FFS Appendix 2. Number of projection lines in DNV RPF 2010 and 2015

From release 3.13C there is a change in the calculation of the number of projection lines in the DNV method.

Before 3.13C the projection lines were calculated with the formula:

Int(sqrt(Diameter / Wall Thickness/Diameter)) + 1

From release 3.13C the projection lines are calculated with the formula:

Int(sqrt(Diameter / Wall Thickness/Diameter))

Example, for a diameter of 10” which is 273.1mm and a wall thickness of 7 mm the number of projection lines before 3.13C was

Int(sqrt(273.1/10))+ 1 = Int(6.24) + 1 = 6 + 1 = 7

From release 3.13C it is Int(sqrt(273.1/10))+ 1 = Int(6.24) = 6, more conservative

References

• 03 w-PIMS Design Data and Sectioning Theory Release 3.0, SR.16.12032
• Web based Pipeline Integrity Management Software Fitness for service assessment of SR.14.13139.
• DNV RP-F101 - Corrodate Pipelines.pdf, this document is available in w-PIMS Help in folder References.
  The ASME’s and ISO 13623 documentation is also available in w-PIMS Help.