As you probably know, a common cause of 1X Vibration is imbalance. Even if the rotor has been balanced perfectly, a hydraulic imbalance can occur that will appear only when fluid is being pumped. This behavior is a consequence of variations in cavity volume from one part of the impeller to...
Sometimes, it is possible to reduce vibration to acceptable levels by reducing VPF excitation. This can be accomplished by increasing the clearance between the vane and the cutwater (sometimes called the B Gap). Of course, this will affect performance somewhat, but is a lot cheaper fix than...