407
Chapter
8
Hydrocarbon Petroleum
tankage and terminal
design
This chapter summarizes but brings together the history and use as well as salient fea-tures of design, operation and maintenance of hydrocarbon liquids storage facilities. Citations are provided in the list of reference to assist readers to source all documents necessary for full comprehension of issues related to components making up such systems. It is a reference chapter only on the subject matter and should not be used as turnkey. Readers are encouraged to refer to and consult all standards listed herein.
8.1 INTRODUCTION AND OVERVIEW
Oil terminals are widely used to store various liquids and gases such as chemicals, crude oil, and natural gas. Oil storage terminals play a vital role in oil transmission sys-tems for temporary parking/storing liquid petroleum products. Such tankage provides the management of product inventory and shipment, side stream injection, pumping and product movement, pipeline maintenance, etc.
A storage tank is a container, usually for holding liquids (hydrocarbon, water, etc.), sometimes for compressed gases (gas tank). The term is also used for reservoirs (artificial lakes and ponds), and for manufactured containers. Tank farms cover a group of tanks for the commercial storage of oil and petroleum products, sited together.
Oil terminals are widely used to store various liquids and gases such as chemicals, crude oil, hydrocarbon liquids, natural gas, LNG/LPG, etc. Oil storage terminals play a vital role in oil transmission systems for temporary parking /storing liquid petroleum products. Such tankage provide the opportunity for the management of product inven-tory and shipment, side stream injection, pumping and product movement, pipeline maintenance, etc.
Figure 8-1 illustrates a typical liquid hydrocarbon pipeline system and storage and shipping facilities.
The tank farm is generally provided with a bund wall and contains pipe racks, drainage, and fire-suppressant piping (Figure 8-2). Such bunds are generally designed to contain any spills from the tank or tank piping.
From a regulatory point of view, Bunding is a legal requirement in many countries particularly around tanks, storage vessels and other plant that contain liquids which may be dangerous or hazardous to the environment.
As well, bunded hydrocarbon storage tanks are generally a requirement from most insurance companies as opposed to single skinned oil storage tanks. Due to the safer oil storage solutions brought about by bunded oil storage tanks, some environmental agencies require to install bunded oil tanks.
Figure 8-1. Liquid hydrocarbon pipeline transportation storage and shipping facilities
The height of the bund walls is typically designed to assure the retention of any fuel spillage from the tanks within the tank farm boundary. The industry requires that the bund containment generally exceed 110% of the storage capability in each bund (or 180% of the volume of the largest tank). Additionally, each tank is also separated by intermediate bund walls to hold minor spills.
One of the key imperative requirements for a tank farm is Health, Safety and Environment (HSE) and that the operators of a depot must ensure that all petroleum products are safely stored and handled and that there are no leakages (etc) which could damage the soil or the water table. Fire protection is a primary consideration, espe-cially for the more flammable products such as gasoline and aviation fuel.
Fire prevention (fire protection/fire safety) often comes within the remit of health and safety professionals as well. The primary need is for safety measures must be in place to prevent fuel from exiting the tanks in which it is stored. Added safety measures are needed for when fuel does escape, mainly to prevent it forming a flammable vapor and stop pollutants from poisoning the environment.
Poor design, layout and lack of safety planning and execution can lead to disas-trous consequences in an event of unforeseen incidents. An example is the fire incident at the Burchfield Oil Depot in the UK in 2005 (Figure 8-3).
The Buncefield fire was an inferno caused by a series of explosions on 11 Decem-ber 2005 at the Hertfordshire Oil Storage Terminal (Total UK & Texaco facilities), an oil storage facility located near the M1 motorway by Hemel Hempstead in Hertford-shire, UK. The terminal was the fifth largest oil-products storage depot in the United Kingdom, with a capacity of about 60,000,000 imperial gallons (about 1.7 × 106 BBLS)
of fuel. Figure 8-3 inset indicates the fire just ten minutes after the explosion.
8.2 HISTORY AND REASONS FOR USE
Petroleum is not a substance new in the History of the World. This historical fact along with timelines indicating major discoveries/events can be illustrated as follows:
> 4000 years ago use of asphalt by Greeks (as per Greek historian Herodotus and confirmed by another Greek Historian Diodorus Siculus), asphalt was employed in the construction of the walls and towers of Babylon, and there were oil pits near Ardericca, a place located not far from Babylon
4000 BC Use of oil for ship caulking in Mesopotamia
Ancient Persian tablets Indicate the medicinal and lighting uses of petroleum in the upper levels of the Iranian society at the time 3rd Century AD The Romans began to use barrels
9th Century 1st distillation of petroleum by Iranian Chemist Zakariya Razi (865–925) producing chemicals such as kerosene
9th Century Exploitation of oil fields in the area around modern Baku, Azerbai-jan to produce naphtha
13th Century Venetian trader and explorer Marco Polo (1254–1324) described the output of those oil wells in Baku area as hundreds of shiploads 1539 1st oil export, Venezuela [3]
1819 Discovery of oil in the USA
1846 Discovery of the process of refining kerosene from coal by Canadian A braham Pineo Gesner
1854 First fractionation of petroleum by distillation by American Benjamin Sil-liman (1770 to 1864), a science professor at Yale University in New Haven (USA)
1854 1st recovery of by-product of oil from salt in the USA
1854 to 1856 Construction of world’s 1st tank farm by Ignacy Lukasiewicz near Jasło, Austrian Empire (now in Poland)
1854 Kier’s Refinery — First in Western Hemisphere, USA [3]. 1856–57 Opening of world’s first large refinery at Ploesti, Romania
1858 The birthplace of oil refining and kerosene distillation, Petrolia. South Africa 1859 1st application of well drilling technology by Edwin Drake
1859 Beginning of oil drilling in the USA
1861 Russian refinery in the mature oil fields at Baku built by Russian Meerzo-eff. At that time Baku produced about 90 per cent of the world’s oil 1861 1st commercial scale refinery in the USA by Lockhart, Frew and partners
(at Brilliant Station on the south bank of the Allegheny River near Negley Run)
1870–80 Passage of the first oil tankers through the Suez Canal 1885 Discovery of oil in Sumatra (Dutch East Indies)
1889 Establishment of Chicago Bridge & Iron Company (CB&I) 1896 Formation of National Fire Protection Agency (NFPA)
1902 Invention of Fire fighting foam (FFF) by the Russian engineer and chemist Aleksandr Loran
1904 Formation of national Board of Fire Underwriters (NBFU), now NFPA 1908 Discovery of oil in Iran (Masjid Soleiman) (Figure 8-4)
1908 Discovery/production of oil in Peru, Venezuela, and Mexico, at an indus-trial level
1910 Discovery of significant oil fields in Canada (in the province of Ontario) 1912 Completion of 1st largest Oil Refinery, Abadan, Iran
1914 1st record of Storage of Oil Fuel [5]
1916 Establishment of National Tank Association (NSTA), now Steel Tank Institute (STI), USA
1916–17 Formation of Underwriters Laboratories (UL) 1919 Formation of American Petroleum Institute (API)
1922 First UL Standard UL142 “Steel Above Ground Tanks for Flammable and Combustible Liquids”
1923 First floating-roof tank for the oil industry By CB&I
1942 Destruction of oil tank farm by the bombing the US Army barracks at Fort Mears, Amaknak Island in Unalaska Bay
1950 Construction of Milford Haven oil port
1951 Formation of Petroleum Equipment Institute (PEI) 1964 The Texaco oil refinery Milford Haven
1964 Construction of 1st Largest Crude Oil Tank(160,000 BBLS, 109 m diam-eter, 18 m height), Kharg Island, Persian Gulf
1974 Construction of the largest Crude Oil Tank, Abu Zabi (182, 000 BBLS) It is difficult to pin point the birth of hydrocarbon tankage and tank farms/depot and early years of professional design tank farms for storage of hydrocarbons fuels in large volumes. The only reference found is due to Lugoff and Camden [5], where in a book published in 1914, titled “Oil fuel for steam boilers”, describe in a chapter the “Storage of Oil Fuel”. There, they have a diagram of what they call a ‘small or medium’ size cylindrical steel tank. They also state that the common sizes of oil tanks. However, search of literature indicates the birth date for large tankage systems to be in the late 19th century.
