Surveyor’s Glossary Hull Terms & Hull Survey
IACS
IACS S U R V EY OR’S GLOSSARY
Recommendation 82
(July 2003)
Surveyor’s Glossary
Hull Terms & Hull Survey
Terms
Rec. 82 / July 2003 2
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Rec. 82 / July 2003 3
1. Introduction
This Surveyor’s Glossary of Hull Terms is intended as a guide to improve the
standardization of survey reporting. It is recommended that the listed terms for
hull structural elements are used throughout report narratives.
The Glossary also includes definitions of common hull survey terms that are
applicable for surveys of hull structures and reporting.
All parties involved in the review of classification survey reports should have
this Glossary available to assist with correct interpretation of the report
narratives.
Rec. 82 / July 2003 4
2. Hull Terms
2.1 General
Accommodation Ladder is a portable set of steps on a ship’s side for people
boarding from small boats or from a pier.
Aft Peak Bulkhead is a term applied to the first main transverse watertight
bulkhead forward of the stern. The aft peak tank is the compartment in the
narrow part of the stern aft of this last watertight bulkhead.
Bay is the area between adjacent transverse frames or transverse bulkheads.
Bilge Keel is a piece of plate set perpendicular to a ship’s shell along her bilges
for about one third her length to reduce rolling.
Bilge Strake is the strake at the turn of bilge extending outward to a point where
the side rises vertically.
Breast Hook is a triangular plate bracket joining port and starboard side
structural members at the stem.
Bulkhead Deck is the uppermost continuous deck to which transverse watertight
bulkheads and shell are carried.
Bulkhead Structure is the transverse or longitudinal bulkhead plating with
stiffeners and girders.
Bulwark is the vertical plating immediately above the upper edge of the ship’s
side surrounding the exposed deck(s).
Cargo Area or Cargo Length Area is that part of the ship that contains cargo
holds and cargo / slop tanks and adjacent areas including ballast tanks, fuel
tanks, cofferdams, void spaces and also including deck areas throughout the
entire length and breadth of the part of the ship over the mentioned spaces.
Cargo Hold Bulkhead is a boundary bulkhead separating cargo holds.
Cargo Port is a door or port in a ship’s side for the loading or discharge of cargo
or stores. Also called side port.
Carlings are supports usually of flat plate, welded in a fore and aft direction
between transverse deck beams to prevent distortion of the plating.
Casing is the covering or bulkhead around or about any space for protection.
Rec. 82 / July 2003 5
Ceilings is wood sheathing or planking fitted on various parts of the ship such as
tank tops, ship’s sides and bulkheads to protect the ship’s structure from
damage and also used to protect the cargo from damage.
Coaming is the vertical boundary structure of a hatch or skylight.
Cofferdams are spaces between two bulkheads or decks primarily designed as
a safeguard against leakage of oil from one compartment to another.
Collision Bulkhead is the foremost main transverse watertight bulkhead.
Companion Way is a weathertight entrance leading from a ship's deck to spaces
below.
Confined Space is a space identified by one of the following characteristics:
limited openings for entry and exit, unfavorable natural ventilation or not
designed for continuous worker occupancy.
Cross Deck is the area between cargo hatches.
Cross Ties are used to support the longitudinal bulkheads of oil tankers against
hydrostatic and hydrodynamic loads.
Dead Covers are plates of bronze or steel working on a hinge serving to protect
the glass port light in heavy weather. Also called dead light.
Deck House is a structure on the freeboard or superstructure deck not extending
from side to side of the ship.
Deck Structure is the deck plating with stiffeners, girders and supporting pillars.
Deep Tank is a tank extending from the bottom or inner bottom up to or higher
than the lowest deck.
Discharges are any piping leading through the ship's sides for conveying bilge
water, circulating water, drains etc. Also called Overboard Discharge.
Double Bottom Structure is the shell plating with stiffeners below the top of the
inner bottom and other elements below and including the inner bottom plating.
