Thanks Khalid for sharing your experience. From your description of how the system works there is a possibility of "Flow Induced Vibration" because of the mixing of flow from discharge line to suction line. Also, this system can then be identified from P&ID if there's a connection between a suction and discharge piping. And maybe the "Energy Institute Guideline" can also be used to evaluate "LOF's" based from the given process parameters. Actually I have remembered one of my Senior Stress Engineer commented on my Stress package when I was still new to Stress Analysis regarding a pump suction. He commented that it's a vibrating system but for other pump suction system he didn't comment the same. So I suspect, that is a minimum flow line. He doesn't want me to use the base support type but rather a shoe type support and also request the structural guys to provide foundation considering vibration. Maybe he experience it before also for this type of line. Sometimes experience is really the "best teacher".

Cheers to all!!!