LNG Piping and Dynamic Forces

The project that I am working on has a load condition I am trying to get my hands around and I would appreciate your input towards its resolution:

The topic is LNG unloading dynamic forces.

The new LNG line we are adding needs to meet FERC requirements. Analysis of dynamic events should be considered when conducting the pipe stress analysis and pipe supports evaluation.

When I first met with our client, he told me that, when the LNG is first received from the loading arms onto the terminal pipeline, there is a dynamic force on the pipe which causes it to jump, and that I should make sure that the supports are adequate for that force. The maximum flow rate is from two arms unloading together. It is 36,000 GPM at 80 PSIG. The new unloading arms are 16" diameter going to a 24" diameter header (see the attached BMP).

In the attached BMP figure the tall vertical cylinders represent the existing unloading arms and the four (4) short ones the new unloading arms which are part of this project. Calculation of the momentum forces at bends gives me 810 pounds for the 24 inch line and 1,230 pounds for the 16 inch line. These loads are too small to account for the phenomenon described.

I think that what is happening is that the first wave of cold LNG is entering into the warm pipe and vaporizing producing a depressurizing wave.

Do think this is the case?

If it is can you suggest a method of putting time history values on this event?

If you don't think that this is what is happening can you suggest another way of analyzing this force?

Thank you for your considered input.

Dejan