Duct Keel is a keel built of plates in box form extending the length of the cargo
hold. It is used to house ballast and other piping leading forward which otherwise
would have to run through the cargo holds.
Enclosed Superstructure is the superstructure with bulkheads forward and/or
aft fitted with weather-tight doors and closing appliances.
Equipment Number is used by classification societies mainly to determine the
size and number of anchors and chain cables for a new ship.
Rec. 82 / July 2003 6
Floor is a bottom transverse member.
Flush Deck Ship is a ship that has no superstructure on the freeboard deck.
Forecastle is a short superstructure situated at the bow.
Forepeak is the area of the ship forward of the collision bulkhead.
Freeboard Deck is normally the uppermost complete deck exposed to weather
and sea, which has permanent means of closing all exposed openings.
Freeing Port is an opening in the bulwarks to allow water shipped on deck to run
freely overboard.
Gangway is the raised walkway between superstructure such as between
forecastle and bridge or between bridge and poop.
Girder is a collective term for primary supporting structural members.
Gunwale is the upper edge of the ship's sides.
Gusset is a triangular plate, usually fitted to distribute forces at a strength
connection between two structural members.
Hatch Coaming is the vertical plating built around the hatchways to prevent
water from entering the hold; and to serve as a framework for the hatch covers.
Hatch Covers are wooden or steel covers fitted over a hatchway to prevent the
ingress of water into the ship s hold and may also be the supporting structure for
deck cargo.
Hatch Ways are openings, generally rectangular, in a ship’s deck affording
access into the compartment below. Also called hatches.
Hopper Side Tanks are tanks used for ballast or for stability when carrying
certain cargoes in bulk carriers. Also referred to as topside wing ballast tanks
and bottom hopper tanks.
Independent Tank is a self-supporting tank.
Keel is the main structural member or backbone of a ship running longitudinal
along centerline of bottom. Usually a flat plate stiffened by a vertical plate on its
centerline inside the shell.
Margin Plate is the outboard strake of the inner bottom and when turned down at
the bilge the margin plate (or girder) forms the outer boundary of the double
bottom.
Rec. 82 / July 2003 7
Midship Section is the cross section through the ship, midway between the
forward and after perpendiculars.
Pipe Tunnel is the void space running in the midships fore and aft lines between
the inner bottom and shell plating forming a protective space for bilge, ballast and
other lines extending from the engine room to the holds.
Poop is the space below an enclosed superstructure at the extreme aft end of a
ship.
Poop Deck is the first deck above the shelter deck at aft end of a ship.
Port Light is another term for side light or side scuttle.
Reduced Scantlings are scantlings that are allowed to be reduced because
approved corrosion control arrangements have been applied.
Representative Spaces is those which are expected to reflect the condition of
other spaces of similar type and service and with similar corrosion prevention
systems.
Scupper is any opening for carrying off water from a deck, either directly or
through piping.
Scuttle is a small opening in a deck or elsewhere, usually fitted with a cover or
lid or a door for access to a compartment.
Shedder Plates are slanted plates fitted in dry cargo holds to prevent undesired
pockets of cargo. The term is also commonly applied to slanted plates that are
fitted to improve the structural stability of corrugated bulkheads and framing
members.
Sheer Strake is the top strake of a ship's side shell plating.
Single Bottom Structure is the shell plating with stiffeners and girders below the
upper turn of bilge.
Skylight. A deck opening fitted with or without glass port light and serving as a
ventilator for engine room, quarters, etc.
Spaces are separate compartments including holds and tanks.
Stay is a term for bulwarks and hatch coaming brackets.
Stem is the piece of bar or plating at which a ship’s outside plating terminates at
her forward end.
Stern Frame is the heavy strength member in single or triple screw ships,
combining the rudder post.
Rec. 82 / July 2003 8
Stiffener is a collective term for secondary supporting structural members.
Stool is a structure supporting cargo hold and tank bulkheads.
Strake is a course, or row, of shell, deck, bulkhead, or other plating.
Strength Deck is normally the uppermost continuous deck. After special
consideration of its effectiveness, another deck may be defined as strength deck.
