18
Troubleshooting
When disassembling or removing the product, wait until the internal
pressure equals atmospheric pressure and the surface of the product
has cooled to room temperature. Disassembling or removing the
product when it is hot or under pressure may lead to discharge of fluids,
causing burns, other injuries or damage.
CAUTION
When the product fails to operate properly, use the following table to locate the cause
and remedy.
Problem Cause
Diagnosis Remedy
(Countermeasure)
The pressure of the
air supply to the
positioner is too high
Check the pressure of the air
supply to the positioner and
confirm product specifications
Adjust the pressure of the
air supply for the positioner
to match the pressure in
the product specifications
The positioner’s zero
point is miscalibrated
Check the actuator air supply
pressure (on the positioner’s
pressure gauge) when the
operation signal is at 4 mA
If the pressure on the
pressure gauge is elevated
(not 0 MpaG (0 psig)), adjust
the positioner’s zero point
The inlet pressure for
the valve is too high
Check the inlet pressure for
the valve
Operate at an inlet pressure
of 1.0 MPaG (150 psig) or
less
The valve plug and
valve seat are off-
center
Move the valve plug & stem
up and down and check to
see if it catches
Reassemble the valve
bonnet section correctly
Valve Leakage
There is a problem
with the sealing
surfaces of the valve
plug and valve seat
Check the valve plug and
valve seat
Replace with a new valve
plug & stem and valve seat
The bellowphragm in
the actuator is
broken
Check to see if a large
amount of air is leaking from
the exhaust tap
Replace with a new
positioner/actuator unit
[Check to make sure that
the valve is not operating
(traveling) too often and
that the ambient
temperature is not too high]
The positioner’s
internal parts are
broken
(the diaphragm is
cracked, etc.)
Check to see if any unusual
noise is coming from the
positioner
Replace with a new
positioner/ actuator unit
[Check to make sure that
the valve is not operating
(traveling) too often and
that the ambient
temperature is not too high]
There is insufficient
air supply pressure
to the positioner
Check the pressure of the air
supply to the positioner and
refer to product specifications
Adjust the supply air
pressure for the positioner
(Confirm product
specifications)
The valve does
not travel
beyond a
certain point
Malfunction of the
signal system
Check to make sure the
controller is emitting a 4 to 20
mA signal and that the wires
are not disconnected, etc.
Inspect the controller and
repair the signal wiring if
necessary
Troubleshooting continued on next page
172-65443A-01 (CV-COS) 17 Nov 2014
