Hello Stressers!!!

Just curious if ASME B31.3 Code considers the Longitudinal & Circumferential Weld Joint Efficiency Factor for "Sustained Stress (W+P1+H)" calculation where the allowable stress Sh will be lower by multiplying with Joint efficiency factor (e.g. 0.85*Sh)? Or it is only used for wall thickness calculation for Hoop or Circumferential Stress? I'm assuming CII have put the input for this joint efficiency factory for other Piping Codes requiring this.

Many Thanks for your input,

When B31.3 first addressed this problem (creep strength of weld material) stress in both the hoop direction and longitudinal direction were included. Hoop: include W in the wall pressure thickness formula and Longitudinal: the allowable stress for sustained loads was set to W*Sh. Soon after, B31.1 released their code update where W affected wall thickness but the longitudinal treatment was declared optional. In the following edition, B31.3 made the long. term optional as well.
In CAESAR II we have two W's - Wl and Wc. These are not Code terms. Wl identifies circumferential or spiral welds (entered after OD and wall thickness with the "Seam Welded" checkbox). This entry will adjust the minimum required wall thickness check. If you wish to consider the effect of weld strength (for axial load and bending moment) in your sustained stress calculation, specify Wc in the auxiliary data tab for "SIFs & Tees". You must also set a configuration switch: "Ignore B31.1/B31.3 Wc Factor" to False.
So, why are Wc & Wl treated differently? Longitudinal and spiral welds must carry the hoop pressure load (as membrane stress through the pipe wall) or fail. Circumferential welds are loaded by sustained axial and bending (dead weight) loads. Excessive bending loads, here, may be carried by nearby pipe and weld material if yield is achieved locally. Because of this load redistribution, application of Wc is not mandatory.

Thanks Dave for that very bountiful information.

Just curious if Caesar is capable of checking the Hoop stress. From the statement above "This entry will adjust the minimum required wall thickness check", seems like Caesar II can check the hoop strength requirement for seam welded pipes considering the Wl strength reduction factor. So far I haven't used this check in Caesar II, just the Expansion and Sustained (W+P1+H).

Just curious, if this is possible, how to perform in Caesar II. Anyway, this requirement is covered by the Material Engineering group in the "Wall Thickness Calculation".

It seems like for ASME B31.3/B31.1 Code, the stress engineer doesn't need to consider "as a mandatory requirement" the Wl and Wc weld strength reduction factors due to seam welded pipe and creep effects since it is used for wall thickness calculation for hoop not in flexibility calculation.

Kindly correct if my statement is wrong above.

Many Thanks,

CAESAR II runs through the code's minimum wall thickness calculation for straight pipe. That's why you enter mill tolerance and Wl. But since the program does not monitor thickness or pressure class for other components, you cannot say that CAESAR II checks the thickness for all components. If your straight pipe thickness is insufficient, the program will throw a warning. This warning will also appear for bends but , in this case, CAESAR II is assuming the bend is bent straight pipe (for which a minimum wall thickness is provided). These calculated thicknesses are displayed in the Miscellaneous Data report

Thanks Dave for that information. I will leave the fittings and other component minimum thickness to our material engineer.

Many Thanks,