I am running an analysis of a piping system for a client with the following properties.

Fluid: Air
Code : B31.3

Inner Linning
Matl.: SB 409 UNS 08810 - 20GA
Temp : 1800 Deg.F

Outer Linning
Matl.: SA 240-304/304L Sch10S
Temp : <400 Deg.F

Air flows from a Ceramic Heat Exchanger through the pipe to a Tubine. The pipe section in question consists of a 6" Dia. inner pipe with some simple slip (lap) style joints, encased in about 2" of, refractory castable insulation, which in turn is encased in a 12" Dia. SA 240-304/304L Sch10S pipe. It appears that the inner linning will not restrain the piping due to the existance of several slip joints (I will confirm this and begin a new thread on modelling issues), and only the outer linner is the actual pipe which will be stressed. My questions are thus:

Assuming that the inner liner is simply for protection of the turbine from insulation particles.
1) Is the material SB409 UNS08810 acceptible in this application since it is listed in both ASME BPV Section I & VIII and B31.3 as "Plate, Sheet and strip"?
(I believe YES, as the liner will not restrain pipe movement.)

2) B31.3 Edition 1999 lists the maximum allowable stress as 1000psi at 1650 Deg.F. Apparently the BPV coe lists it as 500psi at 1800 Deg.F. May I still use this material as a piping liner eventhough B31.3 does not list stress values above 1650?
(I believe YES, as the liner will not restrain pipe movement.)

Assuming the inner liner restrains pipe movement.
1) Same question as above. (I believe NO)
2) Same question as above. (I believe NO)

Thanks for your time an input.
I look forward to your responses.
Kyle Berg