A bimetallic pipe specially manufactured for corrosion resistance has been selected by three U.S. companies for linepipe service in highly corrosive environments, according to Nippon Steel Corp., Tokyo, the pipe's manufacturer.
Louisiana Land & Exploration Co. (LL&E), New Orleans, has announced selection of the mechanically bonded system for flowlines to be installed in its Big Horn project near Casper, Wyo.
The pipeline will carry produced gas containing H2S and CO2 from satellite wells to a gas-processing plant.
Also, Shell Offshore Inc., New Orleans, has ordered the pipe for its Mobile Bay offshore flowline, and ARCO Alaska Inc. of Alaska has ordered the pipe for its Prudhoe Bay flowlines.
THERMAL-SHRINK OPERATION
The bimetallic pipe selected by LL&E consists of a conventional API Grade X65 outer body with a thinner corrosion-resistant internal liner of Incoloy 825 (22% Cr, 42% Ni) produced by Inco International Alloy. Pipe is available for grades X60-X80, for outer pipe, and liner-pipe materials of AISI 316L, DIN 1.4462, Incoloy 825, Inconel 625, or Hasteloy C-276. Pipe sizes range from 2 to 16 in. OD and 0.2-0.9 in. W.T.
Joining the two pipes (Fig. 1) is accomplished by a special thermal-shrink operation called the C-11 process developed by Nippon Steel and licensed by Kawasaki Heavy Industries Ltd. (Fig. 2).
According to Nippon Steel, C-11 pipe offers several engineering advantages over traditional carbon steel or solid high-alloy pipe.
The corrosion-resistant liner is applied with a degree of control that results in a uniform thickness throughout the length of the pipe. This allows the use of a relatively thin liner which minimizes costs.
The high-strength outer body also allows for a reduced wall thickness when compared with pipe of similar pressure ratings constructed of solid corrosion-resistant alloys. This results in easier and more economic installation, says the company.
Sea] welding of both ends of the pipe is performed at the factory with alloys that are chemically similar to the liner. This reduces weld dilution and helps to ensure uniform corrosion performance throughout the entire length of a pipeline.
C-11 pipe also affords a high degree of corrosion-control reliability by eliminating the need for complex inhibition systems.
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