Both the Swash Plate Pump and the Hele-Shaw Pump are types of variable displacement pumps used in hydraulic systems, including marine steering gear. Their working principles differ based on their internal mechanics.

1. Swash Plate Pump

• Construction: Consists of a rotating cylinder block containing multiple pistons arranged axially. These pistons press against a stationary, tilted plate called the swash plate.
• Operation: As the cylinder block rotates, the pistons follow the angle of the swash plate. This forces them to reciprocate within their bores. During the "pull" stroke, fluid is sucked in; during the "push" stroke, it is discharged.

2. Hele-Shaw Pump

• Construction: A radial piston pump where pistons are arranged like spokes on a wheel within a circular housing. It features a central fixed pintle (valve) and a rotating cylinder body.
• Operation: The pistons are connected to a "floating ring" (track ring). When the ring is eccentric (off-center) relative to the cylinder body, the pistons are forced to move in and out as they rotate.

Hele-Shaw pump NO discharge position:

Suction from TOP and Discharge at BOTTOM

Suction from BOTTOM and Discharge at TOP (Opposite condition to above):

Applications in Steering Gear Systems

Both pumps are critical in marine engineering, particularly for Steering Gear. They provide the hydraulic power necessary to move the rudder.

• Swash Plate Pumps are often preferred for modern steering gear systems because their compact size fits well in tight engine room compartments. Their high-speed capability allows for rapid response in dynamic positioning and precise rudder control.
• Hele-Shaw Pumps are the "old-school" workhorse for electro-hydraulic steering. They are prized for their extreme durability and ability to handle high-torque demands over long periods with minimal maintenance, making them reliable for continuous operation in harsh marine environments.