TANKS


Tanks serve many purposes in industry. This page describes three types of tanks, such as the storage tanks shown here.




(Copyright Xerxes Corporation, Minneapolis, MN)

STORAGE


Storage tanks, such as these chemical storage tanks, are used to store materials.



(Copyright Xerxes Corporation, Minneapolis, MN)

GENERAL INFORMATION

Two types of storage tanks are used widely in industry: underground and aboveground. These tanks can be used for storage, mixing, or as vessels for chemical processes. On the left is an example of an underground storage tank. On the right is an aboveground tank used for storing hazardous chemicals.


(Copyright Xerxes Corporation, Minneapolis, MN)

EQUIPMENT DESIGN

Storage tanks come in an assortment of sizes, shapes and designs and are usually constructed of carbon, alloy or stainless steel. Storage tanks can be built either vertically or horizontally. Some of the main categories of storage tanks include:


Underground vs. Aboveground

Storage tanks can be built for aboveground or underground use. Underground tanks do not require much insulation, whereas aboveground tanks may need secondary, outer insulation layers. However, underground tanks need to be stronger, requiring more materials, and they may need special, noncorrosive outer coats.


Rectangular vs. Cylindrical

Storage tanks can be rectangular or cylindrical. Underground tanks are typically cylindrical.


Double wall vs. Single wall

Some tanks may need stronger, sturdier design and construction than others. Tanks can be made stronger using double wall construction, in which the tank walls are composed of two layers of different materials.


The picture below to the left shows an example of a horizontal, cylindrical storage tank. The picture to the right shows a storage tank with four layers of fiberglass filament windings. Each layer provides additional support and wall thickness to the tank, allowing it to be used for multiple applications.

(Copyright Xerxes Corporation, Minneapolis, MN)

Spherical tanks are particularly useful in high pressure applications. They can also be insulated and refrigerated to allow for higher pressures.


USAGE EXAMPLES

Storage tanks play many different roles in industry. The pictures below show examples of storage tanks commonly used in industry. The tanks on the left are fiberglass above ground storage tanks that are corrosion-resistant and used in a wide range of industrial applications.


(Copyright Xerxes Corporation,
Minneapolis, MN)
(Copyright Aura Engineering, Inc.,
Pearland, TX)

Underground storage tanks are frequently used in the petroleum storage industry. The picture below shows an example of a fiberglass underground storage tank. The tank features enhanced internal corrosion resistance to ethanol-blended gasoline as well as a wider range of fuel compatibility compared to steel storage tanks.


(Copyright Xerxes Corporation, Minneapolis, MN)

ADVANTAGES

DISADVANTAGES

  • Lower production costs compared to other tanks.
  • Less demanding storage conditions lead to a wide choice of structural materials.
  • Underground storage tanks allow more flexibility in placement location.
  • Aboveground storage tanks are simpler and cheaper to construct.
  • Aboveground storage tanks have a lower monitoring and record-keeping cost.
  • High maintenance needed due to a susceptibility to corrosion.
  • Corrosion of tank can have expensive environmental consequences.
  • Excavation needed to install underground storage tanks is expensive.
  • Underground storage tanks may contaminate the land as leaks in these system are hard to find.
  • Aboveground storage tanks have a high risk of fire

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SETTLING


Settling tanks are specially designed to settling and separate materials.



(Copyright Delpark Filters, Ace Manufacturing, Inc., Mississauga, Ontario)

GENERAL INFORMATION

Settling tanks are used primarily to separate solids from a solid-liquid mixture. These tanks are equipped with conveyor belts that lift settled solids in the sludge mixture from the bottom of the tank and dump it over the side, as shown in the diagram.



(Copyright Delpark Filters, Ace Manufacturing, Inc., Mississauga, Ontario)

EQUIPMENT DESIGN

Settling tanks are designed to account for minimum slurry turbulence and rapid, constant settling of materials. A conveyor belt is used to remove sludge from a mixture. All settling tanks are also equipped with pumps to recirculate the liquid component of the mixture, and filters to keep solids out of the recirculating pumps.


Modifications can be made to meet process conditions, such as a variance of slurry build up.


The picture below shows a settling tank with a multiple weir design. This design makes it possible for the tank to more efficiently remove solids. Both the settling and clean storage tank have continuous conveyor and weir systems to remove settled deposits and discharge them into sludge bins.



