limited success tomeasure the depth of selective phase corrosion which has occurred at the HAZ. Totalreliability, however, is not guaranteed under all conditions and until a fully approvedreliable NDE method is available these techniques must be restricted to use as an aid fordetecting corrosion with confirmation of corrosion depth verified by an etch and grindprocess.

3.5 Removal of Corrosion

a. On completion of the examinations as per Clause 3.4, and after authorisation bythe Design Authority, corroded areas are to be ground out using suitable toolinge.g. tungsten carbide burrs or grinding wheels.

b. When all of the corrosion has been removed, this is to be verified by etching inaccordance with Clause 3.4.1

3.6 Post Dressing Thickness Gauging

a. All areas where corrosion was present must be thickness gauged using callipers oran approved ultrasonic technique when all the corrosion has been removed.

3.7 Recording of Examination Results

a. A full report of the examination is to be submitted to the Design Authority. This isto include casting sketches showing the location of corrosion, referenced to thedepth of corrosion penetration and casting wall thickness.

b. In addition, a Casting Record of Revalidation Inspection, an example of which isat Annex D, should be filled in. A separate sheet should be filled in for eachcasting. This is used to supply the information required to carry out lifeassessment. The following information should be included in the Table:

(1) The casting description, unique number and previous QA document numberare to be logged at the top of the table.

(2) All weld repairs and other defects where corrosion has been removed are tobe given a number which will be marked on the casting using a felt tipmarker and logged in column 1 of the Table. Note that all areas of corrosionshould be logged, including any grooving at O seals. Grooving or pitting at'O' seals is a special case to be referred to the Design Authority.

(3) Details of weld repairs on sea water wetted surfaces, obtained from previousQA documentation, are to be entered in column 2 of the Table next todefects identified in column 1. Note that some weld repairs may not haveresulted in corrosion but confirmation of this is required. A sketch orphotograph of areas of corrosion, with identification numbers as referencedin column 1 of the Table, is to accompany the Table.


14

(4) Grid based thickness scans for the larger NAB castings should be availablewith the QA documentation in accordance with Part 2 of this DefenceStandard. If these are not available then general wall thicknesses should bemeasured on a gridded sketch at a spacing to be agreed with the DesignAuthority. The measurements should give sufficient detail to provideconfidence on the general wall thickness. For guidance the grid spacing willbe typically 70 mm to 100 mm.

(5) On the castings, measure the maximum surface length 'A' in any onedirection and the maximum depth 'B' for each defect and record these on theTable in columns 4 and 5.

(6) Using a calibrated ultrasonic probe or callipers, measure the thinnest walladjacent to the defect, i.e. measure the wall thickness prior to the grindingout of the defect. This defect free wall thickness 'C' is to be recorded incolumn 6 of the Table. Subtracting the defect depth 'B' from this will givethe remaining wall thickness 'D', where D=(C-B), see column 7 of the Table.This can be confirmed by measuring directly the remaining wall thickness'D'.

(7) Complete columns 8 to 10 in the Casting Record of Revalidation InspectionTable.

3.8 Corrosion Limits

a. Using the results reported in accordance with Clause 3.7, the Design Authority isto decide if the rates of corrosion for the boat sample of NAB castings are withinacceptable limits. The acceptable limits allow the submarine to continueunrestricted operations to the end of her planned commission or until the nextplanned NAB Inspection. If the rates of corrosion found in the sample are higherthan expected, further Inspections may be immediately required or subsequentoperations with diving restrictions might be advised by the Design Authority.Where corrosion has been higher than expected, a safety assessment is to be madefor future operations of the submarine, identifying any operational restrictions asnecessary.

b. It must be remembered that even if all the Inspected castings are replaced (becauseof high corrosion rates), the submarine cannot be returned to unrestricted servicewithout such a safety assessment as there may be other castings in the vessel thatalso exhibit these high corrosion rates.

c. When corrosion is found to be negligible and the casting meets the revalidationcriteria, the casting should be revalidated in accordance with Section 4 of thisDefence Standard and returned to service or stores if applicable.