Similar to liquid pipelines, storage tank systems have played an important role in the transportation industry, particularly in the post-World War II era.
Early in the twentieth century, the oil companies operated the pipelines and stor-age facilities as integrated subsidiaries and often along with refineries. They also often used them to control the oil industry.
Without storage facilities, pipelines are limited in the markets they can serve and would be limited in the commodities they can haul. Pipelines are the only mode of Figure 8-4. Discovery of oil in Iran, Masjid Soleiman, 1908 (left photo [4]) and the Abadan
transportation with no backhaul, i.e., they are unidirectional with products that only move in one direction through the line.
A tank farm includes many tankage systems and appurtenances (Figure 8-5). It is a facility where various petroleum products are stored prior to being transported further, shipped and disbursed to end consumers or retail facilities. They are also referred to as “oil depot.”
Some tank farms are owned by a single company which uses the farm to meet its needs, while others are administered by a group. It is also possible for facilities to have their own tank farms for the purpose of storing fuel on site, with airports being a classic example of a facility which needs to have a large quantity of fuel (mostly jet fuel) on hand.
It is believed that the first permanent, professionally designed tank farm for stor-age hydrocarbon liquids was built at the turn of the century simultaneous with con-struction of major refineries.
8.3 PRODUCTS STORED AND PROPERTIES
Petroleum products that are stored in tanks, tank farms, breakout facilities depends on transportation company systems and the complexities of liquid hydrocarbon mixtures being transported and as well acceptable contamination levels.
It also depends where refineries/terminals are located along pipelines and in major cities and where there are only a few large-long refined products pipelines.
Products transported and/or stored generally include the following: Crude Oil: Heavy · Medium · Light ·
Refined Product: motor gasoline · diesel fuels · aviation fuels ·
Natural Gas Liquids propane, butane and condensate mixture Buffer (slops only) synthetic (semi-processed) oil
Synthetic Oil
Buffer is a synthetic crude oil, a semi-refined, “clean,” crude product which is used as a buffer between the natural gas liquids and the refined products. This ensures that NGL does not migrate into refined products, affect the vapor pressure and thereby impact the flash point of the refined products. Therefore refineries and pipeline com-panies will have separate tanks for storing products used as buffer. Typical volume is about 2000 to 3000 m3 in volume.
Products transported and stored have typical properties as indicated in Table 8-1 below.
Typically product storage depends on what, how, and rate and sequence various products are delivered. For example, crude storage depends on delivery of the crude to a refinery. While a pipeline is normally the preferred mode of transportation (as
TAblE 8-1. typical properties product transported and stored
Commodity Viscosity (CS) Temperature (oC) Density (kg/m3)*
Diesel 6.86 5 847 5.10 15 820 Gasoline (leaded) 0.68 5 711.3 0.61 15 – Gasoline (unleaded) 0.7 5 699 0.63 15 690 (assumed) Jet A Fuel 8 29 774 1.5 0 – Jet B Fuel 1.9 15 – 1.5 35 – Kerosene 3 15 – 2.2 35 708.8 Condensate (sweet) 0.599 15 688.8 0.548 25 572.3 0.199 15 547.5 Condensate (raw) 0.171 30 500.6 0.218 20 483.5
Propane (at 1000 kPa) 0.199 30 446.9
0.166 52 560.8
0.237 25 535.12
0.235 44 529
Butane (at 470–520 kPa) 0.212 52
21.1 83
37.8 3.75
Very Heavy Oil 40 3.28
50 2.44 21.1 37 37.8 19 Heavy Crude 21.1 16.2 37.8 9.41 Medium Crude 21.1 10.2 Light Crude 37.8 6.25
considered more reliable and less affected by weather), the crude tankage depends of various factors including:
Pipeline: Pipeline capacity, Reliability Marine: Capacity of largest ship
Ship unloading rate
Ship travel/turn around frequency Number of ships at one time
For intermediate storage, (the storages that are for transferring and importing), the following are typically applicable:
Crude charge: 1 to 2 days supply per crude grade plus one identical tank ·
Unit rundown: 1 to 4 days production capacity plus one identical tank per ·
group
Blending stock: 5 days storage at production (line blending) rates plus one ·
identical tank per group
Similarly, in the refined product storage, the following applies: Pipeline shipment: for each product, frequency, rate, reliability ·
Truck and Rail: truck or tank car size, Time for loading, loading capacity ·
Marine Shipment: largest ship capacity and ship frequency, Number of ships ·
at one time
The storage of liquid hydrocarbons depends on the quantity and its physical properties.
The physical properties include density/specific gravity and vapor pressure/boil-ing point; Their effects are described below:
Density and specific gravity:
· the density of the liquid is its mass per unit volume. Water has a density of 1 gm/cm3 at 4°C. The density of a liquid plays an important
role in the design of a tank because larger densities require thicker shells.
Specific gravity:
· another important physical property of the liquid stored. It is a measure of the relative weight of one liquid compared to water. Specifically, it is the ratio of the density of the liquid divided by the density of the water at 15.5°C. For example, petroleum oil, kerosene, and gasoline have a specific gravity of 0.82, 0.80, and 0.70, respectively. Care must be exercised if there is a significant increase in the specific gravity of the new liquid because the effec-tive hydrostatic pressure acting on the tank walls will be greater if the design level is not reduced and could cause damage on the cylindrical shell.
Vapor pressure and boiling point:
· the vapor pressure of a pure hydrocarbon
liquid is the pressure of the vapor space above the liquid in a closed container, and increases with increasing temperature. It is an important consideration in order to select the type of tank and its roof and is crucial for the purpose of characterizing fire hazardousness.
The boiling point:
· also important. It is necessary to know the temperatures at which some liquids should be stored, always below its boiling point. For exam-ple, some flammable and combustible liquids are prohibited by the fire codes to be stored at temperatures above their boiling point. A large number of tanks in oil refineries or petrochemical industries, store flammable liquids.
8.4 TYPES OF PETROlEUM STORAGE TANKS
8.4.1 Definition and Classifications
A storage tank is a container, usually for holding liquids, sometimes for compressed gases (such as LNG, NGL, etc.).
Generally (excluding spheres), there are six basic tank designs that are used for hydrocarbon liquid storage vessels: fixed roof (vertical and horizontal), exter-nal floating roof, domed exterexter-nal (or covered) floating roof, interexter-nal floating roof, variable vapor space, and pressure (low and high). These are described further herein.
