Attachment IX - Reference - TECHNICAL MEMORANDUM - REUBEN LASKER Stern Tube Leak Long Term Repair Plan REV A.pdf

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TECHNICAL

MEMORANDUM

Date: 10 JULY 2024

To: Sean Mooney (NOAA)

Cc: Nathan Jones (NOAA) Rob Gibson (ECS)

From: Art Anderson, Spencer Albright - PE

AA Ref: CEECS003.01.019

Client Ref:

Subject: REUBEN LASKER Stern Tube Leak Long Term Repair Plan REV A

References

1. Technical Memorandum – REUBEN LASKER Stern Tube Leak Risk Mitigation and Short

Term Repair Plan, Art Anderson 13 MAR 2024

2. Technical Memorandum – REUBEN LASKER Stern Tube Leak Non-Destructive Testing Recommendation, Art Anderson 16 FEB 2024

3. FSV6-801-08 REV B, Bossing and Stern Frame Scantling

4. IACS Shipbuilding and Repair Quality Standard

Attachments None

Introduction

This document is intended to provide guidance for Long-Term Repairs on the Stern Tube of the NOAA Ship REUBEN LASKER. Repairs are in reference to persistent leaks in the 30” diameter stern tube housing constructed of 1/2” ABS Grade A steel. Short term repairs to the stern tube housing, intended to provide a leak stopgap until the next drydocking event, are detailed in Reference 1.

Long-term repairs as described here-in have been determined by ABS to be accepted under special consideration. Prior to undertaking such repairs, ABS has requested drawings showing the full details of the repair procedure. These drawings will need to be completed during the drydocking period once the full extent of the repair is known.

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Recommendations

Ultrasonic Thickness Measurement

It is recommended to undertake Ultrasonic Thickness Measurements of the stern tube to determine an approximate extent of the repairs required during the next drydocking in accordance with reference 2.

This may have already been accomplished for the purposes of temporary repairs. Identified areas of significant reduction should be temporarily patched in accordance with Reference 1 until the next scheduled drydocking in the winter of 2024. The stern tube is constructed of 0.5” carbon steel plate, rolled to 29” internal diameter. In this instance, significant reduction is noted as a reduction of 0.1” (20%) or more to a measured thickness of 0.4” (80%) or less. All areas with significant reduction shall be repaired in accordance with this document.

Repairs to Reduced-Thickness Areas

Removals

The vessel shall be in drydock and the tail shaft shall be removed from the stern tube prior to repairs and coatings.

All existing coating systems shall be removed from the interior of the stern tube in its entirety. The interior of the stern tube shall be cleaned to SSPC-SP10 Near-White Metal Blast Cleaning to a 3 to 5 mil profile with a chloride free abrasive to remove the existing coating system and corrosion. Grind flat all burrs and weld seams and radius sharp edges. Freshly blasted ferrous surfaces shall be primed immediately in accordance with the coating requirements to prevent oxidation of the surface.

All areas of the stern tube with thicknesses reduced by 10% or greater of the original thickness shall be repaired. Stern tube plate shall be removed to extend 1” beyond any areas found to be reduced by 10% or greater, with the insert area to be a minimum of 12”x12” in accordance with Reference 4. All cutouts and insert plates shall have rounded corners with a minimum radius of 3”. All removals shall be in a manner to facilitate installation of new plate. Sections of the shell plating in adjacent areas may need to be removed to facilitate replacement of stern tube plating.

Repair Material

All repair material utilized in the prescribed repairs shall be ASTM A106 pipe. Per Reference 3, the inner diameter is 29” and the outer diameter is 30”. Thickness shall be ½” or to match the found thickness of the existing pipe, whichever is greater. Repair section edges shall be bevel-ground from the outside of the pipe to facilitate welding as prescribed in following sections of this document. During plate installation, care shall be taken to maintain circular, longitudinal, and transverse alignment. Repair plates shall be aligned to within 1/16”.

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Welding

All repaired sections of pipe shall be welded to the existing stern tube using a vee butt weld with ceramic backing tape on the inside of the stern tube. Welding shall primarily be from the outside of the stern tube except as necessary. All welds shall be neatly finished, have slag and splatter completely removed, and be ground smooth and flush to the existing plate upon completion.

Coating

Test the surfaces for chloride contamination in accordance with standard NV-2 using Chloride Chemical Test Strips in at least 20 random locations. If chloride level is above 7g/cm2, wash all prepared areas with low pressure 1200 psi water. HoldTight102 Flash Rust Inhibitor/Salt Remover (or equal) shall be used at the manufacturers recommended level. Retest areas in accordance with NV-2.

Prepare surface in accordance with coating manufacturers recommendations. Apply one (1) coat of ARCOR EE-121 epoxy Novolac coating at a DFT of 70-80 mils. Measure and record the DFT of the coating system at 30 locations.