ABSTRACT
Introduction 872 Illuminated Rigid Fiber Boroscopes 873 Flexible Illuminated Fiberscopes 873 Special-Purpose Systems 874 Bibliography 874
7.2 Electrical and Intrinsic Safety 875
Introduction 876 Enclosures 876
NEMA Terminology 876 IP Terminology 877
Fuses and Circuit Breakers 877 Grounding 877 Personnel Safety 878 Energy Levels 878
Explosion Hazards 878 NEC Definition of Hazardous Locations 879 IEC Definition of Hazardous Locations 880 Explosions 880
Protection Methods 881 Advantages and Disadvantages of Protection
Methods 881 Safety 881 Cost of the Instrument 881
Cost of Installation 881 Maintenance 882 Flexibility 882
Purging, Pressurization, or Ventilation 882 Air Supply 882 Initial Purging 883 Pressure 883 Alarms and Interlocks 883 Classification of Purging Systems 883
Explosion-Proof Components 883 Intrinsic Safety 884
Energy Levels 884 System Approach 884 Certification of Intrinsic Safety 884
Circuit Analysis 885 Evaluation 885 Construction Review 886
International Regulations 886 Grounding 886 Barriers 886 Cables and Their Installation 886 Terminations 886
References 887 Bibliography 887
7.3 Electrical Meters and Sensors 889
Introduction 890 Analog Measuring Instruments 890
Permanent Magnet Moving Coil Instruments 892
Electronic Components 892 Moving Iron Vane Instruments 893 Electrodynamic Instruments 893 Electrostatic Instruments 893
Digital Measuring Instruments 894 Wattmeters 894
Utilization of Electrical Meters 894 Current Measurement 894
AC Current 894 Current Transformers 896
Primary Turns 896 Secondary Turns 896 Polarity and Inaccuracy 897
Hall Effect Probes 897
DC Current 897 Ammeter Shunts 897 Voltage Measurement 898
AC Voltage 898 Potential Transformers 898
DC Voltage 898 Voltmeter Resistors 899
Power Measurement 899 AC Power 899 Single Element Wattmeters 899 Multielement Wattmeters 900 DC Power 901
Meter Scales 901 References 901 Bibliography 901
7.4 Energy Management Devices (Peak Load Shedding) 903
Introduction 903 Load Shedding Systems 903
Peak Shedding System Costs 904 Electrical Demand 904 Demand Load Shedding 904 Start Signals for Demand Periods 905
Shedding Controls 905 Electromechanical Devices 905 Electronic Demand Limiters 905 Digital Systems 905
Conclusions 906 Bibliography 906
7.5 Excess Flow and Regular Check Valves 908
Introduction 908 Valve Designs 908
Operation 908 Applications 909 Rupture Disc Leakage 909 Gas Station Application 910 Sizing 910 Installation 910 Testing 910
Bibliography 910
7.6 Explosion Suppression and Deluge Systems 912
Introduction 912 Explosion Suppression Systems 912
Explosions 913 Explosion Bomb Test 913
How Suppression Works 913 Explosion Characteristics 914
Suppressant Chemicals 914 Explosion Suppression Hardware 915
Detectors 915 Temperature 915
Infrared Radiation 915 Ultraviolet Radiation 915 Pressure 915
Control Units 916 Actuated Devices 916
Suppressors and Extinguishers 916 Explosive-Actuated Rupture Discs 916 Other Auxiliary Units 917
Applications 917 Ultra-High-Speed Deluge Systems 917
Detectors 917 Control Units 917 Actuated Devices 917
High-Speed Deluge Valve System 918 Pressure-Balanced Nozzle System 918
Applications 918 Bibliography 919
7.7 Flame Arresters, Conservation Vents, and Emergency Vents 920
Introduction 921 Types of Vents 921
Conservation Vents 921 When to Use Conservation Vents 923
Determination of Required Capacity 923 Sizing 924
Emergency Vents 925 Dessicating Vents 925
Flame Arresters 926 Bibliography 927
7.8 Flame, Fire, and Smoke Detectors 928
Introduction 929 Fire and Smoke Detectors 929
Smoke Detectors 929 Ionization Chamber Sensors 929 Photoelectric Sensors 929
Thermal Sensors 929 Flame Sensors 929
Types of Optical Flame Sensors 930 Ultraviolet Detectors 930 Infrared Detectors 931 UV/IR Detectors 931 Dual IR 931 Multispectrum IR 931 Closed Circuit Television 931
