Jastram ENGINEERING SCA 300 - Description of Standard Components

Introduction
Page 4 of 31
Doc No.: MAN01502, 27-02-01 SCA 300 Manual
1.3 Description of Standard Components
Hydraulic Solenoid Valve
A 4-way, proportional, directional solenoid valve, powered by DC voltage,
is common to all SCA 300 systems. This valve directs the flow from the
hydraulic power unit to the steering gear in order to actuate either a port or
starboard turn of the rudder. The proportional solenoid valve can deliver a
variable flow of hydraulic fluid to the steering gear. The rate of this flow is
proportional to the amount of current applied to the valve’s solenoids. The
SCA 300 controls the amount of current applied to the solenoids when a
change in the rudder position is requested.
This proportional steering control system allows the steering gear to be
gently accelerated and decelerated during rudder movements ensuring
smooth quiet operation of the steering gear throughout its entire range of
motion.
An adjustment in the SCA 300 limits the maximum amount of current that
can be applied to the proportional solenoids. This adjustment sets the
maximum speed the rudder can achieve during a large change in the
rudder position.
SCA 300 Input Devices
The input device is where the command to the rudder is given. There are
two types of input devices that can be connected to the SCA. These are
full follow-up and non follow-up units. Electric wheels, lever controllers
and joysticks are examples of full follow-up devices. Jastram’s full follow-
up input devices incorporate potentiometers in their design. The
potentiometer converts the position of the steering input device into a
signal for input to the SCA. This signal is called the rudder order signal.
Jastram's patented CCO 2300 is a unique type of full follow-up input
device. The CCO is hydraulically coupled to the ship's helm pump. When
the helm pump is turned a potentiometer inside the CCO converts flow of
hydraulic oil from the helm pump into a rudder order signal for input to the
SCA. If power to the hydraulic solenoid valves controlling the rudder is
lost, then the CCO automatically changes over to manual steering by re-
directing flow from the helm pump directly to the steering gear.
A jog lever is an example of a non follow-up input device. With this type of
unit the steering gear turns as long as the device is held in either the port
or starboard position. When used with the SCA, Jastram has maintained