Stainless Steel Waste Water Plant
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| NEWTOWN CREEK is scheduled for completion in 2013. This US$2.2-billion wastewater treatment plant makes extensive use of nickel stainless steel both inside and out. | |
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| ARCHITECTURAL FEATURES Stainless steel was chosen as a roofing and paneling material because of its appearance, low maintenance and longevity. | |
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| BLOWER PIPES which introduce air into the bottom of aeration tanks, are all made of S31603 stainless steel because of its corrosion resistance and structural integrity. | |
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Long service life is the key to choosing stainless steel for a major waste water treatement plant in New
York City. By Carroll McCormick.
Nickel magazine, October 2002 -- Corrosion, abrasion, maintenance and life
cycle costs are all key things to consider in specifying stainless steel hardware for wastewater treatment
plants. Such considerations are a matter of routine for New York City's Department of Environmental
Protection (DEP), which specifies stainless steel for much of the hardware in its wastewater systems.
One such system is the US$2.2 billion Newtown Creek Water Pollution Control Plant in the borough of Brooklyn. This 13-year construction project is designed to handle 1.2 billion litres per day. It will be completed in 2013.
"We have extensive experience with S30400 and S31603 stainless steels in our water supply system, dating back to the 1960s," says Ken Moriarty, chief of the DEP's design services division. "In our water treatment plants we noticed some high rates of failures [in carbon steel components]. Therefore, we thought that with the long service life of stainless steel equipment, we could reduce maintenance and replacement costs."
He adds that the cost of labour, excavation, shutdowns is so enormously expensive that the division does not mind spending a little bit extra for stainless steel in order to increase service volumes. Much of the division's equipment in deep, inaccessible sub-surface locations, so it's essential that low-maintenance materials are employed.
"We go through a value engineering process," says Vincent DeSantis, the DEP's director of facilities design. "Quite often stainless steel comes up and it usually survives the life-cycle cost analysis." Which is to say that the total (capital and replacement) cost of a stainless steel component over the life of the project is lower than the total costs of using components made of another material.
Among the stainless steel hardware used at Newtown Creek are 1,510 metres of blower pipe and 3,430 metres of piping and fixtures. These were fabricated by Felker Brothers Corporation, based in Marshfield, Wisconsin, U.S.A., for Sanitaire, another Wisconsin-based company, which manufactures and supplies aeration equipment for wastewater treatment facilities in the U.S.A. The pipe, worth some US$1.8 million, is all S31603 and ranges from 7.6 to 2,400 millimetres in diameter.
The sheet and plate is pickled before being delivered to Felker Brothers. After fabrication and welding, all of the pipe and fittings are immersion-pickled and the stainless steel is passivated by allowing contact with air. Pickle paste is used on spot welds to remove the heat tint, which, because of its inferior corrosion resistance, can lead to corrosion. "We insist on pickling, which is especially important where there are large lags between manufacturing and installation," says Moriarty.
Sanitaire uses S31603 because of its corrosion resistance and structural integrity. It also eliminates the need for periodic maintenance or painting of the piping system. Or as Sanitaire's Don Clement puts it, "stainless steel lasts a very long time."
The Bird Machine Company of Walpole, Massachusetts, supplied 24 centrifuges to the project. Centrifugally cast Duplex stainless steel was chosen for its resistance to corrosion and abrasion and for its higher tensile strength, which means less material is required.
Other applications at Newtown Creek include S31600 slide gates and abrasion- and corrosion-resistant stainless steel collector chains in the primary and secondary tanks. "We ordered tonnes of that equipment," says Moriarty, who notes that carbon steel chain failures have caused shutdowns.
Geoff Baldwin, project manager at Newtown Creek, says stainless steel allows maintenance crews to disassemble and reassemble units with considerable ease. He adds that the project boasts some impressive stainless steel architectural features. For example, S31600 stainless steel with a No. 4 finish is used to clad eight, 11.3-million-litre carbon steel digesters. The egg-shaped tanks measure 25.6 metres in diameter and are 27.4 metres high. Six of the building roofs will also be nickel stainless steel, for appearance, low maintenance and longevity. There is also some stainless steel paneling on the outside of the buildings.
Notes Keith Buernke, sales manager for Felker Brothers. "These wastewater and water facilities are backed by the general population, who realize that stainless steel is the most viable option."
Carroll McCormick is a Montreal-based science writer.
Wayne Azmat Keith Buernke Vincent DeSantis Don Clement |
