Hi Aslam,
Thank you for your reply. Can I summarize it as follows:
Sustained condition can be considered as a variant of operating condition. Here the effect of temperature is not considered for calculation. This is not an installed condition where the pipe is empty and temperature is ambient. Sustained loads will not be affected by the input values of ambient temperature we provide using the special execution parameters or any other temperature.
This topic must have been discussed several times here. But every time I go through the various texts, I feel sustained condition is similar to installed condition-or similar to a condition just after the erection of piping at site and additionally fluid weight and pressure considered as a "margin". Also can I take the expansion case is the algebraic difference between the operating and sustained which gives the pure thermal effect alone.

For further confirmation.
Thanks.