Pipe Thickness Calculations for Process, Hydrogen, and Power Plant Piping: Understanding ASME Codes and Calculation Parameters

Pipe thickness calculations are a critical aspect of piping engineering, ensuring the safety and longevity of process piping, hydrogen piping, power plant piping, and other high-pressure piping systems. Different types of piping systems require different codes and criteria to be followed while calculating the thickness. In this article, we will explore the different codes and criteria used in pipe thickness calculations and how they impact the safety and performance of piping systems.

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ASME B31.1 and ASME B31.3 Codes

ASME B31.1 and ASME B31.3 are two commonly used codes in piping engineering. ASME B31.1 is used for power plant piping, while ASME B31.3 is used for process piping. These codes have different application, allowable stress, design life, factor of safety, pipe wall thickness, post-weld heat treatment, random inspection, and testing requirements.

The ASME B31.1 code is used for power plant piping systems that transport steam, water, or gas at high temperatures and pressures. This code requires a higher factor of safety and thicker pipe walls than the ASME B31.3 code. The design life for power plant piping is typically longer than that for process piping.

The ASME B31.3 code is used for process piping systems that transport various fluids, such as water, chemicals, and gases, at lower temperatures and pressures than power plant piping systems. The allowable stress for process piping is typically higher than that for power plant piping. The design life for process piping is typically shorter than that for power plant piping.

ASME B31.12 and ASME B31.3 Codes

ASME B31.12 and ASME B31.3 are two other commonly used codes in piping engineering. ASME B31.12 is used for hydrogen piping, while ASME B31.3 is used for process piping. These codes have different application, thickness calculation, branch connection requirements, materials, NDE requirements, and welding requirements.

The ASME B31.12 code is used for hydrogen piping systems that transport hydrogen at high pressures and temperatures. This code requires a higher factor of safety and thicker pipe walls than the ASME B31.3 code. The thickness calculation, materials, NDE requirements, and welding requirements for hydrogen piping are different than those for process piping.

Attempt Questions on Pipe thickness

1. Which code specifies the thickness calculation for high-pressure piping systems?

Choose the correct answer:

A) ASME B31.1
B) ASME B31.3
C) ASME B31.12
D) ASME Boiler and Pressure Vessel Code, Section VIII, Division 2

Show Answer

Explanation: High-pressure piping systems use the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, for thickness calculations, which provides rules specific to high-pressure applications.

2. Which code specifies the thickness calculation for external pressure on piping systems?

Choose the correct answer:

A) ASME B31.1
B) ASME B31.3
C) ASME B31.12
D) ASME Boiler and Pressure Vessel Code, Section VIII, Division 1

Show Answer

Explanation: External pressure calculations for piping systems are specified by the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, which covers design considerations for external pressure.

3. According to ASME B31.3, what is the requirement for the actual pipe thickness compared to the required thickness?

Choose the correct answer:

A) Actual thickness should be greater than required thickness
B) Actual thickness should be less than required thickness
C) Actual thickness should be equal to required thickness
D) Actual thickness can be any value as per design engineer’s discretion

Show Answer

Explanation: ASME B31.3 requires that the actual thickness of the pipe should not be less than the required thickness to ensure safety and compliance with design standards.

Thickness Calculations

The thickness calculation is a critical part of pipe thickness calculations. The thickness of a pipe is determined based on various parameters, including the pressure rating, diameter, material, temperature, and external pressure. The thickness calculation is based on different codes, including ASME B31.1, ASME B31.3, ASME B31.12, high-pressure piping, and external pressure.

High-Pressure Piping

High-pressure piping systems require thicker pipe walls than low-pressure piping systems to withstand the high pressures. The thickness calculation for high-pressure piping is based on the ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 2, which provides rules for the design, fabrication, inspection, testing, and certification of pressure vessels and piping systems.

External Pressure

External pressure can also affect the thickness calculation of piping systems. External pressure can occur due to the soil, water, or other external factors that put pressure on the piping system. The thickness calculation for external pressure is based on the ASME BPVC, Section VIII, Division 1, which provides rules for the design, fabrication, inspection, testing, and certification of pressure vessels and piping systems.

