Editorial Note on Part 157
Editorial Note: Nomenclature changes to part 157 appear by USCG-2008-0179, 73 FR 35015, June 19, 2008.

§ 157.03 Definitions. Except as otherwise stated in a subpart: *Amidships* means the middle of the length.
*Animal fat* means a non-petroleum oil, fat, or grease derived from animals and not specifically identified elsewhere in this part.
*Ballast voyage* means the voyage that a tank vessel engages in after it leaves the port of final cargo discharge.
Breadth or B means the maximum molded breadth of a vessel in meters.
*Cargo tank length* means the length from the forward bulkhead of the forwardmost cargo tanks, to the after bulkhead of the aftermost cargo tanks.
*Center tank* means any tank inboard of a longitudinal bulkhead.
*Clean ballast* means ballast which: ( 1 ) If discharged from a vessel that is stationary into clean, calm water on a clear day, would not— ( i ) Produce visible traces of oil on the surface of the water or on adjoining shore lines; or
( ii ) Cause a sludge or emulsion to be deposited beneath the surface of the water or upon adjoining shore lines; or
( 2 ) If verified by an approved oil discharge monitoring and control system, has an oil content that does not exceed 15 p.m.
*Combination carrier* means a vessel designed to carry oil or solid cargoes in bulk.
*Crude oil* means any liquid hydrocarbon mixture occurring naturally in the earth, whether or not treated to render it suitable for transportation, and includes crude oil from which certain distillate fractions may have been removed, and crude oil to which certain distillate fractions may have been added.
Deadweight or DWT means the difference in metric tons between the lightweight displacement and the total displacement of a vessel measured in water of specific gravity 1.025 at the load waterline corresponding to the assigned summer freeboard.
*Dedicated clean ballast tank* means a cargo tank that is allocated solely for the carriage of clean ballast.
*Domestic trade* means trade between ports or places within the United States, its territories and possessions, either directly or via a foreign port including trade on the navigable rivers, lakes, and inland waters.
*Double bottom* means watertight protective spaces that do not carry any oil and which separate the bottom of tanks that hold any oil within the cargo tank length from the outer skin of the vessel.
*Double hull* means watertight protective spaces that do not carry any oil and which separate the sides, bottom, forward end, and aft end of tanks that hold any oil within the cargo tank length from the outer skin of the vessel as prescribed in § 157.10d.
*Doubles sides* means watertight protective spaces that do not carry any oil and which separate the sides of tanks that hold any oil within the cargo tank length from the outer skin of the vessel.
*Existing vessel* means any vessel that is not a new vessel.
*Fleeting or assist towing vessel* means any commercial vessel engaged in towing astern, alongside, or pushing ahead, used solely within a limited geographic area, such as a particular barge fleeting area or commercial facility, and used solely for restricted service, such as making up or breaking up larger tows.
*Foreign trade* means any trade that is not domestic trade.
*From the nearest land* means from the baseline from which the territorial sea of the United States is established in accordance with international law.
*Fuel oil* means any oil used as fuel for machinery in the vessel in which it is carried.
*Inland vessel* means a vessel that is not oceangoing and that does not operate on the Great Lakes.
*Instantaneous rate of discharge of oil content* means the rate of discharge of oil in liters per hour at any instant, divided by the speed of the vessel in knots at the same instant.
*Integrated tug barge* means a tug and a tank barge with a mechanical system that allows the connection of the propulsion unit (the tug) to the stern of the cargo carrying unit (the tank barge) so that the two vessels function as a single self-propelled vessel.
*Large primary structural member* includes any of the following: ( 1 ) Web frames.
( 2 ) Girders.
( 3 ) Webs.
( 4 ) Main brackets.
( 5 ) Transverses.
( 6 ) Stringers.
( 7 ) Struts in transverse web frames when there are 3 or more struts and the depth of each is more than 1 ⁄ 15 of the total depth of the tank.
Length or L means the distance in meters from the fore side of the stem to the axis of the rudder stock on a waterline at 85 percent of the least molded depth measured from the molded baseline, or 96 percent of the total length on that waterline, whichever is greater. In vessels designed with drag, the waterline is measured parallel to the designed waterline.
*Lightweight* means the displacement of a vessel in metric tons without cargo, fuel oil, lubricating oil, ballast water, fresh water, and feedwater in tanks, consumable stores, and any persons and their effects.
*Major conversion* means a conversion of an existing vessel that: ( 1 ) Substantially alters the dimensions or carrying capacity of the vessel, except a conversion that includes only the installation of segregated ballast tanks, dedicated clean ballast tanks, a crude oil washing system, double sides, a double bottom, or a double hull;
( 2 ) Changes the type of vessel;
( 3 ) Substantially prolongs the vessel's service life; or
( 4 ) Otherwise so changes the vessel that it is essentially a new vessel, as determined by the Commandant (CG-CVC).
