How Seismic Use Group Classification affects your Water Storage Tank

Seismic Use Group Bolted Tank

When purchasing a bolted steel tank or a welded steel water storage tank, one of the key criteria determining the design parameters of the tank is the Seismic Use Group (SUG) classification. The term Seismic Use Group is essentially the same as the terms Occupancy Category and Risk Category used by the International Building Code (IBC) and the American Society of Civil Engineers (ASCE). The Seismic Use Group classification is used to determine the magnitude of environmental loading applied to the bolted or welded tank structure. Despite the name, the Seismic Use Group classification is applicable to other environmental loads such as wind, snow, ice, and floods.

The Seismic Use Group along with the seismic accelerations at the site help determine the Seismic Design Category of a structure. Seismic Design Category is a letter rating from A to F with F being the worst case. There are special detailing requirements depending on what Seismic Design Category a structure is in. For example, with steel water storage tanks, the seismic design category impacts how the anchor bolts are designed.

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Superior Tank Installs Innovative Bolted Tank

Superior Tank Co., Inc. (STCI) is proud to have provided the new bolted steel tank for the Cauayan City Water District in Isabela Philippines. The bolted tank is the first of its kind in Northern Luzon and highlights the benefits of a bolted steel tank. The epoxy coated tank provides storage of 79,000 gallons of potable water for Cauayan City and is dedicated to the late Governor Faustino N. Dy and his son Governor Benjamin G. Dy. Their vision and initiatives have resulted in the development and modernization of the Cauayan City Water District and also contributed to the City being branded as “Ideal City of The North”.

The bolted steel tank used for the project was designed and manufactured to provide the city decades of service. Constructed of high strength carbon steel, the bolted tank is constructed for maximum durability and longevity. To meet local building codes and to withstand typhoons, the bolted tank is designed to meet a 200 mph wind load requirement.  To accommodate the city’s future needs and save the city time and money, the bolted tank was designed to be easily expandable by simply adding rings to the tank.  To survive the warm and humid conditions of the Philippines, the epoxy bolted tank features a corrosive resistant powder coating with an additional Silica-Zirconium(Si-Zr) underseal. To resist the harsh sun and UV rays, the exterior of the bolted tank was protected with specially formulated TGIC powder coating.  Our Sky White color was selected to reduce the solar heat gain which helps to keep the water cooler and preserve water quality.  In addition, bolted tanks manufactured by STCI are different than bolted tanks from other companies as it includes a steel floor.  The steel floor ties the shell together and prevents leaks and water loss which can occur with concrete bottom tanks.

The bolted steel tank in Cauayan City is truly an investment in the community and a testament to the vision of Governor Faustino N. Dy and Governor Benjamin G. Dy.

Contact us to learn how we can help you plan for the future!

Complete Solutions for Oil Storage Tanks

Bolted Oil Storage Tank

For over 30 years, Superior Tank Co., Inc. (STCI) has designed, manufactured, installed and serviced bolted tanks and welded tanks for oil storage. STCI is one of the only bolted steel manufacturers which can proudly display the prestigious American Petroleum Institute (API) SPEC 12B monogram on our bolted tanks for oil storage. In order for a bolted tank to include the API 12B monogram, the storage tank must strictly adhere to the API SPEC 12B standards. In addition, the tank manufacturer must be recertified on an annual basis to meet the strict API SPEC Q1/ISO 9001:2008 quality standards.

All STCI bolted tanks for oil storage are engineered and manufactured to meet the strict API SPEC 12B design standard and include numerous elements to increase tank durability and longevity. To seal our tanks, we use heavy duty gaskets made of Buna-N or Viton in place of mastic putty which is incompatible with oil storage. Our custom made Buna-N and Viton gaskets are extremely durable and resistant to crude oil and other corrosive liquids. Also, to increase the lifespan of the bolted tank, our gaskets have high tensile strength to prevent tearing and remain flexible over time. In addition, our gaskets do not require routine replacement thereby decreasing maintenance requirements. To reduce service intervals, our bolted tanks feature premium Scotchkote powder coating which is specifically formulated for oil storage. Our API SPEC 12B bolted tanks range in capacity from 100 to 10,000 bbls and adhere to dimensions determined by the API SPEC 12B specification. Read More “Complete Solutions for Oil Storage Tanks”

What makes a bolted tank “Superior”?

