Emerson 1808 Series Relief Valve Or Backpressure Regulators Data Sheet
2015-03-30
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Bulletin 71.4:1808
July 2010
D100163X012
W3716
W3507
Figure 1. Types 1808 and 1808A Pilot-Operated Relief Valves or Backpressure Regulators
The Type 1808 globe-style and the Type 1808A
angle-style, pilot-operated relief valves or backpressure
regulators are economical, compact devices used in
gas or liquid service to maintain pressure on oil and gas
separators, and in pressure relief applications in gas
distribution systems. The Types 1808 and 1808A are
available with either a Type 6358 or 6358B pilot. The
Type 6358 pilot is used in gas or liquid backpressure
applications throughout the oil and gas production
industry. This pilot offers a low bleed construction so
it only bleeds when it is repositioning the main valve.
Pressure relief applications in the oil and gas industry
are typically handled by the Type 6358B pilot. This pilot
has a bleed restriction to reduce the buildup pressure
required to reach wide-open ow. These units control
pressures from 3 to 125 psig (0,21 to 8,6 bar), and the
set pressure is varied to individual requirements by
the adjusting screw on the pilot. On gas service, the
pilot exhaust can be piped into the downstream piping
or vented to atmosphere. On liquid service, the pilot
exhaust should be piped into the downstream piping or
to a safe location.
• —Units have fewer
parts for reliable service and minimum spare
parts inventory.
• —Less than 12-inches
(305 mm) tall and weighs 25 pounds (11 kg) or
less, these units are easily transported and installed
where space is limited.
•
—Pressure connection in diaphragm
casings and factory-piped pilot tubing mean
no upstream control line is required on standard
installations. There are no mounting restrictions to
limit service.
• —
Pilot exhaust port and standard tapped pilot spring
case (Figure 2) both come with removable vent for
remote piping when necessary. The standard
tapped pilot spring case comes complete with a
gasketed closing cap that permits pressure loading for
remote pneumatic adjustment of the set pressure.
Bulletin 71.4:1808
2
• —With the removal of just two
nuts, the upper and lower casings lift away, exposing
the trim and leaving the main valve body in the line.
•
—For gas service with the Type 6358B
pilot, upstream control line construction is available
to provide wide-open relief ow capacity with less
buildup regardless of set pressure.
• —The Type 1808A angle-body
design has increased capacity and provides
complete process uid drainage from body cavity
during shut-down period or before disassembly of
the main valve.
The Specications section gives some general
specications for the 1808 Series Pilot-Operated Relief
Valves or Backpressure Regulators. The nameplates
give detailed information for a particular regulator as it
comes from the factory.
See Table 1
2 NPT
150 psig (10,3 bar) including buildup
See Table 2
125 psig (8,6 bar)
5 psig (0,34 bar)
Bleeds only when repositioning the main valve
Continuously bleeds while inlet pressure is above
set pressure
See Table 3
See Tables 4 and 5 and Capacity Information section
Internal or External (optional)
1/4 NPT with or without P590 Series lter
-20° to 180°F (-29° to 82°C)
Type 1808 Body: Cast iron or WCC Steel
Type 1808A Body: Cast iron
Diaphram Plates and Diaphragm Casings:
Zinc-plated steel
Diaphragm: Neoprene (CR), Nitrile (NBR)
O-Rings: Nitrile (NBR)
Gaskets: Nitrile (NBR)
Back-up Rings: Polytetrauoroethylene (PTFE)
Spring: Zinc-plated steel
Valve Plug Guide: Stainless steel
Body: Aluminum or CF8M Stainless steel
Spring Case: Aluminum or Stainless steel
Body Plug: Aluminum or Stainless steel
Valve Plug: Nitrile (NBR) or thermoplastic
plug with stainless steel stem
Spring: Zinc-plated steel
Diaphragm: Nitrile (NBR) or Fluorocarbon (FKM)
Spring Seat: Zinc-plated steel
Stem Guide: Stainless steel
Adjusting Screw: Zinc-plated steel
O-Rings: Nitrile (NBR) or Fluorocarbon (FKM)
Closing Cap: Plastic or Stainless steel
Connector Cap: Stainless steel
Tubing: Stainless steel
Fittings: Steel or Stainless steel
Pipe Tees: Galvanized steel
Pipe Nipples: Malleable Iron, Galvanized Steel,
and Stainless Steel
• Upstream control line construction
• Pressure gauge (0 to 160 psig/0 to 11,0 bar/
0 to 1,1 MPa)
• P590 Series Pilot Supply Filter
22 pounds (10 kg)
25 pounds (11 kg)
1. The pressure or temperature limits in this Bulletin and any applicable standard or code limitations should not be exceeded.
