Emerson D100345X012 Instruction Manual

Instruction Manual D100345X012

March 2021

1805 Series Relief Valves

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.

1805 Series

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 1805 Series Relief Valves.

Introduction

Scope of the Manual

This Instruction Manual provides installation, adjustment, maintenance and parts ordering information for 1805 Series relief valves.

P1026

Figure 1. 1805 Series Relief Valve

Description

The 1805 Series relief valves are primarily designed for use in farm tap applications where a safety relief valve is needed between the first and second stage regulators. The 1805 Series is suitable for service on natural gas, air, propane or any operating medium that is not corrosive to the internal parts. Relief pressure ranges from 5 to 125 psi / 0.34 to 8.6 bar. Maximum pressure, including buildup, is 150 psi / 10.3 bar.

1805 Series

Specications

The Specications section lists the specications for the 1805 Series relief valve. The following information

is stamped on the relief valve at the factory: type number, date of manufacture, spring range, maximum inlet pressure and maximum allowable inlet pressure.

Available Constructions

Type 1805-2: Cast iron spring case, closing cap with 1/4 NPT vent placed over the adjusting screw. Available in 3/4 and 1 NPT body sizes. Type 1805-3: Cast iron spring case, closing cap with 1/4 NPT vent placed over the adjusting screw. Available in 1-1/2 and 2 NPT body sizes.

Body Sizes and End Connection Style

3/4, 1, 1-1/2 or 2 NPT

Maximum Inlet Pressure

150 psig / 10.3 bar including buildup

Relief Valve Set Pressure Ranges

See Table 1

Type 1805-4: Cast iron spring case. Available in 3/4 and 1 NPT body sizes. Type 1805-5: Cast iron spring case. Available in 1-1/2 and 2 NPT body sizes. Type 1805-7: Cast iron spring case, closing cap with 1/4 NPT vent placed over the adjusting screw, screen in outlet. Available in 3/4 and 1 NPT body sizes.

Body Style

Flow and IEC Sizing Coefficients

See Table 2

Temperature Capabilities

-20 to 150°F / -29 to 66°C

Approximate Shipping Weights

3/4 to 1 NPT bodies: 5 lbs / 2 kg 1-1/2 to 2 NPT bodies: 13 lbs / 6 kg

Globe body

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

Table 1. Relief Set Pressure Ranges

(1)

BODY SIZE

3/4 or 1 NPT

1-1/2 or 2 NPT

RELIEF PRESSURE RANGE

psig bar In. mm In. mm

5 to 35

10 to 60

20 to 125

5 to 20

10 to 50

35 to 125

0.34 to 2.4

0.69 to 4.1

1.4 to 8.6

0.34 to 1.4

0.69 to 3.5

2.4 to 8.6

SPRING

PART NUMBER

1B986027212 1B788327022 1B788427022

1D892327022 1D665927022 1E543627142

SPRING COLOR

CODE

Green

Silver

Blue

Red Blue

Yellow

SPRING FREE LENGTH

2.25

2.13

1.94

2.94

2.50

2.31

Table 2. Flow and IEC Sizing Coecients

BODY SIZE C

3/4 to 1 NPT

1-1/2 to 2 NPT 0.94 0.44

35 0.79

IEC SIZING COEFFICIENTS

0.73 0.39

57.2

54.1

49.3

74.7

63.5

58.7

SPRING WIRE

0.12

0.14

0.18

0.17

0.22

0.28

DIAMETER

0.89

3.05

3.56

4.57

4.32

5.59

7.11

UPPER SPRING SEAT

1805 Series

A6671

INLET PRESSURE

OUTLET PRESSURE

ATMOSPHERIC PRESSURE

DIAPHRAGM HEAD

UNION NUT

O-RING HOLDER

O-RING WASHER

Figure 2. 1805 Series Operational Schematic

DIAPHRAGM

BODY

O-RING

VALVE GUIDE ORIFICE

O-RING

Principle of Operation

See Figure 2. Relief valves respond to changes in upstream pressure. If upstream pressure increases and exceeds the relief valve setting, the valve will open and allow gas to vent to the atmosphere. When upstream pressure returns to normal level (below the setting of the relief valve), the relief valve automatically closes and normal system operation resumes.

In the 1805 Series relief valves, the upstream pressure registers underneath the diaphragm. Gas reaches the diaphragm through the space between the O-ring holder and the valve guide orifice in 3/4 and 1 NPT bodies or through registration holes in the valve guide

orifice in 1-1/2 and 2 NPT bodies. When the upstream pressure increases beyond the spring setting, the force on the diaphragm overcomes spring compression. The O-ring holder moves upward, carrying the O-ring away from the valve seat. This opens the flow line, allows gas to flow to the atmosphere and relieves the overpressure condition. When upstream pressure registered on the diaphragm decreases to a level below that of the spring setting of the relief valve, the spring force pushes the diaphragm plate and O-ring holder toward the valve seat. Contact between O-ring and valve seat prevents further flow to atmosphere.

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