MJC
Actually your wrong on all accounts and perhaps I didnt give you enough info or the question was too general...my bad
1)Yes the larger fitting could technically be called "spool piece" although in this case it is considered a Class H fitting (Canada) because of its stand alone end use (ie similar to valve). It has to be registered separately as it not being designed for any specific piping system at this time. As such the evaluation need only concern itself with loads resulting from internal pressure such that a MAWP and Design Temp can be applied for registration purposes.
Once it is incorporated into a specific piping system the pipeline designer will determine whether other external loadings (i.e thermal, seismic etc) limit the fitting use when they do a stress analysis on the system.
The "spool piece" itself is made up of standard piping components (WN Flanges, welded piping tees & Weldolets etc) in the 12"Dia to 16"Dia range.
2) Since I am not designing part of any specific existing piping system, the overall MAWP and desing Temp I register the "As fabricated class H fitting" with depends upon the weakest link in the assembly. In this case the desired design temperature is getting up into the 950F - 1000F range, it is made from F9 and P9 materials (9% Cr), as a result the "pucker" factor goes up a bit.
As you well know in terms of the WN flanges I dont need to calculate the max pressure for them I can go to B16.5 and out of table F2-1.14 for a 300# flange my max pressure for the fitting at 1000F is 255 psig, providing I deem there are no other exceptionals loadings resulting from the configuration, B31.3 permits me to use 255 psig as the MAWP for the flange fitting should I desire it (Listed fitting). Obviously a similar pressure rating evaluation has to be done for each of the individual components making up the larger assembly.
3) So my question simply was this: Is there are standard set of pressure-temperature ratings available for standard piping fittings such as Tees & Elbows (butt welding end...not flanged) based on the common piping schedules they are available in?...to my knowledge these components are not assigned class ratings (150#, 300# etc) unless they are provided with a rated fitting.
I have seen Pressure-Temperature rating charts for the various piping materials and pipng schedules (which are generally based on B31.3/B31.1 calcs)...so they do exist for piping, thought someone might have done something up for some of the standard fittings or perhaps its irrelevant as described below.
So my next question is given pressure and temperature are the only variables at this stage is it acceptable to equate the pressure-temperature ratings of standard sized & scheduled straight piping to the equivalent standard "piping fittings" such as tees or elbows....or should I be doing a more formal stress analysis (ie such as a branch connection calculation for a tee) to determine the rating, which they would likely pass when based only on temp & pressure...(to my knowledge B16.9 does not specify what the corner radius is to be in the branch region other than it is assumed to be within the tolerances for piping for the given piping schedule)
Obviously the lowest common denominator determines the final rating of the assembly...the limiting components may very well be the flanges.
Note that I fully understand that once you incorporate the assembly into a piping system it is necessary to evaluate it with regard to the other piping loads that may exist, however that is not the case in this situation I am simply trying to rate the fitting for registration.