Bulletin 71.4:1808
3
Figure 2. Type 1808 with 6358 Series Operational Schematic
E0075
Refer to Figure 2. A pressure relief valve is a control
device that opens to relieve uid to atmosphere during
an overpressure occurrence. A backpressure regulator
is a control device that maintains a constant upstream
pressure throughout a given ow range. It functions
the same as a relief valve in that it opens on increasing
upstream pressure.
A 6358 Series pilot is typically used with one of several
different main valves in a pressure relief or backpressure
application. This pilot is usually used in gas service. It
has an easily-installed valve plug that can be removed
without removing the valve plug stem guide.
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
CCTFF
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 Cg and the desired pressure drop.
2. For Type 1808A capacities, multiply the capacities in this table by 1.27.
Bulletin 71.4:1808
5
As long as inlet pressure remains below setpoint, the
pilot spring keeps the pilot valve plug closed. Inlet
pressure passes through the upper port around the
upper portion of the valve plug then through the hollow
passage in that valve plug. Force from the main spring,
along with inlet pressure bleeding through the pilot,
provide downward loading pressure to keep the main
valve closed.
When inlet pressure rises above the set pressure,
pressure on the pilot diaphragm overcomes the control
spring to close the upper port and stroke the valve plug
to open the lower port. The pilot then exhausts loading
pressure from the top of the main valve diaphragm.
The pilot exhausts only while repositioning the main
valve. The inlet pressure unbalance overcomes the
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.
Types 1808 and 1808A relief valves or backpressure
regulators may be installed in any position as long as
the ow through the main valve corresponds with the
ow arrow on the main valve body (Type 1808) or runs
in through the bottom connection and out through the
side connection (Type 1808A).
Table 5. Capacities for the Type 1808 Using Optional External Control Line and Type 6358B Pilot with High-Gain Restriction
3 to 18
(0,21 to 1,2)
3
5
10
15
(0,21)
(0,35)
(0,69)
(1,0)
0.9
0.7
0.7
0.7
(0,06)
(0,05)
(0,05)
(0,05)
6.0
4.0
1.2
1.0
(0,41)
(0,28)
(0,08)
(0,07)
1.0 (0,07)
37 000
37 000
42 000
52 000
(992)
(992)
(1126)
(1394)
15 to 40
(1,0 to 2,8)
15
20
30
40
(1,0)
(1,4)
(2,1)
(2,8)
0.8 (0,05) 1.1 (0,07)
53 000
63 000
82 000
101 000
(1420)
(1688)
(2198)
(2707)
35 to 125
(2,4 to 8,6)
40
50
60
70
(2,8)
(3,5)
(4,1)
(4,8)
1.4 (0,09) 1.9 (0,13)
102 000
121 000
139 000
157 000
(2734)
(3243)
(3725)
(4208)
80
90
100
110
125
(5,5)
(6,2)
(6,9)
(7,6)
(8,6)
1.6 (0,11) 2.2 (0,15)
176 000
194 000
213 000
231 000
258 000
(4717)
(5199)
(5708)
(6191)
(6914)
1. Set pressure is dened as the pressure at which the pilot exhaust starts to bubble (discharge).
2. Crack pressure is the inlet pressure at which the main valve starts audible ow.
3. Inlet pressure buildup over the set pressure to achieve wide-open capacity.
4. Capacities with inlet piping equal to body size and without outlet piping.
An upstream control line is not required because of
the integral pilot supply tubing; however, for a more
accurate relief valve or backpressure regulator, this
tubing may be disconnected for upstream registration,
and the main valve diaphragm casing tapping plugged.
For liquid service, the pilot exhaust should be piped
to the downstream line or to a safe location. For gas
service, the pilot must be piped to a safe area because,
in enclosed conditions such as inside installations,
exhausting gas can accumulate causing a danger
of explosion. A vent line or stack must be located to
avoid venting gas near buildings, air intakes, or other
hazardous locations, and the line or stack opening must
be protected against anything that might clog it. The
thrust effect of a venting relief valve must be considered
when designing relief valve outlet piping and anchoring.
