Storage Tank Construction Trends and Submerged Arc Welding Solutions

Storage tank welding

To support global energy and manufacturing demands, the outlook for construction of bulk storage tanks and terminals remains positive. With many recent factors at play, including the changing global landscape, the demand for oil and gas is dynamic to say the least. At the forefront, the need for natural gas is evident — not only to fill current voids in the market, but also for its overall role in supporting the long-term global energy transition story.

Every type of tank — whether it be for oil, gas or chemical storage — can present welding challenges due to the tank type, size and the material used to construct it. 

Unlike other industries that measure welding in inches or feet, storage tank construction is measured in miles. This makes it critical for contractors to take advantage of the most productive welding processes and the latest technologies to optimize results. 

Storage tank welding challenges

Four common challenges specific to large storage tank construction for energy markets. 

• Size and design: Welded storage tanks for the oil, gas and chemical markets most commonly fall into two categories — API 620 and API 650. These categories specify the standards for tank design, fabrication and construction. With the rise of natural gas production to support global energy needs, there has been a steep increase in the demand for low-temperature and cryogenic storage tanks. At the forefront is liquified natural gas (LNG), which is the preferred method for storing and transporting natural gas. LNG storage tanks pose many unique challenges and complexities due to their size, double-walled construction and more-difficult-to-weld material. The material is typically a 9% ASTM A353 nickel steel required for strength and structural integrity at extremely low temperatures. To tackle these complicated projects, contractors face a delicate balance between hitting tight parameter windows and achieving the productivity required to maintain profitability and stay on schedule.

• Weld quality: Weld quality drives the schedule and costs. It’s important to avoid rework and failed welds to save time and money. Testing requirements vary based on the type of tank. For many storage tanks, welds may be subject to non-destructive examination (NDE) every 100 or 200 feet. Others, like those built to API 620, could require full or partial testing of all welds. This makes it critical to ensure that all welding is being performed to the absolute highest of standards.

• Timelines: When constructing a storage tank, welding is front and center. While many jobs involve welding — from the floor to the roof and piping systems — achieving the highest levels of productivity when erecting the tank walls is critical to the project’s overall success. These welds can drive the entire project. They are most commonly made using a single- or double-sided automatic girth welder (AGW) with the submerged arc welding (SAW) process. If that machine breaks down or is producing poor-quality welds, it takes the whole job out of rhythm.

• Labor issues: Like many other industries, contractors often face difficulties finding skilled welders — especially those with the knowledge and skill to weld on a storage tank. In a competitive labor market, it’s important that new and existing personnel have the best tools for the job to be confident and successful.

How are contractors addressing challenges? 

For several decades, there has been little advancement in the welding equipment and accessories used for storage tank construction. This has led to an industry-wide practice where many contractors need to source components from multiple brands to adequately piece together a complete submerged arc welding system — particularly those used in an AGW, vertical-up or tractor setup. 

Additionally, the systems in place today are likely a result of numerous iterations and years of trial and error. For many, there is understandably a feeling or mantra of “If it isn’t broke, don’t fix it.” While this is logical, there is also a realization that change is inevitable. This is especially true as each year it becomes harder and more costly to source the components required to service and maintain dated technology.

Through the advancement of digital communication technologies, gone are the days of needing to run and maintain analog accessories (controllers, feeders, etc.) that lack the ability to take full advantage of the capabilities that the newer welding power sources can provide. 

Choose a modular setup designed for interchangeability and deployment among various integrated systems. This helps you realize the full benefits of a streamlined solution.

When choosing submerged arc welding power sources and accessories, look for equipment that offers:

• Seamless integration and simple setup. As one all-inclusive solution, the Miller® SubArc Digital System is portable and simple to set up. Operators of varying experience levels can quickly and easily connect accessories with power sources in the field. A single interface provides a repeatable experience across accessories. 

• Optimal welds. Choose a system with enhanced digital communication. This allows for more consistent steady-state welding, improved arc starts on a wide range of wire diameters and increased arc stability with specialty alloys. Digital solutions provide greater accuracy than analog meters. Operators can be assured of precise settings to meet the requirements of the welding procedure specification (WPS). The digital controller from Miller has the capability to select up to 15 programs. It can also be programmed with locks to ensure that operators stay within the limits of the WPS. 

• Expanded fleet capabilities. With the Miller SubArc Digital System and the SubArc Digital Converter, operators can use their existing Big Blue® engine-driven welders and Dimension™ power sources and pair them with any Miller submerged arc digital accessory, including the SubArc Interface Control, 3-Wheel Tractor, Wire Drive 400 and Low-Voltage Flux Hopper.

Real-world results 

Brent Harrell has decades of experience in the industry. He’s spent his career building above-ground storage tanks all over the world with several industry-leading companies. 

Most recently Harrell implemented a full Miller system with Big Blue engine drives as the power source and digital SAW accessories for wire feeding. The company wanted to take advantage of technology advancements in SAW welding equipment accessories. 

Since the switch, the company has seen greater weld consistency and improved ease of use with their welding systems for storage tank construction. 

“It’s a much more operator-friendly machine,” Harrell says. “If an operator is going to run four weld passes, he can set all of those up in the presets. All he has to do is hit one button and it switches to his next set of parameters.”

The digital gauge helps ensure a quality weld from the moment the operator hits the button. 

“With the digital gauge, if you want 147 inches per minute of wire feed, you can get exactly 147 inches per minute. You’re not guessing,” Harrell says. “Before you had to do a lot of adjusting as you started welding. Now you get a quality weld from the minute you hit the start button. This avoids a lot of rework at the beginning of the weld.”;

The simpler and faster setup and start time also save operators time and get them welding sooner. 

“I started having a lot less problems because the employees could consistently get going faster in the mornings,” Harrell says.”