SSC Project SR 1459 Quarterly Progress Report #2 Review Meeting Minute

SSC Project SR 1459, Quarterly Progress Report #2, Conference Call

Date: September 09, 2009

Time: 1300-1500 EST

Participants:

Marc Cruder (USCG), PTC Chairman

Jason Smith (SSC/USCG)

PTC

Rong Huang,

Robert Sielski

Neil Van De Voorde

Dan Woods

Steve Billy

Nigel Baltrap

Project team

Pedro Santos (ABS)

Rick Neilson (ABS)

Eeteng Khoo (ABS)

George Wang (ABS)

Sameer Kalghatgi (ABS)

Nianzhong Chen (ABS)

Prepared on Sept 14, 2009

Who / Comments / Reply /
General Comments
Robert Sielski / One of my comments made at the kickoff meeting concerned the use of the word “Threshold” in the project title. Now I question the use of the word “Fracture” particularly in view of the “New Paragraphs for Section III” that have been submitted. Part A “Structural Defects” seems to make a differentiation between fractures and fatigue cracking. Indeed there is in terms of fracture mechanics analysis, but the difference absent a metallurgical examination is not apparent to an inspector, regardless of qualifications. A crack is a crack, regardless of cause, and we should be talking about cracks, not fractures. I recommend the following:
a. Change the title to “Criteria for Determining Repair Procedures for Cracks in Ship Structures”
b. In part A of the Section III new paragraphs, take the two paragraphs starting with “Some fractures may not be…” and ending with “…dye penetrant” and move them to follow the next paragraph “Fatigue is the most…type of notch.” Some explanatory words could be added to state that cracks can be caused by certain overload circumstances. / a. The agreement was to retain the current project title: “criteria for determining fracture repair procedures,” maintaining the use of the word “fracture.”
b. Noted and we will consider this suggestions in the report.
Rong Huang / “Crack” and “Fracture” are synonym but slightly different in meaning. Crack is related to the internal property such as chemical composition, welding material and workmanship. Fracture is related to the external force such as bending, buckling and fatigue. Recommend to continue use “fracture’ in the tile. / As suggested, the project will include a list of definition for terms/nomenclature including fracture and cracks in the report. We will use the definition of “fracture” consistent with the terminology adopted by IACS.
AWS defines Crack as a fracture type discontinuity characterized by a sharp tip and a high ratio of length and width to opening displacement.
Focus on contents in NVIC 7-68 that is related to fracture. Wastage and deformation is beyond the scope of this SSC project. / Agree
Add definition of fracture, cracks in the report / Will do
Is the project considering extension of the project / We would like to extend the project for 6 months. The project team will put more resources.
Please make user-friendly presentation of the report. / Agree
Task 1 Material
Marc Cruder / Recommendations for updating NIVC 7-68: The content provided is useful. The source of the info is not clear in all cases and I wonder if there are any copyright or other issues associated with merely cutting and pasting ABS or IACS published information into a CG document. / Our understanding is that we are not going to rewrite NVIC 7-68. This current SSC project is meant to provide information that can be used to update the NVIC.
Nevertheless, we will look into the copyright issue, and options of rewriting paragraphs.
Marc Cruder / Assuming the content can be used and page numbering starts after the cover page:
- Do the footnotes refer to the list of four references on page 10?
- How would a field inspector/surveyor determine the stage of fatigue failure as described on pages 3 and 4?
- Is the dry welding referred to on page 4 only water-backed fillet welding of internal structural components or welding to a temporary backing strip? Assume this does not refer to underwater welding.
- Is there any more detailed ABS history/experience with water-backed welding afloat beyond the generic case-by-case basis? Can we access ABS approvals on this for details and long term success?
- Can you water-backed welding for production welds of intermittent or continuous fillets of framing to sideshell?
- Are there any other parameters like thickness of metals being welded? Assume MT = mag-particle NDT; Assume water-backed welding is not underwater welding.
- What is the difference between the ABS table on steel grades and the table from IACS Pub # 47? Is there a need for both?
-Is your intention on task one to provide a list of topics that need to be in revised NVIC 7-68 or to make a new draft document with the revised info merged in? / to answer the questions:
- yes
- Knowing the causes of failure is important before decisions about repair can be made. Some failure is due to design and construction, and some wear and tear. Design modifications may be needed if a fracture is a result of local high stresses. Agree it would be difficult for a field inspector to figure out what may have caused the problem. But knowing the potential reason is important.
- We will provide information about ABS Guidelines on waterback welding and relevant parameters. Generally, such operation is approved case by case.
See the same
- (Steel grade, etc) Welding in the way of water backing and underwater welding can be addressed. The IACS Table is a cross reference for guidance.
- Rewriting NVIC 7-68 is not the scope of the current SSC project. We plan to provide updated paragraphs, if we have enough materials for such purpose. See also our reply to Marc’s comments on this page.
Marc Cruder / The project team needs to provide recommendations about which repair techniques are outdated, and which new repair techniques are to be covered. / We will report the recommendations in the following months.
Cesare M. Rizzo / I would add the following reference in the task 1 document: IACS Recommendation No. 76 Guidelines for Surveys, Assessment and Repair of Hull Structure Bulk Carriers and IACS Recommendation No. 55 Guidelines for Surveys, Assessment and Repair of Hull Structure General Cargo Ships.
Indeed, referred document are available online (together with other similar ones). One may wish to get them. So far, a link to the issuing institutions/authorities together with a short description of the main information reported would be of help. / Thank you for suggestions.
Robert Sielski / In the comments regarding welding to water-backed plate, the grades of ABS steel for which this is acceptable should be used in addition to the yield strength. (Does this mean that it is permissible to so weld grade HS-36?) / We will provide ABS Guidelines on waterback welding.
