Midterm SEAM 4 Flashcards
when a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the material
Corrosion
Main Factors influencing the Rate of Corrosion
Diffusion
Temperature
Conductivity
Acid
Types of Ion
Electrochemical Corrosion
the process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration
Diffusion
– the measure of hotness or coldness expressed in terms of any of several scales, including Fahrenheit and Celsius
– indicates the direction in which heat energy will spontaneously flow—i.e., from a hotter body (one at a higher temperature) to a colder body (one at a lower temperature)
Temperature
a measure of the ability of water to pass an electrical current
Conductivity
a chemical substance, usually a liquid, which contains hydrogen and can react with other substances to form salts
Acid
occurs when two dissimilar metals are present in an electrolytic medium
Electrochemical Corrosion
– a chemical compound that dissociates into ions and hence is capable of transporting electric charge - i.e.
– an electric conductor; unlike metals the flow of charge is not a flow of electrons, but is a movement
Electrolyte
electrically charged atoms
Ions
Two types of ions
Cations
Anions
positively charged ions
Cations
negatively charged ions
Anions
when metals collect this, an electrochemical reaction causes the steel to corrode
Moisture
– also known as metal oxides
– forms when oxygen reacts with metal atoms
Rust
– a coating which is the major line of defense against corrosion in ballast tanks and void spaces
– in ballast tanks, they are commonly used and there is some interest in using inert gas atmospheres
Hard Epoxy Coating
– a means of preventing electrochemical wastage is required
– a system of preventing corrosion by forcing all surfaces of a structure (e.g. hull) to be cathodes by providing external anodes
Cathodic Protection
A type of Cathodic Protection that can be accomplished by fitting aluminium, magnesium or zinc anodes in tanks or underwater portion of a ship, which waste away by galvanic action
Sacrificial Anode Cathodic Protection
A type of Cathodic Protection that can be achieved by superimposing on the hull an impressed current provided by a remote
power source through a small number of inert anodes
Impressed Current Cathodic Protection
Two Types of Cathodic Protection Method
Sacrificial Anode System
Impressed Current System (ICCP)
– metals or alloys attached to the hull that have a more anodic, i.e. less noble, potential than steel when immersed in sea water
– supply the cathodic protection current, but will be consumed in doing so and therefore require replacement for the protection to be maintained
Sacrificial Anodes
– may be safely employed
– sacrificial anodes made of zinc that are attached to a ship’s hull
– a critical component of a cathodic protection system, which is used to protect the ship’s metal structure from corrosion
– they work by corroding instead of the hull, providing protection against corrosion
Zinc Anodes
– consists of a number of anodes (lead or platinised titanium) fitted to the hull at
selected places below the waterline, and control equipment which automatically
regulates the anode current to the required value
– consists of anodes connected to a DC power source
Impressed Current Cathodic Protection (ICCP)
an electrical device used to convert alternating current (AC) into direct current (DC) by allowing a current to flow through the device in one direction only
Rectifier
The process where diodes work like one-way valves within the rectifier to maintain the flow of current
rectification
the negative or reducing electrode that releases electrons to the external circuit and oxidizes (corrode) during and electrochemical reaction
Anode
the positive or oxidizing electrode that acquires electrons from the external circuit and is reduced during the electrochemical reaction
Cathode
– combined with inappropriate manipulations may lead to damage of a vessel, threatening the cargo, the environment or, even worst, human life
Heavy Weather
– the manual required on all types of ships engaged in the carriage of all cargoes other than solid and liquid bulk cargoes
– cargo units, including containers, shall be loaded, stowed and secured throughout the voyage in accordance with it approved by the Administration
Cargo Securing Manual
must be carried out before reaching the loading port on the cargo/bunkering systems and equipment
Pre-arrival checks
must be agreed with the terminal and understood by all personnel involved in the cargo operations
Ship-Shore Safety Checklist
– everywhere, incur a measure of liability for the safety of the goods
– in common-law countries, liable for any damage or for the loss of the goods that are in their possession as carriers, unless they prove that the damage or loss is attributable to certain excepted causes
Carriers
Exceeding the maximum permissible cargo load in any of the holds of a ship will lead to
overstressing of the local structure
– also considered as ‘material wastage’
– the lead cause for structural deformations and fracturing
– by far the most ‘common’ of all other defects directly related to steel and its components
