Sukup Manufacturing Company • 641-892-4222 • http://www.sukup.com
Researchers come up with ways to boost per-acre yields year after year, particularly with corn, which has been known to top 300 bushels in certain select fields.
And it comes to the elevator faster and faster, as farmers consolidate acreage and add larger and larger equipment. In this climate, elevator managers are scrambling to keep up.
Like farmers and elevator managers, steel tank manufacturers have been scrambling to keep up with the rapidly increasing yields and volumes. Since at least the 1990s, available tank sizes have been increasing, and they’ve been finding customers.
In 2017, Sukup Mfg. Co., Sheffield, IA (641-892-4222), sold the first two of what the manufacturer says is the largest free-span corrugated steel grain storage tank ever built, to date, to an ethanol producer in Iowa.
These monster-size tanks stand 156 feet in diameter, 106-1/2 feet tall at the eaves (29 rings, 44 inches tall each), and 149 feet tall at the peaks holding just shy of 2 million bushels each. Sukup’s largest tank prior to these two was 156 feet in diameter, 80-3/4 feet tall at the eave (22 rings), rated at 1.52 million bushels.
“This particular customer was one of our first customers for tanks in the over 1-million-bushel size when those became available,” says Commercial Accounts Manager Brent Hansen. “They came back to us with a request for a 2-million-bushel tank. Since they still wanted the tank kept to 156 feet in diameter, that meant we had to build taller.”
Sukup’s engineering team had a serious challenge ahead of them given the tremendous amount of force 2 mllion bushels of grain can generate against the tank sidewalls.
In addition, the team had to make sure the tank was built from standard-size Sukup components to the greatest extent possible, so the company’s manufacturing plant in Sheffield would not have to be retooled just to produce one new product.
“We also had to design a new door to allow for the extra grain pressure from a tank that holds nearly 2 million bushels,” Hansen adds.
One major consideration was the concrete foundation and pilings required for a tank this size. Hansen notes that the requirements for foundations will vary from site to site, with soil type and water table being the main factors.
The concrete foundations were installed by the general contractor on the project, Buresh Building Systems Inc., Hampton, IA (641-456-5242), says Buresh Operations Manager Josh Dubberke. Buresh then hired Global Bin Builders, Viroqua, WI (320-413-0312), to erect the tanks.
In order for the ground to support the tremendous weight of the fully-loaded tanks, the facility owner had 680 GeoConcrete columns installed underneath each of the tanks. The columns are 16 inches in diameter and were sunk, on average, 40 feet into the soil.
The force of grain in a tank presses outward toward the sidewalls, which makes this component key to designing a 2-million-bushel tank.
One way manufacturers of very large tanks compensate for this force is by designing sidewalls with multiple laminations going up a certain number of rings from the base, then one less lamination for a certain distance farther up and so on, until the sidewall consists of a single lamination near the top of the tank. Hansen says Sukup keeps the number of laminations and distance up the sidewall proprietary. However, Hansen notes that it took 41 semi-trucks to haul each tank’s components. The tanks are so large that it would take approximately 26 miles of trucks end to end to fill each of these tanks.
Sukup does reveal that it has designed a new patent-pending double-ended stud bolt for use on its largest tanks. This bolt is designed to ensure a tight seal directly to the outer sidewall sheet behind the stiffener, eliminating water infiltration between the sheets and into the grain. Hansen comments that this is a safety consideration, since entrapment incidents often occur when a worker enters the tank to deal with spoiled or clumped grain.
In addition, Sukup included its existing patented splice plates for large commercial tanks that create a double shear point on every bolt, making for a stronger connection due to the proper alignment and more even load on the bolts compared to traditional overlap on vertical seams.
Hansen says the two tanks sold to the ethanol customer are designed to provide 1/10 cfm per bushel of aeration. Providing enough air for 2 million bushels of coarse grain requires ten 60-hp centrifugal fans, which send air through 10 parallel in-floor ducts. Sukup used its own aeration fans and ducting for this project.
Sukup engineers faced the challenge of designing a roof that can hold a 100,000-lb. load plus loads from unbalanced snow and grain temperature monitoring cables suspended from the roof. Buresh Builders reports that the two new tanks in Iowa are outfitted with 49 temperature cables from Tri-States Grain Conditioning.
Strengthening that design required some modifications to the roof, including some larger I-beams to support the cables.
Also, largely as a safety item, designers engineered a 21-foot-diameter deck into the peak of the tank to provide a safe place to work, including sturdy places to tie off a lanyard, and an ideal place to mount catwalks and grain handling equipment.
The new tanks in the Iowa project are designed to be filled at a rate of 60,000 bph, according to Buresh’s Dubberke.
Grain from two receiving pits at the site can reach the tanks via a pair of Schlagel 30,000-bph legs. These feed into two overhead Hi Roller 60,000-bph enclosed belt conveyors, one serving each tank.
The tanks empty onto a Schlagel 10,000-bph drag conveyor in an above-ground tunnel through an 9-foot stemwall.
Construction on the two tanks began in September 2017 was completed in February 2018. Hansen at Sukup notes that the customer was just beginning to load them with corn in May.
“Designing and engineering a tank this size provides a great way for our customers to add storage for the increase we have seen in yields over the last decade or replace temporary ground piles with an upright tank that will last for years to come and maintain better grain quality,” he says.
Reprinted from Grain Journal May/June 2018 Issue