There are many different forms to classify storage tanks. The most funda-mental classification is based upon whether they are above or belowground. There are usually many environmental regulations applied to the design and operation of storage tanks, often depending on tank classification internal pressure (IP) or atmospheric pressure (AP) and on the nature of the fluid contained within. Above-ground storage tanks (AST) differ from underAbove-ground storage tanks (UST) in the kinds of regulations that are applied. The aboveground tanks (AST) have almost all their structure exposed. The bottom part of these tanks is placed directly over soil or on a concrete foundation.
Classification based on the internal pressure: In the case that an internal pressure acts on the tank during storage, it is possible to classify these tanks based on this level of pressure. This pressure effect depends directly of the size of the tank. The larger the tank, the more severe effect of pressure is on the structure. This classification is commonly employed by codes, standards, and regulations.
Classification based on atmospheric tanks: These tanks are the most com-mon. Although they are called atmospheric, they are usually operated at in-ternal pressure slightly above atmospheric pressure. The fire codes define an atmospheric tank as operating from atmospheric up to 3.5 kN/m2 above atmo-spheric pressure.
Low-pressure tanks: Within the context of tanks, low pressure means that tanks are designed for a pressure higher than atmospheric tanks. This also means that these tanks are relatively high-pressure tanks. Tanks of this type are designed to operate from atmospheric pressure up to about 100 kN/m2.
Pressure vessels (high-pressure tanks): Since high-pressure tanks are really pressure vessels, the term high-pressure tank is not frequently used; instead they are called only vessels. Because these kinds of tanks are usually built underground, they are not included in this work and they are not covered in detail herein. How-ever, they are treated separately from other tanks by all codes, standards, and regulations.
In the USA, storage tanks operate under no (or very little) pressure, distinguishing them from pressure vessels. Storage tanks are often cylindrical in shape, perpendicular to the ground with flat/sloping bottoms, and a fixed or floating roof.
Generally Tankage cost in refineries and terminals cost between 25% and 30% of total facilities capital investment. This includes utilities and design.
Tank capacities are determined based on the type of products, crude, intermediate and refined and the transportation system (pipeline, truck, and rail) as well as other requirements such as crude charge, unit rundown, blending stock, etc.
8.4.2 Types
Types of tanks includes the following: Atmospheric
·
Fixed roof, vertical and horizontal ·
Floating roof (external floating roof, domed external (or covered) floating ·
roof, internal floating roof) Pressurized
·
Variable vapor space ·
High pressure ·
Low pressure ·
Heated Tanks (Hot fluids) ·
High viscosity Oil (bitumen, asphalt, etc.) · Refrigerated Tanks · Cryogenic · Refrigerated ·
The shape of the roof is an indicator of the type of a tank because it is explanatory to tank designer, fabricator and erector. The configuration of a vertical aboveground tank design can be either an open top with the roof floating on the stored liquid or a fixed roof. The safe design of floating roof tank offers a considerable level of fire safety over other vertical tank designs. As a result, fire codes allow closer spacing between floating roof tanks and for separation from adjacent properties or operations providing a cost advantage in tank farm layout and arrangement.
8.4.2.1 Fixed Roof Tanks
Fixed roof tanks are generally for hydrocarbon liquids with very high flash points (e.g., heavy crude oil, diesel, heavy kerosene, fuel oil, bitumen/asphalt etc.). Vapor pressure in such tanks is of the order of 3.5 kPa (0.5 Psia). Figure 8-6 illustrates vapor pressure of hydrocarbon liquids commonly transported by pipelines and stored in storage tanks [6]. Similar graphs were presented in Chapter 2, Figure 2-9.
Figure 8-6. Vapor pressure of liquid hydrocarbons commonly transported by pipelines
Losses from fixed roof tanks are caused by changes in temperature, pressure, and liquid level. Fixed roof tanks are either freely vented or equipped with a pressure/vac-uum vent. The latter allows the tanks to operate at a slight internal pressure or vacpressure/vac-uum to prevent the release of vapors during very small changes in temperature, pressure, or liquid level. Of current tank designs, the fixed roof tank is the least expensive to construct and is generally considered the minimum acceptable equipment for storing organic liquids.
Fixed roof tanks have several roof designs (Figure 8-7) including: cone roofs,
·
dome roofs, and ·
umbrella roofs ·
Cone-roof tanks have cylindrical shells in the lower part. These are the most widely used tanks for storage of relatively large quantities of fluid. They have a verti-cal axis of symmetry, the bottom is usually flat (or slightly sloped), and the top is made in the form of shallow cone as illustrated in Figure 8-7. A shallow cone roof deck on a cone roof tank approximates a flat surface and is typically built of a thick steel plate (approximately 4.76 mm thick).
Steel dome roof tanks have the same spherical shape as an umbrella roof. An umbrella roof is nothing more than a stiffened dome roof. If the umbrella roof framing is internal, visually there is very little difference in the appearance of a dome roof and umbrella roof. The dome roof shown in Figure 8-7 is an aluminum geodesic dome roof and looks very different than any other roof due to the triangular panels.
There are several ways to fabricate such tanks. One of these techniques is the tank airlift method, “in which the roof and the upper course of shell are fabricated first, then lifted by air that is blown into the tanks as the remaining lower courses of steel shell are
welded into place” (Figure 8-8). See Section 7 — Petroleum Storage/Terminal Design & Construction.
Cone and dome roofs can be either self-supported or column supported. Cone-roof tanks typically have roof rafters and support columns (Figure 8-9 (column support) and Figure 8-10 (Cone Roof and Roof Hob Details, [8])). Figure 8-9 is an indication of some of the older design.
Umbrella-roof tanks: They are very similar to cone-roof tanks, but the roof looks like an umbrella. They are usually constructed with diameters < 20 to 30 m. Another difference is that the umbrella-roof does not have to be supported by columns to the bottom of the tank, so that they can be a self-supporting structure. The umbrella types are spherical design.
Typical fixed roof storage tank together with appurtenances are shown in Figure 8-11.
Geodesic dome-roof tanks: Although most tanks are made of steel, some fixed-roof tanks have aluminum geodesic dome-fixed-roof. Some advantages include that they have a superior corrosion resistance for a wide range of conditions compared with steel tanks (Figure 8-12). Also they are often an economical choice and are clear-span Figure 8-8. Fixed roof construction (airlift method) [7]
structures that do not require internal supports. They can also be built to virtually any required diameter.
8.4.2.2 Floating Roof Tanks
There are two types of floating roof tanks. There are: External (EFRT
· = External floating roof tank) Internal (IFRT
· = Internal floating roof tank)
Products stored in such tanks have generally higher vapor pressure between 10 kPa and 77 kPa (1.5 to 11 psia). As such light and medium crudes, gasoline, reformate, naphtha and Jet fuels are stored in such tanks.
Figure 8-10. Aluminum geodetic dome roof tank and roof top hub detail [8, 10]
Figure 8-12. Typical external floating roof tank equipped with a geodesic aluminum
dome [12]
These tanks have a roof that floats on the surface of the liquid (Figure 8-13). The floating cover or roof is a disk/pontoon structure that has sufficient buoyancy to ensure that the roof will float under all expected conditions, even if leaks develop in the roof.
External floating roof: An external floating roof tank is a storage tank commonly
used to store large quantities of volatile petroleum products such as crude oil or gaso-line (petrol). The external type floating roof tank is open on top (Figure 8-13) and the float can be of the following design types:
Pan type ·
Pontoon type ·
Double deck type ·
Buoy roof type ·
Most floating decks that are currently in use in the industry are constructed of welded steel plate and are of two general types: pontoon (Figure 8-13) or double-deck (Figure 8-14).
