Emerson 1808A Instruction Manual

Instruction Manual
Form 5116

July 2010

Types 1808 and 1808A

Types 1808 and 1808A Pilot-Operated Relief
Valves or Backpressure Regulators

WARNING

!

Failure to follow these instructions or
to properly install and maintain this
equipment could result in an explosion

and/or re causing property damage and

personal injury or death.

®

Fisher
relief valves must be installed, operated,
and maintained in accordance with
federal, state, and local codes, rules
and regulations, and Emerson Process
Management Regulator Technologies,
Inc. instructions.

backpressure regulators or

W3716

TYPE 1808 GLOBE-BODY

If a leak develops or if the outlet
continually vents gas, service to the
unit may be required. Failure to correct
trouble could result in a hazardous

condition. Only a qualied person must

install or service the unit.

Call a gas service person to service

the unit. Only a qualied person must

install or service the regulator.

Introduction

Scope of the Manual

This manual provides installation, adjustment,
maintenance, and parts ordering information for
Types 1808 and 1808A pilot-operated relief valves or
backpressure regulators. The manual also includes
coverage of the Types 6358 and 6358B pilots and, if

used, a P590 Series lter. Instructions and parts lists

for other equipment used with these regulators are
found in separate manuals.

Description

Types 1808 globe-body and 1808A angle-body,
pilot-operated backpressure regulators or relief valves

W3507

TYPE 1808A ANGLE-BODY

Figure 1. Types 1808 and 1808A Pilot-Operated
Relief Valves or Backpressure Regulators

are economical, compact devices used in either
gas or liquid service to maintain pressure on oil and
gas separators and in pressure relief applications
in gas distribution systems. The Type 6358 pilot is
used in backpressure regulation and pressure relief
applications throughout the oil and gas production
industry, and is used in either gas or liquid service.
Pressure relief and liquid service applications in

www.sherregulators.com

D100347X012

Types 1808 and 1808A

Specications

Body Size and End Connection Style

2 NPT

Maximum Relief (Inlet) Pressure

(1)

150 psig (10,3 bar) including buildup

Set Pressure Ranges

See Table 1

Differential Pressures
Maximum: 125 psig (8,6 bar)
Minimum: 5 psig (0,34 bar)

Type 6358 Pilot Bleed

Bleeds only when repositioning the main valve

Type 6358B Pilot Bleed

Continuously bleeds while inlet pressure is above
set pressure

Pressure Registration
Internal (standard) or External (optional)

Pilot Tubing and Connections

1/4 NPT with or without P590 Series lter

Temperature Capabilities

(2)

-20° to 180°F (-29° to 82°C)

Approximate Weights
Type 1808: 22 pounds (10 kg)
Type 1808A: 25 pounds (11 kg)

Options

• 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

Flow and Sizing Coefcients

See Table 2

1. The pressure/temperature limits in this Instruction Manual and any applicable standard or code limitation should not be exceeded.

Table 1. Types 6358 and 6358B Set Pressure Ranges, Pressure Ratings, and Pilot Spring Information

SET PRESSURE RANGES,

PSIG (bar)

3 to 18

(0,21 to 1,2)

15 to 40

35 to 125

(1,0 to 2,8)
(2,4 to 8,6)

Part Number Color

1B986027212
1E392527022
1K748527202

Green
Yellow

PILOT SPRING INFORMATION

Red

Wire Diameter,

Inches (mm)

0.120

(3,05)

0.148

(3,76)

0.192

(4,88)

Free Length,
Inches (mm)

2.12

(54,0)

2.00

(51,0)

2.19

(55,6)

Table 2. Types 1808 and 1808A Flow Coefcients

FLOW COEFFICIENTS

TYPE

1808 1410 40.1 0.79 35.2 0.78 0.50 0.89

1808A 1800 51.4 0.76 35.0 0.78 0.50 0.87

the oil and gas industry are typically handled by the
Type 6358B pilot. With either pilot, the set pressure
is varied to individual requirements by the adjusting
screw on the pilot. Pilot exhaust can be piped into the
downstream line or vented into the atmosphere on gas

(WIDE-OPEN)

C

g

K

C

v

m

C

1

diameter is indicated by a letter stamped on the
bottom of the pilot body next to the tapped side outlet:
an H for the yellow high-gain restriction and an L for
the blue low-gain restriction. The pilot spring range
appears on the pilot spring case.

IEC SIZING COEFFICIENTS

X

T

F

D

service and should be piped downstream or to a safe
location on liquid service.

Specications

Principle of Operation

A pressure relief valve is a control device that opens

to relieve uid to atmosphere during an overpressure

The Specications section provides ratings and
specications for Types 1808 and 1808A relief

valves or backpressure regulators. Some of the

specications for a given unit as it comes from the

factory appear on the nameplate attached to the upper
diaphragm case. The Type 6358B pilot restriction

occurrence. A backpressure regulator is a control
device that maintains a constant upstream pressure

throughout a given ow range. It functions in the same

manner as a relief valve that opens on increasing
upstream pressure. The Type 1808 or 1808A cannot

be used as an ASME safety relief valves.