Flame Safeguards (Burner Management) 931 Heat Sensors 931 Conduction-Type Detectors 932 Rectification 932
The Rectification Phenomenon 932 Radiation Types 932
Visible Radiation 932 Cadmium-Sulfide Photocell 933 Infrared Radiation 933 Lead-Sulfide Photocell 933
Ultraviolet Radiation 933 Installation 933
Conclusions 934 Flame Guards 934 Optical Fire Detectors 934
Bibliography 935
7.9 Leak Detectors 936
Introduction 937 Aboveground Leak Detection Methods 937
Pressurization or Hydrostatic Testing 937 Using Paints, Dyes, or Bubble Emission 937
Combustible or Toxic Leaks 938 Personnel Alarms 938
Ultrasonic Detectors 938 Thermal Conductivity Detectors 939
Halogen Detectors 939 Other Techniques 940
Loss of Vacuum 940 Thermography 940 Mass Spectrometer 940
Underground Leakage Detection 940 Level Monitoring 940 Soil Detectors 940
Aspirated Sensors 941 Standpipe Detector 942
References 942 Bibliography 942
7.10 Linear and Angular Position Detection 944
Introduction 945 Applications 945 Mounting 945
Sensor Types 945 Potentiometric Sensors 945
Voltage and Current Methods 945 Advantages and Limitations 946
Linear Variable Differential Transformer Type Sensors 946
Magnetostrictive Sensors 946 Hall Effect Sensors 947
Rotary Sensor 948 Transmitters 948
Encoder Type Sensor 948 Transmitter Technologies 949
Analog Transmitters 949 Fieldbus Transmitters 950
Bibliography 950
7.11 Machine Vision Technology 951
Introduction 951 Linear Diode and Linear Charge-Coupled
Device Arrays 952
Example Project 953 Two-Dimensional CCD and Diode Arrays 953
Analog Display Modes 953 Serial Data Transmission 954 Vector Graphics Formats 954
Computer Graphics and Machine Vision 954 References 954
7.12 Metal Detectors 955
Introduction 955 Detector Types 956 Installation on Conveyor Belts 956 Other Applications 956 Bibliography 957
7.13 Noise Sensors 958
Nature of the Measurement 958 Transducer Principles 959
The Inductive Principle 959 The Moving-Conductor Principle 959 Dynamic Microphones 960 Capacitor Microphones 960 Piezoelectric Microphone 960
Microphone Types 960 Ribbon Microphone 960 Diaphragm Microphone 960 Special Microphones 960
Parabolic Reflector Microphone 961 Special Purpose and Ultrasonic Units 961
Microphone Characteristics 961 Sound Sensitivity, Incidence, and Direction 961 Frequency and Amplitude Ranges 962 Hydrophones 962
Environmental Considerations 962 Calibration 963 Reference 963 Bibliography 963
7.14 Proximity Sensors and Limit Switches 964
Introduction 965 Capacitive Sensors 965 Inductive Sensors 966 Magnetic Sensors 967
Hall-Effect Sensors 967 Linear Variable Differential Transformer
Sensors 967 Mechanical Limit Switches 968 Optical Sensors 968
Light Sources 969 Light Detectors 969 Optical Detector Installations 969
Reflective 969 Retroreflective 970
Optical Fibers 970 Pneumatic Sensors 970 Ultrasonic Sensors 970 Digital Outputs and Encoders 971 Applications 971 Bibliography 972
7.15 Relief Valves-Determination of Required Capacity 973
Introduction 973 Applicable Codes and Standards 973
ASME Codes 973 Excerpts from ASME Code 973
UG-125(c) 973 UG-126(b) 974 UG-126(c) 974 UG-126(d) 974 UG-131(d)(1) 974 UG-133(a) 974 UG-133(b) 974 UG-134(d)(1) 974 UG-134(d)(2) 974
API Standards and Recommended Practices 974
NFPA Codes 974 OSHA Codes 975
Causes of Overpressure 975 Substituting for Pressure Relief Devices 975
Fire Protection 975 Gas-Filled Tanks 975 Heat Absorption Across Unwetted Surfaces 975 Low Liquid Inventory Tanks 976 Heat Flux Across Wetted Surfaces 976 Total Heat Absorption 976
API Recommendation 976 NFPA Recommendations 976 Low-Pressure Tanks 977 Free Air Calculation 978
Wetted Area (A) 979 API or NFPA 981 Tank Shape 981 Fire Zone 981 Fire Height 981 Vertical Tanks 981 Horizontal Tanks 982
