available in a large variety of sizes and are custom-engineered
to the specifc application and location. Bolted steel tanks are
cost effective in the capacity range of 10,000 to 2,000,000
gallons. By increasing or decreasing the number of rings or
the number of plates per ring, the height and diameter can
be changed. The height-diameter ratio should be evaluated
to ensure the tank meets the conditions of the site. The tank
manufacturer will engineer and fabricate the tank to meet local building codes as well as snow, seismic and wind loads for
the site. Because bolted steel tanks are modular and use interchangeable plates, they can be easily expanded by adding
rings of plates if the original design allowed for future growth.
It is important to work with an experienced tank engineer
who will guide customers through this complex process.
Bolted steel tank kits include all the proper fttings, piping and ventilation components required for the project. The
customized fttings and accessories are specifc to the application and will facilitate future sampling, inspection and maintenance. If needed, active or passive mixing systems can be
included in the tank package from the factory. These systems
reduce thermal stratifcation and help to better circulate disinfectant, thereby reducing overall disinfectant usage.
Since bolted steel tanks are manufactured off site, they
are available with a variety of fnishes including standard
powder coating,
premium powder coating and
hot dipped galvanizing. Stainless steel tanks
are also available. Each fnish is best suited
for a particular
application and
the fnish coating will impact
the longevity
and long-term
performance of
the tank. With
proper application and proper
maintenance,
the right fnish
will provide over
60 years of service.
FINISHING UP
Of the various
factory-applied fnishes, powder coating is the most common
and its use is well established. The powder is applied at the
manufacturing plant in an environmentally controlled spray
booth, and then baked at moderate temperatures to thermo-
set the coating. High temperatures above 1000˚F are avoided
to prevent panel warping. As the powder is electrostatically
applied in dry form, the process provides 100% coverage
without voids, drips or runs common with liquids.
Different powder formulas are used to provide the maxi-
mum amount of durability depending on storage application
(interior, exterior, brine, wastewater, potable, etc.). Standard
and premium versions of powder coating are available based
on the project requirements. Powder coating is non-porous
and designed to meet AWWA, NSF and FDA standards, and
various colors are offered to meet customer requirements.
Some manufacturers add a liquid seal under the powder coat-
ing as additional corrosion protection. If damage to the coat-
ing should occur, repair is typically very simple as most dam-
age does not penetrate to the steel. Most repairs can be made
by feld personnel using commonly available materials.
Another well established and extremely durable coating
is hot dipped galvanizing. During this process, the individual plates are immersed in hot liquid zinc, which completely
covers the surface. The zinc metallurgically bonds with the
iron in the steel to form several iron/zinc alloy layers. The
top layer of pure zinc is very durable and corrosion resistant.
Only select tank manufacturers can provide NSF approved
galvanized tanks for potable water storage as NSF prescribes
strict guidelines for the galvanization process. In addition, not
all local governing agencies allow galvanized storage tanks
for potable water and your tank engineer can assist with this
determination.
Another option for food processing or highly corrosive en-
Circle No. 21 on Reader Service Card
Tank kits can be delivered to a wide variety of locations and are well
suited to spaces with limited access, high fire danger areas and remote locations.