– if left unattended, is a disaster waiting to happen; either by cargo or fuel oil contamination, structural losses, pollution and finally, possible loss of the ship itself
Corrosion
primarily affects iron and its alloys, such as steel
Rust
can affect various materials including metals (like aluminum, copper, and brass)
Corrosion
– a sub-component defect caused due to damage to steel platings or material failure
– could be a change in shape or physical disfigurement of steel that is caused either by
implosion (caused due to vacuum build up in tanks) or explosion, excessive dynamic (wave bending/loading) as well as static stress (ship’s hogging & sagging conditions) and strains onto the steel structures, and likewise
– should be noted that deformations observed on the ship’s hull are more likely to affect structures on the interior too
Deformation
– due to the propagation of cracks through the steel plating, which has been left unattended
– most of it occurs due to excessive stress concentrated on weakened steel plates
throughout the tanks’ dimensions
– along with fatigue, they are important design criteria for ships to ensure a sufficiently high safety level
Fractures
the stress a ship’s hull or keel experiences that causes the center or the keel to bend upward
Hogging
the stress a ship’s hull or keel is placed under when a wave is the same length as the ship and the ship is in the trough of two waves
Sagging
Wave Parts
Crest
Trough
Wave Height
Wavelength
highest part of a wave
Crest
lowest part of a wave
Trough
the overall vertical change in height between crest and trough
Wave Height
distance between two successive crests or troughs
Wavelength
includes incorrect, improper, and insufficient lashing (not using enough dunnage, chocking, lashing materials), incorrect weight distribution, improper loading affecting the stability of the cargo
Bad Stowage
If the tank surface faces over how much percent of the allowable margin, repairs can be needed
75%
must be inspected on a twelve-monthly basis and a report on the condition of the tank sent to the Management Office
Ballast Tanks
How often are Ballast Tanks inspected
twelve-monthly basis
9 Pointers one should specifically identify while inspecting the steel tanks
- Assessing the Overall Condition
- Condition of Corrosion Levels
- Condition of ‘Sacrificial’ Anodes fitted inside the tank
- Checking for Damages/Cracks/Deformations
- Pitting Corrosion & Blister Formation
- Condition of the tank gauging systems
- Condition of the Safety Devices
- Condition of Mud or Sludge Build Up
- Condition of Cargo Equipment
Immediately on entering the enclosed space, one can figure out the tank’s well being by considering the state of the accessways and the ladders, paint coatings, and closely observing areas susceptible to corrosion, such as near the weld joints.
Assessing the Overall Condition
For example, corrosion on the inner surfaces of the liquid cargo tanks (for example, Crude Oil Tankers) is mainly due to the mixture of corrosive gases, crude oil acids, as well as seawater (Crude oil washing).
Condition of Corrosion Levels
To maintain their integrity, anodes have to be checked and inspected closely for excessive wear and tear. A record of material wastage (deterioration) should be maintained for future examination.
Condition of ‘Sacrificial’ Anodes fitted inside the tank
Deformations may generally not be readily evident when viewed over a larger area. To identify this, it is good to highlight the area using a high beam torch by projecting it parallel to the surface.
Checking for Damages/Cracks/Deformations
– often known to be observed in the bottom plating of ballast tanks, especially near the ‘bell- mouth’, near the ‘bell-mouth’ in a liquid cargo tank, or next to suction wells associated with the submerged pumps fitted within the tanks
– a localized form of corrosion by which cavities or “holes” are produced in the material
– considered to be more dangerous than uniform corrosion damage because it is more difficult to detect, predict and design against
Pitting Corrosion
occurs when oxide scale is swollen during oxidation
Blistering
Gauging systems that include gas measuring gauges, pressure gauges, temperature gauges, remote level sensing meters, sounding pipes, as well as striker plates, should be checked for functional abnormalities.
Condition of the tank gauging systems
ensures accurate level, temperature, and pressure measurements for inventory control, oil movement and overfill prevention, securing efficient operations
Tank Gauging System
fitted in the tanks critical for providing the operators a remote indication of an unwanted threat such as water ingress in the bilges of cargo holds due to sweating or any other reason for that matter
Safety devices
could be detrimental in terms of hiding away serious defects and also to promote the development of structural deterioration underneath the horizontal/parallel surfaces
Accumulation of mud and oily sludge in the tanks
Cargo equipment within the tanks includes heating coils, cargo pumps, crude oil washing machines, remote gauging systems, temperature/heat sensors, etc.
