Flowserve V-378 R1 Edward Equiwedge Gate Valve - Manual (Page 7)

Flow Control Division
Edward Valves
Service Problems
(cont.)
Pressure Seal Gasket Leak
Edward valves have been produced with
two types of pressure seal gasket: Earlier
valves had metal gaskets, while later
designs have composite expanded graphite
gaskets. The valves with composite gaskets
can be identified by a “B” prefix on the fig-
ure number. Assembly and disassembly of
the two gasket types are essentially the
same except the composite gasket designs
have belleville spring washers under the
nuts (or capscrews) of the pull-up bolting,
and the tightening torque requirements for
the pull-up bolting are different.
To guard against leakage, the bolts should
he kept tightened at all times.
A torque wrench should be used for tighten-
ing the bonnet or cover retainer stud nuts or
capscrews which are used to pre-load the
pressure seal gasket.
All nuts/capscrews should be tightened in
an alternating star pattern to insure even
tightening.
The bolting should be tightened to the
torque values shown in Table 2 while the
valve is under full line pressure.
Pressure Seal Leak
Should the leak fail to stop after tightening,
it must be concluded that there is an imper-
fect pressure seal, and the valve will have
to be opened for examination.
(
Note: Regardless of the cause of failure,
opened pressure-seal bonnets should
always be reassembled with a new gasket.
These are available from stock via Air
Express from Raleigh, North Carolina.)
Such a leak may result from any of the
following causes:
1. Incomplete Seal Between Bonnet and
Gasket. An incomplete seal around
the gasket seating surface of the bon-
net (or cover on check valves) may be
caused by corrosion, dirt, chips, or
other foreign matter on the mating sur-
faces of the sealing angle.
2. Incomplete Seal Between Body I.D.
and Gasket. An incomplete seal in the
INITIAL FINAL
FIGURE NUMBERS SIZE TORQUE TORQUE
2.5 26 8
3 26 8
4 26 8
6 29 8
8 44 13
1611, 1611Y, 1711Y 10 67 19
12 72 21
14 76 22
16 95 27
18 121 35
20 127 37
24 156 45
28 221 64
2.5 26 11
3 26 11
4 26 11
6 44 19
8 64 28
1911, 1911Y, 14311Y 10 72 31
12 107 46
14 151 65
16 159 69
18 167 72
20 208 90
24 193 84
2.5 26 19
3 26 11
4 29 21
6 48 35
8 90 65
11511, 11511Y, 12011Y 10 151 109
12 223 161
14 242 175
16 343 247
18 353 255
20 378 273
24 268 193
2.5 26 26
3 26 26
4 29 29
6 101 101
8 133 133
10 155 155
12511, 12511Y, 14411Y 12 311 311
14 199 199
16 442 442
18 311 311
20 503 503
22 663 663
24 806 806
TABLE 1
GLAND BOLT TORQUES, FT-LBS
CLASS 300 & 600 VALVES
TABLE 2
BONNET/COVER BOLT/NUT PULL-UP
TORQUES
(WITH VALVE UNDER PRESSURE)
REQUIRED TORQUE, FT-LBS
BOLT SIZE METAL COMPOSITE
GASKET GASKET
3/8 18 5
7/16 30 5
1/2 45 7
9/16 68 10
5/8 90 15
3/4 150 25
7/8 240 35
1 370 55
1 1/8 533 80
1 1/4 750 110
1 3/8 1020 150
1 1/2 1200 170
1 5/8 1650 230
1 3/4 2250 320
1 7/8 3000 420
2 3300 460
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