A New Material for an Old Technology
THE MAGAGINE DEVOTED TO NICKEL AND ITS APPLICATIONS
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ONE OF TEN MASSIVE metal screws, 3,8 metres in diameter and 15.2 metres long, that will lift wastewater
five metres in the Hyperion Wastewater Treatment Plant in Los Angeles, California, U.S.A.
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AN ARCHIMEDES PUMP employed in a Dutch windmill dating from 1800.
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Ten huge Archimedes screws are slated for a sewage treatement plant in Los Angeles. By Dr. Gerry
Crawford
Nickel magazine, October, 2003 -- To pronounce the Archimedes screw pump a success
would be committing an understatement, given that the device was invented 2,200 years ago by the great
mathematician himself and is still used throughout the world. Essentially, the screw rotates in a closely
fitting inclined cylinder and this causes water to be raised several metres with little loss by backflow. (An
Archimedes pump, together with a Dutch windmill, dating from 1800, is shown in the accompanying sketch.)
Today, two massive screws of S31600 stainless steel have been installed and eight more are under construction for the vast Hyperion Wastewater Treatment Plant in Los Angeles, one of the largest such facilities in the world. Each of the 10 screws is 3.8 metres in diameter and 15.2 metres long, and weighs 36.4 tonnes. In total, 364 tonnes of stainless steel, containing about 12% nickel, will be used to replace the existing epoxy-coated steel screws, which have corroded.
The oceanside Hyperion plant has been operating since 1951, but in the early '90s, a design change forced the installation of an intermediate pumping station (IPS) to raise the wastewater almost five metres so that it flows by gravity through the rest of the plant. The 10 Archimedes screws were the pumps of choice in the IPS.
The first screws were made of epoxy-coated steel, and because hydrogen sulphide is generated by the sewage, the screw pumps were enclosed in a building to prevent odour and pollution in the nearby neighbourhoods. "But unfortunately, hydrogen sulphide combines with moist ocean air in the plant to produce a very corrosive environment," says Michael Lewis, mechanical process engineer consultant to the City of Los Angeles. "After four years, corrosion caused one of the screws to fail catastrophically. The failed screw was repaired and completely recoated with a proprietary, quartz-filled Novalac epoxy, but in less than a year, we noticed that the epoxy coating was blistering and flaking off. At that point, we switched to S31600 stainless, because in a life-cycle, cost-benefit analysis, stainless won hands-down against the alternatives." Technical information, provided by the Nickel Development Institute was critical to the decision to switch to stainless.
The Archimedes screws are being constructed by contractor, Spaans Babcock, in The Netherlands (see accompanying photo). And there's much more stainless in the plant, including piping, digesters, and other components. Indeed, everything about the Hyperion plant is huge: it covers about 58 hectares and serves four million residents through nearly 11 thousand kilometres of sewer pipes, spread over 1,550 square kilometres of Los Angeles; the plant can handle storm peaks of 1,700 million litres per day; and the sedimentation tanks are the size of football fields. Clearly, there is a high demand for stainless steels in water treatment technology, both old and new.
Dr. Crawford is a consultant to the Nickel Development Institute
PHOTOS: courtesy of the Hyperion Wastewater Treatement Plant
 Hyperion Wastewater Treatment Plant Spaans Babcock bv |
Free technical literature on the topic of nickel-containing materials in the wastewater treatment
industry: Steel Package Water and Waste Water Treatment Units
(2000) SCI P245 |
