ARI Armaturen STEVI 423 DN300 EN - Manual (Page 11)

Rev. 0040318001 0410 Page 11
Operating and installation instructions
3-way control valves - STEVI
®
423 (DN300)
9.0 Troubleshooting table
ATTENTION !
- read item 10.0 and 11.0 prior to dismantling and repair work!
- read item 6.0 before restarting the plant !
Fault Possible cause Corrective measures
No flow Valve closed Open valve (using actuator)
Flange covers not removed Remove flange covers
Little flow Valve not sufficiently open Open valve (using actuator)
Dirt sieve clogged Clean / replace sieve
Piping system clogged Check piping system
Kvs value of valve unsuitable Fit valve with higher Kvs value
Stem moves in jerks Stuffing box sealing too tight (for valves
with graphite packings) Tighten packing box flange (pos. 20)
resp. nuts (pos. 22) slightly; valve must
not start leaking
Valve plug slightly seized owing to solid
dirt particles Clean internals, smooth rough spots
Stem or plug cannot be
moved Seatring and plug clogged with dirt Clean seatring and plug with suitable
solvent
Valve plug seized in seatring or guide
owing to deposits or dirt in medium Replace plug and seatring; use parts
made from different material if neces-
sary; refer to item 7.2
Stem leaking In valves with packed stuffing boxes,
tighten screw joint (pos. 22) Tighten packing box flange (pos. 20)
resp. nuts (pos. 22); replace packing if
necessary; refer to item 7.1.2
Leakage too high when
valve is closed Sealing surfaces of plug eroded or worn Replace plug; refer to item 7.2
Sealing edge of seatring damages or
worn
Replace seatring; refer to item 7.2
Seatring and/or plug dirty. Clean internal parts of the valve
Pneumatic actuator not completely
vented; spring force not fully effective Vent actuator air chamber completely
Actuator not powerful enough Install more powerful actuator; check
service data
Stem “hammers” flow in the closing direction Compare flow direction of the media
and flow marking on the valve and if
necessary rotate the valve