Various companies sell bolted steel tanks, but there is only one “Superior Tank”. Is there really a difference between bolted tanks manufactured by Superior Tank Co., Inc. (STCI) and bolted steel tanks and glass-lined bolted steel tanks made by other companies? The answer is in short “yes” for various reasons including STCI’s precise manufacturing processes, premium raw materials, extensive company history, API SPEC Q1 / ISO 9001:2008 certification and outstanding customer service. Superior Tank Co., Inc. is one of the few bolted tank manufacturers in the United States and the only bolted tank company with manufacturing facilities in both California and Texas. Owning and operating State-of-the-Art manufacturing facilities gives STCI complete control of the quality of our bolted tanks and we are not reliant on outside companies for the quality of our bolted steel storage tanks. All of our bolted tanks use quality materials such as heavy duty Grade 5 or Grade 8 high tensile strength bolts and the steel used for our bolted tanks is verified to meet specific quality standards such as surface quality, edge quality, silicone content, squaredness and flatness. In addition, our specially formulated powder coating and corrosion preventing SiZr seal maximize the lifespan of the epoxy coating of the bolted tank. Our heavy duty gaskets ensure our bolted tanks remain in service and do not require storage tanks to be taken offline to replace the mastic which is used with glass-fused-to-steel bolted tanks. We have invested heavily in precision equipment such as CNC machinery, Automated Robotic Technology (ART), and advanced turret punches to ensure our bolted steel tanks are manufactured with exacting precision. As our bolted steel tanks are crafted with such accuracy, components fit together perfectly, eliminating tank leaks and field rework. To confirm our bolted tanks meet or exceed quality standards, STCI has implemented various Quality Management Systems and is API SPEC Q1 / ISO 9001:2008 certified. Various processes and procedures have been put into place to ensure our bolted steel tanks meet customer expectations and delivery schedule. In addition, STCI has earned the reputation of providing exceptional customer service and ensuring our customers are happy with their new epoxy coated bolted tank. The results of these extra efforts are illustrated in our excellent Customer Satisfaction rating and customer testimonials. When all of these factors are considered, it is evident what makes our tanks, “Superior”.

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Fire Protection Storage Done Right

Water storage tanks for fire protection has improved in recent years as technology has advanced, processes have evolved and standards have become more rigorous resulting in increased flexibility, greater durability and lower costs.

Modern ground storage tanks used for fire protection are commonly one of three designs; bolted steel tanks, welded steel tanks and concrete tanks. Concrete tanks are commonly used for projects requiring greater than 80,000 gallons of water storage due to the high set up cost of the required equipment on the job site. This expense makes smaller concrete tanks cost prohibitive relative to other designs. Welded steel tanks for fire protection provide a wider range of capacities anywhere between 25,000 to 3,500,000 gallons. In addition, welded steel tanks are available in a variety of configurations including reservoir style storage tanks and standpipe water tanks. For certain applications, customers prefer the smooth exterior of a welded steel storage tank.

Of the three types of ground storage tanks, bolted steel tanks provides the greatest flexibility, outstanding longevity and best cost efficiency. Bolted tanks provide the larger range of sizes, from 5,000 to 3,500,000 gallons. For most fire protection projects, the storage tanks required range in capacity from 25,000 to 250,000 gallons which is well suited for a bolted steel tank. Bolted steel tanks are frequently used within existing infrastructure to increase water storage or to provide storage in remote areas. For example, when a new warehouse is built and requires water for fire protection, a new bolted steel tank can easily be installed on site, even in areas with constrained space. Alternatively, bolted tanks work well for remote areas and are available in either closed-top or open-top “scoop tank” design. Read More “Fire Protection Storage Done Right”

We Don’t Crack Under Pressure!

