Fisher Regulator Handbook - Technical

1 K - 1 KKThe Technical Reference section includes articles coveringregulator theory, sizing, selection, overpressure protection,noise, freezing, and other topics relating to regulators . Thissection begins with the basic theory of a Regulator and endswith conversion tables and other informative charts. If there ssomething you need to know about a Regulator that s notcovered in this section, please contact your Fisher SalesRepresentative or contact your nearest Fisher Sales PRESSURELOADING PRESSUREOUTLET PRESSUREATMOSPHERICA PRESSURET echnicalTable of ContentsKKREGULATOR COMPONENTSS traight Stem Style Direct-Operated .. K-2 Lever Style Direct-Operated .. K-3 Loading Style (Two-Path Control) Pilot-Operated .. K-4 Unloading Style Pilot-Operated .. K-5 INTRODUCTION TO REGULATORSI ntroduction .. K-6 Types of regulators .. K-6 Direct-Operated (Self-Operated) regulators .

2 K-6 Pilot-Operated regulators .. K-6 Specific Regulator Types .. K-6 Pressure Reducing regulators .. K-7 Backpressure regulators and Relief Valves .. K-7 Pressure Switching Valves .. K-7 Vacuum regulators and Breakers .. K-7 Pressure Reducing Regulator Selection .. K-8 Backpressure Regulator Selection ..K-10 Relief Valve Selection ..K-10 PRINCIPLES OF DIRECT-OPERATED REGULATORSI ntroduction ..K-11 Regulator Basics ..K-11 Essential Elements ..K-11 Restricting Element ..K-12 Measuring Element ..K-12 Loading Element ..K-12 Regulator Operation ..K-12 Increasing Demand ..K-12 Decreasing Demand ..K-12 Weights versus Springs ..K-12 Spring Rate ..K-13 Equilibrium with a Spring ..K-13 Spring as Loading Element ..K-13 Throttling Example ..K-13 Regulator Operation and P2 .. K-14 Regulator Performance ..K-14 Setpoint ..K-14 Droop.

3 K-14 Capacity ..K-14 Accuracy ..K-14 Lockup ..K-14 Spring Rate and Regulator Accuracy ..K-15 Spring Rate and Droop ..K-15 Effect on Plug Travel ..K-15 Light Spring Rate ..K-15 Diaphragm Area and Regulator Accuracy ..K-15 Restricting Element and Regulator Performance ..K-16 Critical Flow ..K-16 Orifice Size and Capacity ..K-16 Orifice Size and Stability ..K-17 Orifice Size, Lockup, and Wear ..K-17 Orifice Guideline ..K-17 Increasing P1 .. K-17 Factors Affecting Regulator Accuracy ..K-17 Performance Limits ..K-17 Cycling ..K-17 Design Variations ..K-17 Improving Regulator Accuracy with a Pitot TubeK-17 Decreased Droop (Boost) ..K-18 Improving Performance with a Lever ..K-18 PRINCIPLES OF PILOT-OPERATED REGULATORSP ilot-Operated Regulator Basics ..K-19 Regulator Pilots ..K-19 Gain ..K-19 Identifying Pilots ..K-19 Setpoint ..K-19 Spring Action.

4 K-19 Pilot Advantage ..K-19 Gain and Restrictions .. K-19 Stability ..K-19 Restrictions, Response Time, and Gain ..K-20 Loading and Unloading Designs ..K-20 Two-Path Control (Loading Design) ..K-20 Two-Path Control Advantages ..K-20 Unloading Control ..K-21 Unloading Control Advantages ..K-21 Performance Summary ..K-21 Accuracy ..K-21 Capacity ..K-21 Lockup ..K-21 Applications ..K-21 Two-Path Control ..K-21 Unloading Design ..K-23K-iTechnicalTable of ContentsKKSELECTING AND SIZING PRESSURE REDUCING REGULATORSI ntroduction ..K-24 The Fisher Regulator Handbook ..K-24 Special Requirements ..K-24 The Role of Experience ..K-24 Sizing Equations ..K-24 General Sizing Guidelines ..K-25 Body Size ..K-25 Construction ..K-25 Pressure Ratings ..K-25 Wide-Open Flow Rate ..K-25 Outlet Pressure Ranges and Springs ..K-25 Accuracy ..K-25 Inlet Pressure Losses.

5 K-25 Orifice Diameter ..K-25 Speed of Response ..K-25 Turn-Down Ratio ..K-25 Sizing Exercises ..K-25 Problem 1: Industrial Plant Gas Supply ..K-26 Problem 2: Steam Space Heater ..K-26 Problem 3: High Pressure Water Supply ..K-27 Problem 4: Corrosive Gas ..K-28 OVERPRESSURE PROTECTION METHODSM ethods of Overpressure Protection ..K-29 Relief Valves ..K-29 Monitoring regulators ..K-30 Working Monitor ..K-30 Series Regulation ..K-30 Shutoff Devices ..K-31 Relief Monitor ..K-31 Summary ..K-32 PRINCIPLES OF RELIEF VALVESO verpressure Protection ..K-33 Maximum Pressure Considerations ..K-33 Downstream Equipment ..K-33 Main Regulator ..K-33 Piping ..K-33 Relief Valves ..K-33 Selection Criteria ..K-34 Pressure Buildup ..K-34 Periodic Maintenance ..K-34 Cost versus Performance ..K-34 Installation and Maintenance Considerations.