A typical external floating roof tank (EFRT) consists of an open-topped cylindri-cal steel shell equipped with a roof that floats on the surface of the stored liquid. The floating roof consists of a deck, fittings, and rim seal system. With all types of external floating roof tanks, the roof rises and falls with the liquid level in the tank.
Figure 8-14. Typical floating roof tank component make up and appurtenances (double
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 breathing losses and greatly reduces the evaporative loss of the stored liquid.
External floating decks are equipped with a rim seal system, which is attached to the deck perimeter and contacts the tank wall. The purpose of the floating roof and rim seal system is to reduce evaporative loss of the stored liquid. Some annular space remains between the seal system and the tank wall. The seal system slides against the tank wall as the roof is raised and lowered. The floating deck is also equipped with fit-tings that penetrate the deck and serve operational functions. The external floating roof design is such that evaporative losses from the stored liquid are limited to losses from the rim seal system and deck fittings (standing storage loss) and any exposed liquid on the tank walls (withdrawal loss).
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.
Components of external floating roof tanks are further detailed in Figure 8-15. Different types of floating roofs design (as per API 650) for floating roof tanks are illustrated in Figure 8-16.
Advantages: External roof tanks are usually installed for environmental or
eco-nomical reasons to limit product loss and reduce the emission of volatile organic compounds (VOC), an air pollutant.
Normally (roof not landed), there is little vapor space, and consequently a much smaller risk of internal tank explosion.
Disadvantages: Rain water and snow can accumulate on the roof, eventually the
roof may sink. Water on the roof is usually drained from a flexible hose that runs from a drain-sump on the roof, through the stored liquid to a drain valve on the
shell at the base of the tank. The hose often develops leaks and drains both water and product.
Domed External Floating Roof Tanks: Domed external (or covered) floating roof tanks have the heavier type of deck used in external floating roof tanks (EFRT) described previously, as well as a fixed roof at the top of the shell like internal float-ing roof tanks. Aluminum floatfloat-ing roofs may also be used in a tank with an aluminum geodesic dome. In many cases the aluminum Internal Floating Roof (IFR) is supported from the dome rather than on legs.
Domed external floating roof tanks usually result from retrofitting an external floating roof tank with a fixed roof. This type of tank is very similar to an internal floating roof tank with a welded deck and a self-supporting fixed roof. A typical domed external floating roof tank is shown in Figure 8-17.
As with the internal floating roof tanks, the function of the fixed roof or geodesic dome is not to act as a vapor barrier, but to block the wind and as well keep rain and snow out of the tank and off the floating roof. The type of fixed roof most commonly used is a self-supporting aluminum dome roof, which is of bolted construction. Like the internal floating roof tanks, these tanks are freely vented by circulation vents at the top of the fixed roof. The deck fittings and rim seals, however, are identical to those on ex-ternal floating roof tanks. In the event that the floating deck is replaced with the lighter IFRT-type deck, the tank would then be considered an internal floating roof tank. Figure 8-16. Sectional view of floating roofs (reproduced from ref. [11]) and a double design
Internal Floating Roof: An internal floating roof tank (IFRT) has both a
perma-nent fixed roof and a floating roof inside. There are two basic types of internal floating roof tanks: tanks in which the fixed roof is supported by vertical columns within the tank, and tanks with a self-supporting fixed roof and no internal support columns. Fixed roof tanks that have been retrofitted to use a floating roof are typically of the first type.
The advantages of using internal floating roofs are as follows: Decrease in the level of evaporation of stored product; ·
Lower risk of fire — there almost are no cases of fire in the world practice; ·
Aluminum internal floating roof. It has low height and storage capacity is ·
increased;
Protection from ambient climatic conditions therefore the tanks could be used ·
in various earth regions;
No requirement for mounting of roof drain. ·
External floating roof tanks that have been converted to internal floating roof tanks typically have a self-supporting roof. Newly constructed internal floating roof tanks may be of either type. The deck in internal floating roof tanks rises and falls with the Figure 8-17. Domed external floating roof tank [13,14]
liquid level and either floats directly on the liquid surface (contact deck) or rests on pontoons several inches above the liquid surface (noncontact deck).
The majority of aluminum internal floating roofs currently in service have non-contact decks (i.e. the floating roof is supported by pontoons on the liquid). A typical internal floating roof tank is shown in Figures 8-18 and 8-19.
Contact decks in IFRT can be:
Aluminum sandwich panels that are bolted together, with a honeycomb alumi-·
num core floating in contact with the liquid;
Pan steel decks floating in contact with the liquid, with or without pontoons; ·
and
Resin-coated, fiberglass reinforced polyester (FRP), buoyant panels floating in ·
contact with the liquid.
The majority of internal contact floating decks currently in service are aluminum sandwich panel-type or pan steel-type. The FRP decks are less common. The panels of pan steel decks are usually welded together.
Noncontact decks are the most common type currently in use. Typical noncontact decks are constructed of an aluminum deck and an aluminum grid framework sup-ported above the liquid surface by tubular aluminum pontoons or some other buoyant structure. The noncontact decks usually have bolted deck seams.
Installing a floating roof minimizes evaporative losses of the stored liquid. Both contact and noncontact decks incorporate rim seals and deck fittings for the same pur-poses previously described for external floating roof tanks. Evaporative losses from floating roofs may come from deck fittings, non-welded deck seams, and the annular space between the deck and tank wall. In addition, these tanks are freely vented by circulation vents at the top of the fixed roof. The vents minimize the possibility of organic vapor accumulation in the tank vapor space in concentrations approaching the flammable range.
It may be noted that an internal floating roof tank that is not freely vented is con-sidered a pressure tank.
Pressurized Storage Tanks: Pressure tanks generally are used for storing hydro-carbon liquids and gases with high vapor pressures and are available in many sizes and shapes, depending on the operating pressure of the tank. These depending on the pressure maintenance requirements will be either low pressure or high pressure as follows:
Low-pressure tanks ·
Cylindrical (15 kPa to 100 kPa, 2.5 to 15 psig) ·
Spheroid (15 to 210 kPa, 2.5 to 30 PSI) ·
Noded Spheroid ·
High-pressure storage tanks ·
Bullets (15–400 PSI), Figure 8-20 ·
Spheres (15–3000 PSI), Figure 8-21 ·
Pressure tanks are equipped with a pressure/vacuum vent that is set to prevent venting loss from boiling and breathing loss from daily temperature or barometric pressure changes.
Figure 8-20. Typical high-pressure horizontal storage bullet [11]
High-pressure storage tanks can be operated so that virtually no evaporative or working losses occur. In low-pressure tanks, working losses can occur with atmo-spheric venting of the tank during filling operations. No appropriate correlations are available to estimate vapor losses from pressure tanks.
Horton sphere was the name given to the storage vessels weld fabricated by the Chicago Bridge & Iron Co. These Horton spheres are at the Gulf Oil Corp. in Port Arthur, TX, completed in 1938, came in two sizes. One is 35 ft, 3 in., and the other 22 ft, 3 in., in diameter. Their respective storage capacities are 4000 and 1000 barrels [17].
