Installation, Operation and Maintenance Manual
MAN 604-1A Rev. 6
March 2021
General Warnings
3
Section 1: General Warnings
Codes
ALGAS
XXX
K
-
YYYYY
-
ZZZZ
-
F
S
C
Actuator Series
Scotch yoke Mechanism
Yoke Shape
C = Canted
S = Symmetric
Spring Cartridge Size
Cylinder Size
Internal diameter in mm
Spring Action
CL = Closing
OP = Opening
Service
Blank = Standard
QA = Quick Acting
Manual Override
Blank = No Manual Override
MHP = Manual Pump
MHW = Manual Handwheel
MRHW = Manual Reduced Handwheel
1.3
Description of the Actuator
ALGAS low pressure pneumatic spring-return, are suitable for the operation of
quarter-turn valves (ball valves, butterfly valves, plug valves) in both ON-OFF and
modulating heavy-duty service.
The actuator is made up of a weatherproof scotch yoke mechanism transforming the linear
movement of the pneumatic cylinder (or mechanical manual override, if foreseen) and of
the spring into the rotary movement, which is necessary for operation.
The spring-return pack incorporates up to four springs, fully encapsulated in a factory
welded cartridge: this ensures safety to personnel and simplifies assembly. The spring
action can be easily changed in the field from to close in to open or from to open in to
close (modular design).
The angular stroke of the yoke is adjustable between 82° and 98° by means of the external
mechanical stops screwed into the end flange of the pneumatic cylinder and into the end
flange of the spring-return pack. The cover of the scotch yoke mechanism is arranged for
the assembly of the required accessories (position-transmitter, signaling-limit switches,
positioner , 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 or a
stem extension. Their internal hole 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 .
Table 1.
Single Acting Low Pressure Pneumatic Actuators (Coding System)
