304 SS vs A333 CS for low temperature ethylene

[Macossay]

Hi. We bring in ethylene through a 2" sch 160 pipeline, at pressures up to 1400 psig. The pipeline is A53 carbon steel, with a minimum temperature rating of -20F.

In the event of a sudden depressurization, the temperature could drop as low as -40F. So we want to replace the pipeline with something rated for a lower temperature.

That seems to leave me with a choice of A333 carbon steel or austenitic stainless. Is one preferable over the other? I'm particularly confused about Charpy testing -- various readings seem to contradict each other as to whether I need to do it on one or the other, or both. What do y'all think?

Many thanks,

John

 

[eliebl]

Macossay,

Changing to an austenitic stainless would easily alleviate the concerns with respect to low temperature. It would be a significant cost compared to carbon steel. The real question comes how low of a temperature do you need to go to? If the limit is -40F like you list, A333 gr 6 mated to A350-LF2 fittings using an appropriate weld procedure would have little problem meeting the B31.3 code requirements for that low of a temperature.

Regards,
EJL