Variable Vapor Space Tanks: Variable vapor space tanks are equipped with ex-pandable vapor reservoirs to accommodate vapor volume fluctuations attributable to temperature and barometric pressure changes. Although variable vapor space tanks are sometimes used independently, they are normally connected to the vapor spaces of one or more fixed roof tanks.
The two most common types of variable vapor space tanks are lifter roof tanks and flexible diaphragm tanks. Lifter roof tanks have a telescoping roof that fits loosely around the outside of the main tank wall.
The space between the roof and the wall is closed by either a wet seal, which is a trough filled with liquid, or a dry seal, which uses a flexible coated fabric.
Flexible diaphragm tanks use flexible membranes to provide expandable volume. They may be either separate gasholder units or integral units mounted atop fixed roof tanks.
Variable vapor space tank losses occur during tank filling when vapor is dis-placed by liquid. Loss of vapor occurs only when the tank’s vapor storage capacity is exceeded.
8.4.3 Emission Control In Storage Tanks
Storage vessels containing organic liquids are common in many industries, including Petroleum producing and refining,
·
Petrochemical and chemical manufacturing, ·
Bulk storage and transfer/distribution/terminal operations, and ·
Other industries consuming or producing organic liquids. ·
Organic liquids/petroleum liquids, generally, are mixtures of hydrocarbons hav-ing dissimilar true vapor pressures (for example, gasoline and crude oil, etc.). Organic liquids in the chemical industry, usually called volatile organic liquids, are composed of pure chemicals or mixtures of chemicals with similar true vapor pressures (for ex-ample, condensate, benzene or a mixture of isopropyl and butyl alcohols).
Once stored, hydrocarbon products (unless they are under pressure) will evapo-rate. Total emission from storage tanks includes withdrawal as well as standing storage losses.
Therefore, storage tanks are usually equipped with seals and vapor controls and sometime leak detection systems to assure minimal emissions and as well increased safety.
8.4.3.1 Tank Rim Sealing Systems: Floating Roof Tanks
Emissions from floating roof tanks are the sum of withdrawal losses and standing storage losses. Withdrawal losses occur as the liquid level, and thus the floating roof, is lowered. Some liquid remains on the inner tank wall surface and evaporates. For an internal floating roof tank that has a column supported fixed roof, some liquid also
clings to the columns and evaporates. Evaporative loss occurs until the tank is filled and the exposed surfaces are again covered.
Standing storage losses from floating roof tanks include rim seal and deck fitting losses, and for internal floating roof tanks also include deck seam losses for construc-tions other than welded decks. Other potential standing storage loss mechanisms in-clude breathing losses as a result of temperature and pressure changes.
Sealing systems consist of primary and secondary rim sealing as follows:
Primary seals are three types
·
Vapor-mounted ·
– highest emissions – fair service history
Liquid-mounted ·
– Tube type: kerosene, foam filled – lowest emissions
– but has poor service history Mechanical-shoe type ·
– relatively low emissions – has best service history
Secondary seals
·
Designed to reduce emissions ·
Additional safeguard against emissions ·
Types include: ·
– Rim type – Mini-tube type – Shoe type: seal fabric – Wiper type: rubber
Mounted above the primary seal ·
– may result in loss of tank capacity
Shoe-mounted secondary seal (not recommended) ·
The rim seal system is used to allow the floating roof to rise and fall within the tank as the liquid level changes. The rim seal system also helps to fill the annular space between the rim and the tank shell and therefore minimize evaporative losses from this area. A rim seal system may consist of just a primary seal or a primary and a secondary seal, which is mounted above the primary seal. Examples of primary and secondary seal configurations are shown in Figures 8-22 through 8-27 and described below.
The primary seal serves as a vapor conservation device by closing the annular space between the edge of the floating deck and the tank wall. As indicated previously, three basic types of primary seals are used on external floating roofs:
Flexible wiper seals ·
Resilient filled (nonmetallic), and ·
Mechanical (metallic) shoe. ·
It may be noted that resilient foam filled primary seals have not been commonly used in the last 20 to 30 years.
Wiper seals generally consist of a continuous annular blade of flexible material fastened to a mounting bracket on the deck perimeter that spans the annular rim space and contacts the tank shell. This type of seal is depicted in Figure 8-22. New tanks with wiper seals may have dual wipers, one mounted above the other. The mounting is such
that the blade is flexed, and its elasticity provides a sealing pressure against the tank shell.
Wiper seals are vapor mounted; a vapor space exists between the liquid stock and the bottom of the seal. For emission control, it is important that the mounting be vapor-tight, that the seal extend around the circumference of the deck and that the blade be in substantial contact with the tank shell. Two types of materials are commonly used to make the wipers. One type consists of a cellular, elastomeric material tapered in cross section with the thicker portion at the mounting. Rubber is a commonly used material; urethane and cellular plastic are also available. All radial joints in the blade are joined. The second type of material that can be used is a foam core wrapped with a coated fabric. Polyurethane on nylon fabric and polyurethane foam are common materials. Figure 8-22. Vapor mounted primary rim seal with secondary seal (left — flexible wiper and
right — resilient foam) [12]
The core provides the flexibility and support, while the fabric provides the vapor bar-rier and wear surface.
A secondary seal (Figure 8-23) may be used to provide some additional evapora-tive loss control over that achieved by the primary seal. Secondary seals can be either flexible wiper seals or resilient filled seals.
A resilient foam-filled seal, can also be mounted to eliminate the vapor space be-tween the rim seal and liquid surface (liquid mounted, Figure 8-24) or to allow a vapor space between the rim seal and the liquid surface (vapor mounted, Figure 8-25). Resil-ient filled seals work because of the expansion and contraction of a resilResil-ient material to maintain contact with the tank shell while accommodating varying annular rim space widths. These rim seals allow the roof to move up and down freely, without binding.
Resilient filled seals typically consist of a core of open-cell foam encapsulated in a coated fabric. The seals are attached to a mounting on the deck perimeter and extend around the deck circumference. Polyurethane-coated nylon fabric and polyurethane foam are commonly used materials. For emission control, it is important that the at-tachment of the seal to the deck and the radial seal joints be vapor-tight and that the seal be in substantial contact with the tank shell.
The scuff band as shown in Figure 8-24 is usually thin metal band that acts as protection against snags and tears in the foam bag fabric from the tank shell.
A mechanical/metallic rim mounted shoe seal (Figure 8-26) uses a light-gauge metallic band as the sliding contact with the shell of the tank. The band is formed as a series of sheets (shoes) which are joined together to form a ring, and are held against the tank shell by a mechanical device. The shoes are normally 1 to 1.5 m (3 to 5 ft) deep, providing a potentially large contact area with the tank shell. Expansion and Figure 8-24. Resilient foam (left) or liquid filled (right) primary rim seal with secondary
contraction of the ring can be provided for as the ring passes over shell irregularities or rivets by jointing narrow pieces of fabric into the ring or by crimping the shoes at intervals. The bottoms of the shoes extend below the liquid surface (as shown in Figure 8-25 above) to confine the rim vapor space between the shoe and the floating deck.
The rim vapor space, which is bounded by the shoe, the rim of the floating deck, and the liquid surface, is sealed from the atmosphere by bolting or clamping a coated fabric, called the primary seal fabric, which extends from the shoe to the rim to form an “envelope.” Two locations are used for attaching the primary seal fabric. The fabric is most commonly attached to the top of the shoe and the rim of the floating deck. To reduce the rim vapor space, the fabric can be attached to the shoe and the floating deck rim near the liquid surface. Rim vents can be used to relieve any excess pressure or vacuum in the vapor space.
