Manoj,

Flare lines can be subjected to two phase flow for obvious reasons. Talk to Process group for the same. Analysis methods are well established.

I am not sure of the rho v^2 issue on the flare system. Rho v^2 is typically a parameter which industry prefers to associate with a phenomenon known as as " flow induced vibration". Lexically, flow induced vibration can be anything which is flow related. However, the above terminology is used to designate the flow transient which results due to pressure pulsations due to flow separation at elbows and flow restrictive devices.The remedy induces, controlling rho v^2 , separation of mechanical and acoustic frequencies ( for an understanding of what acoustic frequenices are , read Fundamentals of Noise and Vibration analysis for engineers by Norton and Karczub. To mention simply , they are the solution of the Eigenvalue problem resulting from the Homogeneous eqn. known as Hemlholtz eqn. and are the frequencies at which standing wave patterns are generated)and computation of Forces due to pulsation ( there are empirical relations ships for the computation of these forces) and the resulting bending stresses at TEE JOINTS. These bending stresses are checked against endurance limit.

Flare lines are subjected ( mostly ) to Acoustic induced Vibration for which the paper mentioned by Samsul is the bible.AIV is a function of D/T ratio and a product of M X Delta P where M is the Mach no. of Flow and Delta P is the pressure drop at restrictive devises.Rho v^2 is not a parameter for AIV as AIV is related to gas flow only and rho is negligible for gas.

Hence, I am not sure why Rhov^2 should be a yardstick for Flare lines which contain gas only ( except for the liquid bolus which results in two phase flow).

Regards