Tank Safety: More Than Meets the Eye

Brian Elliott, Structural

April 06, 2022

Our clients thought something looked off about their industrial bin hopper. A quick visual inspection raised a red flag for me, too.

Determining the extent and severity of the problem required more than an eye test, so we built a finite element model to obtain a better picture of the stresses on the hopper. We then followed up with nondestructive tests to reveal the hopper’s composite material and wall thickness.

The analysis clearly pointed to approaching failure. Because the hopper was situated in a confined space, a rupture would almost certainly result in serious, if not fatal, injuries to any nearby employees. We immediately alerted our client and went to work on designing a new hopper.

Tanks, hoppers, and pressure vessels are some of the most essential components for any industrial facility. When used as designed and properly maintained, they are also some of the most reliable and durable assets in an equipment fleet.

A well-made tank often outlives the work for which it was designed. When a tank is used for a different purpose to suit an owner’s process requirements, problems can emerge. Different process conditions can produce changes in temperature, pressure, and specific gravity that a tank is not designed to handle. In other cases, tanks intended for liquid storage are reused for bulk storage conditions.

 

 

That’s where engineers who specialize in tanks and pressure vessels come in. Tank engineers have the training and experience needed to analyze the operational safety of tanks and pressure vessels – especially when there is a change of service.

A major reason tank engineering has emerged as a specialty is because there are so many different types of tanks. Common above-ground types include fixed-roof tanks, floating-roof tanks, horizontal tanks, liquified natural gas tanks, and variable vapor space tanks – all with different applications. Pressure vessels are designed and manufactured to store and dispense pressurized gases and liquids. Some of the variables that affect the design and ratings of tanks include temperature, pressure, specific gravity, contents in storage, and so on.

Newly manufactured tanks must meet codes established by the American Petroleum Institute (API) and pressure vessels are regulated by the Boiler & Pressure Vessel Code (BPVC) written by the American Society of Mechanical Engineers (ASME). Because of the potential danger of tank ruptures – especially in tanks operated under high pressure – the ASME code was recently amended to require pressure vessels to be stamped and sealed following any type of modification or repair.

Making sure a facility’s tanks, boilers, hoppers, and pressure vessels are up to code fits with mechanical integrity programs that are increasingly being implemented by large industrial manufacturers. From an equipment standpoint, ensuring the sound condition of tanks and vessels ranks high on any organization’s safety checklist.

Specialized tank engineers know the code standards and have the experience to conduct the correct evaluation for repairs, retrofits, or any other modification. Having quick access to nondestructive testing is also critical in situations where manufacturing documentation no longer exists or has been misplaced.

As tanks reach the end of their useful lives, facility managers need to know the safety condition of their fleet. Because, unfortunately, a critical flaw isn’t so easily detected by the eye test.

 

Brian is a senior engineer with Olsson’s Structural team who has more than a decade of experience conducting inspections and evaluations of tanks and pressure vessels. Reach Brian at 515.333.3779 or belliott@olsson.com.

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