Anyone who works in any industrial field requiring the use of aboveground storage tanks (ASTs) knows that these large industrial containers are built to strict specifications to meet the needs of the job they’ve been designed to do. But there’s an extra factor to consider that leaves many people with questions – is it better for your tank to be assembled directly in the field at the site where it will be used (field erected), or should it be built in a traditional shop and then moved to its final destination? This choice is often determined by the size of the AST and the product to be contained.

If you are considering installing a new storage tank and have doubts or questions about building your AST in the field, read on to learn all the most critical information you ought to consider before making a decision. 

How Big Do Field Erected Tanks Get?

One of the defining traits of field-erected tanks is the fact that they are often quite large, as we’ll discuss in more detail a little later on. If you specifically work with storage tanks, you’re probably aware of just how big these containers can be, but if you’re a general contractor or field engineer (someone for whom storage tanks are just one factor of a big project), a common sized field erected storage tank often refers to one that’s at least 15 feet in diameter and capable of holding 45,000 gallons or more. On the other hand, truly large ASTs can approach 5 million gallons or more. Having said that, most fields erected storage tanks fall in the 30,000-300,000 gallon range.

However, this number does not represent an upper limit. As long as a tank meets the requirements set by the API 650 or AWWA D100, in theory, there is no limit on how big a field-erected tank can be! Nevertheless, in practical terms, building a single huge storage tank is rarely done. Once a tank reaches a certain size, it simply becomes more affordable to build multiple smaller containers, not to mention that an accident or serious problem becomes much worse when keeping all your eggs in one basket (or tank, as it were). For these reasons, most companies will prefer a farm of smaller tanks over a single massive one. 

Shop Built or Field Erected: Key Factors

There is a wide range of factors to consider when weighing the choice between shop-built or field erected tanks. At the end of the day, tanks built by either method will be used for the same thing – holding large quantities of material or product, so the significant factors determining which is better are practical and economical.

In terms of practicality, the first and most common concern is size. As we alluded to earlier, field-erected ASTs can be very large, and once they reach a certain size, building them in a shop and moving them to their final location just isn’t practical, or sometimes even possible. 

As for vital economic factors to consider, these can vary a great deal from project to project. Pressure vessels, for example, aren’t needed at every site, but if you do require them, they are generally much more economical to build in a shop. This is due to their more complicated or specialized parts compared to a simple storage tank.

Critical Site Considerations: Necessary Work and Limitations

Oftentimes the specifics of your construction site play a central role in deciding between in-field erection versus shop construction – site access is a major factor to consider. In order to build an AST in the field, all the necessary construction equipment such as trucks, tractors, and cranes must be able to not only access the construction site but also be able to move and operate freely in the space available. If necessary equipment doesn’t have physical access and operating space, shop-built tanks may be a necessity. 

It’s also vital to remember that erecting an AST in the field comes with all the usual site preparation necessary for building any similar large structure. These preparatory steps include, but aren’t limited to:

  • Clearing trees and stumps from the area
  • Demolition of old structures that may be at the site
  • Surveying the area
  • Soil testing
  • Excavating and pouring foundations
  • Installation of pipes and utilities
  • Installing facilities for site security

What Are Field Erected Tanks Built Out Of?

Like any other large storage tank, field erected tanks can be built from a variety of materials. Unlike containers used inside shops or indoor facilities, field-constructed tanks must be able to withstand pressures from harsh weather, a less controlled ambient temperature, and potential chemical stresses that may exist in outdoor conditions. 

For this reason, most tanks are built of stainless steel, carbon steel, or duplex material. More robust metal options like these are, of course, resistant not only to outdoor conditions but are often necessary to contain potentially caustic or dangerous liquids. 

While it is possible to build outdoor tanks out of concrete, it’s rarely a wise decision in the long run since concrete containers have a lower lifespan (60 years compared to the 100 years of steel tanks) and are more vulnerable to cracks, leaks, and buildup of bacterial growth.

That’s the Basics. What’s Next?

We are only as good as the service we provide, and we go the extra mile to ensure all of our personnel are trained to industry standards. 

At NDT Tanknicians, we embrace the tough challenge set in place to be certified by entities such as the Environmental Protection Agency (EPA,) American Petroleum Institute (API,) Steel Tank Institute (STI,) American Society for Nondestructive Testing (ASNT,) and the National Association of Corrosion Engineers (NACE,) to name a few. 

We’re capable of providing top-to-bottom coverage for all of your Storage Tank requirements; servicing a broad spectrum of clientele, both small and large. Our ability to streamline an entire project gives us an edge over the competition by providing our clients with the peace of mind and convenience of trusting one service provider to become familiar with all of their current and future needs, rather than half a dozen. This keeps costs to a minimum, quality control consistent and communication among crews seamless. Request a quote today.