location every fi ve years and expose a length of the pipe and peel back the polyethylene encasement, examine the pipe for corrosion, and test the fi ll to see what its physicals are. So far so good,” said Gregg Horn, executive vice president, Ductile Iron Pipe Research Association (DIPRA). “We’ve looked at it about half a dozen times now over the years and haven’t seen any evidence of corrosion under the wrap. T e fi lm is a good strong fi lm that is protecting that pipeline.” More recently, the industry has

built on the polyethylene encasement with the introduction of the V-Bio polyethylene encasement for corrosion control of underground pipes. It builds on the polyethylene encasement and adds corrosion inhibition and even a biocide, coming in three layers. T e product has been in test sites

for 14 years using corrosion probes to measure the corrosion rate under- neath the V-Bio. So far, they’re get- ting readings that show no corrosion is occurring.

“We’re taking advantage of a rela-

tively new extrusion process and we’re enhancing the fi lm by adding an anti- microbial component and a corrosion inhibitor,” Horn said. “So it provides an active aspect to the protection that traditional polyethylene encasement provides for iron pipe. Our industry bought the patent in December 2012 and introduced it to the marketplace in 2013 and it’s been doing pretty well.” In general, ductile iron pipe can do

well in the toughest of conditions. Many times, ductile iron pipe will be used in an underground environ- ment that’s going to be aggressive to iron pipe. Some soils can promote corrosion, which is the single thing that can have a negative impact on the service life of ductile iron. T at then is why it’s important to protect pipes from corrosion. “Ductile iron’s a tremendously strong

product and takes advantage of the strength to employ some very conserva- tive design assumptions when you go to decide what class of pipe to use for a

given installation,” Horn said. “Taking advantage of that strength, you can get a tremendous service life with proper de- sign and installation practices, including protection in certain aggressive soils. “We do have a model that we use

as a risk-based model that evaluates the likelihood that a soil would cause corrosion and balances that against the consequences of the corrosion related problem to come up with a series of recommendations for corrosion control that make it pretty easy for a utility engineer to know what to do.” As a whole, the industry is look- ing to improve the service that the product provides. Gaston has been at AMERICAN

for many years and in his time there he’s seen his company move from making ductile iron pipe in sand-lined molds with one sand line application for each pipe to a process using per- manent molds and repeated castings with the same mold. “Manufacturing and metallurgi- cal advances like the introduction

Ductile iron pipe is seen in the manufacturing state. Nov/Dec 2016 | METAL CASTING DESIGN & PURCHASING | 21

Courtesy of McWane Ductile.

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