6 K-34 Pop Type Relief Valve ..K-34 Operation ..K-34 Typical Applications ..K-35 Direct-Operated Relief Valves ..K-35 Operation ..K-35 Product Example ..K-36 Pitot Tube ..K-36 Typical Applications ..K-36 Pilot-Operated Relief Valves ..K-36 Operation ..K-37 Product Example ..K-37 Performance ..K-37 Typical Applications ..K-37 Internal Relief ..K-38 Operation ..K-38 Product Example ..K-38 Performance and Typical Applications ..K-38 Selection and Sizing Criteria ..K-39 Maximum Allowable Pressure ..K-39 Regulator Ratings ..K-39 Piping ..K-39 Maximum Allowable System Pressure ..K-39 Determining Required Relief Valve Flow ..K-39 Determine Constant Demand ..K-39 Selecting Relief Valves ..K-40 Regulator Lockup Pressure ..K-40 Applicable Regulations ..K-40 Sizing and Selection Exercise ..K-40 PRINCIPLES OF SERIES REGULATION AND MONITOR REGULATORSS eries Regulation.

7 K-42 Upstream Wide-Open Monitors ..K-42 Downstream Wide-Open Monitors ..K-43 Upstream Versus Downstream Monitors ..K-43 Working Monitors ..K-43 Sizing Monitor regulators ..K-44 VALVE SIZING CALCULATIONSI ntroduction ..K-45 Sizing for Liquid Service ..K-45 Viscosity Corrections ..K-45K-iiTechnicalTable of ContentsKKPredicting Flow Rate ..K-47 Predicting Pressure Drop ..K-47 Flashing and Cavitation ..K-47 Choked Flow ..K-48 Sizing for Gas or Steam Service ..K-51 Universal Gas Sizing Equation ..K-51 General Adaptation for Steam and Vapors ..K-52 Equation Form for Steam Below 1000 psig ..K-52 VACUUM CONTROLV acuum Applications ..K-54 Vacuum Terminology ..K-54 Vacuum Control Devices ..K-54 Vacuum regulators ..K-54 Vacuum Breakers (Relief Valves) ..K-55 Vacuum Regulator Installation Examples ..K-56 Vacuum Breaker Installation Examples.

8 K-57 Gas Blanketing in Vacuum ..K-59 Features of Fisher s Vacuum regulators and BreakersK-59 FREEZINGI ntroduction ..K-60 Reducing Freezing Problems ..K-60 Heat the Gas ..K-60 Antifreeze Solution ..K-60 Equipment Selection ..K-61 System Design ..K-61 Water Removal ..K-61 Summary ..K-61 CHEMICAL COMPATIBILITY OF ELASTOMERS AND METALSI ntroduction ..K-62 Elastomers: Chemical Names and Uses ..K-62 General Properties of Elastomers ..K-63 Fluid Compatibility of Elastomers ..K-64 Compatibility of Metals ..K-65 SULFIDE STRESS CRACKING NACE MR0175 Introduction ..K-67 The Basics of Sulfide Stress Cracking ..K-68 Carbon Steel ..K-69 Cast Iron ..K-69 Stainless Steel ..K-69 Nonferrous Alloys ..K-70 Springs ..K-70 Coatings ..K-70 Stress Relieving ..K-70 Bolting ..K-70 Composition Materials ..K-70 Codes and Standards ..K-71 COLD TEMPERATURE CONSIDERATIONSR egulators Rated for Low Temperatures.

9 K-73 Selection Criteria ..K-73 Low Temperature Fisher regulators ..K-73 POWDER PAINT COATINGI ntroduction ..K-74 Economic Advantages ..K-74 Environmental Advantages ..K-74 Mechanical Properties ..K-75 Corrosion Resistance ..K-75 Regulator TIPSR egulator Tips ..K-76 CONVERSIONS, EQUIVALENTS, AND USEFUL INFORMATIONP ressure Equivalents ..K-78 Pressure Conversion - Pounds per Square Inch(PSI) to Bar ..K-78 Volume Equivalents ..K-78 Volume Rate Equivalents ..K-79 Mass Conversion Pounds to Kilograms ..K-79 Temperature Conversion Formulas ..K-79 Area Equivalents ..K-79 Kinematic-Viscosity Conversion Formulas ..K-79 Conversion Units ..K-80 Other Useful Conversions ..K-80 Converting Volumes of Gas ..K-80 Fractional Inches to Millimeters ..K-81 Length Equivalents ..K-81 Whole Inch-Millimeter Equivalents ..K-81 Metric Prefixes and Symbols.

10 K-81 Greek Alphabet ..K-81K-iiiTechnicalTable of ContentsKKLength Equivalents - Fractional and DecimalInches to Millimeters ..K-82 Temperature Conversions .. and Baum Gravity Tables and Weight Factors ..K-86 Characteristics of the Elements ..K-87 Recommended Standard Specifications for ValveMaterials Pressure-Containing Castings ..K-88 Physical Constants of Hydrocarbons ..K-91 Physical Constants of Various Fluids ..K-92 Properties of Water ..K-94 Properties of Saturated Steam ..K-94 Properties of Saturated Steam Metric Units ..K-97 Properties of Superheated Steam ..K-98 Determine Velocity of Steam in Pipes .. K-101 Recommended Steam Pipe Line Velocities .. K-101 Typical Condensation Rates in Insulated Pipes .. K-101 Typical Condensation Rates without Insulation .. K-101 Flow of Water Through Schedule 40 Steel Pipes .. K-102 Flow of Air Through Schedule 40 Steel Pipes.