Fisher 480 Instruction Manual

Types 480,481, & 489
Fisher Controls Instruction Manual
Type 480,481, and 489
Actuators
I FISHER"~
March 1971 Form 2367A
Actuator Specifications
Type NumberDescription
480 Pneumattralfy o~~tatecl f>iston
actuator with l"tEgrafly
mounted Type 3570 positioner.
Actuator is yokeless, has 4"
maxfmum trael. and is fastened
10 the actuatw mounting plate
of many prel970 Veer
-Ball@ ~afves and Fisher butter-
fly valves. Actuator sizes 30.
40, 60. 80, 100, and 130.
481 Same as Type 480, hut for
on/off service. Positmner is re-
placed with a pressure tap cwer
which is Molted to the top of the
cylinder.
489 Same as Type 480. but pow
tioner is replaced with Type
3579 solenoid manifold which
permfs supply pressure to be
loaded and exhausted in rep
sponse to electrical signals.
3570
Standard positioner basic to
Tvpe 480 actuators.
3579 Standard solenoid manifold
basic to Type 489 actuatws.
Installation
Inspect this equipment on arrival to
Nate any damage which may have oc-
curred in transit. If the actuator is at-
tached to a valve body when received.
install the valve in the pipeline with
flow in the direction of the an~w on
the salve body. (Some valve types,
notably various butterfly valves. can
be installed with flow in either direc-
tion and are unmarked as to proper
flow direction.)
A three-valve bypass around fhe
main valve is recommended to permit
c~nt~nu~~s operation during periodic
matntenance or inspection of the main
valw
When Series 480 actuators are sup-
plied to operate dampers, louvers. or
similar equipment, a suitable mounting
plate should be provided, and the
piston rod of the actuatw connected
to the operating arm of the damper,
etc., with appropriate hnkage.
Principle of Operation
Type 480..
ISee Figure II - The pneumatic
pressure signal from the instrument or
controller is piped to the bellows of
the 3570 positioner. Assume that the
porltmner IS direct-acting and that the
instrument signal has increased. The
bellows expands and m~,ves the beam,
which pivots around the fixed pmnt
and simultaneously uncwers the nw
zle of relay "B" and COYUS the nozzle
of relay "A". Relay "A" nozlle pres-
sure increases due tq the restriction
created by the beam over the nuzzle.
Through relay action, the air pressure
tO the top of the piston increases. Rep
lay "B" reacts to the change in beam
pqsltx," to decrease the prersure on
the underside of the piston. Due to the
unbalanced pressures acting on the
plst~n, it mwes down, changing the
position of the actuator stem and re-
turning the controlled element to the
desired value.
A feedback arrangement consisting
of a range spring between the beam
and the piston rod extension prevents
over-correction and ensures a definite
position of the piston for a given