We Don't Crack Under Pressure! (glass)

In the bolted steel tank industry, two coating options are common; factory powder coating and glass-fused-to-steel coating. Each of the coatings has its own unique properties and characteristics when applied to bolted tanks and steel tanks for water storage.

Bolted tanks with a glass-fused-to-steel coating are attractive to potential buyers as the coating is non-porous and very rigid. The glass is applied directly to the steel then heated to 1500˚F to melt the glass and bond the glass to the steel. In theory, the glass coating isolates the steel from the liquids stored in the bolted tank. Unfortunately, the real world can be very different from theory. Ironically, the same properties which make the glass coating attractive for use with water storage tanks also make the coating vulnerable to cracking. The rigidity of the coating does not allow the glass to flex with the steel tank panels which expand and contract with temperature changes. This difference in expansion rates can lead to the coating cracking under stress. In addition, the extreme rigidity of the glass coating can help to resist very minor impacts but can lead to cracking if impacted with any significant force. When the coating on a glass-lined bolted tank cracks, the steel underneath is exposed and corrosion will likely occur. After the corrosion starts to spread, it can result in undercutting and the overall failure of the coating. As the glass coating is applied to the steel at the factory and melted at a very high temperature, it is not possible to fully repair a bolted tank with a glass-fused-to-steel coating. The only “fix” possible is to cover the cracked area with mastic. The proper way to ensure the panel does not experience corrosion and coating failure is to replace the entire damaged panel as glass-lining cannot be fixed or repaired in the field. The vulnerability of a glass-lined tank to impact makes it critical to protect the storage tank panels during shipping and installation as well as after the ground storage tank is installed. A dropped tool or thrown rock can result in an expensive repair and require the storage tank to be taken out of service to replace an entire panel.

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10 Tips on Tank Preparation for the Winter Season

10 Tips For The Winter Season


With winter weather coming, it is important to prepare your steel water storage tanks. Winter weather and colder temperatures will impact your steel storage tanks, no matter how severe the weather is.


Below are several techniques which can keep your potable water tanks in top operating condition:   • Inspect interior and exterior of tank for evidence of corrosion on metal surfaces • Check screens on roof vents and overflow piping are intact • Examine tank for potential areas of contamination such as roof hatches and other shell penetration • Ensure all access hatches have working locks to prevent unauthorized entry • Visually inspect tank interior for excessive levels of sediment • Inspect tank for safety equipment such as anti-fall systems, roof tie offs and roof railing to ensure components are compliant with current codes. • Perform coating assessment to evaluate remaining lifespan • Review foundation integrity, remove organic debris and determine if potential seismic upgrades are required • Install active tank mixing system to prevent ice buildup and maintain water quality • Develop tank plan service/maintenance schedule  

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No “Tail-Light Warranty” here!

bolted tank warranty

Some bolted steel tank companies’ warranty lasts only as long as you can see the taillights on their trucks as they leave the job site.  We take great pride in the quality of our bolted tanks and the skill of our tank installation teams. Superior Tank Co., Inc. backs all of its bolted tanks with one of the best warranties in the ground storage tank industry.

Over the last 30 years, Superior Tank has earned an outstanding reputation for customer service and our warranty coverage.  We are known for doing business the right way and taking care of our customers. We send out our people to resolve any issues with your steel tank. Our warranty does not require you to uninstall the part, ship the part back then wait for us to decide what to do next. Nor will we ever prorate the value of the part and send you a check and expect that will resolve the problem.

We understand the high cost of having your storage tank out of service or the extensive amount of damage a defective oil or water storage tank can cause. We design, manufacture and install all of our ground storage tanks NOT to have problems in the first place! Our API SPEC Q1/ISO 9001:2008 certification is evident of our commitment to quality.

