172-65260m-05 (S-COS/S-COSR Pressure Reducing Valve) 27 Oct 2008
22
Troubleshooting Chart (continued)
Problem Symptom
Cause
Remedy
Flow rate exceeds
rated flow rate
Check the flow rate,
replace with a larger size
The adjustment screw
has seized
Replace with a new
adjustment screw
The small hole on the
piston is clogged
Clean
The diaphragm is
distorted or damaged
Replace with a new
diaphragm
There is fluctuation in
steam consumption
Check the flow rate,
replace the S-COS/
S-COSR if necessary
Adjustment is
difficult, and set
pressure varies
The selected model is
inappropriate for the
service conditions
(specifications)
Check the model
selection, replace the
S-COS/S-COSR if
necessary
The bypass valve is
leaking
Check, clean, and
replace with a new valve
if necessary
The secondary
pressure
cannot be
adjusted or
increases
abnormally
(continued)
Upon closing the
valves on the
secondary side,
the secondary
pressure abruptly
rises as high as
the primary
pressure
There is a build-up of
dirt on or damage to
the pilot valve or main
valve seating surfaces
Clean
Align
Replace if necessary
Occurs at low
steam demand
It is being operated
below the lower flow
rate limit
Check the volume of
steam supply, replace
with a smaller diameter
valve
There is too high a
reduction ratio
(operated at below
10% of the primary
pressure)
Use a two-stage
reduction arrangement
Hunting never
stops
The selected model is
inappropriate for the
service conditions
(specifications)
Check the model
selection, replace the
S-COS/S-COSR if
necessary
Condensate is
contained, or the trap is
blocked (S-COS only)
Check the trap
Check the piping
Hunting or
chattering
occurs
Chattering never
stops
The selected model is
inappropriate for the
service conditions
(specifications)
Check the model
selection, replace the
S-COS/S-COSR if
necessary
Abnormal
noises
Makes a high-
pitched noise
There is too high a
reduction ratio, the flow
is too great, or there is
a high-speed open /
close valve nearby
Use two-stage reduction
Check the flow rate, use
a larger size valve
Install the valve as far
away as possible
Troubleshooting continued on next page
