ISA Seminars on the Web Live Experts on Hot Topics Standards Certification Education and Training Publishing Conferences and Exhibits CSE PE Exam Review: Measurement II EN00W3 Version 1.4 2011 Standards Certification Education and Training Publishing Conferences and Exhibits 1
Seminar Logistics Seminar materials Downloadable presentation Question and Answer session (audio and email) Survey Earn 1 Professional Development Hour (PDH) Seminar length 60 minute presentation Three 10-minute question and answer sessions Audio Instructions As a participant, you are in a listen-only mode. You may ask questions via the internet, using your keyboard, at any time during the presentation. However, the presenter may decide to wait to answer your question until the next Q&A Session. If you have audio difficulties, press *0. 2
Audio Instructions for Q&A Sessions Questions may be asked via your telephone line. Press the *1 key on your telephone key-pad. If there are no other callers on the line, the operator will announce your name and affiliation to the audience and then ask for your question. If other participants are asking questions, you will be placed into a queue until you are first in line. While in the queue, you will be in a listen-only mode until the operator indicates that your phone has been activated. The operator will announce your name and affiliation and then ask for your question. Introduction of Presenter Gerald Wilbanks, P.E. Vice President of Documentation and Engineering Services in Birmingham, Alabama has over 40 years of experience in engineering, management, consulting, and design in heavy industry. He is a registered professional engineer in 4 states, a member of NSPE, ASQ, and an International Former President (1995) of ISA. Gerald is a graduate of Mississippi State University with a Bachelors Degree in Electrical Engineering and was recognized as the Engineer of the Year in 1991 by the Engineering Council of Birmingham. He is a Distinguished Engineering Fellow of Mississippi State University and is a Life Fellow member of ISA. He has served as an instructor in many courses, seminars, and other educational sessions for ISA and in his own business. 3
Key Benefits of Seminar Improve study effectiveness to assist in passing the PE exam Identify flow measurement types and selection Determine best measurement practices for level Recognize temperature measurement devices and applications Level, flow, and temperature measurement (Domain I) represents 12 questions or about 15% of the CSE PE exam. Section 1: Flow Measurement Basic Terminology Units of Measurement Flow Characteristics Classifying Fluid Flow Measurement Sizing and Selection Applications Installation 4
Fluid Dynamics The Darcy formula, also known as the general formula for pressure drop is: where h is the pressure drop in feet of fluid Notation: g = acceleration of gravity (32.2 ft /sec 2) f = the fanning friction factor D = inside diameter of the pipe V = velocity of fluid L = Length of Pipe Flow Units The measurement unit to express the rate of flow refers to the velocity of the flow. A flow rate is a measure of the distance a particle of a substance moves in a given period of time. Feet per second is a unit commonly used to express velocity. Q = AV Where: Q = the volumetric flow rate A = the area of the pipe V = the fluid velocity Q = 3.12 AV Where: Q = Gallons per Minute A = Square Inches V = Feet per Second 5
Volumetric Flow Rate The method of measurement used to indicate the volume of fluid that passes a point over a period of time is volumetric flow rate. Volumetric flow rate is usually expressed in gallons per minute (GPM) for liquids or cubic feet per hour for gases. Mass Flow Rate Mass flow rate determines the amount of mass that passes a specific point over a period of time. Mass flow rate applications determine the weight or mass of the substance flowing through the system. 6
Reynolds Numbers The performance of flowmeters is also influenced by a dimensionless unit called the Reynolds Number. It is defined as the ratio of the liquid's inertial forces to its drag forces. Flow Characteristics Laminar and turbulent flow are two types normally encountered in liquid flow measurement operations. The Reynolds Number equation is: where: Re = Pipe Reynolds number Q = liquid's flow rate, gpm G = liquid's specific gravity D = inside pipe diameter, in. µ = liquid's viscosity, cp 7