Environmental Factors 982 API’s Environmental Factors 982 API and NFPA Environmental Factors 982
Calculating the Relieving Capacity 983 Latent Heat of Vaporization 983
Protecting Liquid-Full Tanks 983 Fluids at the Critical Point 983
Nonfire Protection Overpressure 983 Thermal Expansion 984
Set Pressure and Sizing 984 Blocked Outlet Conditions 984
Sizing the PRV 984
Process Equipment Considerations 984 Low-Pressure Storage Tanks 985
Thermal Venting Capacity 985 Heat Exchangers 985
Blocked-In Exchangers 985 Liquid Refrigerants 985 Gas-Fired Tubular Heaters 985 Tube Rupture 985
Pumps and Compressors 986 Sizing 986 Set Pressure 986
Distillation Towers 986 Pipe Headers 986
Bypass Valves 987 Chemical Reactors 987 Discharging the PRVs 987 Discharging to Closed Locations 987
Conclusions 988 Terminology and Nomenclature 988 References 989 Bibliography 990
7.16 Relief Valves-Sizing, Specification, and Installation 991
Introduction 992 The Nature of PRVs 992 The Purpose of PRVs 992 System Integrity and Noise 992 Reliability, Testing, and Redundancy 994 Safety Checklist 994 The Sizing of PRVs 994 Backpressure 994
Superimposed Backpressure 994 Built-Up Backpressure 995 Backpressure Effects 995
Sizing for Vapor and Gas Relief 996 Graphical Method 996 Sizing by Calculation 996 Critical Flow Sizing 997 Subcritical Flow Sizing 999 Backpressure Effect on Capacity 999
Sizing for Steam Relief 999 Sizing for Liquid Relief 1000
Calculating the Discharge Area 1000 Viscosity Correction 1001
Sizing for Flashing Liquid Relief 1001 Special Cases 1002
Specification and Selection 1002 Conventional PRVs 1004
PRV Bodies and Bonnets 1004 Seat and Spring 1005 Nozzles and Blowdown Rings 1005 Pop Action 1005 Valve Lift and Capacity 1005
Balanced PRVs 1005 Pilot-Operated PRVs 1005
Integral or External Pilot 1007
Advantages 1007 Disadvantages 1007 Modulating Pilot-Operated Valves 1008 When to Consider Pilot-Operated
PRVs 1008 Specification and Selection Checklist 1009
PRV Operation and Performance 1010 Blowdown 1010
Setting the Blowdown 1010 PRV Chatter 1011
Chatter and Inlet Line Loss in POPRVs 1011 Chatter on Liquid Service 1011
PRV Tightness and Leakage 1011 Using Two PRVs 1011 Seat Designs, O-Rings,
and Temperature 1012 Flatness and Cleanliness 1013
PRV Installation 1014 PRV Location 1014 PRV Mounting 1014 PRV Inlet Piping 1014 PRV Outlet Piping 1014
Calculating the Reaction Force 1015 PRV Block Valves 1015 Multiple PRVs 1015 Spare PRVs 1015
Test, Inspection, and Audit 1015 PRV Testing 1016 PRV Inspection 1016 PRV Audit 1016
References 1016 Bibliography 1016
7.17 Rupture Discs 1018
Introduction 1018 Definitions 1018 Code Requirements 1019 Rupture Discs vs. Relief Valves 1019 When to Use a Rupture Disc 1020
As a Primary or Sole Relief Device 1020 As a Supplemental Relieving Device 1020 Upstream of a Relief Valve 1021 Downstream of a Relief Valve 1021 Explosion Relief 1022
Rupture Disc Types and Features 1022 Nonfragmenting Discs 1022 Graphite Discs 1022 Vacuum Supports 1023 Back-Pressure 1023 Margin between Operating and Burst
Pressures 1023 Dual Discs or Back-Pressure Loading 1024 Special Applications 1024
Pressure Cycling and Water Hammer 1024 Two-Way Relief 1024 Self-Cleaning and Corrosive Services 1024 Explosive Actuated Vents 1025
Selection and Specification 1025 Material Selection 1026 Burst Pressure and Manufacturing Range 1026
Operating Ratio 1027 Minimum Burst Pressure 1027
Disc Holders and Accessories 1027 Accessories 1028
Sizing 1028 Differences in Assumptions and
Standards 1028 Coefficient of Discharge Method 1028 Resistance Method 1029 Combination Capacity Method 1029
Bibliography 1029
7.18 Soft Sensors 1030
Introduction 1030 Flow from Level 1030 Mass Flow from Pressure and
∆
P 1030 Flow from Pump Speed and Power 1030 The Role of Networks 1031
