Specifications; Principle Of Operation - Emerson Fisher 1808 Manual

Type 1808

Specifications

The Specifications section gives some general specifications 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.
Available Configurations
See Table 1
Body Size and End Connection Style
2 NPT
Maximum Relief (Inlet) Pressure
150 psig / 10.3 bar including buildup
Set Pressure Range
See Table 2
Maximum Differential Pressure
125 psig / 8.6 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
Flow and Sizing Coefficients
See Table 3
Main Valve Flow Capacities
See Figure 3, Table 4 and Capacity
Information section
Pressure Registration
Internal (standard) or External (optional)
Pilot Tubing and Connections
1/4 NPT with or without P590 Series filter
Temperature Capabilities
-20 to 180°F / -29 to 82°C
Construction Materials
Main Valve
Type 1808 Body: Cast iron or WCC Steel
Type 1808A Body: Cast iron
Diaphragm Plates and Diaphragm Casings:
Zinc-plated steel
Diaphragm: Neoprene (CR), Nitrile (NBR)
1. The pressure or temperature limits in this Bulletin and any applicable standard or code limitations should not be exceeded.

Principle of Operation

Refer to Figure 2. A pressure relief valve is a control device
that opens to relieve the medium to atmosphere during an
overpressure occurrence as the upstream pressure increases.
A backpressure regulator is a control device that maintains a
constant upstream pressure throughout a given flow range.
The Type 1808 or 1808A cannot be used as an ASME safety
relief valve.
Pilots
A 6358 Series pilot is typically used with one of several different
main valves in a pressure relief or backpressure application.
The Type 6358 pilot is used in gas or liquid backpressure
2
(1)
(1)
Construction Materials (continued)
Main Valve (continued)
O-rings: Nitrile (NBR)
Gaskets: Nitrile (NBR)
Back-up Rings: Polytetrafluoroethylene (PTFE)
Spring: Zinc-plated steel (standard)
Valve Plug Guide: Stainless steel
6358 Series Pilots
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
Mounting Parts
Tubing: Stainless steel
Fittings: Steel or Stainless steel
Pipe Tees: Galvanized steel
Pipe Nipples: Malleable Iron, Galvanized Steel and
Stainless Steel
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
Approximate Weights
Type 1808: 22 lbs / 10 kg
Type 1808A: 25 lbs / 11 kg
applications throughout the oil and gas production industry. It
has an easily-installed valve plug that can be removed without
removing the valve plug stem guide. This pilot offers a low bleed
construction so it only bleeds when it is repositioning the main
valve. The Type 6358B pilot is typically used in pressure relief
applications for the oil and gas industry. This pilot has a bleed
restriction to reduce the buildup pressure required to reach
wide-open flow. 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.