Reciprocating compressors experience high vibration at 100% load operation

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Our facility has two reciprocating compressors, one in operation and one on standby. When Compressor A operates under no-load conditions, its vibration levels are very low: the axial horizontal vibration at the crankcase is less than 2 mm/s, while that at the cylinder head is less than 3 mm/s. Once a load is applied, these vibration values gradually increase. Eventually, the axial horizontal vibration at the crankcase reaches 6–7 mm/s; for the first-stage suction surge tank, it reaches 15 mm/s. At the first-stage cylinder head, the axial horizontal vibration is 10.2 mm/s. At the final bend of the first-stage suction pipeline, the axial horizontal vibration measures 18 mm/s (the vibration of the concrete foundation at this location is 11 mm/s). The vibration level of the first-stage discharge surge tank is 6–7 mm/s； The axial horizontal vibration of the secondary intake buffer tank is 14 mm/s, that of the secondary cylinder head is 11.5 mm/s, and the vibration of the secondary exhaust buffer tank is 4–5 mm/s ； Vibration of the secondary exhaust pipeline is 5~6 mm/s. Adjusting the pipe supports had no effect. Under the same operating conditions, unit B performs very well. At full load, the axial horizontal vibration at the crankcase is between 2 and 3 mm/s, while the vibration at the cylinder head is between 4 and 5 mm/s. Could everyone please analyze this and suggest ways to address the issue of high vibration in unit A.