Flow Type Determination When the Reynolds number is less than 2000, flow is in the laminar region. When the Reynolds number is greater than 4000, flow is considered to be in the turbulent region. This is the desired condition for most flow measurement devices and technology. When the Reynolds number is in the range of 2000 to 4000, flow is transitional. Viscosity is the factor which most affects the value of the Reynolds number. Classifying Fluid Flow Measurement Volumetric Positive Displacement (gallons per minute, cubic feet per minute, liters per minute, etc.) Mass Coriolis Mass (pounds per hour, kilograms per hour, etc.) Velocity Magnetic Oscillatory Turbine Ultrasonic Inferential Differential Pressure Target Variable Area 8
Differential Pressure (DP) DP flowmeters can be used to measure volumetric flow rate of most liquids, gases, and vapors, including steam. DP flowmeters have no moving parts and are easy to use. They create a nonrecoverable pressure loss and lose accuracy when fouled. Flow measurement accuracy depends on accuracy of the pressure measuring device. Differential Pressure Flowmeters Bore = d Orifice Plate Pipe ID = D 9
DP Flowmeter Elements Pressure Profile Bore = d (inches) Orifice Plate The Orifice Plate is the most common differential pressure flow primary element. It is based on proven technology, has no moving parts and is suitable for high temperature and pressure applications. Orifice plates are recommended for clean liquids, gases and low velocity steam flows. They are often chosen for their low initial cost, simplicity of construction and ease of installation. 10
Concentric Orifice D d PIPE UPSTREAM FACE THICKNESS OF THE PLATE DOWNSTREAM FACE (A) β = d D FLOW D d THICKNESS OF THE ORIFICE UPSTREAM EDGE DOWNSTREAM EDGES N OTE: UPSTREAM EDGE VISUALLY DOES NOT REFLECT A BEAM OF LIGHT. (B) Orifice Taps *RADIUS TAPS* D D/2 The upstream tap for pressure is one pipe diameter from the orifice plate face and the downstream tap is one half pipe diameter.. [Above 6 inch lines] 11
Orifice Taps * FLANGE TAPS* The pressure taps are drilled into the orifice flange (300# due to dimensional requirements). [8 INCH LINES AND SMALLER] Orifice Taps *PIPE TAPS* 2½ D 8 D The pressure taps are located 2½ pipe diameters upstream and 8 diameters downstream from the orifice plate. 12
Plant Equation for Orifice Plates S = * LIQUID * Qm Gb N D 2 Gf hm Calculate S value and refer to the table in the Spink book (use Summary of Equations) for the type of taps used and determine the Beta Ratio. The Beta Ratio can then be used to calculate the orifice bore. d = Beta Ratio (Pipe ID) Orifice Flow Meter Terminology Beta Ratio (B) = d/d (0..25 TO 0.75) d = Orifice Bore (inches) D = Inside diameter of pipe (inches) FLOW RATE (Qm) = GPM Specific Gravity (Gf) @ Flowing Temperature Specific Gravity (Gb) @ 60 degrees f Unit Constant (N) = 5.667 FOR GPM Differential (hm) = PRESSURE DROP (inches water) S = Orifice Ratio (Empirical from test data and can be found in the L.K. Spink book on Flow Meter Engineering) 13
Liquid Flow Alternate Equation Where: Q = GPM h = differential in ft. of liquid C =discharge coefficient (.61 for sharp edge orifice) Fa = area factor for thermal expansion D = inside diameter of pipe Plant Equation * STEAM or Gas* S = 359 D 2 W Sw hm Where: Sw = Specific Weight for steam or gas (at temp and pressure) W =Flow in pounds per hour Calculate S value and go to the appropriate table in the Spink book (Summary of Equations) to determine the Beta Ratio. 14
Flow Nozzle Venturi Tube 15
Pitot Tubes STATIC PRESSURE IMPACT PRESSURE STAGNATION POINT INDEPENDENT STATIC TAP IMPACT PRESSURE STATIC PRESSURE COMBINED STATIC AND IMPACT TAPS Methods That Measure Velocity Volumetric Positive Displacement Mass Coriolis Mass (gallons per minute, cubic feet per minute, liters per minute, etc.) (pounds per hour, kilograms per hour, etc.) Velocity Magnetic Oscillatory Turbine Ultrasonic Inferential Differential Pressure Target Variable Area 16
Magnetic Flowmeter ELECTRIC FIELD, E SENSING ELECTRODE FIELD COILS PROCESS PIPE INNER DIAMETER, D CONDUCTIVE PROCESS FLUID FLOW, V MAGNETIC FIELD, B MAGNETIC FIELD Magmeter Application Liquids, Slurries, and Suspended Solids Meter Must Be Full Flowing Material must have a Dielectric Value Minimum Straight Run Requirements Grounding considerations 17