Some primary seals on external floating roof tanks are protected by a weather shield. Weather shields are usually simple metal pieces without fabric barriers but can be of elastomeric, or composite construction and provide the primary seal with longer Figure 8-25. Schematic of resilient filled seal (vapor mounted) [13,14]
Figure 8-26. Typical mechanical shoe primary rim seal with a shoe mounted secondary seal
system, from [11,18,19]
life by protecting the primary seal fabric from deterioration due to exposure to weather, debris, and sunlight. However, it may be noted that when a weather shield is combined with a continuous vapor fabric, it can also can act as a secondary seal. Without such a continuous vapor fabric, it cannot be considered as a secondary seal.
On external floating roofs, the most common secondary seal systems incorporate a compression/protection plate over a continuous fabric to provide additional vapor Figure 8-28. Weather guard secondary seal (from [21])
preservations, besides protecting the primary seal. Some designs incorporate an ex-posed vapor barrier fabric.
Internal floating roofs typically do not have weather shields over the secondary seals, however, more recent designs incorporate steel compression plates and support to increase the longevity of the secondary seal over traditionally used wiper seals.
Internal floating roofs typically incorporate one of three types of flexible, product-resistant seals: Shoe seals, resilient foam-filled seals or wiper seals. It may be noted that rim mounted shoe seals are the most common type of primary seal used in the tanks and that Resilient Foam seals have not been common for many years. Wiper Seals are still used but they are not as common as they were years ago.
Some primary seals on external floating roof tanks are protected by a weather shield, Figures 8-27, 8-28, and 8-29, [20].
Other kinds of floating roof tank sealing systems are illustrated in Figures 8-30 through 8-34.
Consideration for Tank Seal Selection:
Tank floating roof rim seal are selected on the basis of the following: Tank shell wax or other scraping requirements
·
Rain water shedding ·
Sal tip life ·
Fire protection ·
Roof centering ·
In-service installation (retro fitting) ·
Life expectancy ·
Cost (including maintenance) ·
8.4.4 Tank Fittings and Appurtenances
Floating Roof Tanks
Numerous fittings pass through or are attached to floating roof decks to accommodate structural support components or allow for operational functions. Internal floating roof deck fittings are typically of different configuration than those for external floating
Figure 8-30. HMT seal-king (left) and HMT secondary low profile wiper (right) seals
Figure 8-31. Flex-a-seal secondary seal
Figure 8-33. Horton SR-1A mechanical shoe seal [20]
roof decks. Rather than having tall housings to avoid rainwater entry, internal floating roof deck fittings tend to have lower profile housings to minimize the potential for the fitting to contact the fixed roof when the tank is filled. Deck fittings can be a source of evaporative loss when they require openings in the deck.
External Floating Roof: The most common components that require openings in the deck are listed below:
Access hatches
· (Figure 8-35)
Gauge-floats
· (Figure 8-36)
Gauge-hatch/sample ports (Figure 8-37) · Rim vents · (Figure 8-38) Deck drains · (Figure 8-39) Deck legs · (Figure 8-40)
Un-slotted guide-poles and wells
· and slotted (perforated) guide-poles and wells
(Figure 8-41) Vacuum breakers
· (Figure 8-42)
Access hatches. An access hatch is an opening in the deck with a peripheral vertical
well that is large enough to provide passage for maintenance personnel and materials through the deck for construction or servicing (Figure 8-35). Attached to the opening is a removable cover that may be bolted and/or gasketed to reduce evaporative loss. On internal floating roof tanks with non-contact (pontoon type) decks, the well usually extend down into the liquid to seal off the vapor space below the noncontact deck.
Gauge-floats. A gauge-float is used to indicate the level of liquid within the tank
(Figure 8-36). The float rests on the liquid surface and is housed inside a well that is closed by a cover. The cover may be bolted and/or gasketed to reduce evaporation loss. As with other similar deck penetrations, the well extends down into the liquid on noncontact decks in internal floating roof tanks.
Gauge-hatch/sample ports. A gauge-hatch/sample port consists of a pipe sleeve
equipped with a self-closing gasketed cover (to reduce evaporative losses) and allows
hand-gauging or sampling of the stored liquid (Figure 8-37). The gauge-hatch/sample port is usually located beneath the gauger’s platform, which is mounted on top of the tank shell. A cord may be attached to the self-closing gasketed cover so that the cover can be opened from the platform if required.
Rim vents. Rim vents are used on tanks equipped with a seal design that creates a
vapor pocket in the seal and rim area, such as a mechanical shoe seal. A typical rim vent
Figure 8-37. Floating roof deck fittings: gauge hatch/sample port [13,14] Figure 8-36. Floating roof deck fittings: gauge floats [13,14]
Figure 8-38. Floating roof deck fittings: rim vents [13,14]
is shown in (Figure 8-38). The vent is used to release any excess pressure or vacuum that is present in the vapor space bounded by the primary-seal shoe and the floating roof rim and the primary seal fabric and the liquid level. Rim vents usually consist of weighted pallets that rest on a gasketed cover.
Deck Drains. Currently, two types of deck drains are in use (closed and open deck
drains) to remove rainwater from the floating deck (Figure 8-39). Open deck drains can be either flush or overflow drains (Figure 8-39, left illustration). Both types consist of a pipe that extends below the deck to allow the rainwater to drain into the stored liquid. Only open deck drains are subject to evaporative loss. Flush drains are flush with the deck surface. Overflow drains are elevated above the deck surface. Overflow drains are used to limit the maximum amount of rainwater that can accumulate on the floating deck, providing emergency drainage of rainwater if necessary.
Closed deck drains (Figure 8-39, right illustration) carry rainwater from the sur-face of the deck though a flexible hose or some other type of piping system that runs through the stored liquid prior to exiting the tank. The rainwater does not come in con-tact with the liquid, so no evaporative losses result. Overflow drains are usually used in conjunction with a closed drain system to carry rainwater outside the tank.
Float Roof Deck Legs. Deck legs are used to prevent damage to fittings
under-neath the deck and to allow for tank cleaning or repair, by holding the deck at a pre-determined distance off the tank bottom. These supports consist of adjustable or fixed legs attached to the floating deck or hangers suspended from the fixed roof. For adjust-able legs or hangers, the load-carrying element passes through a well or sleeve into the deck. With non-contact decks, the well should extend into the liquid. Evaporative losses may occur in the annulus between the deck leg and its sleeve. Typical deck legs are shown in Figure 8-19 and Figure 8-40 below.
Un-slotted guide-poles and wells. A guide-pole is an anti-rotational device that is
fixed to the top and bottom of the tank, passing through a well in the floating roof. The guide-pole is used to prevent adverse movement of the roof and thus damage to deck fittings and the rim seal system. In some cases, an un-slotted (Figure 8-41A) guide-pole is used for gauging purposes, but there is a potential for differences in the pressure, level, and composition of the liquid inside and outside of the guide-pole.
Slotted (perforated) guide-poles and wells. The function of the slotted guide-pole
is similar to the un-slotted guide-pole but also has additional features as shown in Figure 8-41B. Perforated guide-poles can be either slotted or drilled hole guide-poles. The guide pole is slotted to allow stored liquid to enter. The same can be accomplished with drilled holes. The liquid entering the guide-pole is well mixed, having the same
composition as the remainder of the stored liquid, and is at the same liquid level as the liquid in the tank. Representative samples can therefore be collected from the slotted or drilled hole guide-pole. However, evaporative loss from the guide-pole can be reduced by modifying the guide-pole or well or by placing a float inside the guide-pole. Guide-poles are also referred to as gauge Guide-poles, gauge pipes, or stilling wells.
