Piping Design Standards

▣ Overview and Scope

• Overview

This design standard reflects the Code & Standard for piping design of power plants and the design requirements specified in the contract. It is a standard that stipulates functional adequacy and structural integrity of piping system components when designing piping systems. The technical contents and application standards of this design standard must be reflected in all design deliverables.

• Scope

This standard applies to the piping design of various systems within power plants. However, it does not apply to the piping of HVAC systems, fire protection systems, water supply and drainage systems, and wastewater treatment systems, which are designed according to separate technical specifications and design standards.

▣ Applicable Codes and Standards

• The code applied to the piping design of various systems in power plants is ASME B31.1 Power Piping. Additional applicable Codes & Standards must be applied with the latest versions listed below:
• Domestic Electric Utility Act
• Korea Electric Power Industry Code (KEPIC)
• American National Standards Institute (ANSI)
• American Society of Mechanical Engineers (ASME)
  • ASME Sec. I Power Boiler
  • ASME B31.1 Power Piping
• American Society for Testing and Materials (ASTM)
• American Petroleum Institute (API)
• Manufacturers Standardization Society of the Valve and Fittings Industry Inc. (MSS)
• American Water Works Association (AWWA)
• Korea Industrial Standards (KS)
• National Fire Protection Association (NFPA)
• Korea Fire Protection Code and Relevant Regulation

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▣ General Design Criteria

Unit System

• Unless otherwise specified in the contract, the International System of Units (SI) is used as the standard.

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Nominal Pipe Size

• Pipe sizes are indicated by Nominal Pipe Size (NPS) and thickness (Metric notation is ‘DN’).
• Pipe thickness is applied by Schedule number and Weight.
• Pipe material (Carbon steel, Alloy steel: ASME B36.10, Stainless steel: ASME B36.19).

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Design Pressure and Temperature

• Design pressure and temperature are applied according to the design data of each system and ASME B31.1 Para 122 “Design Requirements Pertaining to Specific Piping Systems.”

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Temperature Pressure Rating of Pipe Material

• Based on the maximum operating pressure and temperature, the basic rating is applied as specified in ASME B16.5, ASME B16.34. The piping material classification table should be prepared and reflected.

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Selection of Pipe Wall Thickness

• Reflect the calculated thickness and apply commercially manufactured pipe thickness. In addition to internal pressure, consider external pressure and vacuum thickness if necessary. For carbon steel, apply Sch.80 for D50 and below, and STD WT for D65 and above. For stainless steel, apply Sch.40S for D50 and below, and Sch.10S and above for D65 and above (indicate pipe thickness per system in the piping material classification table).
• Thickness calculation by internal pressure: According to ASME B31.1 Para 104.1.2 (consider manufacturing tolerance).
• Thickness determination by bending: According to ASME B31.1 Table 102.4.5.
• Pipes subject to external pressure: According to ASME Sec. VIII, Division 1, UG-28~30 and AWWA.
• When applying thicker pipes than the piping material classification table, reflect it in pipe stress analysis and support design.
• Maintain minimum thickness of pipe when machining end for welded connections