Dear friends in one of my plant there 6 nos. SB series Grasso make screw compressors in which 4 nos. has been running since 10 years and 2 compressor are new just added to the system.All of them are connected by -2 deg c and -5 deg c common header.Suppose i have select 2 existing compressor and 1 new compressor on -5 deg c system. At the same time 1 existing and 1 new compressor are running but the ammonia liquid comes on the existing compressor only.their discharge temp falls down and compressor make abnormal noise while the new compressor are running well. Kindly gives yours valuable suggestion as earliest as posible.