4. INSPECTION ACCEPTANCE CRITERIA

Related Documents: Def Stan 02-824, Def Stan 02-872 Parts 2 & 3, MOD Form 77, seealso Annex A

4.1 Cleaning

a. The casting has been satisfactorily cleaned when all fouling and redepositedcopper has been removed. Acceptance is to be confirmed by suitably trainedpersonnel.


15

4.2 Removal of Corrosion

a. Corrosion has been removed when there are no indications of selective phasecorrosion turning black after etching with 10% silver nitrate etch. Acceptancemust be confirmed by suitably trained personnel (see Clause 1.4a).

4.3 Wall Thickness

a. Corrosion free castings with a wall thickness above 90% of the drawing wallthickness are acceptable, as specified in Part 3 of this Defence Standard.

b. The Design Authority is to determine whether further corrosion is to be removedfrom castings once the wall thickness has been reduced to 90% of the originalvalue in way of corrosion.

c. Castings whose thickness has been reduced to less than 90% of the drawingthickness must be referred to the Design Authority. These castings are only to beinstalled into a submarine following receipt of an approved Concession (MODForm 77 - Revised 7/91) issued by the Design Authority.

4.4 Re-installation

a. Acceptable castings are to be re-installed after the examinations are complete ifthere is sufficient time during the Upkeep Period.

b. Castings which are deemed unacceptable by the Design Authority are to bereplaced with castings validated in accordance with Part 2 of this DefenceStandard a previously revalidated casting to Part 3 of this Defence Standard, or aCopper Nickel Chromium casting to Def Stan 02-824.

4.5 Re-Stamping

a. The officer witnessing the stamping of the casting is to sign the RevalidationCertificate. A line is to be stamped through the previous validation date and thenew date stamped as a suffix to the original number.

NOTE: Pressure castings are not to be stamped on the highly stressed region e.g.Critical Test Regions of the castings. The stamping should be positioned on low stressareas as indicated below.

i. Valve bodies should be stamped at the edge of the cover flange or in theabsence of a prominent cover flange then as close to the cover position aspossible. Failing this another flange should be stamped, but stamping on hullflanges is to be avoided.

ii. Flange fittings to be stamped on a flange edge.

iii. Unflanged fittings to be stamped on an area that is thicker than the minimumacceptable wall thickness.

4.6 Certification

a. All castings that are to be re-installed are to be re-stamped in accordance withClause 4.5, and issued with a Revalidation Certificate in the format of Annex E.


16

4.7 Records

a. A full report of the shore based corrosion examination, including wall thicknessrecords, sketches / photographs, and, the Casting Record of RevalidationInspection Table, see Annex D, is to be submitted to the Design Authority.

b. If the casting is re-installed in the submarine, a copy of the RevalidationCertificate and QA certificate of compliance, together with copies of the full set ofQA records, as listed in Annex F, are to accompany the casting. These are to beheld by the Through Life Records Contractor when the casting is fitted to thevessel, and are to be available for future revalidations.

c. The Through Life Records Contractor is to hold the master records.

5. IN SITU EXAMINATIONS

5.1 In Situ Cleaning

a. To be carried out in accordance with Clause 2.3.

5.2 Ultrasonic Thickness Checks

a. In-situ thickness gauging using calipers or an approved ultrasonic technique maybe required by the Design Authority on selected castings, e.g. as an input to lifeassessment for Commission Extension and Life Extension studies.

b. Wall thickness results are to be recorded on a Wall Thickness Recording Sheet insuch a way that they are cross-referenced to a grid based sketch.

c. Grid based thickness sketches for the larger NAB castings should be availablefrom the Design Authority. If these are not available then wall thicknesses are tobe measured on a gridded sketch at a spacing to be agreed with the DesignAuthority. The measurements should give sufficient detail to provide confidenceon the general wall thickness. For guidance the grid spacing will be typically 70mm to 100 mm.

5.3 In Situ Etching Method

a. Etching to reveal corroded areas is to be by the application of a fresh 10% silvernitrate solution. Etching is to be carried out within one hour of dry abrading thesurface, as the surface develops an oxide film resistant to etch solutions after aperiod of time. Precautions will be required to ensure that the etch can becontained and not run into crevices which cannot be flushed.

b. Wash the etched areas thoroughly with fresh water to remove the etchingchemicals.

c. Ultrasonic thickness checks will be required to maintain a record of the level ofdressing.


