The Technical Reference Section includes articles covering regulator theory, sizing, selection, overpressure protection, and other topics relating to regulators. This section begins with the basic theory of a regulator and ends with conversion tables and other informative charts.

If there’s something you need to know about a regulator that’s not covered in this section, please contact your local Sales Office.

• Regulator Components
• Introduction to Regulators
• Principles of Direct-Operated Regulators
• Principles of Pilot-Operated Regulators
• Selecting and Sizing Pressure Reducing Regulators
• Overpressure Protection Methods
• Principles of Relief Valves
• Principles of Series Regulation and Monitor Regulators
• Valve Sizing Calculations
• Vacuum Control
• Freezing
• Chemical Compatibility of Elastomers and Metals
• Sulfide Stress Cracking
• Cold Temperature Considerations
• Powder Paint Coating

Introduction to Regulators

Introduction
Specific Regulator Types
Pressure Reducing Regulators
Direct-Operated (Self-Operated) Regulators
Pilot-Operated Regulators
Backpressure Regulators and Relief Valves
Pressure Switching Valves
Vacuum Regulators and Breakers
Pressure Reducing Regulator Selection
Backpressure Regulator Selection
Relief Valve Selection

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Principles of Direct-Operated Regulators

Introduction
Regulator Basics
Essential Elements
Restricting Element
Measuring Element
Loading Element
Regulator Operation
Increasing Demand
Decreasing Demand
Weights versus Springs
Spring Rate
Equilibrium with a Spring
Spring as Loading Element
Throttling Example
Regulator Operation and P₂
Regulator Performance
Setpoint
Droop
Capacity
Accuracy
Lockup
Spring Rate and Regulator Accuracy
Spring Rate and Droop
Effect on Plug Travel
Light Spring Rate
Diaphragm Area and Regulator Accuracy
Restricting Element and Regulator Performance
Critical Flow
Orifice Size and Capacity
Orifice Size and Stability
Orifice Size, Lockup, and Wear
Orifice Guideline
Increasing P₁
Factors Affecting Regulator Accuracy
Performance Limits
Cycling
Design Variations
Improving Regulator Accuracy with a Pitot Tube
Decreased Droop (Boost)
Improving Performance with a Lever

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Principles of Pilot-Operated Regulators

Introduction
Pilot-Operated Regulator Basics
Regulator Pilots
Gain
Identifying Pilots
Setpoint
Spring Action
Pilot Advantage
Gain and Restrictions
Stability
Restrictions, Response Time, and Gain
Loading and Unloading Designs
Two-Path Control (Loading Design)
Two-Path Control Advantages
Unloading Control
Unloading Control Advantages
Performance Summary
Accuracy
Capacity
Lockup
Applications
Two-Path Control
Unloading Design

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Selecting and Sizing Pressure Reducing Regulators

Introduction
Application Guides
Special Requirements
The Role of Experience
Sizing Equations
General Sizing Guidelines
Body Size
Construction
Pressure Ratings
Wide-Open Flow Rate
Outlet Pressure Ranges and Springs
Accuracy
Inlet Pressure Losses
Orifice Diameter
Speed of Response
Turn-Down Ratio
Sizing Exercises
Problem 1: Industrial Plant Gas Supply
Problem 2: Steam Space Heater
Problem 3: High Pressure Water Supply
Problem 4: Corrosive Gas

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Overpressure Protection Methods

Methods of Overpressure Protection
Relief Valves
Monitoring Regulators
Working Monitor
Series Regulation
Shutoff Devices
Relief Monitor
Summary

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Principles of Relief Valves

Overpressure Protection
Maximum Pressure Considerations
Downstream Equipment
Main Regulator
Piping
Relief Valves
Selection Criteria
Pressure Buildup
Periodic Maintenance
Cost versus Performance
Installation and Maintenance Considerations
Pop Type Relief Valve
Operation
Typical Applications
Direct-Operated Relief Valves
Operation
Product Example
Pitot Tube
Typical Applications
Pilot-Operated Relief Valves
Operation
Product Example
Performance
Typical Applications
Internal Relief
Operation
Product Example
Performance and Typical Applications
Selection and Sizing Criteria
Maximum Allowable Pressure
Regulator Ratings
Piping
Maximum Allowable System Pressure
Determining Required Relief Valve Flow
Determine Constant Demand
Selecting Relief Valves
Regulator Lockup Pressure
Applicable Regulations
Sizing and Selection Exercise

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Principles of Series Regulation and Monitor Regulators

Series Regulation
Upstream Wide-Open Monitors
Downstream Wide-Open Monitors
Upstream Versus Downstream Monitors
Working Monitors
Sizing Monitor Regulators

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Valve Sizing Calculations

Introduction
Sizing for Liquid Service
Viscosity Corrections
Predicting Flow Rate
Predicting Pressure Drop
Flashing and Cavitation
Choked Flow
Sizing for Gas or Steam Service
Universal Gas Sizing Equation
General Adaptation for Steam and Vapors
Equation Form for Steam Below 1000 psig

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Vacuum Control

Vacuum Applications
Vacuum Terminology
Vacuum Control Devices
Vacuum Regulators
Vacuum Breakers (Relief Valves)
Vacuum Regulator Installation Examples
Vacuum Breaker Installation Examples
Gas Blanketing in Vacuum
Features of Fisher's Vacuum Regulators and Breakers

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Freezing

Introduction
Reducing Freezing Problems
Heat the Gas
Antifreeze Solution
Equipment Selection
System Design
Water Removal
Summary

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Chemical Compatibility of Elastomers and Metals

Introduction
Elastomers: Chemical Names and Uses
General Properties of Elastomers
Fluid Compatibility of Elastomers
Compatibility of Metals

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Sulfide Stress Cracking

Introduction
The Basics of Sulfide Stress Cracking
Carbon Steel
Cast Iron
Stainless Steel
Nonferrous Alloys
Springs
Coatings
Stress Relieving
Bolting
Composition Materials
Codes and Standards

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Cold Temperature Considerations

Regulators Rated for Low Temperatures
Selection Criteria
Low Temperature Fisher Regulators

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Powder Paint Coating

Introduction
Economic Advantages
Environmental Advantages
Mechanical Properties
Corrosion Resistance

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