Standards for Piping Stress Analysis and Support Design

▣ Overview of Piping Stress Analysis and Support Design Criteria

When arranging piping according to the Piping and Instrumentation Diagram (P&ID), this section describes and regulates the design criteria and procedures for ensuring the flexibility and safety of the piping system and its supports.

 

 

▣ Stress Analysis Scope and Criteria

The criteria for piping stress analysis are applied based on the pressure, temperature, and importance of the fluid system.

The maximum operating temperature expected in the piping system should be considered in the stress analysis (ambient temperature 21°C).

 

1. Coefficient of Friction

• Steel to Steel: 0.3
• Stainless Steel to PTFE: 0.1

 

2. Seismic Analysis

• Perform seismic analysis using the Static Analysis Method, interpreting calculated seismic loads from the seismic zones specified in the code as static loads in both horizontal and vertical directions.

 

▣ Allowable Stress and Load

1. Allowable Stress for Piping Materials

• Use the allowable stress values specified in ASME B31.1 Appendix A for piping materials and fittings. The allowable stress values under different load combinations (Sustained, Occasional, Thermal Expansion Case) should follow the ASME Code.

2. Allowable Loads for Equipment Nozzles

• Ensure that excessive loads are not transferred from the piping to the equipment nozzles. Reflect "Equipment Nozzle Loads" in the equipment purchase specifications, and ensure that the loads acting on each nozzle during stress analysis are within the limits provided by the equipment manufacturer.

 

3. Design Loads for Piping Supports

• To prevent excessive loads on piping supports, install supports close to concentrated loads and reduce the spacing between supports (select support locations at points with minimal displacement).

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▣ Piping Support and Design Design piping supports based on the stress analysis, with the following design criteria:

• Place piping where support devices can be designed.
• Review interference of piping supports with various equipment, structures, pathways, and maintenance spaces.
• Check for issues caused by thermal expansion when piping passes through walls and floors.
• Select piping support materials that match the design temperature of the piping.
• Standard supports for piping should be made of steel and designed according to MSS SP-58 regulations.
• Design the spacing of piping supports according to the recommendations in ASME B31.1 Table 121.5.
• Spring hangers should have hot and cold indicators, displacement indicators, and locking devices.
• Use snubbers in locations where rigid types are not feasible due to excessive dynamic loads or thermal expansion.