Slow speed device or "Trolling valve"

Controlled clutch slip system

Trolling valve system

Principle of operation

The aim of the "trolling valve" (Masson-Marine term "DML") is to let the clutch slip in a controlled fashion to reduce the rotational speed of the propeller.

In terms of use, this system can be applied to all ships having a fixed pitch propeller and obliged to produce high on-board power while keeping the ship's speed low. This is the case where a vessel is fitted with "energy intensive" equipment, such as large winches.

To satisfy this requirement, the solution consists in letting the main engine (the prime energy source) run as closely as possible to its nominal speed, and to reduce the speed of the output shaft.

To do so, Masson-Marine transmissions can be fitted with a "trolling valve", which is in fact a device to make the clutch slip.

Masson-Marine determine an operating range.

In order to define the operating range of the "trolling valve", while ensuring that the client will not "burn" his propulsion clutch, Masson-Marine compute every case individually.

The calculation is made from the following data:

  • Engine power and speed
  • Operating temperature limit
  • Oil flow rate required for cooling

Based on these different parameters, Masson-Marine determine the operating range of the "trolling valve".

  • Operating pressure
  • Clutch slip and temperature surge limit
  • Critical propeller speeds.

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