Vortex Shedding The frequency of vortices shed from a bluff body placed in the flow stream is proportional to the velocity of the fluid. Velocity times area gives the volumetric flow rate. Vortex flowmeters provide good measurement accuracy with liquids, gases, or steam. They have no moving parts and are fouling tolerant. Vortex meters can be sensitive to pipeline noise and require flow rates high enough to generate vortices. Vortex Shedding Phenomenon 18
Ultrasonic Flowmeter Principles Principle of operation Doppler Time of flight Construction Clamp-on transducer Wetted transducer Applications Large pipes (cost) Flashing fluids Corrosive fluids Hazardous fluids Non-coating service Time of Flight Operation 19
Doppler Effect TRANSMIT SIGNAL TRANSMIT ZONE OF REFLECTION IN STABLE VELOCITY REGION VF FLOW PROFILE RECEIVE Turbine Meter Fluid passing through a turbine flowmeter spins a rotor. The rotational speed of the rotor is related to the velocity of the fluid. Multiplying the velocity times the cross-sectional area of the turbine provides the volumetric flow rate. 20
Methods That Measure Mass Volumetric Positive Displacement Mass Coriolis Mass (gallons per minute, cubic feet per minute, liters per minute, etc.) Velocity Magnetic Oscillatory Turbine Ultrasonic Inferential Differential Pressure Target Variable Area Coriolis Mass Flowmeter FLOW FLUID FORCE FLOW VIBRATING FLOW TUBE FLUID FORCE FLUID FORCES REACTING TO VIBRATION OF FLOW TUBE TWIST ANGLE TWIST ANGLE END VIEW OF FLOW TUBE SHOWING TWIST 21
Coriolis Flowmeter High accuracy (± 0.1%) Multivariable measurement Low maintenance requirements High turn-down ratio (100:1) Non-intrusive design Applications include: Oil Field Service, and cement measurement Well Performance Measurement Net Oil/Water Cut Computation Leased Automatic Custody Transfer Custody Transfer Density and Viscosity measurement Positive Displacement Flowmeters Volumetric Positive Displacement Mass Coriolis Mass (gallons per minute, cubic feet per minute, liters per minute, etc.) (pounds per hour, kilograms per hour, etc.) Velocity Magnetic Oscillatory Turbine Ultrasonic Inferential Differential Pressure Target Variable Area 22
Positive Displacement (PD) PD flowmeters measure the volumetric flow rate of a liquid or gas by separating the flow stream into known volumes and counting them over time. Vanes, gears, pistons, or diaphragms are used to separate the fluid. PD flowmeters provide good to excellent accuracy and are one of only a few technologies that can be used to measure viscous liquids. Positive Displacement Meters are the only device that directly measures volumetric flow. However, they create a nonrecoverable pressure loss and have moving parts subject to wear. Rotary Vane Design 23
Straight Pipe Diameter Requirements Flow Installation Rules of Thumb Up-stream Down-stream Magnetic meter 5 2 Mass flow meter 1 1 Vortex meter 25 10 Turbine meter 15 10 Orifice plate 10 5 (Beta =.5) Orifice plate 15 5 (Beta =.7) Flowmeter Selection 24
Liquid or Steam Flowmeter DP Transmitter Air or Gas Flowmeter DP Transmitter Pressure Transmitter 25
Review of Key Points There are many ways to measure flow and application is the key to success Inferential flow measurement is a physical parameter is measured and another value is inferred from it Differential Pressure is economical, simple and practical with limitations in accuracy and application Straight runs of both upstream and downstream pipe are needed for all types of devices Volumetric flow is the normal measured variable There are new state of the art devices in use Be familiar with installation requirements Exam items will probably include application selections Live Question and Answer Session During Q&A, questions may be asked via your telephone line. Press the *1 key on your telephone key-pad. If there are no other callers on the line, the operator will announce your name and affiliation to the audience and then ask for your question. If other participants are asking questions, you will be placed into a queue until you are first in line. While in the queue, you will be in a listen-only mode until the operator indicates that your phone has been activated. The operator will announce your name and affiliation and then ask for your question. 26
Section 2: Level Measurement Basic Definitions Principles of Measurement Units Applications Installation Considerations Level / Inventory Measurement 27
Level Measurement Techniques Differential Pressure (Hydraulic Head) Capacitance Probes Ultrasonic Radar Floats and Displacers Nuclear Radiation Rotating Paddle Gauge Glass Capacitance Probe 28
