ARI Armaturen STEVI 462 EN - Manual (Page 12)

Page 12 Rev. 0040307000 0410
Operating and installation instructions
Straight through control valves - STEVI
®
422 / 462
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
Valve stem moves in jerks. Stuffing box sealing too tight
(for valves with graphite packings) Slacken stuffing box gland or hex. nut
(pos. 22) slightly,
valve must nor start leaking!
Valve plug slightly seized owing to
solid dirt particles Clean internals, smooth rough spots
Valve stem or plug cannot be
moved. Seating and plug clogged with dirt;
especially with V-port and perforated
plugs Clean seating and plug with suitable
solvent
Valve plug seized in seating or guide
owing to deposits or dirt in medium Replace plug and seating; use parts
made from different material if neces-
sary
Valve stem leaking. Stuffing box gland too slack in valves
with stuffing box packings Tighten or repack stuffing box gland or
nuts (pos. 22); refer to item 7.1.1
Bellows defective in valves with bellow
seal Replace bellows unit; 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 v
Sealing edge of seating damages or
worn Replace seating; refer to item 7.2.1,
fit dirt sieve if necessary
Piston sealing ring worn
(pressure-relieved valves) Replace sealing ring
Seating and/or plug dirty. Clean internals of valve, fit dirt sieve if
necessary
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