DNV RECOMMENDED REPORTING PRINCIPLES FOR ULTRASONIC IBICKNESS MEASUREMENT OF HULL STRUCTURES

Transcription

1 GUIDELINES NO.IO DNV DNV RECOMMENDED REPORTING PRINCIPLES FOR ULTRASONIC IBICKNESS MEASUREMENT OF HULL STRUCTURES SEPTEMBER 1993 DET NORSKE VERITAS CLASSIFICATION AS Veritasveicn 1, N-1322 H0Vfr, Noiway Tel.: Fax:

2 FOREWORD Det Norske Veritas is an independent Foundation with the objective of safeguarding life, property and the environment at sea and ashore. Classification, certification and quality assurance of ships, offshore installations and industrial plants, as well as testing and certification of materials and components, are main activities. Det Norske Veritas possesses technological capability in a wide range of fields, backed by extensive research and development efforts. The organization is represented worldwide in more lhan 100 countries. Guidelines are publications which give information and advice on technical and formal matters related to the design, building, operating, maintenance and repair of vessels and other objects as well as the services rendered by the Society in this connection. Aspects concerning classification may be included in the publication. An updated list of Guidelines available is given in the latest edition of the Introduction-booklets to the «Rules for Classification of Ships», the «Rules for Classification of Mobile Offshore Units,. and the «Rules for Classification of High Speed and Light Craft>. Det Norskc Veritas 1993 Computer Typesetting by Division Ship and Offshore, Det Norske Veritas Classification AS Printed in Norway by Det Norske Vcritas It 11 egreed that save as provided below Oet Norako VefltU, its subsidiaries, bodies, offlcera, directors, employees and agents ahall have no lloblltty for any los. damage or expen e allegedly caused directly or indir ect!~ by tnelr miatoke ct negligence, b each of warrenly, OI any otner ect, omission or cnor by tl'iom, including oro negligence o: wilful mlscorduct by any 1uch pot11on with the exception of groh neolloe11cc ot wilful misconduct by the oovcmlng bodies ' senor executive officers of Oet Norske Verites. TIU applies regardless of whether the loss, domoge or expense has affected anyone with wham Det Norske Vet1tH hes 1 contract or a third party who has octcd Ot relied on decisions metle or Information given by or on behalf of Oet Norske Veritos. * However, if any person use the services of Oct Norske Veritas or its sub$idiories or rehes on any decis ion made or Information given by or on beholf of them and jn consequence suflctt 1 loss, domage or expenoc proved to be due to their negligeru:e, omission ot default. then Oet Notske Veritas will pay by way of eompenution to such person a,..,. representing hia proved loss. * In the event Oet Norake Veritas or its si.bsidianes may be held hablc In accordance w ith the sections above, the 1r'l'\0\#1t of compensation shall under no c1rcl.l'ntt1nce1 exceed the 4mount of the fee. if any. cherged for that p.-rticul1r servrce. decision.. advice ' 1n form1tion. * Under no c:irci.mtt1nees whltsoever shall the r.d.ividuel or individuals who hive personal y.caused the loss. d1maoc 01 expense be. held ll1ble. 1t In die event thet any PfOvts ion tn thi1 socuon shlll be inva~d under the law of af\y iori diction, the validity of the rem ining prolnsi<>ns shall not on ony way be affected.

3 CONTENTS 1. Introduction DNV Ultrasonic Thickness Measurement (UTM) Procedures General Application UTM Procedures - Brief description DNV UTM Reporting System General description UTM Reporting - Detailed Description Appendix A DNV UTM Reporting Format Appendix B Set-up for UTM Reporting B.1 Set up for Thickness Measurement Reporting:.....

