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An external floating roof tank is a storage tank commonly used to store large quantities of petroleum products such as crude oil or condensate. It consists of an open- topped cylindrical steel shell equipped with a roof that floats on the surface of the stored liquid. The roof rises and falls with the liquid level in the tank. [1] As opposed to a fixed roof tank there is no vapor space (ullage) in the floating roof tank (except for very low liquid level situations). In principle, this eliminates tank breathing loss and greatly reduces the evaporative loss of the stored liquid. There is a rim seal system between the tank shell and roof to reduce rim evaporation.
The roof has support legs hanging down into the liquid. At low liquid levels the roof eventually lands and a vapor space forms between the liquid surface and the roof, similar to a fixed roof tank. The support legs are usually retractable to increase the working volume of the tank.
External roof tanks are usually installed for environmental or economical reasons to limit product loss and reduce the likelihood of emission of volatile organic compounds (VOCs) and other potential air pollutants.
Normally, the roof of the tank rests directly on the surface of the stored liquid, leaving little vapor space and consequently leading to a much lower risk of rim space fire. [2]
Snow and rain water can accumulate on the roof. Roofs are exposed to sunlight and weather which can accelerate corrosion. [3]
Water on the roof is usually drained by a special flexible hose or other special drain line system that runs from drain-sumps on the roof, through the stored liquid to a drain valve on the shell at the base of the tank. A hose is the shortest quickest route, Other drain systems are available both rigid and semi-rigid. These are named 'Articulated' as they use straight lengths of steel pipes with mechanical swivel joints or consist of steel pipes with flexible sections.
In order for crude oil storage tanks to avoid a buildup of explosive gases, the rooftop rests on the oil directly.
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.
A heat pipe is a heat-transfer device that employs phase transition to transfer heat between two solid interfaces.
A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.
A hose is a flexible hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called pipes, or more generally tubing. The shape of a hose is usually cylindrical.
A fuel tank is a safe container for flammable fluids, often gasoline or diesel fuel. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine. Fuel tanks range in size and complexity from the small plastic tank of a butane lighter to the multi-chambered cryogenic Space Shuttle external tank.
A tanker is a ship designed to transport or store liquids or gases in bulk. Major types of tankship include the oil tanker, the chemical tanker, cargo ships, and a gas carrier. Tankers also carry commodities such as vegetable oils, molasses and wine. In the United States Navy and Military Sealift Command, a tanker used to refuel other ships is called an oiler but many other navies use the terms tanker and replenishment tanker. Tankers were first developed in the late 19th century as iron and steel hulls and pumping systems were developed. As of 2005, there were just over 4,000 tankers and supertankers 10,000 LT DWT or greater operating worldwide.
An oil terminal is an industrial facility for the storage of oil, petroleum and petrochemical products, and from which these products are transported to end users or other storage facilities. An oil terminal typically has a variety of above or below ground tankage; facilities for inter-tank transfer; pumping facilities; loading gantries for filling road tankers or barges; ship loading/unloading equipment at marine terminals; and pipeline connections.
The AP 42 Compilation of Air Pollutant Emission Factors is a compilation of the US Environmental Protection Agency (EPA)'s emission factor information on air pollution, first published in 1968. As of 2018, the last edition is the 5th from 2010.
Storage tanks are containers that hold liquids or compressed gases. The term can be used for reservoirs, and for manufactured containers. The usage of the word "tank" for reservoirs is uncommon in American English but is moderately common in British English. In other countries, the term tends to refer only to artificial containers. In the U.S., storage tanks operate under no pressure, distinguishing them from pressure vessels.
An evaporator is a type of heat exchanger device that facilitates evaporation by utilizing conductive and convective heat transfer, which provides the necessary thermal energy for phase transition from liquid to vapour. Within evaporators, a circulating liquid is exposed to an atmospheric or reduced pressure environment causing it to boil at a lower temperature compared to normal atmospheric boiling.
An oil production plant is a facility which processes production fluids from oil wells in order to separate out key components and prepare them for export. Typical oil well production fluids are a mixture of oil, gas and produced water. An oil production plant is distinct from an oil depot, which does not have processing facilities.
Onshore, when used in relation to hydrocarbons, refers to an oil, natural gas or condensate field that is under the land or to activities or operations carried out in relation to such a field.
An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets.
Offshore concrete structures, or concrete offshore structures, are structures built from reinforced concrete for use in the offshore marine environment. They serve the same purpose as their steel counterparts in oil and gas production and storage. The first concrete oil platform was installed in the North Sea in the Ekofisk oil field in 1973 by Phillips Petroleum, and they have become a significant part of the marine construction industry. Since then at least 47 major concrete offshore structures have been built.
A loading arm permits the transfer of liquid or liquefied gas from one tank to another through an articulated pipe system consisting of rigid piping and swivel joints to obtain flexibility.
Pumpable icetechnology (PIT) uses thin liquids, with the cooling capacity of ice. Pumpable ice is typically a slurry of ice crystals or particles ranging from 5 micrometers to 1 cm in diameter and transported in brine, seawater, food liquid, or gas bubbles of air, ozone, or carbon dioxide.
A volatile corrosion inhibitor (VCI) is a material that protects metals from corrosion. Corrosion inhibitors are chemical compounds that can decrease the corrosion rate of a material, typically a metal or an alloy. NACE International Standard TM0208 defines volatile corrosion inhibitor (VCI) as a chemical substance that acts to reduce corrosion by a combination of volatilization from a VCI material, vapor transport in the atmosphere of an enclosed environment, and condensation onto surface in the space, including absorption, dissolution, and hydrophobic effects on metal surfaces, where the rate of corrosion of metal surfaces is thereby inhibited. They also called vapor-phase inhibitors, vapor-phase corrosion inhibitors, and vapor-transported corrosion inhibitors.
A liquefied natural gas terminal is a facility for managing the import and/or export of liquefied natural gas (LNG). It comprises equipment for loading and unloading of LNG cargo to/from ocean-going tankers, for transfer across the site, liquefaction, re-gasification, processing, storage, pumping, compression, and metering of LNG. LNG as a liquid is the most efficient way to transport natural gas over long distances, usually by sea.
A fixed roof tank is a type of storage tank, used to store liquids, consisting of a cone- or dome-shaped roof that is permanently affixed to a cylindrical shell. Newer storage tanks are typically fully welded and designed to be both liquid- and vapor-tight. Older tanks, however, are often riveted or bolted, and are not vapor tight. A breather valve, commonly installed on many fixed roof tanks, allows the tank to operate at a slight internal pressure or vacuum. This valve prevents the release of vapors during very small changes in temperature, barometric pressure, or liquid level. Fixed roof tanks without breather valves will generally be freely vented; thus the emissions from a fixed roof tank can be non-trivial. Gauge hatches, sample wells, float gauges, and roof manholes provide accessibility to these tanks, and also act as potential sources of volatile emissions.
A dry-seal Wiggins gasholder is a device designed to hold gas.