Installation, Operation and Maintenance Manual
MAN 608 Rev. 5
December 2020
General Warnings
3
Section 1: General Warnings
1.3
Introducing the Actuator
The hydraulic actuator OLGAS was engineered and is manufactured to provide fail safe
operation for any quarter turn application such as ball, plug, butterfly valves or dampers, in
both On-Off and Modulating heavy duty service.
The actuator (see Figure 2) is made up of a weatherproof scotch yoke mechanism
transforming the linear movement of the hydraulic cylinder (on closing or opening) into
the rotary movement, which is necessary for operation. The spring module incorporates
up to four springs, fully encapsulated in a factory-welded cartridge: this ensure safety to
personnel and simplifies assembly. The spring action can be easily changed in the field
from “to close” in “to open” or vice- versa. The angular stroke of the yoke is adjustable
between 82° and 98° by means of the external mechanical stops screwed into the spring
cartridge and into the end flange of the hydraulic cylinder. The cover of the scotch yoke
mechanism is arranged for the assembly of the required accessories (positioner, signalling
limit switches, position transducer, etc.) by means of proper matching units. The above
mentioned accessories are operated by the actuator drive sleeve. The housing of the scotch
yoke mechanism has a flange with threaded holes to fix the actuator to the valve either
directly or, if required, with the interposition of an adaptor flange or a mounting bracket.
The actuator yoke has a hole with keyways suitable for the assembly of an insert bush
the internal hole of which is machined (by Biffi or at Customer's care), according to the
shape and dimensions of the valve stem. Biffi can supply different types of control system
following Customer's requirements.
The expected lifetime of actuator is approximately 25 years .
1.4
Data Sheet
Supply fluid
Hydraulic oil, special versions for fire-resistant fluids
Operating temperature
Standard: from –30 °C to +100 °C
Optional: from –60 °C to +140 °C
Design pressure
12 bar maximum
Supply pressure
Please refer to technical document: “actuator data-sheet”
Figure 2
Identification of actuator parts
Spring cartridge
Valve position indicator
Hydraulic Cylinder
Valve Coupling
Scotch yoke
mechanism