4 4 Guidelines - No Introduction Ultrasonic thickness measurement (UTM) is an important tool to assess the condition of hull structures. In order to take full advantage of the information obtained from thickness measurements, DNV has established a system intended to provide a consistent quality of the measurement and reporting as well as documentation readability and conditions for verification of measurements. 2. DNV Ultrasonic Thickness Measurement (UTM) Procedures 2.1 General The DNV system for UTM is based on the principles agreed to in the International Association of Classification Societies {IACS) as a part of the Enhanced Survey Program for huli surveys of Oil Tankers and Bulle Carriers. Furthermore, the system is based on both formal and informal procedures practised by DNV for a Long time. Hence the UTM procedures as described in this Guideline represents a continuity and expansion of previous procedures. 2.2 Application The DNV UTM procedures are applicable to all vessels when subject to thickness measurement. Requirements for extent of UTM are given in the DNV rules for classification of ships, Pt.7 Ch UTM Procedures - Brief description The DNV procedure for thickness measurement is consisting of the following parts: a) Approval of thickness measurement firms; b) Establishing of Minimum thickness lists (usually available to the attending DNV surveyor of the respective vessel)..:) Thickness measurement (nonnally supervised by a surveyor from DNV); dj Possible extended measurements if the structure is found substantially corroded. e) Reporting of thickness measurements; f) Verification of thickness measurement report; g) Evaluation of thickness measurements A standardized reference system has been developed aiming to provide a generally more consistent production system in all parts of the above procedure, and in particular to ensure satisfactory readability of UTM reports. It is considered important that similar reporting method and extent is applied for all vessels, regardless of UTM company. Such a common reference system is intended to provide an improved basis for consideration of a vessels structural condition. Approval of firms engaged in UTM is therefore made conditional on reporting in accordance with the DNV UTM reporting system. Generally the attending DNV surveyor will select areas to be gauged. However, for vessels subject to the enhanced hull survey program, i.e. dry bulk cargo vessels and oil carriers, transverse sections subject to UTM at Renewal survey are to be nominated as a part of the survey planning. The survey planning is to be carried out by the ship owner in cooperation with the Society well in advance of the survey. 3. DNV UfM Reporting System 3.1 General description The basic motivation behind the DNV UTM reporting system is to obtain a unified UTM reporting standard for all DNV classed vessels built up logically with respect to both assessment of the vessels structural strength capacity and document readability in general. Furthermore, it is also intended to be a flexible system which may relatively easy be adopted by UTM firms. The main features in the UTM reporting system recommended by DNV are as follows: One page of general particulars (See Appendix A); A standard table covering all structural elements. This is to be supplemented by measurements marked on drawings as considered necessary and sufficient (See Appendix A); 14 element groups which may be selected as relevant, e.g. deck, side, inner bottom etc. (See Appendix B); Each element group consisting of single elements which may be selected as relevant (See Appendix B); Reporting of element groups and single elements in a fixed sequence in order to increase the readability with respect to: - structural strength evaluation; - intuitively logical approach, e.g. deck longitudinals to be reported together with deck girders and plates etc.; - easy comparison with for instance minimum thickness lists (if provided); The number of the respective element groups indicates the reporting sequence of the UTM. Generally it has been experienced that a combination between forms and drawings in most cases will give a better overview than only reporting in tables. It is therefore recommended that the reporting form to a large extent is supplemented by drawings indicating location of measurement points, in order to ensure unambiguous reporting and to increase the readability. 3.2 UTM Reporting - Detailed Description Properly documented thickness measurements is considered to be of great importance. No ambiguous description of location should be left in the report. The sheet of general particulars as shown in Appendix A is considered self-explanatory. The reporting sequence of the measurements should generally be as follows (as applicable): a) Complete deck and bottom plating, wind and water strakes; b) Transverse sections; c) Other areas gauged, e.g. transverse bulk.heads, web frames, sundry spot checks etc. With reference to the column/space numbers indicated on the UTM form in Appendix A, the following guidance should therefore be followed: 1. Ship's Name. 2. Id.No.. DNV Identification Number (five digits). 3. Report No. UTM firm's report no. DET NORSKE VERITAS

5 Guidelines - No Element group. The relevant group heading (1-14) as per appendix B. Only one element group is to be reported per sheet. Tank/Hold/Space No. Indicate in which tank, hold or space the measurements reported at the respective UTM form have been taken. This may not be relevant for UTM reporting of complete deck and bottom plating, wind and water strakes and transverse sections (ref. point a. and b. above), as these usually will cover several tanks/holds/spaces. Transverse section No. Indicate in which transverse sections the measurements reported at the respective UTM form have been taken. This will normally not. be relevant for UTM reporting of complete deck and bottom plating, wind and water strakes and other areas that cover several transverse sections. Structural Element. Structural elements encompassed by the relevant element group heading, as per Appendix B. The reporting should be made in the same sequence as in the elements list. If more than one measurement is reported for a structural element. the element has to be dedicated more lines in the UTM form accordingly. Element/ rame no. The location of the measurement point should be given by means of frame number, plate number, longitudil!lal number etc., as found from the ship's drawings. Drawing reference. It is intended that the reporting forms should be supplemented by drawings indicating the position of the measurements as necessary. In cases where panels are measured, e.g. bulkheads, deck plating and bottom plating, drawings are always to be attached to the report. Drawings are also to be attached showing the transverse sections subject to UTM. It should be noted that the reporting fonn will have to be filled for each measurement point at each structural element, as it is considered impractical to note all necessary data on a drawing. 10. Original thickness (mm). The original thickness should be taken from the "as built" drawings. If hull modifications have been carried the new approved thickness after modification should be used as basis. 11. Gauged Port/Stbd (mm). The measured thickness at a given location. Port and Starboard are referring to the respective sides of the vessels centre line. For instance, when measuring a transverse section the measured thickness for similarly located elements (stiffeners, plates etc.) at each side of the vessel should be reported in the Port and starboard column respectively. 12. Diminution. The present diminution of the respective structural elements is to be noted in both (mm) and ( % ) with reference to the original thickness. 13. Comments. When found during UTM, comments should be given concerning structural defects such as buckles, cracks and deformed structural elements; extreme corrosion or significant pitting attack. corrosion of welds in Heat Affected Zone (HAZ) When such findings are made by UTM operators, the fact will be made subject to a detailed survey by the classification society. Furthermore damaged coating and surface fmish is to be noted. Readings taken in pits, grooves etc. are also to be specially noted. If necessary, additional comments should be given at a separate sheet. 14. Operator's Signature. 15. Page numbers. DET NORSKE VE.RITAS

