The allowable stress range for RCC-MR-RD & RC code is given in CAESAR after adding the unused sustained stress from the sustained stress case. Please let me know where the code mentions this explicitly.B31.1 has an explicit mention of this option.

Rearrange equation 8 (in C3653.2.b).

Dear Richard Ay

Please let me know which equation you are talking about. The equation for allowable expansion stress in RCC-MR-RD code is given in RD3626.2.

I'm using the 1988 edition of RCC-M. Section C3653.2 is titled "Thermal expansion stress range requirements". This section contains equations (7) and (8).

<font color="0000ff">NOTE: In the equations below, ".LE." is "less than or equal to". These forums won't allow the left bracket for "less than", because it indicates the start of an HTML tag.</font>

(7) SE = i * Mc / Z .LE. Sa

(8) STE = PD/4t + 0.75i * Ma/Z + i * Mc/Z .LE. (Sh + Sa)

In equation (8), [PD/4t + 0.75i * Ma/Z] is Sl, from equation (6) in Section C3652. So ...

STE = Sl + i * Mc/Z .LE. (Sh + Sa)
STE = i * Mc/Z .LE. (Sh + Sa - Sl)

Finally, substituting for Sa yields

STE = i * Mc/Z .LE. f(1.25Sc + 1.25Sh - Sl)

I am using the 2002 Edition of RCC-MR-RD in which the approach to class 3 components are changed as per service levels like ASME Section III. For Level A loading
Sl .LE. 1.5Sh
SE .LE. Sa OR
And a third equation which adds both
(Sl+SE) .LE. (1.5Sh + Sa)

This signifies that the difference in the sustained stress can be used for the expansion stress range.
Thanks for your guidance.