Performance and reliability are essential to dredging operations, yet few applications have the challenges that are faced by the pump drivetrain on a dredging vessel, including massive power requirements, huge inertial loads and the risk of a blockage.
Marine propulsion systems typically use hydraulically operated and oil cooled ‘wet’ clutches located in the gearbox for applications that require the drive to be disconnected from the engine, or during forward and reversing manoeuvres. However, dredging operations are best handled by pneumatically operated ‘dry friction’ clutches that can provide protection against torque overloads, explains Wichita.
The diesel/mechanical drive systems often power both the propulsion system and the dredging pump via their respective gearboxes. However, not only do the impellers have a huge inertia, but this is often a two or three speed gearbox which adds further to the inertia at start-up. So, the clutch connecting the pump to the engine must be engineered to withstand the rigours of the application.
Wichita Clutch has therefore developed a sinter metallic friction clutch. The new clutch plate material can withstand much higher interface temperatures without breaking down; and it can also handle higher peak powers and energy inputs while significantly reducing the wear rates seen in organic plates.
Once the pump is up to speed and under load, the clutch, together with the integrated control system, acts as a torque limiting device to protect the pump and gearbox from excessive loads resulting from a partial or complete pump blockage. Effectively, the clutch can be set up to slip at a pre-determined overload limit in the event of excessive torque demand from the engine. The controls then disconnect the clutch rapidly to protect all drivetrain components including the clutch.
To suit the demands of each vessel, Wichita tailors each solution, including sizing the clutch itself and adapting the bearing housing design to suit the preferred flexible coupling, which is required to accommodate equipment dynamic misalignment and torsional vibration damping.
The company also designs and builds the clutch engagement control panel, which is responsible for ensuring a smooth start-up, minimising wear and ensuring that the drive is disengaged in the event of a pump blockage or overload.