6 6 Guidelines - No. 10 Appendix A DNV l)tm Reporting Format THICKNESS MEASUREMENT REPORT DET NORSKE VER.IT AS

7 DET NORSKE VERITAS THICKNESS MEASUREMENT REPORT GENERAL PARTICULARS Ships name: IMO number: Class identity number: Port of regis1ry: ,, ,,.,..,,,,_,,,,_,, Gross tons: _,,_ ,_, Deadweight: Date of build: Classification society:, Name of firm performing thickness measurement: , Thickness measurement firm certified by: Approval No.: _, Approval valid from to Place of measurement: First date of measurement: Last date of measurement: Renewal survey I intermediate I other survey due: * _ Details of measurement equipment: Qualification of operator: Report Number: Consisting of..... Sheets Name of operator: Name of surveyor: Signature of operator: Signature of surveyor: Firm official stamp:_ --~--- _ Classification Society Official Stamp: ~ ---- * Delete as appropriate. DET NORSKE VERITAS CLASSIFICATION AS, VERJTASVEIEN 1, N-1322 H0VIK, NORWAY, TEL. INT: , TELEFAX: Form No.: 40.65a Issue: September 93

8 !4 DET NORSKE VERITAS THICKNESS MEASUREMENT REPORT DNv Ship's Name G) Id.No. 0 Report _0 Element gr.cup: ( 4) Tank I Hold I Space No.: ( 5) Transverse section No.: ( 6) Structural element Element I Draw ref. Orig thk. Gauged Frame No. mm Port Stbd mm mm mm ~ 1) Ca) ( 9) (10) ~11) (11) :~12) Port Diminution Stbd % mm % ~12J ~1 2) (12) ~13) Comments Operator's Signature -- - DET NORSKE VERITAS CLASSIFICATION AS, VERITASVEIEN 1 N-1322 H0VJK, NORWAY, TEL. INT: , TELEFAX: Form No.: 40.65a Issue: September 93 Page@of

9 Guidelines - No Appendix B Set-up for UTM Reporting, comigated, corrugated Longitudinals, web Longs., web B.1 Set-up for Thickness Measurement Reporting: Longitudinals, flange Longs., fl. Vertical stiffener, web Vert. stiff., web A. Longitudinal strength plating with stiffening Vertical stiffener, flange Vert. stiff., fl. Abbreviation Stringer, web Stringer, web 1.0 Deck: Stringer, flange Stringer, fl. 7.0 Hopper tank: Rounded gunwale Rounded gunwale Longitudinals, web Longs., web Sloping top plate Sloping top plate" Longitudinals, flange Longs., fl. Horizontal plate to side Horiz. plate to side Transverse beam, web Transv. beam, web Longitudinals, web Longs., web Transverse beam, flange Transv. beam, fl. Longitudinals, flange Longs., fl. Centre line girder, web Centre line girder, web Transverse stiffener, flange Transv. stiff., web Centre line girder, flange Centre line girder, fl. Transverse stiffener, web Tramv. stiff., fl. Side girder, web Side girder, web Stringer, web Stringer, web Side girder, flange Side girder, fl. Stringer, flange Stringer, fl. 2.0 Bottom: Longitudinal girder, web Long. girder, web Keel plate Keel plate Longitudinal girder, flange Long. girder, fl. 8.0 Top wing tank: Bilge plate Bilge plate Longitudinals, web Longs., web Vertical plate to deck Vert. plate to deck Longitudinals, flange Longs., fl. Sloped bottom plate Sloped bottom plate Transverse frame, web Transv. fr., web Horizontal plate to side Horiz. plate to side Transverse frame, flange Transv. fr., fl. Longitudinals, web Longs., web Centre line girder, web Centre line girder, web Longitudinals, flange Longs., fl. Cent.re line girder, flange Centre line girder, fl. Transverse stiffener, flange Transv. stiff., web Side girder, web Side girder, web Transverse stiffener, web Transv. stiff., fl. Side girder, flange Side girder, fl. Stringer, web Stringer,-web 3.0 Side: Stringer, flange Stringer, fl. Longitudinal girder, web Long. girder, web Sheer strake Sheer strake Longitudinal girder, flange Long. girder, fl. Longitudinals, web Longitudinals, flange Frame, web Frame, flange Stringer, web Stringer, flange 4.0 Inner bottom: Longitudinals, web Longitudinals, flange Longs., web Longs., fl. Frame, web Frame, fl. Stringer, web Stringer, fl. Longs., web Longs., fl. B. Remaining strength members. 9.0 Transverse bulkhead: corrugated Horizontal stiffener, web Horizontal stiffener, flange Vertical stiffener, web Vertical stiffener, flange Abbreviation, corrugated Horiz. stiff., web Horiz. stiff., fl. Vert. stiff., web Vert. stiff., fl. Transverse frame, web Transv. fr., web Stringer, web Stringer, web Transverse frame, flange Transv. fr., fl. Stringer, flange Stringer, fl. 5.0 Inner side: Vertical girder, web Vert. girder, web Vertical girder, flange Vert. girder, fl. Longitudinals, web Longs., web, lower stool, lower stool Longitudinals, flange Longs., fl. Top plate, lower stool Top pl., lower stool. Vertical stiffener, web Vert. stiff., web Stiffener, lower stool, web Stiff., lower stool, web V crtical stiffener, flange Vert. stiff., fl. Stiffener, lower stool, flange Stiff., lower stool, fl. Stringer, web Stringer, web Web frame, lower stool, web Web fr, lower stool, web Stringer, flange Stringer, fl. Web frame, lower stool, flange Web fr, lower stool, fl 6.0 Longitudinal bulkhead:, upper stool, upper stpol DET NORSKE VER.ITAS