*MARPOL 73/78* means the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating to that Convention. A copy of MARPOL 73/78 is available from the International Maritime Organization, 4 Albert Embankment, London, SE1
*New vessel* means: ( 1 ) A U.S. vessel in domestic trade that: ( i ) Is constructed under a contract awarded after December 31, 1974;
( ii ) In the absence of a building contract, has the keel laid or is at a similar stage of construction after June 30, 1975;
( iii ) Is delivered after December 31, 1977; or
( iv ) Has undergone a major conversion for which: ( A ) The contract is awarded after December 31, 1974;
( B ) In the absence of a contract, conversion is begun after June 30, 1975; or
( C ) Conversion is completed after December 31, 1977; and
( 2 ) A foreign vessel or a U.S. vessel in foreign trade that: ( i ) Is constructed under a contract awarded after December 31, 1975;
( ii ) In the absence of a building contract, has the keel laid or is at a similar stage of construction after June 30, 1976;
( iii ) Is delivered after December 31, 1979; or
( iv ) Has undergone a major conversion for which: ( A ) The contract is awarded after December 31, 1975;
( B ) In the absence of a contract, conversion is begun after June 30, 1976; or
( C ) Conversion is completed after December 31, 1979.
*Non-petroleum oil* means oil of any kind that is not petroleum-based. It includes, but is not limited to, animal fat and vegetable oil.
*Oceangoing* has the same meaning as defined in § 151.05 of this chapter.
*Officer in charge of a navigational watch* means any officer employed or engaged to be responsible for navigating or maneuvering the vessel and for maintaining a continuous vigilant watch during his or her periods of duty and following guidance set out by the master, international or national regulations, and company policies.
*Oil* means oil of any kind or in any form including, but not limited to, petroleum, fuel oil, sludge, oil refuse, and oil mixed with wastes other than dredged spoil. This includes liquid hydrocarbons as well as animal and vegetable oils.
*Oil cargo residue* means any residue of oil cargo whether in solid, semi-solid, emulsified, or liquid form from cargo tanks and cargo pump room bilges, including but not limited to, drainages, leakages, exhausted oil, muck, clingage, sludge, bottoms, paraffin (wax), and any constituent component of oil. The term “oil cargo residue” is also known as “cargo oil residue.”
*Oil residue* means— ( 1 ) Oil cargo residue; and
( 2 ) Other residue of oil whether in solid, semi-solid, emulsified, or liquid form, resulting from drainages, leakages, exhausted oil, and other similar occurrences from machinery spaces.
*Oil spill response vessel* means a vessel that is exclusively dedicated to operations to prevent or mitigate environmental damage due to an actual or impending accidental oil spill. This includes a vessel that performs routine service as an escort for a tank vessel, but excludes a vessel that engages in any other commercial activity, such as the carriage of any type of cargo.
*Oil tanker* means a vessel that is constructed or adapted primarily to carry crude oil or products in bulk as cargo. This includes a tank barge, a tankship, and a combination carrier, as well as a vessel that is constructed or adapted primarily to carry noxious liquid substances in bulk as cargo and which also carries crude oil or products in bulk as cargo.
*Oily mixture* means a mixture, in any form, with any oil content. “Oily mixture” includes, but is not limited to— ( 1 ) Slops from bilges;
( 2 ) Slops from oil cargoes (such as cargo tank washings, oily waste, and oily refuse);
( 3 ) Oil residue; and
( 4 ) Oily ballast water from cargo or fuel oil tanks, including any oil cargo residue.
*Oily mixture* means a mixture with any oil content.
*Other non-petroleum oil* means an oil of any kind that is not petroleum oil, an animal fat, or a vegetable oil.
*Permeability of a space* means the ratio of the volume within a space that is assumed to be occupied by water to the total volume of that space.
*Petroleum oil* means petroleum in any form, including but not limited to, crude oil, fuel oil, sludge, oil residue, and refined products.
*Primary towing vessel* means any vessel engaged in towing astern, alongside, or pushing ahead and includes the tug in an integrated tug barge. It does not include fleeting or assist towing vessels.
*Product* means any liquid hydrocarbon mixture in any form, except crude oil, petrochemicals, and liquefied gases.
*Segregated ballast* means the ballast water introduced into a tank that is completely separated from the cargo oil and fuel oil system and that is permanently allocated to the carriage of ballast.
*Slop tank* means a tank specifically designated for the collection of cargo drainings, washings, and other oily mixtures.
*Tank* means an enclosed space that is formed by the permanent structure of a vessel, and designed for the carriage of liquid in bulk.
*Tank barge* means a tank vessel not equipped with a means of self-propulsion.
*Tank vessel* means a vessel that is constructed or adapted primarily to carry, or that carries, oil or hazardous material in bulk as cargo or cargo residue, and that— ( 1 ) Is a vessel of the United States;
( 2 ) Operates on the navigable waters of the United States; or
( 3 ) Transfers oil or hazardous material in a port or place subject to the jurisdiction of the United States. This does not include an offshore supply vessel, or a fishing vessel or fish tender vessel of not more than 750 gross tons when engaged only in the fishing industry.
*Tankship* means a tank vessel propelled by mechanical power or sail.
*Vegetable oil* means a non-petroleum oil or fat not specifically identified elsewhere in this part that is derived from plant seeds, nuts, kernels, or fruits.
*Wing tank* means a tank that is located adjacent to the side shell plating.
[CGD 96-026, 61 FR 33666, June 28, 1996; 61 FR 36786, July 12, 1996, as amended by CGD 91-045, 61 FR 39788, July 30, 1996; USCG-2000-7641, 66 FR 55572, Nov. 2, 2001; USCG-2004-18939, 74 FR 3378, Jan. 16, 2009; USCG-2014-0410, 79 FR 38437, July 7, 2014]