ASME B31.1 vs. ASME B31.3: conoscere i codici di progettazione delle tubazioni

Introduzione

Nella progettazione e nell'ingegneria delle tubazioni, la selezione del codice di tubazioni appropriato è essenziale per garantire sicurezza, efficienza e conformità agli standard del settore. Due dei codici di progettazione delle tubazioni più ampiamente riconosciuti sono Normativa ASME B31.1 E Normativa ASME B31.3Sebbene entrambi provengano dall'American Society of Mechanical Engineers (ASME) e governino la progettazione e la costruzione di sistemi di tubazioni, le loro applicazioni differiscono in modo significativo. Comprendere il ASME B31.1 contro ASME B31.3 Il dibattito è fondamentale per selezionare il codice corretto per il tuo progetto, che si tratti di centrali elettriche, processi chimici o impianti industriali.

Panoramica: ASME B31.1 vs. ASME B31.3

What is ASME B31.3 or Process Piping Code?

Normativa ASME B31.1 è lo standard che regola la progettazione, la costruzione e la manutenzione dei sistemi di tubazioni delle centrali elettriche. Si applica ai sistemi di tubazioni nelle centrali elettriche, negli impianti industriali e in altre strutture in cui è coinvolta la produzione di energia. Questo codice si concentra fortemente sull'integrità dei sistemi che gestiscono vapore ad alta pressione, acqua e gas caldi.

Applicazioni tipiche: Centrali elettriche, sistemi di riscaldamento, turbine e sistemi di caldaie.
Campo di pressione: Sistemi a vapore e fluidi ad alta pressione.
Intervallo di temperatura: Servizio ad alta temperatura, in particolare per applicazioni a vapore e gas.

What is ASME B31.1 or Power Piping Code?

Normativa ASME B31.3 applies to the design and construction of piping systems used in chemical, petrochemical, and pharmaceutical industries. It governs systems that transport chemicals, gases, or liquids under different pressure and temperature conditions, often including hazardous materials. This code also covers the associated support systems and the safety considerations of handling chemicals and dangerous substances.

Applicazioni tipiche: Impianti di lavorazione chimica, raffinerie, stabilimenti farmaceutici, stabilimenti alimentari e delle bevande.
Campo di pressione: Generalmente inferiore all'intervallo di pressione specificato nella norma ASME B31.1, a seconda dei tipi di fluido e della loro classificazione.
Intervallo di temperatura: varies depending sui fluidi chimici, ma è in genere inferiore alle condizioni estreme in Normativa ASME B31.1.

Difference Between ASME B31.3 and ASME B31.1 (ASME B31.3 vs ASME B31.1)

Sr No	Parametro	ASME B31.3-Process Piping	ASME B31.1-Power Piping
1	Scopo	Provides rules for Process or Chemical Plants	Provides rules for Power Plants
2	Basic Allowable Material Stress	Basic allowable material stress value is higher (For example the allowable stress value for A 106 B material at 250 Deg C is 132117.328 Kpa as per ASME B31.3)	Basic allowable material stress value is lower (For example the allowable stress value for A 106 B material at 250 Deg C is 117900.344 Kpa as per ASME B31.3)
3	Allowable Sagging (Sustained)	The ASME B31.3 code does not specifically limit allowable sagging. An allowable sagging of up to 15 mm is generally acceptable. ASME B31.3 does not provide a suggested support span.	ASME B31.1 clearly specifies the allowable sagging value as 2.5 mm. Table 121.5-1 of ASME B31.1 provides suggested support span.
4	SIF on Reducers	Process Piping Code ASME B31.3 does not use SIF (SIF=1.0) for reducer stress calculation	Power Piping code ASME B31.1 uses a maximum SIF of 2.0 for reducers while stress calculation.
5	Factor of Safety	ASME B31.3 uses a factor of safety of 3; relatively lower than ASME B31.1.	ASME B31.1 uses a safety factor of 4 to have higher reliability as compared to Process plants
6	SIF for Butt Welded Joints	ASME B31.3 uses a SIF of 1.0 for buttwelded joints	ASME B31.1 uses a SIF of up to 1.9 max in stress calculation.
7	Approach towards SIF	ASME B31.3 uses a complex in-plane, out-of-plane SIF approach.	ASME B31.1 uses a simplified single SIF Approach.
8	Maximum values of Sc and Sh	As per the Process Piping code, the maximum value of Sc and Sh are limited to 138 Mpa or 20 ksi.	For the Power piping code, the maximum value of Sc and Sh are 138 Mpa only if the minimum tensile strength of the material is 70 ksi (480Mpa); otherwise, it depends on the values provided in the mandatory appendix A as per temperature.
9	Allowable Stress for Occasional Stresses	The allowable value of occasional stress is 1.33 times Sh	As per ASME B31.1, the allowable value of occasional stress is 1.15 to 1.20 times Sh
10	The equation for Pipe Wall Thickness Calculation	The equation for pipe wall thickness calculation is valid for t<D/6	There is no such limitation in the Power piping wall thickness calculation. However, they add a limitation on maximum design pressure.
11	Section Modulus, Z for Sustained and Occasional Stresses	While Sustained and Occasional stress calculation the Process Piping code reduces the thickness by corrosion and other allowances.	ASME B31.1 calculates the section modulus using nominal thickness. Thickness is not reduced by corrosion and other allowances.
12	Rules for material usage below -29 Deg. C	ASME B31.3 provides extensive rules for the use of materials below -29 degrees C	The power piping code provides no such rules for pipe materials below -29 degrees C.
13	Maximum Value of Cyclic Stress Range Factor	The maximum value of cyclic stress range factor f is 1.2	The maximum value of is 1.0
14	Allowance for Pressure Temperature Variation	As per clause 302.2.4 of ASME B31.3, occasional pressure temperature variation can exceed the allowable by (a) 33% for no more than 10 hours at any one time and no more than 100 hours/year, or (b) 20% for no more than 50 hours at any one time and no more than 500 hours/year.	As per clause 102.2.4 of ASME B31.1, occasional pressure temperature variation can exceed the allowable by (a) 15% if the event duration occurs for no more than 8 hours at any one time and not more than 800 hours/year or (b) 20% if the event duration occurs for not more than 1 hour at any one time and not more than 80 hour/year.
15	Progettare la vita	Process Piping is normally designed for 20 to 30 years of service life.	Power Piping is generally designed for 40 years or more of service life.
16	PSV reaction force	ASME B31.3 does not provide specific equations for PSV reaction force calculation.	ASME B31.1 provides specific equations for PSV reaction force calculation.

Conclusione

La differenza critica nel ASME B31.1 contro ASME B31.3 il dibattito verte sulle applicazioni industriali, sui requisiti dei materiali e sulle considerazioni sulla sicurezza. Normativa ASME B31.1 è ideale per sistemi di generazione di energia e ad alta temperatura, concentrandosi sull'integrità meccanica. Allo stesso tempo, Normativa ASME B31.3 is tailored for the chemical and process industries, emphasizing the safe handling of hazardous materials and chemical compatibility. By understanding the distinctions between these two standards, you can decide which code best suits your project’s requirements, ensuring compliance and safety throughout the project’s lifecycle. Whether you are involved in power plant design or system’ processing, choosing the correct piping code is crucial for a successful project.