Reasons for Using Soft Sensors 1031 Application Examples 1031
Detection of Instrument Failure 1031 Using Redundant Instruments to
Advantage 1031 Sensorless Flux Vector Control 1032 Viscosity Control in Rubber Blending 1032
Determination of Errors 1032 Combining Instrument Errors 1032
General Expression for the Error 1032 Implementing the Error Calculation 1033 Digital Calculation Errors 1033
Digital Signal Processing 1033 Time Delay 1034
Implementation Considerations 1034 Integrators and Low-Pass Filters 1034 Low-Pass Filters 1034
Implementation Considerations 1034 Integrators 1035
Implementation Considerations 1036 Differentiators and High-Pass Filters 1036
Interpolation and Predictive Filters 1036 References 1037
7.19 Tachometers and Angular Speed Detectors 1038
Introduction 1039 Handheld Tachometers 1039 Tachometer Operating Principles 1039
Impulse Tachometers 1039 Optical Encoders 1040 Photoelectric Sensors 1040
Noncontacting Optical Tachometers 1040 Stroboscopic Tachometers 1041
Fiber-Optic Stroboscopes 1041 AC Tachometers 1041
DC Tachometer 1041 Induction Sensors 1041 Magnetic Sensors 1041
Inductive Sensors 1041 Hall Effect Sensor 1042 Magnetoresistive and Variable Reluctance
Sensors 1043 Pneumatic Speed Transmitter 1043
Speed Switches 1043 Conclusions 1044 Bibliography 1044
7.20 Thickness and Dimension Measurement 1045
Introduction 1046 Dimension Measurement 1046
Automated Gauging Machines 1046 Thickness Gauging 1046
Contacting Gauges 1047 Ultrasonic Thickness Gauging 1047
Noncontacting Gauges 1048 Capacitance Gauges 1048 Laser Gauging 1049 Optical Micrometer and
Interferometers 1049 Radiation Type Thickness Gauges 1049 Coating Thickness Detection
by Radiation 1050 Bibliography 1050
7.21 Torque and Force Transducers 1051
Force Measurement 1052 Measurement Principles 1052 Mechanical Dynamometers: Load Cells 1052
Sensing Elements 1053 Strain Gauges 1053
Piezoelectric Dynamometers 1054 Torque Measurement 1055 Rotating Transducers 1055
Direct Contact 1056 Inductive Coupling 1056
Stationary Transducers 1057 Magnetostrictive Torque Transducer 1057 Angular Displacement Type Torque
Transducers 1058 Conclusions about Torque Transducers 1058
Test Gauges and Test Stands 1058 References 1059 Bibliography 1059
7.22 Vibration, Shock, and Acceleration 1061
Introduction 1062 Acceleration as a Phenomenon
and Dynamic Characteristics 1063 Vibration and Shock 1064
Periodic Vibrations 1065 Stationary Random Vibrations 1065 Nonstationary Random Vibrations 1065 Transients and Shocks 1065
Seismic (Inertial) Sensors 1065 Piezoelectric Sensors 1067
Piezoresistive and Strain Gauge Sensors 1068 Piezoresistive Sensors 1068 Strain-Gauge Sensors 1069
Electromechanical Sensors 1070 Coil-and-Magnetic Accelerometers 1070 Induction Accelerometers 1070
Capacitive and Electrostatic Sensors 1071 Electrostatic-Force-Feedback
Accelerometers 1071 Capacitive Accelerometers 1072
Micro-and Nanosensors 1073 Velocity Sensors 1074 Noncontact or Proximity Sensors 1075 Mechanical-Magnetic Switches 1075 Optical Sensors 1075 Conclusions 1076 Reference 1076 Bibliography 1076
7.23 Weather Stations 1077
Introduction 1078 Meteorological Station 1078 Solar Radiation Measurement 1078
Historical Background 1078 Multijunction Thermopile 1079 Photovoltaic Cells 1079 Thermal Radiometers 1079 Pyrheliometers 1079
Wind Direction and Speed 1079 Wind Direction 1079 Wind Speed 1080
Rain Gauges 1080 Barometric Pressure Gauges 1081 Air Temperature Detection 1081 Dew Point and Relative Humidity Sensors 1081 Sensor Accessories 1081
Readouts 1081 Locations 1081 Instrument Shelters 1082
Bibliography 1082
7.24 Weighing Systems: General Considerations 1084
Introduction 1084 Weighing Glossary 1084
What is Weighing? 1086 Force and Weight 1087 Historical Considerations 1087 Advantages of Weighing 1087
