In addition to the many clarifications, updated references to codes and standards, updates to basic allowable stresses, and added listed materials, there are several substantive changes to the 2016 Edition of ASME B31.3, Process Piping, which is scheduled to be issued on January 4, 2017. These changes are:
Severe Cyclic Conditions
The definition for severe cyclic conditions was changed.
Old Definition: conditions applying to specific piping components or joints in which SE computed in accordance with para. 319.4.4 exceeds 0.8SA (as defined in para. 302.3.5), and the equivalent number of cycles (N in para. 302.3.5) exceeds 7000; or other conditions that the designer determines will produce an equivalent effect.
New Definition: conditions applying to specific piping components or joints for which the owner or the designer determines that construction to better resist fatigue loading is warranted
The new definition is expected to lead to a more appropriate application of requirements for severe cyclic conditions.
MPa Allowable Stresses
Although MPa allowable stress values have appeared in the Code since the 2010 edition, these values have been for information only. That is, the Code required us to use the psi values. In the 2016 edition, either the MPa or the psi values may be used.
Specific B31.3 fatigue analysis requirements for expansion joints were deleted in Appendix X because the latest edition of the EJMA standards included incorporated appropriate safety margins in fatigue design. The fatigue curves in EJMA previously provided average number of cycles to failure without any safety margin.
Flange Joint Assembly
The 2016 edition added that assembly requirements for bolted flanged joints and flanged joint assembler qualifications shall be considered in the engineering design. It references ASME PCC-1 and the BPV Code, Section VIII, Division 1, Appendix S for guidance.
Ultrasonic Examination Acceptance Criteria
Alternative ultrasonic examination fracture mechanics based acceptance criteria were added as Appendix R. They provide criteria for ultrasonic techniques that size the defects found, in contract to those that assess the amplitude of the reflected signal (pulse-echo). These criteria may be used for Code piping in lieu of those described in para. 344.6.
Category M Fluid Service Examination
The 2016 edition changed the radiographic or ultrasonic examination of circumferential butt welds from 20% random examination to 100%.
Leak Testing of Instrument Connections
In earlier editions, the only connections exempted from leak testing were flanged joints. In 2016, the Code also exempted threaded joints and tubing joints used to connect instruments to previously leak tested piping.
Leak Testing of Vacuum Systems
The Code required externally pressurized systems to be leak tested by applying an internal pressure. In 2016, the Code allows use of vacuum leak testing as an alternate.
Leak Testing of Insulated Systems
The Code required that all joints be exposed during leak testing. In 2016, the Code permits the owner to allow joints to be covered by insulation during the leak testing of Category D fluid service piping. The Code requires that consideration be given to increasing the test period to allow time for possible leakage to pass through the insulation and weather sheathing.
Leak Testing of Assembled Piping
The Code allows joints to be assembled without testing. In 2016, guidance was added describing the leak testing practice of many system operators:
…consideration should be given to performing an additional leak test of the assembled piping system prior to initial operation. The test fluid should be non-hazardous to the process and the people performing the examination. Examination for leaks should be at all joints that have not been previously examined for leaks, or that have been reassembled after being examined for leaks…