Condition of Cargo Equipment
necessary to confirm hatch covers are weathertight and will remain weathertight throughout the voyage
test and a visual inspection
generally sufficient to prove that the hatch covers are in order
satisfactory ultrasonic or hose test
provide evidence that the condition of the hatch covers does not pose a threat to the cargo
SGS Hatch Inspections
– visually inspect hatch covers at departure and arrival for water tightness and proper operation
– look for obvious damage, holes and leak points that may jeopardize the quality of the cargo
SGS Inspectors
a multinational company headquartered in Geneva, Switzerland, that provides inspection, verification, testing, and certification services
SGS
SGS Meaning
Société Générale de Surveillance
a Non-Destructive Testing (N.D.T.) whereby, with the use of the appropriate equipment, tightness of Hatch Covers can be tested against leakages which can cause charterers claims and affect seaworthiness of vessels
Ultrasonic Hatch Leak Inspection
8 Most Commonly used NDT in Hatch Cover Techniques
- Visual NDT (VT)
- Ultrasonic NDT (UT)
- Radiography NDT (RT)
- Eddy Current NDT (ET)
- Magnetic Particle NDT (MT)
- Acoustic Emission NDT (AE)
- Dye Penetrant NDT (PT)
- Leak Testing (LT)
makes the voyage uncomfortable and dangerous by causing the ship to roll, pitch, or yaw, potentially causing cargo shift, equipment damage, or injuries to the crew
High Swells & Rough Seas
6 Types of Ship Motion during Rough Seas
- Heaving
- Surging
- Swaying
- Rolling
- Pitching
- Yawing
Moving up and down along the vertical axis
Heave (Heaving)
Moving left and right along the lateral horizontal axis
Sway (Swaying)
Moving forwards and backwards along the longitudinal horizontal axis
Surge (Surging)
Rotating about the longitudinal horizontal axis
Rolling (Roll)
Rotating about the lateral horizontal axis
Pitch (Pitching)
Rotating about the vertical axis
Yaw (Yawing)
– the inspection of foreign ships in national ports to verify that the condition of the ship and its equipment comply with the requirements of international regulations and that the ship is manned and operated in compliance with these rules
– a ship inspection program whereby foreign vessels entering a sovereign state’s waters are boarded and inspected to ensure compliance with various
Port State Control
– the country in which the ship is registered
– it is its duty to ensure that the ship entitled to fly its flag is safely constructed, equipped and
subsequently properly maintained and manned as per regulation based on the International
Convention developed by IMO for this purpose
– carries out survey and inspection on the vessel for issuance of various statutory certificates
Flag State
– when a country exercises control over a ship that is registered in that country
– limited to ensure that valid certificates are onboard (Statutory Certificates)
Flag State Control
A Port State Control visit on board a ship will normally start with, as a minimum and to the extent applicable, with an examination of the documents in accordance with Annex
Annex 10 of the Paris MOU Memorandum
Ship Particulars
Form A
details about the vessel, including its length, breadth, depth, gross tonnage and where the ship was built
Ship Particulars
details about the ship’s engine, including the make and model and a description of the engine
Ship Engine Particulars
Deficiencies
Form B
These ships are designed with multiple layers of safety features and redundancies to minimize the risk of accidents or incidents
Low Risk Ships
How often are low risk ships inspected
every third year
a vessel that is designed and built to meet the requirements of a specific classification society, such as the American Bureau of Shipping (ABS), Lloyd’s Register (LR), or Det Norske Veritas (DNV)
Standard Risk Ships
How often are Standard Risk Ships inspected
every year
ships of a risk type (chemical tanker, gas carrier, oil tanker, NLS tanker, bulk carrier and passenger ship) and more than 12 years old are eligible for an expanded inspection
High Risk Ships
How often are High Risk Ships inspected
every six months
shall include a check of the overall condition, including the human element where relevant
Expanded Inspection
– involves checking of several aspects of the ship in both deck and engine departments of the ship
– involves important checking of documents, technical details, and structural elements of the ship
Port State Control Inspection
General Inspection of the Ship
Initial Inspection
Initial Inspection of Certain Type of Ships of Certain Age
Expanded Inspection
Detailed Inspection based upon the findings (clear grounds) of non compliance
More Detailed Inspection
Any of the three inspections that focus on specific areas where high levels of deficiencies have been encountered by PSCOs, or where new convention requirements have recently entered into force
Concentrated Inspection Campaign
Resolution the Organization adopted on Regional co-operation in the control of ships and discharges promoting the conclusion of regional agreements
A.682(17)
