Vilter VSSH Single Screw oil injection vibration

[HwT]

Hello!
We have customer that has several Vilter single screw compressor,
It’s a single stage system with heat pump system in the discharge side of the first stage.
The first stage has no problems, but the heat-pumps (vilter vssh) has problems with the oil injection piping vibrations, this occurs at all frequencies and capacities, but decreases as the compressor runs completely loaded.
Has anybody seen these problems before or has any good input to give?
We have tried to installed special dampening device from vilter (works like a Expansion tank) located in the oil injection line to damping the pulses in the oil supply line.
Different arrangements of pipe support has been carried out, but no change in vibrations.
The compressor-skid is not produced by vilter and is therefore not supported by vilter either..
Vertical oil separator.
Vibrations measured is 40mm/s limit by vilter is 7mm/s

[RANGER1]

HwT,
Do you have any pictures of package & problem line?
Show what happens to fractured line ie on thread for example.

[HwT]

The pipe has been broken at the red pointers showing.
The pipe is heavy duty with approx. 5mm wall thickness
Service valves located at the oil pipe has flexibles hoses that run to pressure transmitters.

[RANGER1]

Post not relevant in wrong area