17

5.4 Ultrasonic Corrosion Measurements

a. In situ ultrasonic corrosion measurements using a NDE Time-of-Fight method(e.g. ZIPSCAN) may be required by the Design Authority on selected castings tobe used as a guide to the condition of the castings.

b. The procedure for NDE corrosion measurement is to be agreed with the DesignAuthority.

5.5 Records

a. The format for recording the results of the work specified to be undertaken by theDesign Authority is to be in accordance with Clause 3.7.

b. All records must contain the unique radiographic number for the casting and are tobe forwarded to the Design Authority.

c. A copy of all the records is to be passed to the Through Life Records Contractor,and is to be available for future revalidations.

d. The Through Life Records Contractor is to hold the master records.

5.6 Acceptance Criteria

a. The records from Clause 5.5 are to be assessed by the Design Authority foracceptability, as appropriate.


18

ANNEX A.

RELATED DOCUMENTS

A1. The following documents and publications are referred to in this Defence Standard:

JSP 430 MOD Ship Safety Management System Handbook

DGS 348 Cast Nickel Aluminium Bronze

DGS 8520 Cast Nickel Aluminium Bronze

Def Stan 02-747 Requirements for Nickel Aluminium Bronze Castings and ingots

Part 1 - Nickel Aluminium Bronze (Naval alloy) centrifugal castings andingots

Part 2 - Nickel Aluminium Bronze (Naval alloy) sand castings and ingots

Part 4 - Nickel Aluminium Bronze (Naval alloy) sand castings withwelding restricted to the non-wetted surface (Class I and II castings only)

Def Stan 02-824 Copper Nickel Chromium sand castings and ingots

Def Stan 02-872 Procedure for First Level Nickel Aluminium Bronze Castings

Part 1 Policy

Part 2 Validation

Part 3 RevalidationDef Stan 68-188 Emulsifier for solvent cleaner

Def Stan 80-20 Cleaning compound, solvent, cold bath type, for metal (cresylic acid/dichloromethane)

MOD Form 77 Concession Application

SSP 25 Quality Assurance for Safety in Submarines

Memo D/DGFS(S)/SM511A/743/20/GEN-T dated February 1995


19

ANNEX B.

DEFINITIONS AND ABBREVIATIONS

B1. For the purposes of this Defence Standard the following definitions and abbreviations apply:

Design Authority Authority within MOD with design responsibility for the equipment

ExaminationContractor

Organization contracted to carry out the examination of the castings

First Level QualityAssured

Where the consequences of failure of a hull area, system or equipment aresuch that it would lead to loss of the submarine, these areas, systems andequipments will be classified First Level and additional Quality Assurancemeasures will be implemented. SSP 25 refers.

HAZ Heat Affected Zone around a weld.

NAB Nickel Aluminium Bronze to DGS 8520, DGS 348 or Def Stan 02-747

NABWETLIFE MOD in-house code for determining the life of NAB castings based onstatistical analysis

NDE Non Destructive Examination

NSN NATO Stock Number

QA Quality Assurance

RAMP Revalidation Assisted Maintenance Period. This replaces the obsolete termRUP (Revalidation Upkeep Period).

Revalidation Examination of used NAB castings during their life to the requirements ofPart 3 of this Defence Standard to determine the castings fitness for furtherservice

Through LifeRecords Contractor

Organization contracted to maintain the QA records for NAB castingsthrough life

Validation Examination of new NAB castings prior to fitting in critical positions to therequirements of Part 2 of this Defence Standard.

ZIPSCAN Proprietary time of flight ultrasonic examination technique developed byAEA which has been used for the detection of selective phase corrosion


20

ANNEX C.

PROCUREMENT CHECK LIST

Notes:C.1 This check list is to ensure that certain aspects of this Naval Engineering

Standard are consulted when preparing a Procurement Specification for aparticular application.

C.2 Clauses where a preference for an option is to be used or where specific data isto be added are included in the Check List.

