LIFE-TIME STRUCTURAL INTEGRITY AND TANKER

OPERATIONS Dr. Michael(MIKE) B. Kennedy, Hellespont Steamship Corp.

Naval Arch/Marine Eng. since 1975 (MIT PhD 1979) mostly oil tankers. Assoc. with Hellespont(Papachristidis) from 1982 - prev. eng./broking. White double hull ULCCs(Discovery TV Superships Hellespont Fairfax)

MD, Supt.,Operator, auditor - Korea, China, India, Philippines. Recently recruited leader of Offshore Fleet and dlvd 5 PSV 2009/10.

Basic Ideas Of The Talk Structure is a key part of design, construction, operation. The operator

cannot change the design or construction.

Good practices: drawings ship+shore; bridge team monitoring of bow forces and bending moments; inspect/record tank and hull condition.

Structure Failing: Steel/Coating - Condition Assessment Programme

A DESIGN AND CONSTRUCTION FRAMEWORK

DESIGN: Common Structural Rules(CSR)? Initial Scantling Evaluation; a FEA with coarse mesh; generic 50% fatigue failure models; a few FEA fine mesh models target 50% failure lifetime.

CONSTRUCTION(STEEL): IACS’s No.47 Ship and Repair Quality Std? "Standard" Tolerance and "Maximum" Limits;

How and when to apply negotiation during production. Material control.

CONSTRUCTION(COATINGS): Performance Stds for Prot. Coatings(PSPC)? regulation for ballast tanks - only recommendation for void+cargo spaces. Interpretation problems.

WHY SITE TEAM? Yard is a fixed price contractor. Yard pays Class.

Basic Design is contractual but DETAILED OUTFITTING DESIGN? Consider hot spots both basic and outfitting connections (TSCF reports). May have to retrofit fixes (slot collars, support brackets, toes).

Poor welding (tank leaks), poor coatings (corrosion, drilling) Should have supv. in yard. Each failure means checking "the rest".

Wrong or mistreated HT steel - how to check? Paint - use IR. Over dependency on material control chain - manual labels? All failures mean extensive operator checking and possible "repair".

CONSTRUCTION ISSUES BECOME OPERATOR ISSUES

OPERATING A STRUCTURE - OVERALL GOOD PRACTICES

More Info is better - Drawings, FEA Results, Design Calcs. OPS: Trim+Stab, Loadicator, GA, Capacity, Mooring, Hull Piping

R/M: Midship Section and BHDs, Shell Exp/ConProf, Paint Scheme GEN: FEA / Fatigue Results - Color hot stress levels, fatigue life.

POSSIBLE RETRO-FIT FOR DRIVING THE SHIP MORE SAFELY Install Hull Monitoring for hull bending moment and bow acceleration. Bridge in a tanker high aft wheelhouse cannot see the flexing or bow. Weather Routing is macro scale and ship needs actual/micron conditions Change heading, route,trim and speed. Record for commercial disputes

TANK INTERNALS AND OPERATIONAL INSPECTIONS

Tanks are more difficult than the hull. PV venting checked too.Avoid tank implosion/bulkheads from P/V or vent failure.

IGS good but unless double scrub sulfur corrosion near IG outlet.

Inspect any tank at every chance. Always date photos for control.

Inspection: Struct. Ext. (HULL) and Int. (TANKS). Sched Blst and Cargo tanks and Opportunistic inspections Hull Inspect for CLASS, Prop polish, etc. - overall hull photos

Photos of problems areas but also standard test positions. Measure paint DFT and steel thickness. AND paint X scribings. Check anodes. Remove loose anodes. Scrape tight anode scale.

Tank Cathodic Prot. - blst tanks - AgCl Cell 850mVgood. Plot mV thru time. Tanks must polarize at 850mV in < 2days Slower? add more anodes. Less than 850mV? ADD anodes and INSPECT asap – if lot lower prepare – possible steel job

MORE BLST/CARGO TANK OPERATOR IDEAS

Crew can only repair minimal mech damages in tanks. Damage: FW rinse, de-rust, sand adj. paint, solvent wipe, paint. Cathodic: remove loose anodes, scrape anodes, add anodes, mV?

Sulfur Reducing Bacteria - generally no but if mud? Crew to periodically wash out the mud and inspect.Fixed (COW) Washing mach. cargo/crude residues.Terminals want no COW. Residues preferential corrosion sites Inert Gas System - double scrub for Cargo and BLST Tank. IGS SOX about 0.1% of Fuel’s Sulfur after normal scrub. E.g. 3% Sulfur is 300ppm. Double scrub/equiv less 2ppm. Put 2ppm SOX, 5% O2 IG in anoded ballast tanks - no corrosion.

CONDITION ASSESSMENT PROGRAMME - OPERATIONS

PSPC if made correct - TSCF guess of 15+ years no problems. First failure are edges where PSPC is weakest. Or bad paint.

CAP-HULL-1: Very Good Condition. Superficial - no mnt/repair req. CAP-HULL-2: Good Cond.. Minor Defic. - thicker than Class. No repair CAP-HULL-3: Satisfactory. Some substantial corros. no immed repair CAP-HULL-4: Unsatisfactory. Class Issues with below renewal levels.

FIXING COATING IS DIFFICULT – QUANTITY AND ACCESS. Staging in ballast tank hoppers,cargo tank underdeck, high sides. Scrape loose scale. FW wash. Grind/blast incl lightly nearby good area Check before painting. Paint 2+ coats to 300+. Check, paint more. On the run, about 20-30 USD/m2.Yard 20-40 USD/m2. PLUS TIME.

STRUCTURAL SAFETY - GOOD OPERATING PRACTICES

Ship drawings and plans ashore and onboard - including studies

Inspect periodically and by opportunity hull and all tanks

Make sure PV, IGS and venting systems all working well.

Wash out mud, check anodes( 850mV cathodic in 2 days or less).

Hull bending and bow accelerometer with display on bridge.

Anytime divers - photograph entire hull, clean seachests.

If problems more anodes and consider inerting good IG.

Check deck and outfitting for cracks - fix damages and paint.

NEVER EVER PAINT OVER RUST.