Flowserve V-376 R4 Edward Valves - Manual (Page 7)

8
Flow Control Division
Edward V
alves
The guides must be close enough to bring the disk accurately down into the seat to make a tight joint.
Fig. 160
Screwed-Cover
, Cover
-guided Ball Check,
Screwed-in Set
Foreign material in the flow medium may wedge between guiding sur
faces with the
possibility of making the disk stick. It is recommended that piston check valves be used where the fluids are clean and where tight seating is impor
tant. In smaller sizes,
it is recommended that ball type check valves be used where the problem of stick- ing open is of serious consideration. V
alves
sized too large for flow condition will sometimes have excessive wear
, chatter
and noise. Backseat Edward stop valves have a backseat inte- gral with the bonnet. The seating face on the bonnet is generally a bevel and the seating sur
face on the disk, disk nut, or
stem is provided with either a radius or a bevel. Care must be taken of sealing sur- faces on both the bonnet and the radius, which seals against it to obtain a tight backseat.
Integral Backseat Construction
Packings Edward valves are packed with all-purpose packing sets. This is a combination of packing using braided rings at the top and bottom of the packing chamber and flexi- ble graphite packing in the center section. Packing glands should be tightened down enough to prevent leakage but not enough to develop excessive operating torque. When the gland has advanced approxi- mately half way into the packing chamber
,
it is recommended that additional packing rings be added. T
o
obtain best results, the
stem should be thoroughly cleaned. Replacement packing should be the same as that originally fur
nished. Edward valve
packings are inhibited to prevent stem pitting in ser
vice.
W
e recommend packing be purchased
from Edward V
alves to assure packing with
the proper density and corrosion inhibitors is always used.
IMPOR
TANT
:
•
Long ser
vice life from moder
n
graphitic packing requires that ade- quate preloads be applied when repacking.
•
All par
ts should be clean and not
scored or pitted, especially the stem.
•
The stem, disk and bonnet should be
in the valve prior to installing the new packing.
•
Position split packing with the ends of
adjacent rings rotated 90°.
•
Standard
packing
Top Ring
Braided Ring
Center Ring
Flexible Graphite Ring
Bottom Ring
Same as top
•
Clean and lubricate the gland bolts.
•
Tamp the packing down by hand
using the gland.
•
IMPOR
TANT
:
Apply the recommended
torque to the gland nuts evenly with- out cocking the gland. See table.
•
T
ighten nuts to the initial values
shown, then loosen and retighten to the final range.
•
Stroke the stem and then recheck the
torque on the gland bolts.
Backseat and Packings