As usual, "it depends."

If you have predictable pipe reactions (i.e. slug frequency << natural frequency), then you'd request measurements of the displacements as well as the frequency at which they occur. Once you have this info, you can back out slug loads.

If your pipe is moving unpredictably, that means your slug frequency is near or greater than the piping natural frequency, and you may not be able to be supplied reliable information by which to form an analysis.

There is no good way to predict what the inputs of a system are based on erratic unpredictable outputs of the system. Perhaps you can get lucky and come to a reasonable approximation if you have displacement data through trial and error. However, my opinion is that if they have erratic vibrations, you should be supplying them information on how to improve the system from "bad and unknown" to "maybe bad but known, but definitely not making things worse." Once they stiffen up the system, you can then evaluate whether the new configuration is adequate.