Stringer Plate is the outside strake of deck plating.
Superstructure is a decked structure on the freeboard deck extending for at
least 92% of the breadth of the ship.
Suspect Areas are locations showing substantial corrosion and/or which are
considered by the Surveyor to be prone to rapid wastage.
Tank Bulkhead is a boundary bulkhead in a tank for liquid cargo, ballast or
bunkers.
Topside Wing Ballast tanks are ballast tanks in bulk carriers that normally
stretch along the length of the ship’s side and occupy the upper corners of the
cargo hold.
Tween Decks is an abbreviation of between decks, placed between the upper
deck and the tank top in the cargo holds.
Void is an enclosed empty space in a ship.
Wash Bulkhead is a perforated or partial bulkhead in a tank.
Watertight Bulkhead is a collective term for transverse bulkheads required for
subdivision of the hull into watertight compartments.
Wind and Water Strakes are the strakes of a ship's side shell plating between
the ballast and deepest load waterline.
Rec. 82 / July 2003 9
2.2 Nomenclature for typical hull structures
1 Strength deck plating 14 Bilge longitudinals
2 Stringer plate 15 Longitudinal bulkhead lower strake
3 Sheer strake 16 Side shell longitudinals
4 Side shell Longitudinal plating17 bulkhead 5 Bilge plating 18 Longitudinal bulkhead longitudinals
6 Bottom shell Deck platcinegn2tr5e transverse tank
7 Keel plate 26 Bottom transverse centre tank
8 Deck longitudinals 27 Deck transverse wing tank
9 Deck girders 28 Side shell vertical web
10 Sheer strake longitudinal 29 Longitudinal bulkhead vertical web
11 Longitudinal bulkhead top strake 30 Bottom transverse wing tank
12 Bottom longitudinals 31 Cross ties
13 Bottom girders 32 Transverse web face plate
Figure 1: Single Hull Tanker — Typical Transverse Section
28
Rec. 82 / July 2003 10
1 Strength deck plating 16 Side shell longitudinals
2 Stringer plate 17 Longitudinal bulkhead plating
3 Sheer strake 18 Longitudinal bulkhead longitudinals
4 Side shell Inner plating19 bottom 5 Bilge plating 20 Inner bottom longitudinals
6 Bottom shell Deck platcinegn2tr5e transverse tank
7 Keel plate 26 Bottom transverse centre tank
8 Deck longitudinals 27 Deck transverse wing tank
9 Deck girders 28 Side shell vertical web
10 Sheer strake longitudinal 29 Longitudinal bulkhead vertical web
11 Longitudinal bulkhead top strake 30 Bottom transverse wing tank
12 Bottom longitudinals 31 Cross ties
13 Bottom girders 32 Transverse web face plate
14 Bilge longitudinals 33 Double bottom floor
15 Longitudinal bulkhead lower strake 36 Hatch coamings
Figure 2: Single Hull Oil / Ore Carrier — Typical Transverse Section
Rec. 82 / July 2003 11
Figure 3: Double Hull Tanker — Typical Transverse Section
Rec. 82 / July 2003 12
Figure 4: Double Hull Tanker — Typical Transverse Bulkhead
Rec. 82 / July 2003 13
Figure 5: Single Skin Bulk Carrier — Typical Cargo Hold Structural
Configuration
Rec. 82 / July 2003 14
Figure 6: Single Skin Bulk Carrier — Typical Transverse Section
Rec. 82 / July 2003 15
Figure 7: Bulk Carrier — Typical Transverse Watertight Bulkhead
Rec. 82 / July 2003 16
Figure 8: General Dry Cargo Ship — Typical Transverse Section
CL
CL
Upper deck plating
(Strength deck plating )
Hatch cover
Bulwark
Upper deck longi tudinal
(Strength deck longitudinal)
Hatch side coaming
Hatch side girder
Web beam
(Cantilever beam)
Side shell web frame
Side shell plating
Side shell frame
(Hold frame)
Inner bottom plating
(Tank top)
Inner bottom longi tudinal
Bottom side girder Bottom center girder
Double bottom tank floor
Strut
Stiffener
Bracket
Bottom shell plating
Bottom longi tudinal Bilge shell plating
Keel plate
Tween deck
(Second deck)
Tween deck beam
(Second deck beam)
Side st ringer
Side shell frame
(Tween deck frame)
Side shell frame
(Hold frame)
Tween deck cant ilever beam
Double bottom tank
Rec. 82 / July 2003 17
3. Hull Survey Terms
Abrasion is the removal of material by mechanical, i.e. rubbing or frictional,
means.
