Not quite. I have a cross-country pipeline, that will have two-phase flow. I have been given lots of friendly advise from co-workers on designing for slug flow (ie. my two fhase flow seperates into gas and liquid during its travel through the pipeline, then as it transits through an expansion loop I get the water hammer effect on the elbows)
I've been in the gas pipeline industry for 25 years and have never run across water hammer on two phase flow. You may have to calculate the velocities of the liquid and gas phase to see if there is an errosion problem (especially if this is a production line that could have sand or solids. The gas phase will act as the shock absorber. Normally during the design of the line, sudden changes in pipe direct will have some momentum forces that must be absorbed. Most pipeline companies will pour concrete anchors on pig recivers risers and above ground risers bends to hold the line in place. This is normally for 6" and larger lines.
Out of curiosity, are the expansion bends there for thermal expansion? I've seen what looks like 25R radius bends in lines that lesson the momentum effect of the slug or pig in a pipeline as it goes through a long above piping where thermal expansion was problem.
