What is FE107?
FE107 is written by Vessel Engineers for Vessel Engineers.
FE107 uses finite element technology to provide stress analysis of nozzle connections on piping and
pressure vessel. FE107 replaces WRC 107 as a calculation tool that can be applied
when WRC 107 correlational methods are limited. FE107 is useful for piping and pressure vessel engineers
and designers.
FE107 can be applied to a wide range of geometries.
Branch or Nozzle
- Straight (Unreinforced)
- Pad reinforced
- Barrel reinforced (Self-reinforced)
Header or Vessel
- Conical head
- Cylindrical shell
- Elliptical head
- Flat head
- Flanged and dished
- Hemispherical head
What is wrong with WRC 107 and WRC 297?
WRC 107 and WRC 297 are very good documents for engineering practice. It is based on an analytical treatment
of openings in cylindrical shell and hemispherical heads. This said, there are fundamental
assumptions in WRC 107 and correlations that are used in the correlations that limit the
application of WRC 107 in industrial applications. Commonly, computer programs do not provide
warnings or guidance when the limitations are violated.
In general WRC 107 comparisons to FE/Pipe results are excellent when thin shells are analyzed and
when the model is within the accepted parameters of WRC 107. Nozzles in the centers of heads are
evaluated most accurately. Most WRC 107 programs give the stress intensity at four points around
the nozzle on both the inside and outside of the geometry. This stress is usually compared to 3Sm
(Sm is the average of the hot and cold allowable stress)
and is caused by all operating loads on the nozzle. The resulting stresses from a WRC 107 run of
this type should be compared to the Pl+Pb+Q stresses from the finite element calculation. Note
that Pl stresses evaluated in accordance with ASME Section VIII Division 2 are membrane stresses.
These are the average stresses through the thickness and do not include the bending stress
component at the junction. (See ASME Section VIII Division 2 Appendix 4 Table 4-120.1.)
WRC 297 comparisons in the vessel or header tend to be good but become overly conservative when
the high stress moves into the branch when the t/T ratio becomes less than 1.0. This result is
certainly demonstrated in the finite element calculation.
WRC 107 tends to be somewhat less conservative than finite element results, but that WRC 107
results parallel FE calculations through d/D ranges of 0.1 to 0.8, where the WRC and Finite
element curves cross, the WRC 107 results becoming much more conservative beyond this range.
(When the approach used outside of WRC curve parameters is “last curve value.”)
The following list summarizes areas where WRC 107 and WRC 297 are considered weak, or where
there is cause for concern.
- d/D > 0.5
- t/T > 1.0
- Pad reinforced nozzles
- Hillsides or laterals
- Area replacement rules for pressure are barely satisfied and large diameter divided by thickness ration (D/T).
- Temperatures are approaching the creep regime.
- Cycles are greater than 5000.
- Design and operating conditions are approximately the same.
- The load consists of high-pressure stresses and high loads.
- The Piping attached to the nozzle is long, flexible, and somewhat unrestrained.
MatPRO Integration
FE107 offers tight integration with MatPRO to provide the convenience and
reliability of material properties lookup. The PRG database that contains
a full set of the 2000, 2002 and 2004 ASME Section II Part D material databases.
FE Viewer
FE107 includes the FE-Viewer utility that allows you to interrogate the finite element analysis
calculation so that you better understand the results of the finite element calculations.