February 2022
Installation, Operation and Maintenance Manual
VCIOM-15345-EN Rev. 1
40
Operation
Section 6: Operation
6.4
Functional Description
The following is a functional description of the Biffi Electro-Hydraulic Actuator and a brief
explanation of the main components. Throughout this explanation, numbers which appear
in [ ] correspond to components labeled on the wiring diagram. Numbers in ( ) correspond
to components labeled on the schematic diagram. Information in (( )) is descriptive.
NOTICE
Refer to the Hydraulic Schematic specified for the actuator being worked on to determine
what options were supplied.
6.4.1
Power Stroke ((OPEN/CLOSE))
During a normal power cycle, the motor drives the hydraulic pump. Hydraulic fluid
from the pump is forced into the Accumulator which can hold the fluid under pressure.
This fluid under pressure from the accumulator is used in actuator’s Hydraulic Power
Cylinder and moves the actuator to the OPEN/CLOSE position which compresses the spring
in the Spring-Return Module.
6.4.2
Spring-Return Stroke
In an on/off application, the normally close solenoid valve (5) is energized open by the
controller. The hydraulic fluid flows back to reservoir (4) from actuator cylinder forced
by the spring in the Spring-Return Module. The spring forces the actuator to the
Fail-Safe Position.
6.4.3
ESD Operation ((Optional))
In an ESD application, the ESD 2-way normally open solenoid valve (17) is constantly
held energized, as long as a customer supplied electrical ESD signal is present. In case of
electrical ESD signal loss, ESD Solenoid Valve (17) will de-energize. Hydraulic fluid will flow
from the actuator’s hydraulic cylinder, forced by the Spring-Return Module, through speed
control (7), through normally open ESD 2-way valve (17) and return to the reservoir (4).
6.4.4
Electric Fail-Safe ((Optional))
The Biffi EHO Control can be configured to stroke the actuator to Fail-Safe Position upon
loss of electrical power.
