process piping code vs power piping code – What Is Piping: All about Piping Engineering

What is B 31.3 or Process piping Code? ASME B 31.3 or Process Piping Code provides rules for piping design for petroleum refineries; onshore and offshore petroleum and natural gas production facilities; chemical, pharmaceutical, textile, paper, ore processing, semiconductor, and cryogenic plants; food and beverage processing facilities; and related processing plants and terminals. This code is known as The Bible for Process Piping Professionals. So this code dictates the design considerations of process plants. What is B 31.1 or Power Piping Code? ASME B 31.1 or Power Piping Code provides rules for piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems. This code is very important for Power piping Professionals as this code governs the design rules for power generation plants. Difference Between ASME B 31.3 and ASME B 31.1 (B 31.3 vs B 31.1) From the above discussions, it is clear that both ASME B 31.3 and ASME B 31.1 codes i.e Process Piping Code and Power Piping code are different. Both are related to piping design aspects but different in design considerations. In this article we will tabulate the major differences as prescribed in these codes. Sr NoParameterASME B 31.3-Process PipingASME B 31.1-Power Piping1ScopeProvides rules for Process or Chemical PlantsProvides rules for Power Plants2Basic Allowable Material StressBasic 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 B 31.3)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 B 31.1)3Allowable Sagging (Sustained)ASME B 31.3 code does not specifically says about any limit of allowable sagging. An allowable sagging of upto 15 mm is acceptable in general. B 31.3 does not provide suggested support span.ASME B 31.1 clearly specifies the allowable sagging value as 2.5 mm. Table 121.5-1 of ASME B 31.1 provides suggested support span.4SIF on ReducersProcess Piping Code ASME B 31.3 does not use SIF (SIF=1.0) for reducer stress calculationPower Piping code ASME B 31.1 uses a maximum SIF of 2.0 for reducers while stress calculation.5Factor of SafetyASME B31.3 uses a factor of safety of 3; relatively lower than ASME B 31.1.ASME B 31.1 uses a safety factor of 4 to have higher reliability as compared to Process plants6SIF for Butt Welded JointsB 31.3 uses a SIF of 1.0 for butt welded jointsB 31.1 uses a SIF of upto 1.9 max in stress calculation.7Approach towards SIFASME B 31.3 uses a complex in-plane, out-of-plane SIF approach.ASME B 31.1 uses a simplified single SIF Approach.8Maximum values of Sc and ShAs per the Process Piping code, the maximum value of Sc and Sh are limited to 138 Mpa or 20 ksi.For 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 is dependent on the values provided in the mandatory appedix A as per temperature.9Allowable Stress for Occasional StressesAllowable value of occasional stress is 1.33 times ShAs per ASME B 31.1, the allowable value of occasional stress is 1.15 to 1.20 times Sh10Equation for Pipe Wall Thickness CalculationThe equation for pipe wall thickness calculation is valid for t<D/6There is no such limitation in Power piping wall thickness calculation. However, they add a limitation on maximum design pressure.11Section Modulus, Z for Sustained and Occasional StressesWhile Sustained and Occasional stress calculation the Process Piping code reduces the thickness by corrosion and other allowances.B 31.1 calculates the section modulus using nominal thickness. Thickness is not reduced by corrosion and other allowances.12Rules for material usage below -29 Deg. CB 31.3 provides extensive rules for use of materials below -29 Deg CPower piping code does not provide any such rules for pipe materials below -29 deg C.13Maximum Value of Cyclic Stress Range FactorMaximum value of cyclic stress range factor f is 1.2Maximum value of is 1.014Allowance for Pressure Temperature VariationAs per clause 302.2.4 of ASME B 31.3, occasional pressure temperature vaiation can exceed the allowable by (a) 33% for no more than 10 hour at any one time and no more than 100 hour/year, or (b) 20% for no more than 50 hour at any one time and no more than 500 hour/year.As per clause 102.2.4 of ASME B 31.1, occasional pressure temperature vaiation can exceed the allowable by (a) 15% if the event duration occurs for no more than 8 hour at any one time and not more than 800 hour/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/year15Design LifeProcess Piping is normally designed for 20 to 30 years of service lifePower Piping is generally designed for 40 years or more of service life.16PSV reaction forceB 31.3 provides does not provide specific equations for PSV reaction force calculation.ASME B 31.1 provides specific equations for PSV reaction force calculation.Differences between process piping and power piping codes The following image (Fig. 1 ) shows a rough estimate of different stress values of the same system with code change in Caesar II-2018 software: Fig. 1: Stress values for the same system with code change Few other useful differences for you.Differences between ASME B 31.4 and ASME B 31.813 major differences between Seamless and Welded Pipe10 Differences between Pressure and StressDifference between Tee and Barred TeeDifference between Stub-in and Stub-on Piping ConnectionDifference between Centrifugal and Reciprocating CompressorDifference between PDMS and PDSDifference between Piping and PipelineDifference between Pipe and TubeDifference between Primary load and Secondary loadDifference between Caesar II and Start-ProfDifference between API and ANSI Pump