July 2020
Installation, Operation and Maintenance Manual
MAN 573 Rev. 8
1.2
Identification Plate
!
WARNING
It is forbidden to modify the information and the marks without previous written authorization
by Biffi Italia s.r.l.
The plate fastened on the actuator contains the following information (see Figure 1).
Figure 1
Data Plate
1.3
Introducing the Actuator
RPS actuators are pneumatic low-pressure Spring-Return, suitable for any quarter-turn application
such as ball, plug, butterfly valves or dampers, in both ON-OFF and modulating heavy-duty service.
The actuator is made up of a rack and pinion mechanism, which transforms the linear movement
of the pneumatic cylinder, in one direction, and of the spring, in the opposite direction, into the
rotary movement for the valve operation. An adjustable bronze sliding block supports the
transverse force exerted on the rack by its engagement with the pinion. The rack is nitride
for ensure the minimal friction.
The spring module incorporates one or two springs in series, depending on the model, and is fully
encapsulated. This assures safety to personnel and ease of assembly. External travel stops allow
precise angular stroke adjustment between 80° and 100°.
Totally enclosed, weatherproof housing, made of nodular cast iron for maximum strength and
suitable for use in hostile environments.
The mounting flange is identical on both (upper and lower) faces of the housing; the shaft output
drives have the same dimensions but is positioned at 90°. This allows the actuator to be used as
spring to close or spring to open without modification.
The actuator is assembled onto the valve by connecting the actuator housing flange to the valve
flange by a spool piece and the actuator shaft to the valve stem by a stem extension.
Actuator manual emergency operation in opposition to the spring action, is performed by rotating
the jackscrew by a wrench or by a hand-wheel (available on request).
The mounting flange, on the housing top, can be utilised for the assembly of limit switches, position
transmitter, positioner etc., which are actuated by the actuator output shaft.
General Warnings
2
Section 1: General Warnings