Active Corrosion means gradual chemical or electrochemical attack on a metal
producing loose scale, by atmosphere, moisture or other agents.
Allowable Corrosion or Wastage Limit is the acceptable thickness diminution
of structural elements.
Anode is the positively charged metal surface and the corroding part of an
electrochemical corrosion cell at which the oxidation or loss of electrons occurs.
Sacrificial anode or impressed current anode.
Antifouling is paint for use on underwater areas on hulls. Antifouling contains
agents who prevent the adhesion and growth of organisms on the hull.
Bacterial Corrosion or Microbially Influenced Corrosion (MIC) is corrosion
which is induced or accelerated by the presence of micro organisms.
Blasting or Shot-Blasting is the cleaning of a metal surface by a stream of
abrasive particles.
Blister - a raised area, often dome shaped, resulting from loss of adhesion
between a coating or deposit and the substrate.
Brittle Fracture is the separation of a solid accompanied by little or no
macroscopic plastic deformation. Typically, brittle fracture occurs by rapid crack
propagation with less expenditure of energy than for ductile fracture. Brittle
tensile fractures have a bright, granular appearance and exhibit little or no
necking.
Buckling: a bulge bend or other wavy condition of the structure caused by in
plane compressive stresses and /or shear stresses.
Butt Joint is a joint between two structural members lying in the same plane.
Typically a butt joint is used to describe the welded connection between two
plates in the transverse direction.
Cathode is the negatively charged metal surface and the non-corroding or
protected part of an electrochemical corrosion cell.
Cathodic Protection is the partial or complete protection of a metal from
corrosion by making it a cathode, using either a galvanic or an impressed current
to bring a metal to a potential where it is thermodynamically stable.
Cavitation Damage is degradation of metal surfaces, characterized by pitting, in
which the pit profile is irregular, occurring when very turbulent fluids are in
contact with the metal surface, and associated with the formation and collapse of
Rec. 82 / July 2003 18
cavities in the liquid at the solid — liquid interface.
Close-up Survey is a survey where the details of structural members are within
the close visual inspection range of the surveyor, i.e. normally within the reach of
hand.
Coating Evaluation Criteria is normally an assessment of the extent of damage
registered in terms of coating breakdown area and/or rust scales in % of area
under consideration, normally the complete tank, with additional information on
coating damage to edges and weld connection. Typical coating failures may be
given as additional information.
Coating, often synonymous with Painting, i.e. a protective film of thickness
usually about 0,2 - 0,5 mm, applied to prevent corrosion mainly via a three main
mechanisms; the barrier effect, the cathodic effect or by inhibition / passivation.
Collision Damage is damage caused by physical impact between two or more
ships used for navigation.
Condition Assessment Programme (CAP) is a voluntary system, which gives a
detailed assessment of a tanker’s actual condition at the time of inspection and is
available to both charter-parties and owners.
Condition Survey is a survey normally of limited scope and time and intended to
identify any anticipated structural or corrosion related deficiencies and give an
overall visual impression of the structural integrity.
Contact Damage is damage caused when the ship strikes something other than
another ship. (see also ‘Grounding’).
Corrosion Fatigue is the process in which a metal fractures prematurely in a
trans-crystalline manner under conditions of simultaneous corrosion and
repeated cyclic loading of lower stress levels or fewer cycles than would be in the
absence of a corrosive environment
Corrosion is the chemical or electrochemical reaction between a material,
usually a metal and its environment that produces a deterioration of material and
its properties, usually an oxide is formed.
