Hello Phil,

As long as there are liquid slugs being carried along the piping by the flow of nitrogen, you can expect the piping to take a beating. "Plan B" would involve the installation of "knock out vessels" ("drums" or "pots") which would remove the liquid from the stream by impingement or centrifugal separation. The knock-out drums would have to be solidly anchored (which implies that more expansion loops would be included). A variation of this scheme would involve in-line baffle chambers, each made from perhaps, NPS 8 pipe, with a labyrinth of baffles (somewhat like an automobile muffler) and with a drain pipe for the separated liquid. The chambers would be about a foot or so long and would include B16.9 reducers at each interface with the NPS 3 piping. You would have to solidly restrain (anchor) the piping at these chambers to take the impingement forces to the ground (again, more expansion loops). Of course, the knock-out drums or chambers would remove the liquid but it would have to be collected and pumped to the terminal point (tank). I recognize that this scheme might add an unacceptable degree of complication to the system. Maybe it would be possible to slope ("pitch") the NPS 3 line back to a collection vessel (continuous nitrogen cover) and pump the liquid to the terminal point ?

In piping where OCCASIONAL steam hammer events (e.g., SRV blow-down events) are expected, mechanical snubbers (the hydraulic type are maintenance intensive) are included in the design. I personally do not like to employ this method because designing proper pipe attachments is a concern (I have seen pipe form a plastic hinge at the attachment clamp in a fossil fueled power plant due to the violence of the impact event - total load rejection turbine trip). We sometimes design "doubler plates" to be attached to the pipe locally to spread the load over a greater area and effectively increase the pipe thickness at the point of snubber attachment.

You can see that the "stop it before it begins" approach is the best (most simple), but if it is not possible some rather creative (and perhaps expensive) alternatives may be necessary.

Still looking for additional input from our esteemed colleagues!

Best regards, John.