Vacuum breakers. A vacuum breaker equalizes the pressure of the vapor space
across the deck as the deck is either being landed on or floated off its legs. A typical vacuum breaker is shown in Figure 8-42. As depicted in this figure, the vacuum breaker consists of a well with a cover. Attached to the underside of the cover is a guided leg long enough to contact the tank bottom as the floating deck approaches. When in con-tact with the tank bottom, the guided leg mechanically opens the breaker by lifting the cover off the well; otherwise, the cover closes the well. The closure may be gasketed or ungasketed. Because the purpose of the vacuum breaker is to allow the free exchange of air and/or vapor, the well does not extend appreciably below the deck.
Internal Floating Roof Tank (IFRT) Fittings
Fittings used only on internal floating roof tanks include Column wells (Figure 8-43),
·
Ladder wells (Figure 8-44), and ·
Stub drains. ·
Columns and wells. The most common fixed-roof designs are normally supported
from inside the tank by means of vertical columns, which necessarily penetrate an internal floating deck (Figures 8-43 and 8-44). (Some fixed roofs are entirely self-supporting and, therefore, have no support columns.) Column wells are similar to un-slotted guide pole wells on external floating roofs. Columns are made of pipe with circular cross sections or of structural shapes with irregular cross sections (built-up). The number of columns varies with tank diameter, from a minimum of 1 to over 50 for very large diameter tanks.
The columns pass through deck openings via peripheral vertical wells. With noncon-tact decks, the well should extend down into the liquid stock. Generally, a closure device exists between the top of the well and the column. Several proprietary designs exist for this closure, including sliding covers and fabric sleeves, which must accom-modate the movements of the deck relative to the column as the liquid level changes. A sliding cover rests on the upper rim of the column well (which is normally fixed to Figure 8-43. Internal floating roof tank (IFRT) — support (un-slotted), [13,14]
the deck) and bridges the gap or space between the column well and the column. The cover, which has a cutout, or opening, around the column slides vertically relative to the column as the deck raises and lowers. At the same time, the cover slides horizon-tally relative to the rim of the well. A gasket around the rim of the well reduces emis-sions from this fitting. A flexible fabric sleeve seal between the rim of the well and the column (with a cutout or opening, to allow vertical motion of the seal relative to the columns) similarly accommodates limited horizontal motion of the deck relative to the column.
Ladders and wells. Some tanks are equipped with internal ladders that extend
from a manhole in the fixed roof to the tank bottom. The deck opening through which the ladder passes is constructed with similar design details and considerations to deck openings for column wells, as previously discussed. A typical ladder well is shown in Figure 8-45.
8.5 PETROlEUM STORAGE TANKS STANDARDS (FOR DESIGN,
OPERATION, AND PROTECTION)
Below is a list of frequently used storage tank standards and practices that may be referred to for the design, operation, maintenance, and protection of storage tanks [22–24]. There may be other applicable standards.
Note: The current (or most recent) edition/revision of a publication should be applicable.
A — American Petroleum Institute (API) Standard/RP # Title and/or Description A-1 Construction Standards:
API Spec 12D Specifications for field welded tanks for storage of production liquids API Spec 12F Shop welded tanks for storage of production liquids
API Spec 12P Specifications for fiberglass reinforced plastic tanks
API Std 620 Design and construction of large, welded, low-pressure storage tanks API Std 650 Welded steel tanks for oil storage (replaced API 12 series Spec’s) API Std 2000 Venting atmospheric and low-pressure storage tanks
API Std 2610 Design, construction, operation, maintenance, and inspection of ter-minal and tank facilities
A-2 Inspection Standards: (including construction modification, and reconstruction standards)
API Std 510 Pressure vessel inspection code (maintenance inspection, rating, re-pair and alteration)
API Std 570 Inspection, Repair, alteration, and rerating of in-service piping systems API Std 653 Tank inspection, repair, alteration, and reconstruction
API Std 2015 Requirements for safe entry and cleaning of petroleum storage tanks A-3 Recommended Practices (RP):
API RP 12H Installation of new bottoms in old storage tanks
API RP 12R Setting, maintenance, inspection, operation, and repair of tanks in production service
API RP 574 Inspection practices for piping system components API RP 575 Inspection of atmospheric and low-pressure storage tanks API RP 580 Risk-based inspection
API RP 651 Cathodic protection of aboveground petroleum storage tanks API RP 652 Lining of aboveground petroleum storage tank bottoms API RP 1107 Pipeline maintenance welding practices
API RP 1110 Pressure testing of liquid petroleum pipelines API RP 1604 Closure of underground petroleum storage tanks API RP 1615 Installation of underground petroleum storage systems
API RP 1626 Storing and handling ethanol and gasoline-ethanol blends at distri-bution terminals and service stations
API RP 1627 Storing and handling of gasoline-methanol/cosolvent blends at dis-tribution terminals and service stations
API RP 1631 Interior lining and periodic inspection of underground storage tanks API RP 1632 Cathodic protection of underground petroleum storage tanks and
piping systems
API RP 1637 Using the API color-symbol system to mark equipment and vehicles for product identification at gasoline dispensing facilities and distri-bution terminals
API RP 2003 Protection against ignitions arising out of static, lightning, and stray currents
API RP 2016 Guidelines for entering and cleaning petroleum storage tanks API RP 2021 Management of atmospheric storage tank fires
API RP 2027 Ignition hazards involved in abrasive blasting of atmospheric stor-age tanks in hydrocarbon service
A-4 Other API Publications:
API-334 A Guide to leak detection for aboveground storage tanks
API Pub 2009 Safe welding, cutting and hot work practices in the petroleum and petrochemical industries
API 2517 Evaporating losses from external floating roof tanks API 2519 Evaporating losses from internal floating roof tanks
API Pub 2200 Repairing crude oil, liquefied petroleum gas, and product pipelines API-2207 Preparing tank bottoms for hot work
API Pub 2217A Guidelines for work in inert confined spaces in the petroleum industry API 2550 Measurements and calibration of petroleum storage tanks
B — Petroleum Equipment Institute (PEI) B-1 Recommended Practices:
PEI RP 100 Recommended practices for installation of underground liquid stor-age systems
PEI RP 200 Recommended practices for installation of aboveground storage sys-tems for motor vehicle fueling
C — National Leak Prevention Association (NLPA) C-1 Recommended Practices:
NLPA Std 631 Entry, cleaning, interior inspection, repair and lining of underground storage tanks
D — National Association of Corrosion Engineers (NACE International — The Corrosion Society)
D-1 Inspection Standards:
NACE TM 01-01 Measurement techniques related to criteria for cathodic protec-tion on underground or submerged metallic tank systems NACE TM 04-97 Measurement techniques related to criteria for cathodic