Attempt Question on Pipe Thickness Calculation methods

1. What is a critical factor in determining the pipe wall thickness for process piping?

Choose the correct answer:

A) Internal pressure
B) Pipe material cost
C) External temperature
D) Installation time

Show Answer

Explanation: The pipe wall thickness for process piping is primarily determined by the internal pressure to ensure structural integrity and safety.

2. What is a key consideration when calculating pipe wall thickness for hydrogen service?

Choose the correct answer:

A) External corrosion
B) Pipe diameter
C) Hydrogen embrittlement
D) Paint thickness

Show Answer

Explanation: When calculating pipe wall thickness for hydrogen service, consideration must be given to hydrogen embrittlement, which affects material selection and thickness requirements.

3. In power plant piping, what factor is critical for determining the pipe wall thickness?

Choose the correct answer:

A) External coating
B) Fluid velocity
C) Valve spacing
D) Steam pressure

Show Answer

Explanation: In power plant piping, the fluid velocity plays a critical role in determining pipe wall thickness to avoid erosion and maintain structural integrity.

Actual Calculations and Comparison

The actual calculations and comparison are critical to ensure the safety and performance of piping systems. The actual calculations involve determining the actual thickness of the pipe based on the parameters and codes used in the thickness calculation. The comparison involves comparing the actual thickness with the required thickness to ensure that the pipe can safely withstand the pressure and temperature of the fluid being transported.

ASME B31.1, ASME B31.3, and ASME B31.12 codes require that the actual thickness of the pipe should not be less than the required thickness. High-pressure piping systems and external pressure systems also require the actual thickness of the pipe to be greater than the required thickness to ensure the safety and longevity of the piping system.

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FAQs on Pipe Thickness Calculations

What codes and standards govern pipe thickness calculations in process piping?

• Pipe thickness calculations typically follow codes such as ASME B31.3 for process piping, ASME B31.12 for hydrogen piping, and ASME B31.1 for power plant piping.

How is the design pressure determined for pipe thickness calculations?

• Design pressure is typically determined based on process conditions, including operating pressure, transient pressure, and pressure surges, considering safety margins.

What factors influence the determination of pipe wall thickness?

• Factors include design pressure, operating temperature, material properties, corrosion allowances, and specific service conditions such as fluid characteristics and external loads.

What is the role of corrosion allowances in pipe thickness calculations?

• Corrosion allowances account for expected metal loss due to corrosion over the design life of the piping system, ensuring longevity and integrity.

How are mechanical loads accounted for in pipe thickness design?

• Mechanical loads such as weight, thermal expansion, wind, seismic forces, and pipe supports are considered to determine additional thickness requirements beyond pressure containment.

What methods are used to verify the integrity of pipe thickness calculations?

• Methods include stress analysis using finite element methods (FEM), checking against allowable stress limits, and ensuring compliance with fatigue and vibration requirements.

How does material selection impact pipe thickness design?

• Material selection affects pipe thickness calculations by influencing allowable stress values, corrosion resistance, and overall mechanical properties under specified operating conditions.

What are the considerations for insulation and jacketing in pipe thickness calculations?

• Insulation and jacketing thicknesses are considered to maintain process temperatures and prevent external corrosion, impacting overall thermal and mechanical design requirements.

What are the differences in pipe thickness calculations for high-pressure hydrogen piping?

• ASME B31.12 specifies additional requirements for hydrogen service, including hydrogen embrittlement concerns and unique material considerations affecting thickness design.

How are pipe thickness calculations adjusted for power plant piping subject to cyclic loading?

• Power plant piping, subjected to cyclic thermal and mechanical loading, requires fatigue analysis to ensure the design life expectancy under operational conditions.

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In conclusion, pipe thickness calculations are an essential aspect of piping engineering, ensuring the safety and performance of piping systems. Different types of piping systems require different codes and criteria to be followed while calculating the thickness. ASME B31.1, ASME B31.3, ASME B31.12, high-pressure piping, and external pressure codes are commonly used in pipe thickness calculations. The thickness calculation is based on various parameters, including pressure rating, diameter, material, temperature, and external pressure. Actual calculations and comparison are critical to ensure that the pipe can safely withstand the pressure and temperature of the fluid being transported. By following these codes and criteria, piping engineers can design and build piping systems that are safe, reliable, and long-lasting.