ARI Armaturen PREDU 700 EN - Manual (Page 15)

Rev. 0040701000 1714 Page 2-15
Operating and installation instructions
PREDU
®
9.0 Troubleshooting table
ATTENTION !
- read point 10.0 and 11.0 prior to dismantling and repair work !
- read point 5.0 and 6.0 before restarting the plant !
Fault Possible cause Corrective measures
No flow Flange covers not removed. Remove flange covers.
Little flow Dirt sieve clogged. Clean / replace sieve.
Piping system clogged. Check piping system.
Kvs value of valve unsuitable. Fit valve with higher Kvs value.
Downstream pressure rises
quickly when the users are
turned off
Seat / Disc leakage, very dirty Change valve or, if necessary,
seat/plug
Control line or flow restrictor blocked Clean control line or flow restrictor
Diaphragm defect Change diaphragm
Thread plug blocked Open hole in the vent plug screw
Pressure balancing hole in the disc
blocked
Open pressure balancing hole
Balanced bellows defect Renew balanced bellows
Valve in the control line closed Open valve in the control line
Actuator not fitted proper Loosen lock nut. Tighten actuator.
Fix lock nut.
Flange broken. Damage during transport. Replace pressure reducing valve.
Flange bolts not evenly tightened. Replace pressure reducing valve.
Transfer of unsafe forces such as
bending or torsional forces. Install free of tension.
Media comes out of the
vent plug hole
Diaphragm leaking. Change diaphragm.
Downstream pressure can
not be adjusted in the full
capacity range
Valve laid out to small. New layout of valve.
Valve setting is wrong. Reset valve.
Valve doesn’t regulate Control line or flow restrictor blocked. Clean control line or flow restrictor.
Diaphragm defect. Change diaphragm.
Control line is connected to the vent
plug hole.
Fix control line pipe to the control pipe
connection.
Downstream pressure
unstable
Flow restrictor not installed. Install flow restrictor.
The ratio of upstream to downstream
pressure to high.
Reduction over two stages. Install pres-
sure reducing valve in row.
Media exit out of the bon-
net (at the spindle leakage)
Sealing bellows defect. Change sealing bellows.
Downstream pressure can’t
be altered
Manometer defect. Change manometer.
Bonnet thread damaged. Change bonnet.
Valve closed in the control line. Open valve in the control line.
Valve stem moves in jerks. Valve plug slightly seized owing to solid
dirt particles.
Clean internals, change plug and
guide bush.