I guess the answer is hidden in how you make the load changes. Do you play with RPM of the compressor to achieve the load reduction/increase in the system, I guess you do. So you change the forcing frequency without consulting the originator of the system, and now some of the forcing frequecies might be coinciding with the natural frequency of the piping.

If you need to work in all those loads you really needed to discuss it with the piping design engineer and the pulsation specialts.

I believe it is still not late to do it if you want to see the plant working under those conditions. They might be making some or substantial modification in the supporting system of the piping to get away from the cooincidental frequencies. Or you may be giving us some of the operations in case the cost become enourmous.

Plaesa note that the reciprocation compressor piping is fined tuned piping, changing the operating conditions without consulting to the specialist might be very costly.

Good luck.

Ibrahim Demir