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Five Critical Parts For Your Steel Storage Tank

Bolted Tank Parts and Accessories

Every year, we sell hundreds of parts for bolted tanks and welded steel tanks. Even though many ground storage tanks needing parts were not originally manufactured by Superior Tank Co., Inc., we can provide standard replacement components for steel storage tanks or can fabricate custom parts and accessories to fit.


Over the last 32+ years, we have discovered there are five storage tank elements which are key to ensuring your water and oil storage tanks achieve their maximum lifespan:

1 Ground storage tank bottoms
2 Roof rafters
3 Ladders and safety railings
4 Hardware, gaskets and appurtenances
5 Powder coating touch up kits


While these seem to be the fundamental oil and water storage tank components, we have found many ground tanks in the field require one of more of these items.


For example, it is not unusual for welded steel tanks to experience bottom corrosion and subsequent steel loss as the underside cannot be coated. In addition, select hot dipped galvanized bolted tanks which are over 30 years old can experience bottom corrosion and require new components. Our fabrication department will custom manufacture replacement steel tank bottom sections to any size or dimensions to fit either bolted tanks or welded steel tanks.


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Bolted Tanks: “Designed to” vs. “Certified”

bolted tank

Most bolted tank companies use the term “designed to” when referring to industry and quality standards. At Superior Tank Co., Inc. we can positively confirm all of our bolted steel tanks meet or exceed the expected design and quality objectives.


Superior Tank has undergone the very rigorous API SPEC Q1 and ISO 9001:2008 certification process which reviews the various elements of bolted steel tank manufacturing including tank order, engineering, production, delivery, installation and service. During the certification, countless processes were audited to ensure policies and procedures were in place to guarantee our steel tanks comply with set standards, meet or exceed customer expectations and are delivered within the prescribed timeframe. For example, the external ISO audit team reviewed our procedure to exactly transfer all bolted steel tank specifications from the approved Sales Order to our Engineering Department for design.  Our Engineering Department maintains an extensive electronic central library of steel tanks and steel tank components which have been verified to industry standards and exact specifications. Starting with solid and consistent design elements ensures our bolted steel tanks will meet engineering performance standards.  Raw materials such as steel used for staves is verified to meet specific quality standards. For example, surface quality, edge quality, silicone content, squaredness and flatness are checked and materials not meeting standards are rejected. Inferior and low quality materials are never used. Another element of the certification process is making sure our ground storage tanks are manufactured to precise tolerances using the latest CNC and robotic welding machinery. Quality inspectors are located at key stages to ensure finished parts meet various established specifications. Any non-conforming parts are discovered during manufacturing stage and are rejected. At the completion of the production cycle, the various steel tank components are final inspected by a designated quality control auditor and the complete inventory of parts is compared to original production checklist for accuracy.


In addition to being certified under the API SPEC Q1 and ISO 9001:2008 process, critical aspects of our tanks have been tested by an independent laboratory. Our factory powder coating has been stress tested for various characteristics including resistance to abrasion, significant impact, salt spray, high humidity, temperature and corrosive chemicals. In separate testing, our Silica -Zirconium (SiZr) underseal was verified to prove its ability to prevent corrosion and coating undercutting if the powder coating is damaged by a thrown rock or dropped tool. In all areas of testing, our powder coated bolted steel tanks meet or exceed performance standards for durability.


We understand we could save money by eliminating our strict quality standards but we have witnessed competitor’s tanks fail due to inferior materials and processes and we are unwilling to compromise quality.


When purchasing your next bolted steel tank, look for companies which have been API SPEC Q1 / ISO 9001:2008 certified to ensure you are actually receiving what you ordered. At Superior Tank, we can confidently state that all of our bolted steel tanks meet or exceed design and performance expectations. We do not simply try to “design to”; we succeed!