Reassembling Pressure-Balanced Megastream; Troubleshooting Megastream Control Valves - Flowserve Valtek MegaStream Installation, Operation & Maintenance Instructions

6. Lift the actuator bonnet and plug assembly from
body, taking care not to damage the sleeve bore or
plug head.
7. Remove the sleeve attenuator, seat ring and gaskets
from the body.
8. The attenuator may now be cleaned according to
established industry methods. If uncertain as to
which methods to use with a particular attentuator
and application, refer to factory.
Reassembling Pressure-balanced
MegaStream
Refer to Figure 2 and proceed as follows:
1. Install new seat gasket and reinstall seat ring.
NOTE: All gaskets should be replaced whenever
the valve is disassembled.
2. Install attenuator and sleeve. Replace bonnet and
sleeve gaskets, and plug seals.
3. Lower the actuator, bonnet and plug assembly
squarely into the sleeve bore. If Teflon seals are
used, the plug may remain retracted. With metal
piston ring seals, the plug must be extended a few
Problem Probable Cause
Jerky 1. Galling or scoring between
stem travel plug and pressure-balanced
sleeve
2. Overtightened packing
3. Service temperature exceeds
operating parameter of trim design
4. Inadequate air supply
5. Malfunctioning positioner
Excessive 1. Insufficiently tightened
leakage bonnet flange bolting
2. Worn or damaged seat ring
3. Worn or damaged plug seals
4. Worn or damaged gaskets
5. Inadequate actuator thrust
6. Incorrectly adjusted plug
Restricted 1. Dirty attenuator
flow
2. Incorrectly adjusted limit-
stop or handwheel
Excessive 1. Improper flow direction
noise 2. Excessive pressure drop
3. Jerky or improper stemtravel
4. Throttling too close to the seat
5. Loose parts
Flowserve and Valtek are registered trademarks of Flowserve Corporation.
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FCD VLAIM018-05 ©1999 Flowserve Corporation. Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611

Troubleshooting MegaStream Control Valves

Corrective Action
1. Superficial scoring or galling may be removed with a light application
of emery cloth; if more serious damage exists, contact factory
CAUTION: Trim parts are machined to close tolerances which are essential
for correct functioning of the valve; attempting to remove deep scratches
could result in high leakage rates or improper functioning of valve.
2. Adjust the packing box nuts to slightly over finger-tight (over-tightening
will cause excessive packing wear and high stem friction)
3. Reconfirm service conditions and contact factory
4. Check for leaks in air supply or instrument signal system; tighten any
loose connections and replace any leaky lines
5. Refer to positioner maintenance instructions
1. Refer to "Reassembly" section for correct tightening procedure
2. Disassemble and replace or repair seat ring (for correct procedure on
remachining seat, see Maintenance Instructions 1)
3. Disassemble and replace plug seals
4. Disassemble and replace gaskets
5. Check for adequate air supply to the actuator; if supply is okay, reconfirm
service conditions and contact factory.
6. Refer to Maintenance Instructions 1 for correct plug adjustment
1. Disassemble and clean attenuator, using established industry
cleaning methods
2. Check stroke limiting device and correct, if necessary
1. Check installation for flow direction under the seat; reinstall, if necessary
2. Check design service conditions
3. See corrective action under "Jerky stem travel"
4. Recommended throttling should be 5 percent or more open
5. Check all external bolts and nuts for tightness; if noise is internal,
disassemble, check for damaged, scored parts or missing seat gasket
inches to allow the use of a ring compressor on the
metal rings. A suitable sized screw-type hose clamp
will also serve to compress the rings for reassembly.
Care should be taken to avoid damaging the sealing
surfaces while fitting the plug into the sleeve bore.
4. Once the bonnet is resting on the body, reinstall and
tighten the bonnet flange bolting fingertight.
5. Using the actuator, seat the plug two or three times
to center the seat ring.
6. Leaving the plug in the extended (or closed) posi-
tion, begin tightening the bonnet flange bolting in a
crisscross pattern that will keep the bonnet square
with the valve. Tighten the first bolt
tighten the bolt directly opposite
7. Continue tightening all bolting until the bonnet is
firmly seated, metal to metal, in the body. This can
be easily felt through the wrench.
8. Slowly stroke the plug up and down to check the
alignment of the plug with the attenuator. If binding,
sticking or scraping noises are heard, stop stroking
valve immediately. Disassemble the valve to deter-
mine noise and to detect possible damage.
1 / turn, then
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1 / turn.
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