Major Stress related differences in Between 2012 edition and 2010 edition of ASME B 31.3

Every new code always comes with more clarifications, new updated references related to codes & standards, additional updates to the basic allowable stresses, and newly added listed materials, So ASME B 31.3 is not an exception. In the new edition of 2012 code there are lots of substantive changes with respect to 2010 edition of ASME B31.3, Process Piping. This article will try to list down the changes which are important for a piping stress engineer.

1. Displacement Stress Range Allowable:The allowable displacement stress range is now limited to 414 MPa (60,000 psi) in the current 2012 edition. Normally High strength steels have higher tensile and yield strengths and so certainly higher allowable stresses. Accordingly, they also have higher allowable displacement stress ranges while calculated using the old code formula. But, these Materials have Fatigue strengths which is similar to the common steels, that is why this limit is added in 2012 edition.

2. Stress Equation for Flexibility :

The axial stress is added to the flexibility stress equation. Earlier (in 2010 edition) the same was addressed by Appendix P only. While Axial stress may not be that important in most piping systems, it can be significant for jacketed or buried piping.

3. Category D Fluid Service:

The definition of Category D fluid service is revised to include piping system with design minimum temperatures below -29 degree Centigrade (-20 degree Fahrenheit) if the lower temperature is generated from ambient conditions.

4. Preheating:

The 2012 edition changed “recommended” preheat temperatures to “required” preheat Temperatures . All metals now must be preheated to 10 degree centigrade (50°F) or higher before welding.

The above are important changes for a stress engineer. Additionally following few changes can be noted:

1. New Appendix “Appendix N: Application of ASME B31.3 internationally” is added.
2. Appendix H And J has been revised.
3. Welding Qualification: Earlier Restrictions to acceptance of previously qualified welding procedures are removed. Use of Specific language about use of standard welding procedures is added as permitted by ASME Boiler and Pressure Vessel Code, Section IX.
4. Owner’s Inspector: The qualification needs for an Owner’s Inspector are broadened in the current 2012 Edition.