(Copyright Delpark Filters, Ace Manufacturing, Inc., Mississauga, Ontario)

For example, settling tanks with only one section are used when shutting down the process to remove the solids is a convenient option due to slow buildup of materials. These tanks are usually equipped with a sludge removal door.


If sludge buildup is moderate, continuous removal is not required. However, shutting down the process would be inconvenient, and a different type of tank can be used. Such settling tanks are divided into two sections, so that one section can be in operation while the solids are removed from the other.


USAGE EXAMPLES

Commercial uses for settling tanks include:

  • Primary dewatering of salvageable materials from a solid-liquid mixture
  • Quick quenching and efficient handling of hot materials
  • As an alternative to more expensive filtration systems

ADVANTAGES

DISADVANTAGES

  • Applications with slow sludge build-up allow continuous operation of tank.
  • Use limited to mixtures that are not hazardous when exposed to the atmosphere.

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PRESSURE VESSELS


Seamless pressure vessels are designed to contain high-pressure compressed gases and fluids.


GENERAL INFORMATION

Pressure vessels are tanks used to store and transport highly pressurized materials. Pressurizing materials to a minimum volume and using pressure vessels is a highly efficient and economical way to store materials.


EQUIPMENT DESIGN

Most pressure vessels are long and cylindrical, and made of seamless, steel pipe for maximum strength.


Pressure vessels are usually stored and transported in vessel assemblies. These assemblies include racks that secure the pressure vessels in rows.


USAGE EXAMPLES

Examples of the use of pressure vessels can be as simple as a helium tanks for balloons, or the propane tank for a gas grill. Some industrial examples are shown in this section.


ADVANTAGES

DISADVANTAGES

  • By using high pressures, greater quantities of gases or fluids can be stored in the same space as in storage tanks.
  • Materials used to construct vessels are often brittle and the possibility of brittle fracture increases with wall thickness.
  • Regulatory codes limit use by allowing only specific materials to be stored under a specific range of conditions.

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EXPANSION TANKS


Expansion tanks are designed to allow space for a fluid to expand in a system.


GENERAL INFORMATION

Expansion tanks allow for the expansion of a fluid. A properly implemented and maintained tank will allow the system equipment in the system to have a longer life span, be safer to operate, and be simpler to maintain.


EQUIPMENT DESIGN

The expansion tank is normally placed in the system at its highest point. This allows for a positive pressure difference to make pumping easier and allows for simple venting. The legs of the tank are designed to allow a circular flow around the tank. Valves are placed at each of the legs to control the flow to the tank and expansion of the materials inside of the tank. Normally, only a single leg is open to allow for the expansion of the fluid while the second is closed to block flow through the tank. The size of the tank depends on the thermal expansion of the fluid volume, which can be estimated by multiplying the volume of expansion by two.




(Copyright Chemical Engineering, Access Intelligence, LLC)

USAGE EXAMPLES

Expansion tanks are normally used in heat-transfer systems where fluids will expand as they are heated.


ADVANTAGES

DISADVANTAGES

  • Allows for thermal expansion of the fluid
  • Extends equipment life
  • Make operations safer
  • Allows for easier maintenance
  • Oxidation can make the fluid more acidic and corrode the tank

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ACKNOWLEDGEMENTS


Aura Engineering, Inc., Pearland, TX
Chemical Engineering, Access Intelligence, LLC
Delpark Filters, Ace Manufacturing, Inc., Mississauga, Ontario
Matrix Service Company, Orange, CA
Xerxes Corporation, Minneapolis, MN


REFERENCES


Bravo, Jose L., James R. Fair, Jimmy L. Humphrey, Chris L. Martin, Albert F. Seibert, and      Sudhir Joshi. Fluid Mixture Separation Technologies for Cost Reduction and Process      Improvement. Park Ridge, NJ: Noyes Publications, 1986.
Jenkins, Scott. "Facts at your Fingerprints: Aboveground and Underground Storage Tanks"      Chemical Engineering November 2009: 32
Jenkins, Scott. "Facts at your Fingerprints: Heat Transfer Expansion Tank Design" Chemical      Engineering August 2012: 33
Li, Norman N., and Joseph M. Calo. Separation and Purification Technology. New York, Marcel      Dekker Inc., 1992.
Muralidhara, H.S. Advances in Solid-Liquid Separation. Columbus: OH, 1986.


DEVELOPERS


Matthew Skindzier
Mike Africa
Steve Wesorick
Abigail Nalbandian
Keith Minbiole
Thomas Plegue


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