Corrosion Prevention System is considered a full hard coating; alternatively a
full hard coating supplemented by cathodic protection.
Crack is a fracture type discontinuity without complete separation characterized
by a sharp tip and high ratio of length and width to opening displacement.
Crevice Corrosion is localized corrosion of a metal surface at, or immediately
adjacent to, an area that is shielded from full exposure to the environment
because of close proximity between the metal and surface of another material. It
is usually associated with small volumes of stagnant water; within lapped joints,
Rec. 82 / July 2003 19
under heads of fastenings, under gaskets and packings, under marine organisms
and porous deposits.
Critical Structural Areas are locations which have been identified from
calculations to require monitoring or from the service history of the subject ship or
from similar ships to be sensitive to cracking, buckling or corrosion which would
impair the structural integrity of the ship.
Cumulative Damage is an aggregation of damage due to various physical
causes, specifically applied to fatigue under various stress ranges and
frequencies.
Damage Survey is a survey requested as a result of hull damage or other
defects.
Deformation is a change in the form of a structure due to stress, thermal
change, change in moisture, or other causes.
Delamination is peeling from undercoat or substrate.
Deposit Attack is an attack under, or around, the edge of a local deposit formed
on a metal surface in the presence of an electrolyte.
Ductile Fracture is the separation of a solid accompanied by gross plastic
deformation.
Edge Corrosion is local corrosion at the free edges of stiffeners, brackets,
flanges, manholes etc.
Elasticity means the structural member's capability of sustaining stress without
permanent deformation, i.e. to recover its original size and shape after the stress
has been removed.
Electrochemical Corrosion is corrosion associated with the passage of an
electric current. If the current is produced by the system itself it is called Galvanic
Corrosion and if it results from an impressed current it is called Electrolytic
Corrosion.
Erosion Corrosion is a combined action involving corrosion and erosion in the
presence of a moving corrosive fluid, leading to the accelerated loss of material.
Erosion corrosion is characterized by grooves, gullies, waves, valleys etc.,
usually with directional pattern and with bright surfaces free from corrosion
products.
Erosion Damage is the physical removal of material from a surface by
mechanical means such as e.g. flowing liquid and it may be accelerated by
corrosion.
Excessive Corrosion is an extent of corrosion that exceeds the Allowable
Corrosion.
Rec. 82 / July 2003 20
Extensive Corrosion is an extent of corrosion consisting of hard and/or loose
scale, including pitting, over 70% or more of the area under consideration,
accompanied by evidence of thickness diminution.
FAIR condition is a term used to describe the condition of a hard coating; with
local breakdown at edges of stiffeners and weld connections and/or light rusting
over 20% or more of areas under consideration, but less than as defined for
POOR condition.
Fair is to smooth or fair up a ship's lines and eliminating irregularities.
Fatigue is the phenomenon leading to fracture under repeated or fluctuating
stresses having a maximum value significantly less than the ultimate tensile
strength of the material.
Fracture is the propagation of a crack through the thickness of a material.
( see ‘Brittle’ and ‘Ductile’ Fractures )
Galvanic Corrosion is electrochemical accelerated corrosion of a metal
because of an electrical contact with a more noble metal or nonmetallic
conductor in a corrosive electrolyte.
Galvanizing is the deposition of zinc on to the surface of steel to provide
corrosion protection by both protecting the steel from contact with the
environment and giving sacrificial protection.
General Corrosion or Overall Corrosion appears as non-protective, friable rust
of a uniform nature on uncoated surfaces. Rust scale continually breaks off,
exposing fresh metal to corrosive attack. Visual judgment of thickness loss is
difficult until serious wastage has occurred.
GOOD condition is a term used to describe condition of hard coating; with only
minor spot rusting.
Grooving Corrosion is local corrosion normally adjacent to welding joints along
abutting stiffeners and at stiffener or plate butts or seams.
