impact to pipeline yield at elevated temperature

[Hybrid123]

Hello,

I have an application for an existing pipeline in ISO 13623, where the design temperature has risen from 85°C to proposed 100°C. Pipeline material is X52.

To validate WT at this proposed design temperature 100°C, I need to determine the yield of X52 at 100°C. ISO 13623 sect. 8.1.7 doesn't define means to determine yield over 50°C.

For reference I've used the de-rating stress values in DNV-OS-F101 for C-Mn steel. However is anyone aware of an accurate means to determine yield at elevated temperature?

Thanks.