protec-tion on underground or submerged metallic piping systems D-2 Recommended Practices:
NACE 1/SSPCSP5 Steel Structures Painting Council: “White Metal Blast Cleaning” NACE 2/SSPCSP10 Steel Structures Painting Council: “Near White Metal Blast
Cleaning”
NACE 3/SSPCSP6 Steel Structures Painting Council: “Commercial Blast Cleaning” NACE 4/SSPCSP7 Steel Structures Painting Council: “Brush Off Cleaning” NACE 10/SSPCPA6 Steel Structures Painting Council: “Fiberglass-Reinforced
Plas-tic (FRP) Linings Applied to Bottoms of Carbon Steel Above-ground Storage Tanks”
NACE RP 0169 Control of External Corrosion on Underground or Submerged Metallic Piping Systems
NACE International — The Corrosion Society
NACE RP 0172 Surface preparation of steel and other hard materials by water blast-ing prior to coatblast-ing or recoatblast-ing
NACE SP 0177 Mitigation of alternating current and lightning effects on metallic structures and corrosion control systems
NACE RP 0178 Design, fabrication, and surface finish of metal tanks and vessels to be lined for chemical immersion service
NACE RP 0187 Design considerations for corrosion control of reinforcing steel in concrete
NACE SP 0188 Discontinuity (holiday) testing of new protective coatings on con-ductive substrates
NACE RP 0193 External cathodic protection of on-grade carbon steel storage tank bottoms
NACE RP 0275 Application of organic coatings to the external surface of steel pipe for underground service
NACE RP 0285 Corrosion control of underground storage tank systems by cathodic protection
E — National Fire Protection Association (NFPA) see also 37 PA Code Chapters 11 and 13, Flammable & Combustible Liquids Handbook
E-1 Construction Standards:
NFPA 70 (NEC) National electric code® NFPA 77 Static electricity
NFPA 30 Flammable and combustible liquids code
NFPA 30A Motor fuel dispensing facilities and repair garages NFPA 303 Marinas and boatyards
NFPA 326 Safeguarding tanks and containers for entry, cleaning, or repair E-2 Recommended Practices:
NFPA 11 Standard for low-, medium-, and high-expansion foam
NFPA 15 Standard for water spray fixed systems for fire protection
NFPA 17 Standard for dry chemical extinguishing systems
NFPA 30 Flammable and Combustible Liquids Code NFPA 72 National Fire Alarm Code
NFPA 1561 Fire Department Incident Management System
F — Underwriters Laboratories (UL) Construction Standards:
UL Std 58 Standards for Steel Underground Tanks for Flammable and Combus-tible Liquids
UL Std 142 Standard for Steel Aboveground Tanks for Flammable and Combus-tible Liquids
UL Std 567 Standard for Emergency Breakaway Fittings, Swivel Connectors and Pipe-Connection Fittings for Petroleum Products and LP-Gas UL Std 842 Standard for Valves for Flammable Fluids
UL Std 860 Standard for Pipe Unions for Flammable and Combustible Fluids and Fire Protection Service
UL Std 971 Standard for Nonmetallic Underground Piping for Flammable Liquids UL Std 1316 Glass-Fiber-Reinforced Plastic Underground Storage Tanks for
Pe-troleum Products, Alcohol and Alcohol-Gasoline Mixtures
UL Std 1746 Standard for External Corrosion Protection Systems for Steel Under-ground Storage Tanks
UL Std 2085 Standard for Protected Aboveground Tanks for Flammable and Combustible Liquids
UL Std 2245 Standard for Below-grade Vaults for Flammable Liquid Storage Tanks
American Society of Mechanical Engineers (ASME)-American National Standards Institute (ANSI)
Construction Standards:
ASME B31.3 American Society of Mechanical Engineers: “Process Piping” ASME B31.4 American Society of Mechanical Engineers: “Liquid Transportation
Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Am-monia and Alcohols”
Recommended Practices:
ASSE Z117.1 American Society of Safety Engineers: “Safety Requirements for Confined Spaces”
American Society for Testing and Materials (ASTM) Construction Standards:
ASTM A182/A182M Standard Specification for Forged or Rolled Alloy Stainless Steel Pipe Flanges, Forged Fittings and Valves and Parts for High-Temperature Service.
ASTM D2996 Standard Specification for Filament-Wound Fiberglass (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe ASTM D4097 Standard Specification for Contact-Molded
Glass-Fiber-Reinforced Thermoset resin Corrosion Resistant Tanks ASTM D5685 Standard Specification for Fiberglass
Reinforced Thermosetting- Resin) Pressure Pipe Fittings Recommended Practices:
ASTM E797 Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method
ASTM D2794 Standard Test Method for Resistance of Organic Coatings on the Effects of Rapid Deformation (Impact)
Steel Tank Institute Construction Standards:
STI P3 Specification and Manual for External Corrosion Protection of Underground Steel Storage Tanks
STI F841 Standard for Dual Wall Underground Steel Storage Tanks STI F894 Act-100® Specification For External Corrosion Protection of FRP
Composite Steel USTs (See also Association of Composite Tanks)
STI F921® Standard for Aboveground Tanks with Integral Secondary Containment
STI F922 Specification for Permatank®
STI F941 Standards for Fireguard® Thermally Insulated Above-ground Storage Tanks
STI R951 Specification for Tanks Using Low Levels of Pressure in the Tanks Interstice
STI F961 ACT-100 U Specification for External Corrosion Protection of Compos-ite Steel Underground Storage Tanks
Inspection Standards:
STI SP001 Standard for Inspection of In-Service Shop Fabricated Aboveground Tanks for Storage of Combustible and Flammable Liquids
Recommended Practices:
STI SP031 Standard for Repair of In-Service Shop Fabricated Aboveground Tanks for Storage of Combustible & Flammable Liquids
STI R821 sti-P3 Installation Instructions STI R891 RP for Hold Down Strap Isolation
STI R892 RP for Corrosion Protection of Underground Piping Networks Associ-ated with Liquid Storage and Dispensing Systems
STI R912 Installation Instructions for Shop Fabricated Aboveground Storage Tanks for Flammable, Combustible Liquids
STI R913 Act-100® Installation Instructions STI R923 Permatank® Installation Instructions STI R931 F921® Installation Instructions
STI R942 F Fireguard® Installation & Testing Instructions for Thermally Insu-lated, Lightweight, Double Wall Fireguard Aboveground Storage Tanks
STI R971 ACT-100-U® Installation Instructions
STI R972 RP for the Addition of Supplemental Anodes to sti-P3® USTs Steel Structures Painting Council (SSPC) see also NACE International Recommended Practices:
SSPC Painting Manual volume I SSPC Painting Manual volume II
Association of Composite Tanks Construction Standards:
ACT 100 Specification for the Fabrication of FRP Clad Underground Storage Tanks
Fiberglass Petroleum Tank and Pipe Institute Recommended Practices:
FPTP 1 Fiberglass Piping Systems Installation Check List for Underground Petroleum Pipe
FTPI RP T-95-02 Remanufacturing of Fiberglass Reinforced Plastic (FRP) Under-ground Storage Tanks
American Concrete Institute (ACI) Recommended Practices:
ACI 350 Environmental Engineering Concrete Structures
8.6 REGUlATIONS AFFECTING TERMINAl AND
STORAGE FACIlITIES
The Regulations Governing Aboveground Storage Tanks (AST) that exist are gener-ally intended to address sources of pollution that may result from ASTs operation. To ensure the prevention and early detection of a Release of a Substance should one occur, new ASTs are required to meet acceptable design and installation criteria. An example of such a regulation is cited in ref. [25].
Regulations are purely for storage tanks and therefore generally the following types of aboveground facilities are not covered