Piping system materials, selection tubing

Appendix A contains a materials selection guide for aerated freshwater systems. As indicated in Note 27 of Appendix A, in freshwater systems, admiralty brass should be limited to a maximum pH value of 7.2 from ammonia and copper-nickel alloys and should not be used in waters containing more sulfides than 0.007 mg/L The materials selection guide is also satisfactory for seawater, although pump cases and impellers should be a suitable duplex stainless steel or nickel-aluminum-bronze (properly heat treated). Neoprene-lined water boxes should be considered. For piping, fiber-reinforced plastic (up to 150 psi [1,035 kPa] operating pressure) and neoprene-lined steel should also be considered. Titanium and high-molybdenum SS tubes should be considered where low maintenance is required or the cost can be justified by life expectancy. 

Materials selection for a large sub-sea production system is illustrated by the following example from a field in the North Sea [10.11] for the production tubing and the well equipment (whieh are not to be welded) a 13% Cr steel was seleeted, and in the Xmas tree (valve tree) a martensitie stainless steel of the type ASTM A 182 F6NM (13%) Cr, max l%o Si). The manifold module, whieh is a welded pipe system, was made of a ferritie-austenitie stainless steel with the eomposition 22Cr5Ni3Mo, which also was selected for pipelines for supply of hydraulie oil and methanol (used for preventing hydrate formation) to die sub-sea stations. The well flame and gas pipeline were made of a non-stainless steel. 

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