The latest edition of the American Society of Civil Engineering (ASCE) 7-16 Standard for Minimum Design Loads and Associated Criteria for Building and Other Structures published in August 2017, includes an exception to the AWWA D103.  Section 15.7.7.2 relating to bolted steel tanks, includes new requirements regarding bolted tanks with an embedded steel base setting ring:

• “b. For Type 6 tanks, the overturning ratio, J, as determined using AWWA D103, Eq. (14-32) shall not exceed 0.785.” This new verbiage has significance to bolted tank design as it impacts where a bolted tank with a Type 6 foundation can be used.

A Type 6 bolted steel tank utilizes a steel base ring shell embedded into the concrete foundation which also serves as the tank bottom.  The J ratio relates to the seismic loading and is a criteria used to determine if the storage tank requires anchorage.  A value of less than 0.785 indicates the tank wall will not experience uplift and does not need anchorage. Conversely, a J ratio greater than 1.54 requires the bolted tank to be mechanically anchored. Ratios between the two values may or may not require mechanical anchorage depending on other factors.

Essentially, the ASCE is requiring embedded shell bolted steel tanks not to be used in areas where uplift occurs due to seismic activity. The concern is there are no specific design requirements for  the anchorage of the shell to foundation and the concrete bottom included in the AWWA D103 therefore it is difficult to ensure ductility of the tank to foundation connection. There is a risk of the shell separating from concrete tank bottom during a seismic event as a design criteria does not exist to ensure the connection is properly designed. ASCE 7-16 does not restrict bolted tanks with other foundation types; only tanks with an embedded shell.

For most applications, Superior Tank Co., Inc. will design our bolted tanks to use foundation types 1 through 5. With foundation types 1 through 5, the storage tank will include a steel bottom which structurally ties into the bolted tank shell creating one uniform structure.

This new terminology is another example of how bolted tank standards are continuously evolving resulting in more resilient bolted steel tanks.

Superior Tank Company is proud to announce we have recently earned NSF International Certification for our bolted steel tanks over 14,309 gallons. NSF/ANSI 61 and 372 Certification of our bolted tanks demonstrates compliance to the internationally recognized health effects standard for drinking water system components. NSF International led the development of the American National Standards for all materials and products coming into contact with drinking water and NSF/ANSI 61 & 372 sets health effects criteria for many water system products, components and materials. For example, NSF International standards are used to verify the safety and performance of water treatment and plumbing components and to ensure these products do not leach harmful levels of contaminants into drinking water.

Read More “NSF International Certification for Bolted Tanks”

One of the first questions we are asked is “how much does a bolted steel tank cost”? Unfortunately, the answer is a little complex as the price of a bolted tank is impacted by a variety of factors. Elements include storage tank design specification, relevant local building codes, quality of raw materials, scope of work included in the contract, manufacturer experience and tank installation team skills/training.

The various design specifications such as AWWA D103, NFPA 22 and API 12B determine tank appurtenances, shell design, steel thickness and even tank size in some cases. For example, the American Water Works Association (AWWA) D103 standard applies to all bolted tanks used for potable water storage and mandates the interior epoxy coating is NSF 61 certified. Bolted tanks for fire protection need to comply with the National Fire Protection Association (NFPA) 22 standards which requires specific tank components such as tank heating systems when needed and reinforced concrete ringwall foundation. When a bolted tank is used for oil storage, the American Petroleum Institute (API) 12B standard is commonly used as a reference but tanks do not have to comply. However, for customers desiring a guaranteed level of quality, the API 12B monogram program ensures the tank meets very specific design criteria and the bolted tank manufacturer is API Spec Q1 / ISO 9001:2008 certified.

Read More “How Much Does A Bolted Steel Tank Cost?”

Superior Tank Co., Inc. (STCI) has been engineering, manufacturing and installing bolted steel tanks since 1984. Over the last 33 years, STCI has manufactured thousands of bolted tanks which have been successfully installed throughout the world.

Our history has shown STCI has the strength and structure to last. STCI is one of the few bolted tank manufacturers in the United States and the only company which is family owned and operated providing our customers with the confidence that they are purchasing from a company with the highest values and standards. As we operate our own State-of-the-Art bolted tank manufacturing plant and welded steel tank fabrication facility, we have complete control of our quality and tank production schedule. Our bolted steel tank production facilities also include a powder coating line allowing us to offer various powder coating formulas including epoxy and TGIC polyester as well as specialized Scotchkote for extremely corrosive liquids.

Read More “Over 33 YEARS of Building Bolted Steel Tanks!”

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”