C.3 Each item is to be marked either:

= includedNA = not applicable

CHECKNo. CHECK

CLAUSENo.

orNA


ANNEX D.

CASTING RECORD OF REVALIDATION INSPECTION

Revalidation Date Material

Casting Unique RadiographicNumber

Previous Radiographic No. (ifdifferent)

Component Description

1 2 3 4 5 6 7 8 9 10

Defect Depth (mm)DefectID No

Radiographposition

numbers forweld repairs(see previous

QA documents)

Type ofDefect

e.g. HAZ,Plug,

O Seal

DefectLength(mm)

A

Ultrasonic Etch &Grind

B

Defect FreeWall

Thickness(mm)

C

RemainingWall

Thickness(mm)

D=(C-B)

DrawingWall -10%

(mm)

E

D>E =

D

22

ANNEX E.

REVALIDATION CERTIFICATE FOR NAB CASTINGS

PART I - IDENTIFICATION

A. EQUIPMENT SERIAL No. F. PIL No (VSN/ )

B. UNIQUE RADIOGRAPH No. G. PIL LINE ENTRY No

C. COMPONENT DRAWING No. H. COMPONENT ADREFNO

D. SHIP FITTING No. (e.g. BS 123) I. MANUFACTURER

E. COMPONENT DESCRIPTION MATERIALSPECIFICATION

PART II - REVALIDATION ACTION Signature

A. ALL PREVIOUS CONCESSIONS ASSESSED

B. CLEANED ETCHED AND GROUND TO DETECT CORROSION

C. THICKNESS RECORDS IN WAY OF CORRODED AREAS ATTACHED

D. CASTING RECORD OF REVALIDATION INSPECTION TABLE COMPLETED FORALL DEFECTS AND ATTACHED WITH SKETCH.

PART III - RECLAMATION AND REVALIDATION

A. PREVIOUS VALIDATION DOCUMENTATION SCRUTINIZED

B. SUBSEQUENT WELD REPAIR

C. COMPONENT RADIOGRAPHED AND DP EXAMINED

D. DIMENSIONAL CHECKS

E. WELD AREAS RE-MACHINED

F. INTERNAL WELD REPAIRS

Indicate action taken by signature (or NA if not applicable in appropriate box).

CONCESSION NOS

CONCESSIONS GRANTED FOR ABOVE COMPONENT

I certify that the above NAB casting has been revalidated in accordance with Def Stan 02-

872 Part 3 and stamped *

SIGNATURE

NAME IN BLOCK LETTERS

AUTHORITY/DEPT

DATE

* CASTING IDENTIFICATION TO BE INSERTED


23

ANNEX F.

CHECK LIST FOR DOCUMENTS TO BE INCLUDED IN QA PACK FORREVALIDATED CASTINGS

F.1. All certification and record sheets for the revalidated castings are to be annotated withthe appropriate ship fitting number or pump serial number (as applicable), description,and unique radiographic number.

