- Published: Friday, 14 October 2011 16:43
- Written by CP Staff
Valmont Newmark elevates spun cast poles to keep power transmission current
While ramping up its expanded spun cast, prestressed concrete pole operation over the summer, Valmont Newmark attributed a higher-than-normal defection rate among new recruits to a heat wave that saw temperatures somewhere in Texas reach triple digits for 70-plus days. “Some wouldn’t come back after lunch on their first day, others might give it a little longer to decide this wasn’t for them,” says Plant Manager Gerald Carter, who is building a pre-expansion payroll of 70 toward a projected 100.
Some production line candidates might bring concrete or construction experience to the Bellville, Texas, site, but few if any will be familiar with spin casting—a fabrication method limited to perhaps 20 North American precast/prestressed plants. Carter is well qualified to recruit and train newcomers, having worked his way up from the production line into management, and through two plant upgrades in the past decade.
The sooner he can attain targeted productivity rates with new and seasoned crew members, the more key customers can bolster the state’s power grid via renewable energy sources. Completed mid-year, the plant upgrade combines improved batching and mix delivery with increased casting bed area and new formwork. It equips Valmont Newmark to fabricate poles up to 140-ft. long, capable of carrying newer generation 345kV lines to transmit power from west Texas wind farms to electricity customers in the state’s eastern markets. Beyond demand driven by new transmission capacity for wind-derived power, Valmont Newmark has seen utility customers increasingly deploy the 345kV lines for infrastructure upgrades.
In contrast to the 120-ft. products that had been the Bellville plant’s largest offering, the 140-ft. poles hit an engineering sweet spot when measured against steel pole or lattice-type structure installations. Valmont Newmark’s newest pole tapers from 5-ft. diameter at the base to 2 ft. at the top. Its prestressed concrete composition affords a) ductility, key to tall structures subject to high wind loads and proven on test poles’ 10-ft., pre-failure deflection measurements; b) a small, foundation-free footprint, owing to embedment of 15 to 40 ft., depending on soils; and, c) height and strength characteristics required for the 345kV lines.
“Spun cast prestressed concrete poles are most competitive in medium-sized applications, with wood and light-duty steel on the small end and heavy steel and lattice tower on the large end,” says Valmont Newmark General Manager Clyde Reeves, P.E. “We want to offer customers a range of concrete, steel or hybrid solutions, whereas our competitors are in one market or the other.”
Reeves brings much field perspective to a one-stop supplier like Valmont Newmark, which he joined after managing the Texas transmission infrastructure of Gulf States Energy. During his tenure at the subsidiary of New Orleans-based Entergy, he approved installation of thousands of spun cast poles in the Lone Star State. After early-1990s experiments with some of the Bellville plant’s initial poles, Reeves saw how prestressed concrete structures perform in appropriate size classes against wood and steel alternatives.
He now oversees a plant where he had been a valued customer, plus Valmont Newmark’s newest concrete operation, in Barstow, Calif. (Concrete Products, October 2004). The company has four other spun cast pole operations, in Florida, Georgia and Alabama, plus eight steel-pole plants in five states—including one in Brenham, Texas, less than 20 miles from Bellville—and Mexico. The concrete and steel product businesses, each market leaders, form the Utility Support Structures Segment of Valmont Industries, Omaha, Neb. With annual shipments of about $500 million, the segment represents nearly a quarter of Valmont revenues.
TALL PRODUCT, HIGH BARRIERS
Confined to pole and round pile products, spin casting is among the most specialized and laborious segments of prestressed concrete. Pole fabrication begins with preparation of long, cylindrical molds, fabricated in 10-ft. increment segments. After plant crews finish securing tightly spaced prestressing strand and spiral reinforcement, molds are transferred to a mix placement station, filled about halfway with low-slump concrete, bolted shut, pretensioned, then hoisted to a spinner.
A 10- to 20-minute spinning cycle at up to 300 rpm draws considerable water off the relatively dry mixes, netting a dense, high strength concrete. Valmont Newmark targets finished concrete of 12,000-psi compressive strength; its standard mix design, formulated with Type I cement and Sika ViscoCrete high-range water reducers, achieves 12,000 psi in regular test cylinders, where all batch water is retained. Poles have the potential for extended life cycles, owing to the surface density and their tendency to self-heal cracks developed during extreme deflection moments. In lieu of carrying PCI Plant Certification, which customers do not specify for prestressed pole producers, Valmont Newmark meets utilities’ quality requirements by adhering to standards of the Task Committee on Concrete Transmission Pole Structures—organized under the ASCE Structural Engineering Institute’s Electrical Transmission Structures Committee.
Set on a 150-acre site dotted with old-growth pecan and live oak trees, the expanded Bellville plant is an appropriate next step for a company that has almost single handedly propelled the market for prestressed concrete poles beyond their roots in decorative, municipal lighting applications. Valmont Newmark is the successor of Sherman Utility Structures, a 1980s joint venture of Germany’s Pfleiderer GmbH and Birmingham, Ala.-based Sherman International. The latter had strong German ties via its principal stakeholder, Lehigh Portland Cement Co., and ultimate parent company HeidelbergCement.
As Lehigh Portland scaled back the diversified portfolio of Sherman Intl. to ready mixed and block, Pfleiderer rebranded its North American business Newmark in 1998. Newmark International, Inc., operated as a wholly owned Pfleiderer subsidiary until 2004, when it was acquired by Valmont Industries, which saw large, utility-grade prestressed concrete poles as a good companion to its steel pole business.
The Bellville plant expansion underscores the acquisition’s success. The upgrade has seen delivery of a new batch plant, mix placement and environmental equipment, plus additional pole formwork—all equating to a potential doubling of capacity. “Our existing batch plant had reached the end of its service life,” says Bellville Assistant General Manager John Webb, P.E. “The production line was expandable to build the bigger product where we see additional opportunity for prestressed concrete.”
To minimize or eliminate disruption of their production schedule, he and Clyde Reeves opted for a design/build approach. They enlisted San Antonio-based Plant Architects + Plant Outfitters for permitting, construction and management of request for proposals among batch plant and mix delivery equipment manufacturers. The Columbia Machine Batching Division was awarded a contract for a single-mixer replacement plant, tied to an existing, 400-ton, underground aggregate bin. The plant has a new overhead aggregate bin of the same capacity, plus skip hoist, twin cement silos, flying bucket and mix spreader—the latter mounted on rails running pole form lengths.
With a nod from Plant Architects + Plant Outfitters, Valmont Newmark added to the contract design and installation of environmental management equipment to address prospective future regulations. The Bellville plant, whose permit requirements in 2011 differ sharply from those of the site’s construction 20 years ago, has closed-loop, process-water recycling. That feature is the result of a mix reclaimer, receiving flying bucket and mix spreader washout; a filter press capturing fines from reclaimer and spinning process water; and, a pH adjustment device and storage tank to enable full reuse of post-filter press water.
“The design/build arrangement allowed us a nearly two-month overlap to program and test the new batch plant while the existing equipment kept pole production on schedule,” says Webb. “[Plant Outfitters] crews handled heavy foundation work required for a new spinning station without affecting our regular fabrication. The investment in water management systems now will help avoid disruption from new operating requirements in the future.”