280/281 7. Hydraulics Pump Drives The real art of achieving an integrated system installation that is efficient and trouble-free is the design of the pump drive system. Lewmar have hundreds of designs that have been giving reliable service for years. The design of such a system is a very careful balance between the performance characteristics of the power source (main engine, gearbox or generator), choice of thruster drive motor, and set up of the control system. Lewmar specify variable displacement pump and fixed displacement pump drive systems dependant on system requirements. Careful consultation between Lewmar and the engine manufacturer will assure a pump drive that will give a good spread of power from idle to higher RPM. Obviously some engines are better suited than others but most of the higher torque models will offer good results. Lewmar recommend the fitment of an electromagnetic clutch in order that the pump can be disconnected when not required.This saves energy, heat and noise. A speed trip can also be fitted to ensure that the engine is not stalled at low RPM, or the pump is not damaged at high RPM. Main Engine Pump Drive - PTO (Power Take Off) Valves ▪ Simple on-off or fully proportional control is available ▪ Valves can control pressure ranges up to 350 bar (5000 psi) ▪ In the case of specialist hydraulic functions a custom designed valve manifold can be supplied. Generator Drive If the generator can provide sufficient usable power, this is an excellent way of achieving thrust without disturbing the main engine. The major generator manufacturers can provide a clutched PTO output if specified. Lewmar can then match a pump to suit.The advantage of this system is that the generator runs at a constant high RPM, so the pump size can be smaller for the same horsepower. No speed trip is required, as the RPM is constant. Gearbox Drive Some gearbox manufacturers can provide a PTO output if specified. Some are clutched and some are direct coupled. Again, with careful consultation we can provide a pump drive to suit. Even without a clutch we can provide a speed sensor that will allow the pump to run at standby if the RPM are too low or too high. These systems offer fingertip control of power selection, are extremely energy efficient as you only generate the power demanded and generate less noise.The various types of drive offer different benefits, but all depend on correct engineering. A range of modular valve solutions are available to tailor the hydraulic power for precise control of any individual hydraulic function
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