25
Model EA91A＆EA90A
TROUBLESHOOTING
8
※Since the positioner is to be installed under several conditions, non-conformance that is difficult to predict might occur.
If non-conformance occurs, contact our sales office or sales agency for purchase.
Problem
Cause
Corrective Action
Positioner does not
work normally
Excessive vibration in
control valve
Abnormal response
speed, hunting
Supply air pressure is
out of the standard
Output pressure does
not increase
Valve opening changes
wiggly.
Poor repeatability
Large hysteresis error.
Poor linearity
Slow response speed
Hunting exists
Troubleshooting Chart
Following problems and causes are non-conformances expected to encounter in routine operation. Take
following remedy if the non-conformances are encountered.
Positioner does not work
Positioner does not work normally
Abnormal control valve
Wear of contacting face
between nozzle and flapper
Incorrect selection of orifice plate,
dislocation of assembling position
Supply air does not serve
normally
Leakage in output air pipe
Zero position is dislocated
Manual switching screw is
set to "M" side
Electric wire is disconnected
Electric line is short
-circuited
Filter and/or restriction is
clogged
Contacting face between
nozzle and flapper is
improper
Noise influences the signal.
Signal itself changes wiggly.
Zero position is dislocated
Mounted or tightened part
is loosened and twisted
Filter and/or restriction is
clogged, Air leakage from
joint
Too small capacity of actuator
(Be careful if capacity is less than
300cc)
Turn manual switching mechanism to "M", adjust
supply air pressure, and check whether control
valve works normally or not. If abnormality is
present, disassemble control valve.
Remove short-circuited part, and then change
input signal from 50% to between 25% to 75%
to ensure that short-circuiting is absent.
Move flapper with finger, and check whether
output increases or decreases. If output air
pressure could not be obtained, clean filter
and /or restriction to remove clogging.
Check for contact by inserting seal tape
b e t w e e n n o z z l e a n d f l a p p e r . I f n o t o u t -
putting, replace pilot.
Check each part listed below for loose-
ness, and tighten securely.
○ Looseness in stroke adjustment knob.
○ Prevention of backlash in zero adjust-
ment screw. Looseness in screw.
○ Dislocation of cam.
Clean filter and/or restriction, or retighten
joint part to stop air leakage. If response
speed is still slow, replace pilot.
Exchange, orifice plate to V-groove 3 of
standard orifice plate or No. 2 of orifice
plate.
Retighten and adjust mounted or tight-
ened part listed below.
○ B a c k l a s h a n d l o o s e n e s s i n m o u n t e d
part of back lever.
○ L o o s e n e s s i n a r m a t u r e o f f e e d b a c k
spring and balance spring with tightened
parts.
○ L o o s e n e s s a n d t w i s t i n j o i n t , f i t , o r
connecting part to transmit force.
Replace positioner.
Check air pipe for leakage.
Change to "A" side.
Check in accordance with nameplate
stuck to pilot cover.
Apply 50% input signal, and turn zero adjust-
ment knob to check whether air is output.
Check electric lines, and tighten each
wire securely.
Change the signal wiring to the shield one.
Adjust the gain of the Electro-controller.
Check supply air filter regulator,
Check air pipe for leakage.
