- March 18, 2020
Aboveground Storage Tanks: A Complete Guide for Users
Industrial entities and manufacturing sectors are in need of reliable storage units to keep huge quantities of fuel and petroleum products.
Petrochemical industry in particular, need tanks for bulk storage and transfer operations. Aboveground storage tanks (ASTs) serve the purpose well fulfilling storage needs of the industry.
Advanced technology has made these tanks robust engineering them to perfection to meet customized needs. In keeping with demands, manufacturers attach top priority to features, pressure acceptance, and temperature compatibility of these tanks when designing them.
What are Above Ground Storage Tanks?
Aboveground storage tanks are large vessels and containers used for storing water, chemicals, crude oil, gases, gasoline and petroleum products in bulk quantities.
They’re placed on surface of the earth on stable platforms giving them the name and are usually made of stainless steel, fiberglass or polyethylene.
Modern units have huge storing capacities and can hold up to 30,000,000 gallons of industrial petroleum products safely. They are also equipped with secondary containment vessel to prevent spilling and leakage of liquids.
Built to counter corrosion, these tanks also come armed with overfill prevention mechanism to prevent releases and can identify leaks.
Advanced storage aboveground tanks for industries are fabricated to prevent discharge of liquids with the following features:
• Audible or visual high liquid level or surveillance station for constantly continuous monitoring of liquid flow in the vessels.
• Audible or code signals to communicate between container gauge and pumping station directly.
• Digital computers, telepulse, discrete vision gauges that offer fast response to regulate the level of liquid in the tanks.
• Pump cut-off devices that prevent spilling of liquid by 95%.
Let’s take a look at the different types of industrial aboveground storage tanks:
• Fixed-roof tanks: These are designed to have a cone or domed shaped roof permanently attached to its cylindrical shell. They are primarily used for storing water.
• Internal floating roof tanks: These tanks are equipped with floating roofs which in turn are covered with fixed roofs. Such tanks are specially designed to weather severe weather conditions likes lashing of the rain or the hazards of strong winds.
• External floating roof tanks: Such tanks are designed to store crude oil and petroleum products safely in bulk quantities. They have a cylindrical shell made of steel on top which remains open and floats on the surface of the fluid stored inside the vessels.
• Domed external floating roofing tanks: They are similar to the external floating roof tanks except that the roof is lighter in structure.
• Pressure tanks: Pressure containers and vessels are made to store gases and liquids at pressures considerably different from normal air pressure. They are usually made of fiberglass with their sizes ranging from 2 to 500 liters. These units have expandable vapor reservoirs to adjust to vapor volume oscillations caused by temperature and atmospheric pressure changes.
• Horizontal tanks: They are best-suited to hold water and chemicals in large quantities without seepage. The units are smaller in size and can be moved and installed effortlessly.
• LNG tanks: These are specialized vessels that are used for holding liquefied natural gas. You can install them both underground and aboveground as per your requirement.
• Variable vapor space tanks: They are spherical-shaped vessels capable of maintaining structural integrity even at high pressures.
Are Above Ground Storage Tanks Regulated?
Regardless of the substance stored inside, aboveground storage tanks are regulated by the 40 CFR 112 and thus carry the label “bulk storage container” rather the term “aboveground storage tank”.
Bulk storing vessels, as defined by 40 CFR 112, are any vessels used for storing huge quantities of oil prior to use, during use, and prior to further commercial distribution.
Who regulates Aboveground Storage Tanks?
Aboveground industrial storage tanks are regulated by a complex network of diverse federal acts and local requirements enforced by state and local authorities. However, there is no uniform federal program regulating them.
Some ASTs are required to adhere to additional state and local regulatory requirements to protect human health and prevent environmental hazards.
For instance, if a tank is used for storing explosive organic liquids, hazardous materials, and petroleum products, then obtaining the CAA (clean air act) is mandatory while also abiding by the federal statues concerning it.
Aboveground Storage Tank Foundation Design
While manufacturing aboveground fibreglass tanks, special emphasis is laid when designing it and constructing its foundation.
A bad foundation can lead to failure of the vessel and trigger differential settlement caused by thin walls and spaces left behind while welding.
Besides that, the design and build of a tank are co-related. It cannot be carried out without considering the direct relationship between the upper body and soil basement of the tank.
The bottom of all aboveground tanks are carefully designed and made to serve their specific purposes. There are four options available when it comes to designing the base or foundation of the ASTs.
• Cone up bottom
• Cone down bottom
• Flat bottom without slope
• Flat bottom with single slope
Since the foundation on which these tanks are placed is a crucial factor determining efficiency, the choice of material to build it is as important. There are 4 options to choose from when it comes to construction it. They are as follows:
Foundation from compacted soil
Reinforced concrete ring not placed under the shell
Reinforced concrete ring wall foundation
Reinforced concrete slab
How often do above ground storage tanks need to be inspected?
