Data Sheet
Bulletin 71.4:1808
4
Table 4. Capacities
(1)(2)
for the Type 1808 Using Standard Internal Control Line and a Type 6358 or 6358B Pilot with High-Gain Restriction
Table 3. Flow and Sizing Coefcients
C
C
C
T
F
F
1808 1410 40.1 35.2 0.79
0.78
0.89
0.50
1808A 1800 51.4 35.0 0.76 0.87
As long as the inlet pressure is below the set pressure,
the pilot control spring keeps the pilot valve plug
closed. Inlet pressure passes through the pilot
restriction and registers as loading pressure on top of
the diaphragm. Force from the main spring, in addition
to inlet pressure bleeding through the pilot restriction,
provide downward loading pressure to keep the main
valve closed.
When the inlet pressure rises above the set pressure,
the pressure on the pilot diaphragm overcomes the
pilot control spring and opens the pilot valve plug. The
Table 2. Types 6358 and 6358B Set Pressure Ranges, Pressure Ratings, and Pilot Spring Information
3 to 18
15 to 40
35 to 125
(0,21 to 1,2)
(1,0 to 2,8)
(2,4 to 8,6)
1B986027212
1E392527022
1K748527202
Green
Yellow
Red
0.120
0.148
0.192
(3,05)
(3,76)
(4,88)
2.12
2.00
2.19
(54,0)
(51,0)
(55,6)
Table 1. Available Congurations
1808
6358 Globe-style body for backpressure applications
6358B Globe-style body for relief applications
1808A
6358 Angle-style body for backpressure applications
6358B Angle-style body for relief applications
pilot then exhausts the loading pressure from the top
of the main valve diaphragm. The pilot continuously
exhausts gas when the inlet pressure is above the set
pressure. The inlet pressure unbalance overcomes
the main spring force and opens the main valve.
As the inlet pressure drops, the pilot control spring
begins to close the pilot valve plug and the exhaust
slows. This causes the inlet pressure to build in the
main valve diaphragm casing, allowing the control spring
to close the main valve. Once the main valve is closed,
the pilot valve plug closes and the exhaust stops.
5
12
20
30
40
(0,34)
(0,83)
(1,4)
(2,1)
(2,8)
32
41
56
67
85
(0,9)
(1,1)
(1,5)
(1,8)
(2,3)
46
55
73
89
105
(1,2)
(1,5)
(2,0)
(2,4)
(2,8)
50
65
80
99
120
(1,3)
(1,7)
(2,1)
(2,7)
(3,2)
61
74
89
108
127
(1,6)
(2,0)
(2,4)
(2,9)
(3,4)
70
84
99
117
136
(1,9)
(2,3)
(2,7)
(3,1)
(3,6)
80
93
108
127
145
(2,1)
(2,5)
(2,9)
(3,4)
(3,9)
89
102
117
136
154
(2,4)
(2,7)
(3,1)
(3,6)
(4,1)
50
60
70
80
(3,5)
(4,1)
(4,8)
(5,5)
94
(2,5)
120
135
150
161
(3,2)
(3,6)
(4,0)
(4,3)
137
152
168
180
(3,7)
(4,1)
(4,5)
(4,8)
145
163
181
200
(3,9)
(4,4)
(4,8)
(5,4)
154
172
190
201
(4,1)
(4,6)
(5,1)
(5,4)
163
181
200
218
(4,4)
(4,8)
(5,4)
(5,8)
172
190
209
227
(4,6)
(5,1)
(5,6)
(6,1)
- - - -
- - - -
- - - -
90
100
110
125
(6,2)
(6,9)
(7,6)
(8,6)
- - - -
- - - -
- - - -
- - - -
170
183
197
201
(4,6)
(4,9)
(5,3)
(5,4)
192
209
223
241
(5,1)
(5,6)
(6,0)
(6,5)
213
231
246
267
(5,7)
(6,2)
(6,6)
(7,2)
227
245
263
284
(6,1)
(6,6)
(7,0)
(7,6)
236
254
272
298
(6,3)
(6,8)
(7,3)
(8,0)
245
263
281
(6,6)
(7,0)
(7,5)
- - - -
Shaded areas indicate capacities with main valve wide-open.
1. Capacities based on 0 psig (0 bar) outlet pressure. If outlet pressure is not 0 psig (0 bar), shaded capacities may be recalculated using the wide-open C
g
and the desired pressure drop.
2. For Type 1808A capacities, multiply the capacities in this table by 1.27.