||Welcome to Ask Tom!, a monthly column by our resident water treatment guru, Tom Keenan of
National Environmental Services Agency (NESA).
Tom addresses the issues that bug you the most. And Tom
knows!! With 35 years experience in providing
environmental support services to public and private sector
clients on a wide range of environmental issues.
articles visit the Ask Tom!
Water & Wastewater
– Liquid Tank Selection
by Bill Neighbors, Tank Connection
liquid storage containment, quality and value drives today’s
tank selection process. With advances in fabrication
technologies, engineering design, coating processes and field
construction techniques, some storage products utilized in the
past have become outdated, while other products have pushed to
the “front of the line” in product development and field
The process of
selecting a water or wastewater storage tank starts with a
series of questions and considerations. This is one of the main
problems witnessed in liquid storage containment applications.
Many times tank selection is based on a preferred “construction
type” in lieu of field performance requirements. In reviewing
different types of tank construction, always remember to start
with the field performance requirements, which will lead you to
define the “value attributes” of each type of tank construction.
In most cases, a review of “value attributes” (the value aspects
defined by your client as important, i.e., long life, low
maintenance, cost efficient, etc.) and “life cycle costs” will
guide and simplify your selection process.
The “top 10” list
below includes basic considerations that should be addressed on
every liquid storage tank application. If the application under
review is routine and no special conditions exist, a standard
quotation can be requested from a vendor of choice. If any items
listed are a concern, a specialist in liquid storage
applications should advise you on the correct approach.
Water, Wastewater & Industrial Liquid Storage Applications
requirements in gallons/cubic meters
- Project design
conditions and applicable codes
- Are there any
unique “storage process” requirements
- pH and
temperature of stored liquid
- What materials
of construction should be used
requirements / interface responsibility
allowance and/or cathodic protection requirements
guarantee and/or warranty requirements
You don’t need to
have all the answers, but you do need to know a reliable
storage/containment specialist that can advise you in these
areas. With the basics covered, the selection process can be
narrowed for customer review and preference.
application required multiple liquid storage tanks for
wastewater treatment. Application required multiple clarifiers
in sizes up to 2.4 million gallons each. The tank selection
process is narrowed down to field-weld, concrete and bolted RTP
(rolled, tapered panel) construction. Bolted RTP design is
selected due to recognized field performance of non-leak design
and factory applied powder coat system.
Municipal Water Treatment
5000 cubic feet of hydrated lime storage. Based on the capacity
requirements, a shop-welded tank is selected for the
application. Based on experience with the material stored and an
extensive number of applications in the field, a flow aid device
is required. A bin activator sized at half the tank diameter
will provide reliable material discharge from the tank. A bin
activator provides a “funnel flow” material discharge pattern.
The material does not need to be tested. Material degradation is
not a concern.
Municipal Water Storage
water storage application requires ~ 4.5 million gallons of
containment. A condensed field construction schedule is critical
to the project. AWWA specification requirements are applicable.
Tank selection is narrowed to bolted RTP (rolled, tapered panel)
and field-weld construction. Based on expedited schedule
requirements and superior performance of factory applied powder
coat systems available for potable water storage, bolted RTP
tank construction is selected. Specialized jacking process is
utilized which allows the XL bolted tank to be built entirely
from grade level.
Note: Field installation completed within 12 weeks.
Standpipe Water Storage
application required ~100,000 gallons of water storage. Welded,
bolted RTP and API 12B tank construction were evaluated. RTP
construction was selected based on advanced coating system,
leak-free design and expedited schedule requirements.
Note: Standpipe was jacked in place from grade level. Field
construction completed in 3 weeks.
application – Client review of bolted RTP design with LIQ Fusion
7000 coating system, glass coated tanks and field weld
construction. Bolted RTP construction was selected based on
perceived value of product quality, future low maintenance cost
and advanced, safe field construction processes.
Note: Field construction completed in less than half the time
required for welded construction.
Potable Water Storage
required water storage containment of ~ 600,000 gallons. Client
specification requested a bolted steel tank with bolted steel
bottom for placement on compacted fill with grade ban
arrangement (no foundation). Bolted RTP and FP (flat panel)
construction were reviewed. Bolted RTP construction was selected
as precision design and premier installed quality.
Note: Bolted steel bottoms allow flexibility in foundation
Potable Water Storage
Bechtel project for
Dept. of Energy requires two 250,000 gallon potable water tanks
for Area 51 location. Specification requirement for field-weld
construction with aluminum geodesic dome covers.
Location: U.S, Area
Note: Welded tank construction and field installation per AWWA
In general, water
storage applications requiring a volume of less than 90,000
gallons will utilize a shop-welded or smoothwall bolted tank.
Both products are used interchangeably in municipal and
industrial applications. Both shop-weld and bolted construction
maintain advantages as listed above. Under review, the total
installed costs (material + freight + field installation) are
comparable between both products.
Bolted RTP (rolled,
tapered panel), field-weld, concrete and hybrid tank
construction are typically utilized in large volume liquid
storage applications. All four designs are routinely specified
in the power industry. In industrial and municipal applications,
bolted RTP and hybrid steel construction are the most cost
efficient tank designs. Field-weld and concrete construction
require extended field installation timeframes, which equates to
higher installed cost.
Beyond the rhetoric
of vendor promotion in the marketplace, when “value attributes”
are reviewed and compared to installed costs and life cycle
costs, some simple facts become pronounced in ground storage
- Specifying a
water or wastewater tank in or below ground, the best
installed product is concrete tank construction with
aluminum dome cover (as applicable)
- Specifying a
water or wastewater tank above ground, the best
installed product is steel tank construction with steel or
concrete bottom and aluminum dome cover (as applicable).
- Specifying a
cover over a concrete or steel tank, the best installed
product is an aluminum dome cover.
bolted tank construction for water or wastewater storage, the best installed product is bolted RTP (rolled, tapered
panel) steel tank construction with steel or concrete bottom
and aluminum dome cover (as applicable).
- Specifying field welded construction for water and
the best installed product is a field welded steel tank
sidewall and bottom with aluminum dome cover (as
“materials of construction” selection, bolted, shop-weld and
field-weld tanks are available in coated carbon steel and
stainless steel construction. All tanks are customized for the
application and are available for installation at grade level or
elevated. Typical tank accessories include manway accesses,
level control nozzles, maintenance access platforms, agitators,
heaters, insulation, caged ladders, spiral stairways, perimeter
guardrails, and custom requirements for system integration.
In summary, if the
basics are covered in tank selection, years of trouble-free
containment can be expected. Today, in industrial and
municipal storage applications, there are steel storage tanks
throughout North America that are over 100 years old. Based on
proper maintenance of a storage tank and its coatings, a high
quality, properly designed and installed steel storage tank can
be maintained for an indefinite service life. Quality and value
should drive your future tank selection process.
Tank Connection, LLC
1801 South 21st Street
Parsons, Kansas 67357
Web site: http://www.tankconnection.com/
Help others by posting
your comments, suggestions and experiences with water or
wastewater treatment or any other concerns you may have on
our On-Line Help Forum. For
past Ask Tom! Articles, visit the
Guest articles for the
Ask Tom! Column are always welcome, for more information please
contact Tom Keenan directly at his email address: firstname.lastname@example.org