QA CERTIFICATE OF COMPLIANCE

CHEMICAL ANALYSIS RESULTS RECORD SHEET

MECHANICAL TESTS RESULTS RECORD SHEET

VISUAL INSPECTION RESULTS RECORD SHEET

LIQUID PENETRANT RESULTS RECORD SHEET

RADIOGRAPHY/ULTRASONIC RESULTS RECORD SHEET

HEAT TREATMENT CERTIFICATE

PRESSURE TEST RESULTS RECORD SHEET/ CERTIFICATE OF COMPLIANCE

GRIDDED SKETCH FOR WALL THICKNESSES

WALL THICKNESS RECORDING SHEET CROSS-REFERENCED TO GRIDDEDSKETCH

SKETCH/PHOTOGRAPH OF WELD REPAIRS

WELD REPAIR RECORDING SHEET CROSS-REFERENCED TO SKETCH/PHOTOGRAPH

REVALIDATION CERTIFICATE

CASTING RECORD OF REVALIDATION INSPECTION TABLE

All QA records complete: SIGNATURE

NAME IN BLOCK LETTERS

AUTHORITY/DEPT

DATE


24

AAbbreviations 19Acceptance 14, 16Alumina grit 10

B

Biofouling 11

CCasting

Copper Nickel Chromium 15Nickel Aluminium Bronze 2, 8

Cleaning 10, 11, 15, 16Concessions 15Corrosion 8, 9, 10, 11, 12, 13, 15

DDesign Authority 2, 8, 9, 11, 12,

13, 15, 16Drawings 9, 13

EHAZ 8, 10, 12Etching 9, 10, 11, 12

FFirst Level 2

HHealth and Safety 4

IIdentification 8, 13

LLife assessment 13, 16

NNABWETLIFE 2, 8

PPhotographs 16

QQuality Assurance Documentation 9, 11, 13

RRadiographic number 8, 16Redeposited copper 9, 10, 12, 15Related Documents 4, 18Revalidation Certificate 15, 22

SSilver Nitrate 15Sketches 11, 12, 15, 16

TThrough Life Records Contractor 16

UUltrasonics 12, 13, 16

WWall Thickness 2, 9, 11, 12, 13, 14, 15,

16

ZZIPSCAN 12, 16

ALPHABETICAL INDEX(Note: Page Numbers are given)


Inside Rear Cover

Crown Copyright 2002

Copying Only as Agreed with DStan

Defence Standards are Published by and Obtainable from:

Defence Procurement AgencyAn Executive Agency of The Ministry of Defence

UK Defence StandardizationKentigern House65 Brown Street

GLASGOW G2 8EX

DStan Helpdesk

Tel 0141 224 2531/2 Fax 0141 224 2503

Internet e-mail [email protected]

File Reference

The DStan file reference relating to work on this standard is D/DStan/69/02/872 Pt 4.

Contract Requirements

When Defence Standards are incorporated into contracts users are responsible for their correctapplication and for complying with contractual and statutory requirements. Compliance witha Defence Standard does not in itself confer immunity from legal obligations.

Revision of Defence Standards

Defence Standards are revised as necessary by up issue or amendment. It is important thatusers of Defence Standards should ascertain that they are in possession of the latest issue oramendment. Information on all Defence Standards is contained in Def Stan 00-00 Standardsfor Defence Part 3 , Index of Standards for Defence Procurement Section 4 Index of DefenceStandards and Defence Specifications published annually and supplemented regularly byStandards in Defence News (SID News). Any person who, when making use of a DefenceStandard encounters an inaccuracy or ambiguity is requested to notify the Directorate ofStandardization (DStan) without delay in order that the matter may be investigated andappropriate action taken.

CONTENTSSCOPEFOREWORDSponsorshipConditions of ReleaseCategories of Naval Defence StandardRelated DocumentsHealth and Safety1. GENERAL REQUIREMENTS1.1 NABWETLIFE Code1.2 Selection of Castings for Inspection1.3 Identification1.4 Pre-Requisites

2. CLEANING OF CASTINGS2.1 General2.2 Shore Based Cleaning and General Etching2.3 In Situ Cleaning

3. SHORE BASED ETCHING AND EXAMINATION FOR CORROSION3.1 General3.2 Visual Examination3.3 Thickness Check3.4 Detection of Corrosion3.5 Removal of Corrosion3.6 Post Dressing Thickness Gauging3.7 Recording of Examination Results3.8 Corrosion Limits

4. INSPECTION ACCEPTANCE CRITERIA4.1 Cleaning4.2 Removal of Corrosion4.3 Wall Thickness4.4 Re-installation4.5 Re-Stamping4.6 Certification4.7 Records

5. IN SITU EXAMINATIONS5.1 In Situ Cleaning5.2 Ultrasonic Thickness Checks5.3 In Situ Etching Method5.4 Ultrasonic Corrosion Measurements5.5 Records5.6 Acceptance Criteria

ANNEX A. RELATED DOCUMENTSANNEX B. DEFINITIONS AND ABBREVIATIONSANNEX C. PROCUREMENT CHECK LISTANNEX D. CASTING RECORD OF REVALIDATION INSPECTIONANNEX E. REVALIDATION CERTIFICATE FOR NAB CASTINGSANNEX F. CHECK LIST FOR DOCUMENTS TO BE INCLUDED IN QA PACK FOR REVALIDATED CASTINGSALPHABETICAL INDEX