Storage tank terms
Tank: A tank is a storage unit
that seldom has pressure applied to it's contents. Tanks
usually have thicker walls at their base to better support the
contents.
Vessel: Vessels are containers that hold contents under pressure. The construction of a vessel must meet rigid specifications that put equal pressure on all parts of the vessel rather than on the base, as it is the case with a tank.
Head: The head is the top and bottom portion of a vessel. There are three basic forms of vessel heads: hemispherical, torispherical and elliptical. Hemispherical is one-half of a sphere. Torispherical vessels have a two-part head. The first part is the crown, and the knuckle connects the crown to the shell. Elliptical heads are oval shaped.
Shell: The shell is the cylindrical part of the tank or vessel. Pressurized vessels have metal shells, while tank shells can be plastic, metal or concrete. Depending on the intended use of the shell, it may or may not have a lining.
Buffer Tank: A buffer tank serves as a pressure release source for a vessel. If necessary, overflow may run into a buffer tank. A buffer tank can also work efficiently to keep the contents of a vessel at a precise temperature.
Couplings: Tank and vessel couplings are used to connect storage containers with hoses or pipes. Couplings extend from the head and are female-threaded connections.
Cathodic protection: any one of several methods for protecting underground tanks and pipelines from corrosion. Corrosion results from an electric current which is caused by contact between metal surfaces, water, and the chemicals present in soils and water; cathodic protection counteracts this current.
Level gauging systems and alarms: Any engineering control that indicates the level of liquid inside the tank and that is installed on tanks to prevent overfilling and spilling of liquid and damage to the tank(s).
Specific gravity: the ratio of the density of a substance to the density of water.
Tank appurtances: in addition to the tank itself, the additional pieces of equipment necessary to bring the tank into service. Examples of tank appurtences include, but are not limited to:
Ladders and Platforms
Shell Manways
Inlet-Outlet Connections
Drawoffs (condensate, water and product)
Gauge Hatch
Vent Connections
Liquid Gauges and Alarms
Vessel: Vessels are containers that hold contents under pressure. The construction of a vessel must meet rigid specifications that put equal pressure on all parts of the vessel rather than on the base, as it is the case with a tank.
Head: The head is the top and bottom portion of a vessel. There are three basic forms of vessel heads: hemispherical, torispherical and elliptical. Hemispherical is one-half of a sphere. Torispherical vessels have a two-part head. The first part is the crown, and the knuckle connects the crown to the shell. Elliptical heads are oval shaped.
Shell: The shell is the cylindrical part of the tank or vessel. Pressurized vessels have metal shells, while tank shells can be plastic, metal or concrete. Depending on the intended use of the shell, it may or may not have a lining.
Buffer Tank: A buffer tank serves as a pressure release source for a vessel. If necessary, overflow may run into a buffer tank. A buffer tank can also work efficiently to keep the contents of a vessel at a precise temperature.
Couplings: Tank and vessel couplings are used to connect storage containers with hoses or pipes. Couplings extend from the head and are female-threaded connections.
Cathodic protection: any one of several methods for protecting underground tanks and pipelines from corrosion. Corrosion results from an electric current which is caused by contact between metal surfaces, water, and the chemicals present in soils and water; cathodic protection counteracts this current.
Level gauging systems and alarms: Any engineering control that indicates the level of liquid inside the tank and that is installed on tanks to prevent overfilling and spilling of liquid and damage to the tank(s).
Specific gravity: the ratio of the density of a substance to the density of water.
Tank appurtances: in addition to the tank itself, the additional pieces of equipment necessary to bring the tank into service. Examples of tank appurtences include, but are not limited to:
Ladders and Platforms
Shell Manways
Inlet-Outlet Connections
Drawoffs (condensate, water and product)
Gauge Hatch
Vent Connections
Liquid Gauges and Alarms
EPOXY BOLTED, Glass lined, WELDED TANK, WHICH DO I NEED?
When choosing a liquid or dry bulk storage system
you take into consideration several key issues such as quality of the
tank material, suitability of the tank material for the product to be
stored, price of the tank and construction type.
The most common tank designs are
bolted steel
(carbon steel, stainless steel and
glass-lined steel),
field welded,
factory welded,
fiberglass and concrete.
Bolted Carbon Steel Tanks are excellent choices for larger jobs
due to their quick installation and corrosion resistant epoxy coating.
They also have the benefit of being able to be disassembled and
moved to another location. They also may be installed
without skilled labor, with only a supervisor to guide the installation.
Glass Lined Steel Tanks are a cost effective, low
maintenance alternative to welded steel tanks. They offer fast
construction and are easily expandable. Glass lined steel tanks
are often the choice for use in potable water storage.
Field Welded Steel Tanks are notable for their
ability to hold product in very large capacities. UIG
offers welded tanks up to 12 million gallons in size.
Shop Welded Tanks are generally smaller in volume.
They are coated in the factory and are shipped and ready to
connect when they arrive at the site.
Concrete Tanks have been popular for many years
because they can accommodate almost unlimited sizes of storage volume.
Concrete, being porous, is highly susceptible to cracks and
corrosion and is very difficult to repair.
Fiberglass Tanks are often chosen for their ability
to resist corrosion. Common applications include
alkyds, alkali, bleaches, brines, chlorides, solvents, oxidizers and
other corrosive chemicals. Sizes range up to 14 feet
for shop fabricated fiberglass tanks to 50 feet for field installed
fiberglass tanks.
