33
8.3.2 INDICATION: LIKELY REASON: REMEDY:
Differential pressure
across the
FMA 5400A/5500A
controller is within
specification but LCD
reading and actual flow
are not stable (oscillate
1-4 times per second).
Valve
compression
spring is over
adjusted and PID
control cannot
handle stable
flow.
1. Make sure differential pressure across
the FMA 5400A/5500A is within
specification.
2. Install control set point to 100% F.S.
This should remedy the oscillation
conditions.
3. See operating manual page 17
(Figure 6-1). Unscrew hex nut cover on
the top of the solenoid valve.
4. Using screwdriver readjust adjustment
screw on the top of the valve to CCW
(counter clock wise) direction until
reading on the display will be stable. Be
very careful during adjustment: make
only 15 degree turn each time and
wait about 15 seconds due to sensor’s
response time. If reading oscillates
make another 15 degree turn. Do not
over adjust valve. If you noticed that
flow rate is constant and more than
105% of full scale, it means you over
adjusted valve and it has leakage. In this
case make adjustment to CW (clock
wise) in order to fix this problem until
reading will go back to 100% full scale.
5. Adjust zero set point (or valve close
command), wait about 3 minutes and
check if valve is able to close.
6. This is not a shut off valve. It is normal
to observe up to 0.5 % of F.S. leakage.
7. Install hex nut cover on the top of the
solenoid valve.
To Next Page
Loading...
