Influence of Front Driven Equipment on Viscous Damper and System Behaviour

Driving a generator, a hydraulic pump or another piece of equipment off the front of an engine is commonplace in industrial and marine applications. The (front-driven) equipment is sometimes an afterthought, a retrofit applied without due attention and proper analysis. How risky can this be? Additional equipment will, as a minimum, change the natural frequencies of the system. Adding another natural frequency that can be excited within the operating range of the system is quite common. In addition to this, if the added equipment is of substantial moment of inertia and connected to the damper rigidly enough, it may change the damper behaviour to the point of endangering the engine crankshaft. What should we know and which analysis should be completed before the decision is made to “just drive that PTO off the front of the main engine”?