Many storage tank providers offer only the tank and
immediate accessories, leaving the end-user the task of contacting
several other suppliers to purchase all the other items needed to enable
the tank to become part of the bigger picture. It is prudent to take
into consideration companies that offer a complete package, thus
ensuring that everything fits together and is a complete answer to their
specific bulk storage and handling solution. Additionally,
many tank suppliers sell only one type of tank and will attempt to make
it fit into your project.
While ostensibly welded and bolted tanks are
designed and fabricated to specific nationally and internationally
recognized standards, for example in the case of welded tanks to API
650- field welded construction for Dry Bulk Storage, not all
manufacturers follow all the rules all the time. Although metal
thickness, welding procedures, coatings, etc. are
specified, these are not always adhered to. These are some of the
factors that will determine the longevity and suitability of the tank
for a specific bulk storage application and cutting corners can produce
disastrous results.
It is not unknown for tank manufacturers to have
their tank design written into the specifications provided to end-users
by ‘independent’ Consultants and Designers, in an attempt to disqualify
any competition. Whether a specific and ‘unique’ type of coating, use of
‘special’ gaskets or other intangibles, it will prove beneficial to
check on these matters to be certain that you receive competitive
quotations from as many accredited sources as possible. Some guidelines
to follow when choosing a tank are:
l Are there any characteristics to the material to be stored that would be a concern in the design of the tank (e.g.: large particles, dissimilar ingredients, abrasive, non-free flowing, products that liquefy, products that clump or stick together).
l What is the best and most economical material of construction? What type of discharge is needed? (funnel flow, mass flow, expanded flow, etc.)
l Is an aid device needed for reliable discharge? (hopper, reclaimer, etc.)
l Is a system interface needed? What is the tank configuration type? (flat bottom, sloped bottom, elevated, floating roof, domed roof, etc.)
l Are there any corrosion allowance or cathodic protection requirements? What type of foundation is planned? Are there any specific design codes requirements.
l Is a PE stamp required?
It is also prudent to plan for accessories needed as well.
l Access manways
l Level control nozzles
l Maintenance access platforms
l Agitators
l Heaters
l Insulation
l Caged Ladders
l Spiral Staircases
l Perimeter Guardrails
l Piping
l Other custom requirements for system integration
Once you and your storage tank system manufacturer have discussed all of your challenges and options, the most economical and reliable tank choice will be made.
Make sure that the tank system is specifically fabricated to your projects application and that you obtain as many quotations as possible from reputable companies.
If you are looking for more than just a tank, it is better to deal with companies that are able to offer an integration option, ensuring that all the parts of the jigsaw fit together. That the conveying system or other material handling equipment being supplied will integrate into your existing system or satisfy your new requirements.
l Consider who wrote the specifications that you are following and if they are providing you with all the technical options and pricing.
l Always make sure that the offers you receive provide you with individual elements of the tank design, including plate thicknesses, coatings, welding methods and the certainty that the tank offered will fit into your overall design and is suited to your specific needs
l If you are acquiring a field welded or field installed bolted tank ensure that the tank provider has a valid construction license, adequate insurance cover and safety certifications
l Obtain a written guarantee of the life-span of the tank and other accessories and integrated components for your overall system.
l If you receive competitive bids, be sure to compare like with like and as time is usually of the essence - investigate the installation methods that are to be employed. For example the tank jacking system allows the tank to be installed without the use of cranes and scaffolding. This is a faster and safer system and enables tanks and silos to be installed in areas where space is critical
l When looking at price, don’t be tempted to opt for the cheaper product without first investigating if the lower price is due to the use of cheaper materials and inferior construction methods.
Whether you are looking for a traditional welded tank or silo or looking at the fast growing RTP-Rolled, tapered panel bolted tank or silo, follow the above guide lines and the correctly selected tank fabricator will be able to provide you with a product that should have a lifespan of more than 40+ years and that will be an integral and reliable part of your bulk storage and storage system.
Some information to provide your tank manufacturer to help design your storage tank system.
l How much material is to be stored in the tank? What capacity will be needed to contain the material?l Are there any characteristics to the material to be stored that would be a concern in the design of the tank (e.g.: large particles, dissimilar ingredients, abrasive, non-free flowing, products that liquefy, products that clump or stick together).
l What is the best and most economical material of construction? What type of discharge is needed? (funnel flow, mass flow, expanded flow, etc.)
l Is an aid device needed for reliable discharge? (hopper, reclaimer, etc.)
l Is a system interface needed? What is the tank configuration type? (flat bottom, sloped bottom, elevated, floating roof, domed roof, etc.)
l Are there any corrosion allowance or cathodic protection requirements? What type of foundation is planned? Are there any specific design codes requirements.
l Is a PE stamp required?
It is also prudent to plan for accessories needed as well.
l Access manways
l Level control nozzles
l Maintenance access platforms
l Agitators
l Heaters
l Insulation
l Caged Ladders
l Spiral Staircases
l Perimeter Guardrails
l Piping
l Other custom requirements for system integration
Once you and your storage tank system manufacturer have discussed all of your challenges and options, the most economical and reliable tank choice will be made.
Corporate Office: 11 Rancho Cir., Lake
Forest, CA 92630
Mailing Address:
P O
Box 8009, Newport Beach, CA 92658 -
Phone (949) 759-3200
© 2011 United Industries Group, Inc.
www.unitedind.com - email
info@unitedind.com