Piping system materials, selection

The variety of lining materials in the line of DOW piping products allows the engineer designing a piping system to select components best suited for that particular service. The complete line includes ... 

Design parameters as a function of temperature and design temperature limits are set forth in the ANSI/ASME B31 Piping Codes for a very broad range of materials. These codes, and the additional information available from manufacturers, vendors, and technical societies such as the National Association of Corrosion Engineers provide ample data for the selection of materials for piping systems (1—13). 

Code requirements for design and construction include service requirements, which affect selection and application of materials, components, and joints. Service requirements include prohibitions, limitations, and conditions, such as temperature or pressure limits. Code requirements for a piping system shall be the most restrictive of those which apply to any of its elements. 

Whilst carbon and stainless steels are commonly used materials of construction, increasing use is being made of non-metallic and rubber lined equipment. The selection of the material of construction should take into account the cases of the worst process conditions that may occur under foreseeable conditions and should be applied to all components including valves, pipe fittings, instruments and gauges. Both composition (e.g., chlorides, moisture) and temperature deviations can have a significant direct effect on the rate of corrosion. The operator should demonstrate that procedures are in place to ensure that potential deviations in process conditions such as fluid temperature, pressure and composition are identified and assessed in relation to the selection of materials of construction for piping systems. 

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-handling equipment is logically divided into continuous and batch types, and into classes for the handling of liquids, solids, and gases. Liquids and gases are handled by means of pumps and blowers in pipes, flumes, and ducts and in containers such as drums, cylinders, and tank cars. Solids may be handled by conveyors, bucket elevators, chutes, lift trucks, and pneumatic systems. The selection of materials-handling equipment depends upon the cost and the work to be done. Factors that must be considered in selecting such equipment include ... 

For small or uncomplicated jobs, a simple template may be preferred. A customized template is not usually needed for replacing or revamping a couple of vessels or a small piping system, or for a unit involving only a few, if any, corrodents. A rubber stamp template, with a process flow diagram, may be used to quickly create a materials selection diagram, as illustrated in Example 21.1. 

Gupta, Materials Selection for Corrosion Control, ASM International, Materials Park, OH, 1993. (d) P. Schweizer, Corrosion-Resistant Piping Systems, Dekker, New York,... 

T q)ically, cost analysis should be done on the basis of installed cost plus operating cost considering the useful service life of the equipment. It is also possible to base the selection solely on the initial cost of the equipment which consists of equipment and installation costs. A more accurate basis would consider the cost of the equipment over its useful life. This calculation is based on some discounted cash flow considerations and depreciation of the cost overthe life ofthe equipment. Tables 12.1-12.3 compare the costs of piping, vessels, and lining systems for different material selections. The reader should consult these tables to compare the initial equipment cost. 

Finally, an extensive waste-air collection and piping system had to be constructed. Corrosion problems in the lines had to be ruled out by selecting suitable materials. 

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. 

In sewerage schemes alternative systems apply. The water companies controlling the sewers are less concerned with material selection for sewer pipes and so the contract to install a sewerage scheme will, in general, leave pipe purchasing responsibility with the contractor. It is then far more likely that pipe will be bought with price as the main factor rather than any other specified property. 

Recommendations for Selecting Inhibitors for Use as Sucker Rod Thread Lubricants Sulfide Stress Cracking Resistant Metallic Materials for Oil Field Equipment Metallic Materials for Sucker Rod Pumps for Hydrogen Sulfide Environments Control of Internal Corrosion in Steel Pipelines and Piping Systems... 

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