Читать книгу Fabrication of Metallic Pressure Vessels - Maan H. Jawad - Страница 17

Some design choices must typically involve the customer because they involve significant product cost differences that can only be amortized over the long run. An example of this occurs with a vessel that will contain a corrosive medium. In this case, material choices may make a significant difference in short term vessel costs. A vessel might be fabricated with a corrosion allowance, anticipating that at the end of some term (approximately five years, for example) the vessel will simple be replaced. Another approach would be to fabricate it entirely of a material that does not undergo corrosion in its particular internal and external environments, or to clad it with such a corrosion‐resistant material. The cost of fabricating a pressure vessel of high alloy steel or other material may be significantly greater – perhaps double or more – than that of a fabrication using steel. If a more expensive product allows essentially unlimited life versus five years for the steel pressure vessel, then amortizing the cost of the single vessel versus initial vessel purchase plus replacements, and downtime and labor for the replacement, can make the farsighted decision attractive. Whichever way this decision goes, all other cost issues still apply.