Stainless Steel Valves
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THE MAGAZINE DEVOTED TO NICKEL AND ITS APPLICATIONS |
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| THE VAN CORTLAND PARK valve chamber houses thirty-two, 22-tonne valves. Every day, about 1.4 billion
litres of water flow through each of these valves to the different boroughs of New York City. |
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THE NO. 3 TUNNEL runs from the northern New York City line, under the Bronx, the length of Manhattan
Island, under the East River and the boroughs of Queens, Brooklyn and back under the river to Staten
Island. |
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TWENTY RISER SHAFTS bring potable water to surface for distribution along Tunnel No. 3. Each shaft
contains four, stainless steel riser valves. |
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| VALVES CONSTRUCTED ENTIRELY of stainless steel were first installed in the Tunnel No. 3 water distribution system in 1987 during Stage 1 of the project. |
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| THE MOTTO FOR MATERIALS selection in the New York City water tunnel project is as follows:
"The fewer metals other than stainless steel in the environment, the better," says Jessy James, deputy
chief group leader of the Mechanical/Electric Section I, Division of Waterworks Design. |
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For other recent Nickel Magazine articles on the use of nickel-containing materials in the
water industry, click here. |
Are the cornerstone of New York City's water distribution system. By Carroll McCormick
Nickel magazine, March, 2004 -- New York City has a huge thirst for water, with projects for supplying that water dating back to 1837. Its most recent endeavour, a US$6-billion mega -project known as Water Tunnel No. 3, began in 1970 and is due for completion in 2020. It is a huge user of nickel-containing stainless steel.
The New York City Department of Environmental Protection, which manages the project, needed valves that would provide low- or no-maintenance service for 100 years under conditions of 100% relative humidity. Based on corrosion immersion tests run in the 1960's, S30403 and S31600 stainless steel offer the best corrosion-resistance, lowest maintenance and best life-cycle costs of any material suitable for carrying potable water.
"As we supply water to citizens of New York, we can't really afford to have these systems down. We have to design [the system to be] so strong and corrosion-resistant, that we can have controlled maintenance shutdowns. A major breakdown would be catastrophic and replacement costs are very high," says Jessy James, deputy chief group leader of the Mechanical/Electrical Section 1, Division of Wateworks Design.
Stainless steel owes its corrosion resistance and long service life to a thin chromium oxide film that forms in the presence of air or water, which replenishes itself if scratched. The very agitation, turbulence and high velocity of water that are so damaging to carbon steel are normally beneficial to the durability and performance of stainless steel, due to the presence of this oxide film.
Valves constructed entirely of stainless steel were first installed in the Tunnel No. 3 water distribution system in 1987 during Stage 1 of the project. Additional units were installed in 2003 during Stage 2. Kubota of Japan manufactured the stainless valves for Stage 1, which are 10-tonne units with a throat diameter of 1.22 metres. Voest-Alpine of Austria manufactured similar sized units that weigh 6.4 tonnes apiece. The stainless steel valves installed in Stage 2 were manufactured by Argentina-based Mendoza.
A bird's-eye view of the No. 3 Tunnel project shows 99 planned kilometres of the tunnel (see accompanying diagram at left). It runs from the northern New York City line under the Bronx, the length of Manhattan Island, under the East River and the boroughs of Queens, Brooklyn and back under the river to Staten Island.
Tunnel No. 3 starts at about 90 metres below surface where it taps into tunnels bringing water from reservoirs north of the city. It descends to a depth of over 240 metres as it heads south. Along its length are more than 20 riser shafts that bring water to the surface for distribution. Each of these, 1.2-metre-diameter shafts is lined with stainless steel plate, 5 millimetres (mm) in thickness.
A typical riser shaft configuration has four, 1.2-metre riser valves in each distribution chamber. A total of 20 stainless steel riser valves and 34 stainless steel distribution valves will be installed by 2020, according to James.
Although every riser shaft has a valve chamber, the Van Cortland Park valve control chamber, located under the Bronx, is unusual for its size, function and enormous valves. Put into service in 1998, it lies 60 metres below surface and measures 37 metres long by 18 metres wide.
Seventeen pipelines route water to different city boroughs. The water can be reversed through each pipeline, and each is fitted with an upstream and a downstream quarter turn butterfly valve. Each of the 32 valves weighs 22 tonnes, is 2.82 metres high and about 5.08 metres long, with 2.44-metre-diameter throats. Also, each has a contracted throughput of 1.4 billion litres per day, with an emergency capacity of 6.0 billion litres per day.
The valve bodies in this case are cast and machined carbon steel, though the closure members are made of stainless steel S30403. The closure members consist of a disc, 17.8 mm in thickness and 2.44 metres in diameter, which pivots on a solid stainless steel shaft.
The valves were manufactured by Kubota, of Osaka Japan, in 1975, and the selection of materials was based on the results of corrosion immersion tests in New York State's Roundout Reservoir. These tests were designed to determine which alloys could provide an anticipated life service of 100 years. A number of alloys, including aluminum and manganese bronze alloys, brasses, bronzes and copper-nickels, were immersed in water for 10-13 years. Only the stainless steel samples and some nickel base alloys performed with virtually no corrosion, with stainless steel offering the most cost effective selection.
The new, stainless valves in Tunnel No. 3 are spectacular examples of the application of stainless steel in potable water applications.
The Van Cortland Park valve chamber's 17 venturi water meters, measuring more than 4.6 metres long with 183-mm throats and a maximum inside diameter of 2.44 metres, are also made entirely of S30403, as are all of the accessories, rods and bolts that hold them together. Other riser shafts have 914-mm valves with carbon steel bodies.
The No. 3 Tunnel, with its stainless steel valves, is expected to help distribute water throughout New
York City for at least the next 100 years.
Carroll McCormick is a Montreal-based freelance writer.
PHOTOS/ILLUSTRATIONS: courtesy of New York City Department of Environmental Protection
Natalie Millner |
