Vapor Control Valve (VCV) - This valve is used in conjunction with closed and restricted measurement equipment to allow measurements in ship's tanks that are closed to the atmosphere. Once a portable measurement unit (PMU) is attached to the VCV, the valve is opened and the PMU's probe is dropped into the tank to perform the required measurements.

Vapor Recovery System (VRS) - Procedures and equipment for the collection of hydrocarbon vapors from vessel's tanks and the transfer to shoreside recovery equipment.

Vessel Experience Factor (VEF) - A factor based on the compilation of the history of the total calculated volume (TCV) vessel measurements, adjusted for on-board quantity (OBQ) or remaining on board (ROB), compared with the TCV shore measurements. This factor if developed according to the latest industry standards may be used to obtain a better ship shore comparison of volumes.

Vessel Sizes and Uses
Tankers and barges come in all sizes from the small harbor/lake variety to the biggest things ever built by man that move. The size of any particular tanker depends on many factors. Use, cargo type, amount and demand, passage length and port restrictions at both loadport and the discharge port are among the most important of these. Tankers were generally classified as follows:

Clean Tanker categories

Under 16,500 DWT - Coastal, Small, Harbor/Lake Tankers

16,500 - 24,999 DWT - General Purpose Vessels

25,000 - 49,999 DWT - Medium Range Vessels

50,000 - 79,999 DWT - LR1 (Large Range 1)

80,000 - 159,999 DWT - LR2 (Large Range 2)

Crude Tanker Categories

55,000 - 79,999 DWT - Panamax Crude Carrier

80,000 - 119,000 DWT - Aframax Crude Carrier

120,000 - 199,999 DWT - Suezmax Crude Carrier

200,000-- 319,999 DWT - VLCC (Very Large Crude Carrier)

320,000 DWT & above - ULCC (Ultra Large Crude Carrier)



Coastal, Small, Harbor/Lake Tankers - Under 16,500 DWT

These small ships supply terminals with a variety of products from heating oils, gasolines and kerosene, to more exotic fuels and chemicals. They are predominantly product carriers and are also are used extensively for bunkering service in harbors and busy ports.

General Purpose Vessels - 16,500 - 24,999 DWT

On a worldwide basis, this class of vessel probably covers the largest range and variety of cargoes carried. This class of ship includes chemical carriers, special service product and crude oil vessels and serve mostly coastwise terminal trades.

Medium Range Vessels - 25,000 - 49,999 DWT

Medium sized tankers cover a broad range of vessel types. Ships of this size category are capable of carrying almost any kind of petroleum product. The smaller group will usually carry gasolines, jet fuels, chemicals and heating oils. The larger size of the group will carry heavier fuel oils and crude oils.

LR1 (Large Range 1) - 50,000 - 79,999 DWT (Clean Products)
LR2 (Large Range 2) - 80,000 - 159,999 DWT (Clean Products)

Vessels in this class that are less than 100,000 dwt are divided into two basic categories namely, "Dirty " and "Clean". The "dirty" vessels carry the "black" or dirty cargoes such as crude oil , heavy fuel oils, asphalt etc. The "clean" vessels carry the refined "white" clean products such as gasoline, jet fuels, kerosene etc. Chemical carriers would also fall into the "clean" category. Because of the strict tank inspection requirements for clean products, most proprietary vessels or those on long term charter or do not routinely change their trading patterns from clean to dirty or vice versa. However market requirements and charter economics do require vessels to sometimes slip in and out of these clean and dirty trades. Vessels in this class that are over 100,000 dwt tend to be crude oil carriers only.

Panamax - A tanker whose dimensions enable her to transit the Panama Canal where lock width is the determining factor. Ships are approximately 55,000 to 79,999 dwt.

Aframax - A tanker of approximately 80,000 to 119,000 dwt.

Suezmax - A tanker whose dimensions enable her to transit fully loaded through the Suez Canal. Ships are approximately 120,000 to 199,999 dwt.

VLCC (Very Large Crude Carrier) - 200,000-319,999 DWT

ULCC (Ultra Large Crude Carrier) - 320,000 DWT and above

Because of their huge sizes these vessels have been almost exclusively only used for the carriage of crude oils. Only the smallest of this category has carried any type of refined products. Several of these ULCC classed vessels were over 500,000 and the biggest of these ships had a deadweight of 564,939 tons.

Vetting - The general process of approving a vessel for use. (From old English "To Vet" - to look at or review again.) Note: actual procedure varies from company to company.

VLCC - Very Large Crude Carrier of 200,000 - 319,999 DWT. See also Vessel Sizes.

Volume - The amount of space occupied by a fluid at certain conditions of temperature and pressure. Various types of VOLUMES used in marine custody transfer are defined as follows:

Gross Observed Volume (GOV) - The total volume of all petroleum liquids and sediment and water, excluding free water, at observed temperature and pressure.

Gross Standard Volume (GSV) - The total volume of all petroleum liquids and sediment and water, excluding free water, corrected by the appropriate volume correction factor (Ctl) for the observed temperature and API gravity, relative density, or density to a standard temperature such as 60°F or 15°C and also corrected by the applicable pressure correction factor (Cpl) and meter factor.

Indicated Volume - The change in meter reading that occurs during a receipt or delivery.

Net Standard Volume (NSV) - The total volume of all petroleum liquids, excluding sediment and water and free water, corrected by the appropriate volume correction factor (Ctl) for the observed temperature and API Gravity, relative density, or density to a standard temperature such as 60°F or 15°C and also corrected by the applicable pressure correction factor (Cpl) and meter factor.

On Board Quantity (OBQ) - The material remaining in vessel tanks, void spaces, and/or pipelines prior to loading. On-board quantity includes water, oil, slops, oil residue, oil/water emulsions, sludge, and sediment.

Remaining On Board (ROB) - The material remaining in vessel tanks, void spaces, and/or pipelines after discharge. Remaining on board quantity includes water, oil, slops, oil residue, oil/water emulsions, sludge, and sediment.

Total Calculated Volume (TCV) - The total volume of all petroleum liquids and sediment and water, corrected by the appropriate volume correction factor (Ctl) for the observed temperature and API gravity, relative density, or density to a standard temperature such as 60°F or 15°C and also corrected by the applicable pressure factor (Cpl) and meter factor, and all free water measured at observed temperature and pressure (gross standard volume plus free water).

Total Observed Volume (TOV) - The total measured volume of all petroleum liquids, sediment and water, and free water at observed temperature and pressure.

NOTE: Where the term 60°F or 15°C is used, it is referring to two different reference standards and does not indicate that the two temperatures are equal.

Voyage Charter - A contract in which a charterer pays a shipowner for the use of a ship's cargo space for one, or sometimes more than one, voyage. The shipowner is the operator, responsible for paying both operating costs and voyage costs. Also Spot Charter.

Voyage Costs - Fuel costs, port charges and canal dues (or tolls) incurred during the course of a voyage.