Weighing Applications 1088
Weighing System Specification 1088 Weighing vs. Metering 1090 Bulk Weighing 1090 Weighing Platforms 1090
Weighing Platform Transducers 1090 Beam-Type Platforms 1091 Portable Platform Scales 1092
Truck, Monorail, and Railway Scales 1092 Truck Scales 1092 Treadle Scales 1092 Monorail Weighing Transducer 1092
Types of Weighing Systems 1093 Mechanical Lever Scales 1093 Spring-Balance Scales 1093 Load Cell Weighing 1093
Factors Influencing Performance 1094 Temperature Effects 1094
Mechanical Lever Scales 1094 Load Cell Weighing Systems 1094 Electronic Load Cells 1094 Hydraulic Load Cells 1094 Pneumatic Load Cells 1094
Errors Caused by Vibration 1094 Errors Caused by Ambient Conditions 1095 Maintenance Requirements 1095 Installation Requirements 1095
Vessel Stabilization 1095 Stabilizing Devices 1095 Piping Connections 1096 Types of Vertical Forces 1096 Spring Rates of Pipes 1098
Flexible Connections 1099 Calibration 1099
Bibliography 1100
7.25 Weight Sensors 1101
Introduction 1103 Load Cell Selection 1103
Selection Factors 1104 Mode of Loading: Tension or
Compression 1104 Ambient Temperature 1105 Lateral Restraints 1105 Structure Vibrations 1105
Number of Load Cells 1105 Capacity and Type 1106
Load Cell Types 1106 Classes of Load Cells 1106
Load Cell Installation 1106 Load Cell Adapter 1107 Rocker Assembly 1108 Vessel Expansion 1108
I-Beam Flexure 1109 Expansion Assemblies 1109
Mechanical Lever Scales 1109 Balancing Devices 1109
Scale Ranges 1110 Applications 1110
Gravimetric Feeders 1110 Batch Additives 1110 Output Signals 1110
Advantages and Limitations 1110 Hydraulic Load Cells 1111
The Rolling Diaphragm Design 1111 Performance 1111
All Metal Design 1111 Hydraulic Totalizers 1112
Electronic Totalizers 1112 Other Features 1112
Pneumatic Load Cells 1112 Electronic Load Cells 1113 Strain-Gauge-Type Load Cells 1113
Operating Principle 1113 Design Variations 1114
Bending or Cantilever Elements 1114 Beam-Type Load Cells 1114 Shear Elements 1115 Direct Stress or Column-Type
Elements 1115 Transducer Design 1116
Strain Gauge Backings and Bonding 1116 Strain Gauge Circuits 1116 Performance of Strain Gauge Load Cells 1117
Other Load Cell Designs 1117 Semiconductor Strain Gauge 1117 Nuclear Radiation Sensors 1117 Inductive Sensing 1118 Variable Reluctance Sensing 1118 Inductive and Reluctance Load Cells 1119 Magnetostrictive Sensing 1119
Magnetostrictive Load Cells 1119 Linearization of Load Cells 1120 Load Cell Housings and Safety 1120
Intrinsic Safety 1121 Special Application 1121
High Temperature Load Cells 1121 Weighing of Tank Legs 1121
Developing New Sensors 1121 New Load Cells 1122
Thin-Film Strain Gauges 1122 Hydraulically Damped Load
Cells 1123 Microprocessors and Networks 1123
Interfacing with Programmable Logic Controllers 1123
The Role of the Personal Computers 1123 Verified Weighing with PCs 1123 Networks and Buses 1123
Calibration and Testing 1124 Aircraft Weighing 1124 Packaging Industry 1125
References 1125 Bibliography 1126
INTRODUCTION
Boroscopes (also spelled borescopes) are visual inspection tools providing high image quality. They were originally designed for inspecting gun barrels, but currently have many applications in modern technology. They are used to inspect
remote or limited access locations, such as drill holes, vessels and chambers, chemical reactors, heat exchangers, process lines, and much more. Illuminated boroscopes and fiberscopes provide bright, sharp images for visual observations and are camera-adaptable for permanent record keeping. They enable critical internal inspections with speed, safety,
and certainty in the field or on the factory floor. Table 7.1a gives a partial list of applications that speed testing, inspection, and quality control.