10 10 Guidelines - No. 10 Bottom plate, upper stool Bottom pl, upper stool Side coaming bracket, web Side ooaming brkt, web Stiffeners, upper stool, web Stiff., upper stool, web Side coaming bracket, flange Side ooaming brkt, fl Stiffeners, upper stool, flange Stiff., upper stool, fl. End coaming bracket, web End coaming brkt, web Ww frame, upper stool, web Web fr, upper stool, web End coaming bracket, flange End coaming brkt, fl. Web frame, upper stool, flange Web fr, upper stool, fl. Stiffener, web Stiff., web 10. Wash bulkhead: Stiffener, flange Stiff., fl Hatch cover Horizontal stiffener, web Horiz. stiff., web Horizontal stiffener, flange Horiz. stiff., fl. Longitudinal stiffener, web Long. stiff., web Vertica.l stiffener, web Vert. stiff., web Longitudinal stiffener, flange Long. stiff., fl. Vertical stiffener, flange Vert. stiff., fl. Transverse stiffener, web Transv. stiff., web Stringer, web Stringer, web Transverse stiffener, flange Transv. stiff., fl. Stringer, flange Stringer, fl. Longitudinal girder, web Long. gird., web Vertical girder, web Vert. girder, web Longitudinal girder, flange Long. gird., fl; Vertical girder, flange Vert. girder, fl. Transverse girder, web Transv. girder, web 11.0 Transverse web frames/floors: Transverse girder, flange Transv. girder, fl. Deck, web Deck, web Deck, flange Deck, fl. Bottom, web Bottom, flange Floor Bilge, web Bilge, flange Side, web Side, flange Inner side, web Inner side, flange Longitudinal bulkhead, web Longitudinal bulkhead, flange Hopper tank, web Hopper tank, flange Top Wing Tank, web Top Wing Tank, flange Cross tie, web Cross tie, flange Bracket, web Bracket, flange 12.0 Deck between hatches: Longitudinals, web Longitudinals, flange Transverse beam, web Transverse beam, flange Centre line girder, web Centre line girder, flange Bottom, web Bottom fl. Floor Bilge, web Bilge, fl. Side, web Side, fl. Inner side, web Inner side, fl. Long. bhd, web Long. bhd, fl. Hopper tank, web Hopper tank, fl. Top wing tank, web Top wing tank, fl. Cross tie, web Cross tie, fl. Bracket, web Bracket, fl. Longs., web Longs., fl. Transv. beam, web Transv. beam, fl. Centre line girder, web Centre line git'der, fl. Side girder, web Side girder, web Side girder, flange Side girder, fl. Hatch end beam, web Hatch end beam, flange 13.0 Hatch coamidg: Side coaming, plate Side coaming, top plate End coaming, plate End coaming, top plate Hatch end beam, web Hatch end beam, fl. Side coam., pl. Side coam., top pl. End coaming, pl. End coaming, top pl. DET NORSKE VERITAS

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