Does diameter reduction on the pressure side shortly after the pump induces overexertion of the impeller? This is the setup: suction line: 8" - length: 20' ; high pressure centrifugal pump powered by a engine at approx. 2000 rpm ; pressure line: 6" at a length of 18" directly followed by a manifold of 2x 4". Pump distance after this is approx. 200 m. Pump medium: water. The experience is that the pump intermittently vibrates heavily. Could this be overexertion of the pump impeller?