The tank arrangement plan (TAP) should be re-assessed every 5 years or every time a modification or alteration is made to the facility that impacts the plan.
Aboveground Storage Tanks Inspection Checklist
It’s important to inspect aboveground vessel thoroughly on a regular basis as it will help you assess their exact condition and prevent leakage of stored liquids. Here is the complete checklist for you.
Containment: Inspecting the drainage pipes and valves to find out whether they adhere to the regulations laid by NEPA is important. They should be examined or checked once a month for safety reasons.
Base: Evaluating the strength and reliability of the foundation is necessary. Check out whether there are cracks on the concrete pad or wing wall.
Shell: The shell must be free of cracks, dents, bulging, corrosion, and other defects.
Electrical Equipment: While checking, make sure the control boxes and grounding lines of the tank are in good condition.
External Coating: The external coating should be checked for depreciation and if it’s found to lose its effectiveness, then the tank is susceptible to leakage. Make sure the external coating is strong and can endure the adverse effects of weather and sunlight.
Roof: The roof of the tank should be inspected thoroughly. Make sure standing water does not accumulate on top and identify whether there are dents, cracks, and other flaws.
Insulation: If you’re an inspector then you shouldn’t forget to examine if there are moisture, mold, impairment, and other damaging signs in the tank’s insulation.
Fuel gauge: Examine the fuel gauge and make sure it’s functioning smoothly. In case of double-walled tanks, you should scrutinize the interstitial monitor and ensure that it’s working fine.
Tank’s internal walls: Checking the exteriors alone is not enough, you should also inspect the interior of the tank. This should be done to make sure that there is no bacterial contamination or erosion. If you spot them, find proper remedies and treatments to deal with them immediately.
Aboveground Storage Tank Sizes
Aboveground storage vessels come in various sizes and dimensions. Let’s take a look at some of them.
• Tanks that can hold 550 gallons and measure 48″ x 6′-0″.
• Tanks that have a holding capacity of 1,100 gallons and measure 48″ x 12′-0″.
• On the other hand, tanks that can hold 1,000 gallons and measure 64″ x 6′-0″.
• Those that can hold 1,500 gallons and measure 64″ x 9′-0″.
What are the Secondary Containment Requirements for Aboveground Storage Tanks?
Secondary containment in aboveground tanks is an area that captures the contents of the largest tank in the containment area when an abrupt leakage occurs due to spilling of liquids stored inside.
Here’s an outline of the secondary containment requirements for ASTs:
Construction material: Only impervious substances are used for constructing secondary containment area. These include compacted clay, concrete, geosynthetic clay liner, synthetic membrane, fiberglass, and fabricated steel.
Volume: Secondary containment areas in aboveground tanks should have a volume at least 110 percent of the size of the largest tank if exposed to precipitation. If the areas are not exposed to precipitation, the capacity should be at least 100 percent of the size of the largest tank.
Compatibility: The materials stored in the secondary containment areas should be compatible.
Aboveground Fuel Tank
Aboveground fuel tank is a large vessel or container that is primarily used for storing crude oil, gasoline and other petroleum products.
They are specially designed to store hazardous and combustible substances safely in bulk quantities.
Well manufactured and installed aboveground fuel vessels are always better options than underground tanks. It’s because they detect leaks quickly and facilitate visual analysis.
Besides that, they can be painted to prevent corrosion that makes them less susceptible to leakage.
Double-walled tanks are ideal for all purposes as they protect the inner tank from the hazards of intense heat, rainfall, and cracks.
There are certain electrical requirements that must followed for safety reasons while installing above ground fuel tanks at the construction site. They are as follows:
Aboveground fuel vessels must be deployed at a minimum distance of 25 feet from any building or electrical equipment.
Since they’ll be storing gasoline and petroleum products that are explosive in nature, the containers must clearly exhibit class, group, and temperature range. The temperature should not exceed 40 degree Celsius.
For safety, it’s important to adhere to the guidelines laid by National Environment Policy Act (NEPA).
Recommendations are given on wiring methods, wiring connections, capacitors, transformers, fuses, circuit breakers, flexible cords, conductor insulation, attachment plugs, ventilation piping, meters, relays, generators, resistors, and more.
NEPA has also made it compulsory to thread the electrical channels for safety reasons. They have specified that containers must be pulled tight by using a reliable conductor known as bonding jumper.
To conclude, aboveground storage industrial tanks are extremely beneficial and resourceful due to their highly advanced safety features, incredible performance, ease of use, and durability.
With technology becoming more advanced, new features are incorporated every day in manufacturing these vessels that make them more efficient and safer.
Hopefully, the blog will help you to explore different aspects associated with ASTs and choose the best product.
For purchasing and installing all kinds of tanks, get in touch with GSC Tanks.
The company provides high-quality underground and aboveground storage tanks that can be tailor-made to meet your specific requirements.
Order stainless steel tanks, fiberglass tanks, field erected tanks, polyethylene tanks and much more at competitive prices.
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