F

L

2

UPPER PORTION
OF VALVE PLUG

TO EXHAUST
PORT

LOWER PORTION
OF VALVE PLUG

TO MAIN VALVE
DIAPHRAGM

DIAPHRAGM
ASSEMBLY

HOLLOW
PASSAGE
IN VALVE
PLUG STEM

RESTRICTION PLUG

Types 1808 and 1808A

PILOT EXHAUST

PILOT

TYPE 6358 BACKPRESSURE SERVICE

UPPER PORTION
OF VALVE PLUG

TO EXHAUST
PORT

LOWER PORTION
OF VALVE PLUG

TO MAIN VALVE
DIAPHRAGM

INLET PRESSURE
ATMOSPHERIC PRESSURE
OUTLET/EXHAUST PRESSURE
LOADING PRESSURE

E0075

TYPE 6358B RELIEF SERVICE

DIAPHRAGM
ASSEMBLY

HOLLOW
PASSAGE
IN VALVE
PLUG STEM

FIXED RESTRICTION

Figure 2. Type 1808 with 6358 Series Operational Schematics

Relief Valve

As long as the inlet pressure is below set pressure,
the pilot control spring keeps the 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.

SPRING

DIAPHRAGM

VALVE PLUG

MAIN VALVE

Backpressure Regulator

As long as inlet pressure remains below setpoint, the

pilot spring keeps the 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 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
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.

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.

3

Types 1808 and 1808A

Installation

WARNING

!

Installing a Type 1808 or 1808A where its
capabilities can be exceeded or where
proper operation might be impaired
may cause personal injury, property
damage, or leakage due to bursting of
pressure-containing parts or explosion of
accumulated gas or liquid. To avoid such
conditions, install the Type 1808 or 1808A
backpressure regulator or relief valve
where service conditions are within the

unit capabilities given in the Specications

section and unit is protected from
exposure to physical damage and/or
corrosive substances.

1. When installing the relief valve or backpressure
regulator, make sure that the system installation
complies with applicable local, state, and federal
codes and regulations.

2. Use qualied personnel when installing, operating,

and maintaining the relief valve or backpressure
regulator. Before installing the unit, inspect the
main valve body, pilot, and pipelines for any
damage or foreign material that may have
collected. Apply pipe compound to the external
pipeline threads only. Do not use pipe compound
on any internal threads.

3. The relief valve or backpressure regulator may

be installed in any position as long as pipeline ow
complies with the ow arrow on the main valve

body (Type 1808) or runs in through the bottom
connection and out the side connection
(Type 1808A). Superior performance may be
obtained by disconnecting the pilot supply tubing
from the elbow (key 36, Figures 3 and 4),
removing the elbow, installing 1/4 NPT pipe plug
into the lower casing (key 2), and connecting the

pilot supply tubing to an upstream location.

WARNING

!

Types 1808 and 1808A relief valves or
backpressure regulators vent gas or
liquid from the main valve outlet, pilot
exhaust, and pilot vent. In hazardous

or ammable gas or liquid service,

personal injury or property damage may

occur due to re or explosion of vented

gas or liquid that has accumulated.

To prevent such injury and damage,
provide piping or tubing to vent the gas
to a well ventilated location. Also, when
venting a hazardous gas or liquid, piping
or tubing should be located far enough
from any buildings or windows so as not
to create a further hazard.

Protect the main valve body, pilot
exhaust, and pilot spring case vent
against anything that could clog
them. For safety during shutdown of
backpressure regulators, install vent
valves immediately upstream and
downstream of the main valve.

4. The pilot exhaust may be piped directly into the
main valve outlet (if the exhaust is to be retained,
as in liquid service) or vented to the atmosphere.

In either case, the diameter of the exhaust line or

stack should be as large as practical with a
minimum number of bends or other restrictions.
When installing this unit in relief service, be sure
to consider the jet thrust effect that will occur when
it relieves.

Overpressure Protection

Relief ranges are from 3 to 125 psig (0,21 to 8,6 bar).
The individual spring range of your relief valve is
stamped on the nameplate.

Maximum inlet pressures depend upon body material

and temperature. See the Specications section

for the maximum inlet pressure of the valve. The
valve should be inspected for damage after any
overpressure condition.

Startup

1. With installation completed, slowly open the
upstream shut-off valve while using a gauge to

monitor inlet pressure. On backpressure

applications using an isolating bypass, open the
downstream shut-off valve, and close the
bypass valve.

2. If set pressure adjustment is necessary, adjust a

Type 6358 or 6358B pilot by following the
procedures in the adjustment section.

4