FMI SPD - Manual (Page 3)

Variable speed Control.
The best speed-regulation system is composed of two pressure regulators and two valves connected as
shown in the sketch.
When the load decreases, the motor's speed increases. This increased speed causes more air to flow. But
because P5 is constant and the flow through the orifice is also constant, P4 must increase. P3 increases
until the pressure differential (P3-P4) across the motor supplies only enough torque to maintain speed. Any
adjustment of R1 will, of course, affect P2 and P3.
The startup procedure is as follows:
• Close valve A; turn the larger regulator's (R2) adjustment all the way in and open valve B all the way.
• Turn the pressure adjustment on the small pressure regulator (R1) until P2 = 70 psi (or slightly more).
• Slowly open valve A until the conveyor is running at the desired speed with full load. If adequate speed
regulation is achieved with just these components, the large regulator and valve B are not needed and
may be removed. If not, go on to the next step.
• Adjust valve B so that P4 = 5 psig; readjust valves A and B so that a speed slightly greater than that de-
sired is obtained.
• Adjust the large regulator until a slight drop in air motor speed is observed. The pressure across the air
motor now will be automatically regulated to minimize the effect of load on the set speed.
R 1 =REGULATOR SIZED FOR ALL MOTORS
INTAKE PORT
R
2 = REGULATOR SIZED ONE SIZE LARGER
THAN R 1
P
1
P
2
P
3
P
4
P
5
= IN-LINE PRESSURES
Plant air line
pressure
Muffler
(Low-restriction)
Air Motor
0/30 psi pressure gauge 0/100 psi pressure gauge
Valve
A
Valve
B R 1
P 1
P 2 P
3
P
4 P 5
R 2
IN PD431-03
PRINTED IN U.S.A.