Grounding is contact of the ship’s bottom with the sea floor.
Hard Coating is a coating which chemically converts during its curing process,
normally used for new construction, or non-convertible air drying coating which
may be used for maintenance purposes. Hard coating can be either organic or
inorganic and covers typical marine coatings such as those based on epoxy, coal
tar epoxy, polyurethane, chlorinated rubber, vinyl, zinc epoxy, zinc silicate.
Hose Testing is carried out to demonstrate the tightness of structures not
subject to structural (hydrostatic) or leak testing and to other components that
contribute to the watertight or weathertight integrity of the hull.
Rec. 82 / July 2003 21
Hydropneumatic Testing is a combination of hydrostatic and air testing.
Indent is deformation of structural members caused by out of-plane loads like
bottom slamming and bow impact forces, contact with other objects etc.
Inhibitors are substances used to prevent or retard a chemical or
electrochemical reaction, often used to render corrosion products less soluble
and thereby tending to stifle electrochemical corrosion processes.
Insignificant Corrosion or Minor Corrosion is an extent of corrosion with minor
spot rusting and such that an assessment of the corrosion pattern indicates
wastage generally not exceeding of 30% of the allowable corrosion limits.
Lamination is an excessively large, laminar, non-metallic inclusion, producing a
defect appearing in sheets or strips as segregation or in layers.
Lap Joint is a joint between two structural members that overlap each other.
Leak Testing is an air or other medium test carried out to demonstrate the
tightness of the structure.
Local Corrosion is by name local in nature, often appearing at areas with local
breakdown of coating or at areas with stress concentrations.
Loose Scale is sheets of rust falling off if the surveyor hits the structure with his
test hammer. Loose scale can best be removed by hand or power tool cleaning
or a combination of these.
Mill Scale is thick oxide film formed on wrought-metal products which have been
hot-rolled or forged and allowed to cool in air, the term is principally applied to
steel on which the oxide is essentially magnetic black oxide.
Necking Effect is a term describing local corrosion at junction of plating and
stiffeners due to flexure effects caused by reverse, cyclic loading with loss of
coating or shedding of scale exposing fresh steel to further corrosion. The
corrosion rate may be rather high and accelerates with thinning of the material.
On-hire/Off-hire Survey is surveys carried out to state the ship's condition prior
to or after her chartering. The main purpose is to record deficiencies or damages.
Overall Survey is survey intended to report on the overall condition of the hull
structure and determine the extent of additional close-up surveys.
Paint can be described as a liquid material capable of being applied or spread
over a solid surface on which it subsequently dries or hardens to form a
continuous adherent, obliterating film.
Paint Cracking is deep cracks in paint that expose substrate.
Rec. 82 / July 2003 22
Periodical Survey is a collective term of classification surveys carried out after
the delivery a ship and at prescribed time intervals, i.e. annual, intermediate and
renewal/special surveys.
Pinholing is tiny, deep holes exposing substrate.
Pinpoint Rusting is local rusting at pinholes or holidays.
Pitguard Anode is a sacrificial anode placed just above tank bottom in order to
mitigate the general and pitting corrosion process.
Pitting Corrosion is local, random scattered corrosion mainly on horizontal
surfaces and at structural details where water is trapped, particularly at bottom of
tanks. For coated areas the attack produces deep and small diameter pits which
may lead to perforation. Pitting of uncoated areas in tanks, as it progresses,
forms shallow but very wide scabby patches (e.g. 300 mm in diameter) and the
appearance resembles condition of general corrosion.
Plasticity is the property of a material that allows it to be extensively repeatedly
deformed without rupture when acted upon by a force sufficient to cause
deformation and that allows it to retain its deformed shape after the applied force
has been removed.
POOR condition is a term used to describe condition of hard coating; with
general breakdown of coating over 20% or more or hard scale at 10% or more of
areas under consideration.
Prompt and Thorough Repair is permanent repair completed at the time of the
survey to the satisfaction of the surveyor, therein