Tables 4 and 5 give relief capacities at selected
set pressures for the Type 1808 backpressure
regulator or relief valve. Flows are in thousands of
SCFH ( 6 0 ° F a n d 1 4 . 7 p s i a ) a n d t h o u s a n d s o f N m ³ / h
(0°C and 1,01325 bar) of 0.6 specic gravity natural
gas. To determine equivalent capacities for air,
propane, butane, or nitrogen, multiply the Table 4 or 5
capacity by the following appropriate conversion factor:
0.775 for air, 0.625 for propane, 0.548 for butane, or
0.789 for nitrogen. For gases of other specic gravities,
multiply the given capacity by 0.775, and divide by
the square root of the appropriate specic gravity. If
capacity is desired for the Type 1808A, multiply by 1.27.
Bulletin 71.4:1808
6
Figure 3. Dimensions
1808
1. To determine capacities at set pressures or
buildups not given in Tables 4 and 5, use one
of the following formulas, and convert according
to the factors in the preceding paragraph
if necessary:
Q = (P1 + buildup)abs Cg
520
GT
2. For pressure drops lower than critical (absolute
outlet pressure greater than one-half of absolute
inlet pressure), use the following formula:
Q = Cg(P1
+ buildup)abs SIN Deg.
520
GT
ΔP
(P1 + buildup)abs
3417
C1
where,
Q = ow capacity in SCFH
G = specic gravity of gas
T = absolute temperature of gas at inlet in °Rankine
(°Rankine = °F + 460)
C
g = sizing coefcient from Table 3
(P1 + buildup)abs = absolute inlet pressure
= P1 + Patm + buildup
= P1 + 14.7 + buildup
C
1 = Cg/Cv (See Table 3)
ΔP = pressure drop across the valve in psig
To determine relief capacities in U.S. gallons per
minute, use the Catalog 10 liquid sizing procedures
in conjunction with the appropriate liquid sizing
coefcient (Cv) and recovery coefcient (Km) from the
Specications section. Then, if capacity is desired in
Nm3/h, multiply U.S. gallons per minute by 0.2271.
Refer to the Specications section on page 2. Fill
out the order guide on page 7, carefully review the
description of each specication. Always specify the
type numbers of other desired equipment as well as
the main valve and pilot.
Bulletin 71.4:1808
7
(Select One)
1808 (globe body)***
1808A (angle body)**
(Select One)
Cast iron***
WCC Steel (Type 1808 only)*
(Select One)
Type 6358 (for backpressure application)***
Type 6358B (for relief application)***
(Select One)
3 to 18 psig (0,21 to 1,2 bar), Green***
15 to 40 psig (1,0 to 2,8 bar), Yellow***
35 to 125 psig (2,4 to 8,6 bar), Red***
(Select One)
Nitrile (NBR)***
Fluorocarbon (FKM)**
(Select One)
Stainless steel tubing and steel ttings***
Stainless steel tubing and stainless steel ttings***
(Optional)
Yes
(Optional)
Yes
(Optional)
Yes
(Optional)
Yes, please send one parts kit to match this order.
(Optional)
Yes, please send one parts kit to match this order.
* * * Readily Available for Shipment
* * Allow Additional Time for Shipment
*Special Order, Constructed from Non-Stocked Parts.
Consult your local Sales Ofce for Availability.
Availability of the product being ordered is determined by the component with the
longest shipping time for the requested construction.
Specic Use
Line Size
Gas Type and Specic Gravity
Gas Temperature
Brand of upstream regulator?
Orice size of the upstream regulator?
Wide-open coefcient of the upstream regulator?
Maximum Inlet Pressure (P1max)
Minimum Inlet Pressure (P1min)
Downstream Pressure Setting(s) (P2)
Maximum Flow (Qmax)
Accuracy Requirements?
Need for Extremely Fast Response?
Bulletin 71.4:1808
The Emerson logo is a trademark and service mark of Emerson Electric Co. All other marks are the property of their prospective owners. Fisher is a mark owned by Fisher Controls, Inc., a
business of Emerson Process Management.
The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, they are not to be construed as warranties or
guarantees, express or implied, regarding the products or services described herein or their use or applicability. We reserve the right to modify or improve the designs or specications of such
products at any time without notice.
Emerson Process Management does not assume responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use and maintenance of any Emerson
Process Management product remains solely with the purchaser.
©Emerson Process Management Regulator Technologies, Inc., 1978, 2010; All Rights Reserved
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