Robert Sielski / The welding on water-backed plate section apparently calls for heating the plate to at least 38C (100F). If this possible, or must some two-welder procedure be used with one person heating immediately followed by another welding. / See above.
Robert Sielski / Is it necessary to include all of the material from the ABS rules on steel properties? Some of this information may change in the future, leaving outdated guidance for the inspectors who are the target audience of this report / These tables are meant to be reference. They will not appear in a USCG document.
Robert Sielski / The weld repair section includes the words “The initial step in determining the repair procedure is to first determine the grade or grades of steel involved in the weldments under consideration.” No guidance is provided. Consider providing the following:
a. Review of the drawings for the ship should be the first source of information.
b. An inspection should be made to determine if prior repairs have been made to the area because substitute materials could have been used.
c. There may be no easy way to determine if for some reason substitute materials were used during initial construction but not annotated on the ship’s drawings.
d. Chemical analysis is sometimes used to confirm material composition; although it will not confirm the heat treatment the steel has received. / Thank for the suggestions.
We will address your suggestions when we work on Task 5.
Robert Sielski / The entire IACS comments on repairs, while useful, should be placed as an appendix to the report, if included at all. / Agree.
John Koster / Recommendations to USCG Circular No. 7-68 Notes on Inspection, Repairs, & Welding, I particularly like the inclusion in V.(C) of the mechanical properties of steels of various Grades, although I think it would be useful to also include data in the inch-pound system of units. Also, since one of the primary reasons for this project is to provide guidance to relatively junior personal working in the field, suggest they be directed to seek information on the grade or grades of steel of involved hull plating from the shell expansion drawing, if available. / Will do, including inch-pound system.
Rong Huang / Definitions and structural nomenclature shall be clearly defined and consistent for this project and the to be revised NVC 7-68. Agreed and recommend to use the IACS deficiencies - Material Wastage, Fractures and Deformations (instead of deterioration, hull defects and hull damage). / As suggested previously, the project will include a list of definition for terms/nomenclature including fracture and cracks in the report.
Rong Huang / This project title has been revised to “Criteria for Determining Fracture Repair Procedures” and NVC7-68 is titled “Notes on Inspection and Repair of Steel Hull”, therefore recommend to concentrate the effort only on the “fracture”. The revision of the “entire” NVC7-68 shall be a separate USCG internal project to be funded by USCG and to be performed separately. Request the PTC chairman to clarify this point. / PTC chairman cited SR-1459 overview statement: “The final report is expected to provide information…that can lead to revision of U.S. Coast Guard NVIC 7-68.” Thank you for clarifying the scope of this project.
Rong Huang / “Waterback welding” while the ship is afloat has been commonly used since early ’80 for the bottom pit welding repair that been approved by all classification societies. Recently ABS has approved the waterback welding procedures developed by O.K. Marine Group, North Ireland for all positions at 10 degreesC for plate thickness more than 15mm (19/32”). Waterback welding procedures have been used in steel repairs for offshore storage tanks in West Africa (ExxonMobil) and China (Chevron) offshore. / Guidelines on these types of welding will be included in the report. Welding parameters that needs to be taken into account during the process of welding will be listed and briefly explained.
Rong Huang / Welding repair while afloat by the use of cofferdam fitting externally of the ship has been accepted by major classification societies. This welding repair method shall be included. / Agree.
Rong Huang / Pitting corrosion does occur in un-coated steel where water is entrapped. / Thank you for your input
Nigel Barltrop / A. Structural defects
Elastic buckling may not be obvious…
Buckle amplitude may not (so far) have been large.
Plates may be lightly stressed and flat when inspected.
Buckling can also lead to larger dynamic stresses and show itself through fatigue cracks. / Thank you for your input
Nigel Barltrop / Reword:
One or more of the following fracture detection procedures may be required if deemed necessary and should be operated by experienced qualified technicians:
to:
The following fracture detection procedures may be needed to find defects, they should be operated by experienced qualified technicians: / Thank you for your suggestion
Nigel Barltrop / Fatigue failures can generally be considered to have three stages:
• Initiation
• …
Usually in welded structures the small defects left after welding are initial cracks and so, at welds, the initiation stage can be ignored. / Thank you for your input
Nigel Barltrop / (B) Dry welding …
IV NOTES ON REPAIRS
Add; (f) If available defect histories from sister vessels and, especially for atypical trading routes, similar ships on a similar routes.
For detailed guidance on preheat etc I would prefer to see reference to an accepted standard, as in (d). Duplication of very specific numerical guidance can cause conflicts, especially if standards change.
V WELDING
As for IV it is best to simply refer to latest ABS requirements for material properties rather than reprinting them as they stand at a particular time. / Thank you for your suggestion
Nigel Barltrop / APPENDIX IACS COMMENTS ON REPAIRS
This IACS document contains a lot of repetition, if it is planned to incorporate the ideas into the SSC report then a general section followed by area specific and detail specific recommendations would be a better, more compact format / The document is only a draft and compilation of the materials researched. The final report will be a summary of all the relevant information gathered.
Task 2 Data Analysis - Fracture Findings
Marc Cruder / While I understand how time intensive this working thru the data is, I am concerned about this task because it is the crux of the project and should be driving the outcome. I envision it to be more than a statistical exercise. This is the meat of the project and should tell us what kind of fractures occurred, how we handled them and why as a basis for future repair decisions, both temporary and permanent.
- When do you envision having sufficient details for PTC review/comment and discussion.
- What type of analysis do you envision at this point? / Yes we will assign additional resources and analyze all the fracture findings. We may need some more time to get this completed.