Float and Cable Arrangements SCALE WEIGHT FLOAT Ultrasonic Measurement GENERATOR and TRANSMITTER TIMING GENERATOR LOGIC and DISPLAY RECEIVER and AMPLIFIER TRANSDUCERS TIMED GAIN CONTROL WAVE SHAPING TRANSMITTED BURST RECEIVED BURST (ECHO) OBJECT BEING SENSED ELAPSED TIME PROPORTIONAL TO DISTANCE 29
Radar Air Bubble System (Rotameter) 30
Magnetostriction The electric current pulses in the waveguide cause a torsional strain in the waveguide at the intersection of the magnetic field and the permanent magnet. The torsional pulse travels in both directions along the waveguide. Electronic circuitry convert the time of travel to level. Factors to Consider Vessel Dimensions Specific Gravity Pressure Pascal s Law Boyle s Law Charles Law Type of Material 31
Basis of Selection Conversion Factors 2.31 feet of Water = 1 PSI 27.7 inches of Water = 1 PSI 13.6 inches of Water = 1 inch of Mercury.49 PSI = 1 inch of Mercury 8.33 lbs = 1 gallon of water @ 60 degrees F 7.48 gallons = 1 cubic foot of liquid 62.4 lbs = 1 cubic foot of water @ 60 degrees F 32
Flanged Mounted Level Vented Tank No low pressure connection is needed Transmitter Tank Mounted Level T01 Distance Between Taps Liquid S.G. Location of Transmitter Differential Pressure Transmitter 33
Span and Range Calculation Practice System A System B Maximum Maximum 20 In. Sp. Gr. 1.2 20 In. Sp. Gr. 2 Minimum H L Minimum Vent 2 In. H L System C Vent 20 In. Maximum H20 Wet Leg Sp. Gr. 2 Minimum H L Review of Key Points Level is one of the key primary variables in process control Applications vary according to the physical conditions of the vessel or tank Installation considerations include coating, fouling, and interference with insertion devices Care must be exercised in applying external transmission type devices 34
Live Question and Answer Session During Q&A, questions may be asked via your telephone line. Press the *1 key on your telephone key-pad. If there are no other callers on the line, the operator will announce your name and affiliation to the audience and then ask for your question. If other participants are asking questions, you will be placed into a queue until you are first in line. While in the queue, you will be in a listen-only mode until the operator indicates that your phone has been activated. The operator will announce your name and affiliation and then ask for your question. Section 3: Temperature Measurement Thermometers Bimetallic elements Thermocouples RTDs Thermistors Radiation Pyrometers 35
Temperature Scales Bimetallic Thermometer 36
Thermocouples T1 T2 MEASURING JUNCTION REFERENCE JUNCTION THERMOCOUPLE INSTRUMENT MEASURING JUNCTION REFERENCE JUNCTION Standard Thermocouple Materials 37
Standard Thermocouple Materials (cont d) Standard Thermocouple Extension Leads Thermocouple Measuring Junction + - Connection Head Extension Wires Instrument + - Reference Junction ISA Type Extension Wire Color Code Temperature Range?F Limits of Error Couple Used With TX Copperconstantan + (blue) - (red) -75 to +200 ±1 1/2 F Copper constantan JX Ironconstantan + (white) - (red) 0 to 400 ±4 F Ironconstantan WX Ironcupronel + (green) - (red) 75 to 400 ±6 F Chromelalumel KX Chromelalumel + (yellow) - (red) 75 to 400 ±4 F Chromelalumel SX Copper- CuNi alloy + (black) - (red) 75 to 400 ±10 F Platinum Rhodiumplatinum 38
Typical Thermocouple Assembly RTD - Resistance Temperature Detectors RTD IN A CUTAWAY VIEW SHOWING MEASURING ELEMENT PLATINUM LEADS RESISTANCE ELEMENT 39
Basic RTD Circuit (2 Wire) EXCITATION Ra R c OUTPUT LEAD RESISTANCE RTD Rb Variable Resistance 3 Wire Circuit EXCITATION R a R c LEAD RESISTANCE OUTPUT RTD Variable Resistance R b 40
Thermistors Electrical resistance of material varies greatly with temperature Limited spans, low cost High accuracy and stability Limited to low-medium temps Sensor Comparison 41
Element Selection Quick Selection Guidelines RTDs: Offer stable output within broad temperature ranges; Can be recalibrated for verifiable accuracy; Are stable over the long term; Follow a more linear curve than thermocouples; Have high sensitivity; and Provide accurate reading over narrow temperature spans. Thermocouples: Operate at temperatures over 1,200 F (648.88 C); Perform in extremely rugged applications; Offer very fast response to temperature changes; Are small in physical size; and May have a lower initial cost in some applications. Radiation Pyrometers A. IDEAL CONDITIONS TARGET SENSING HEAD TRANSMISSION PATH IRCON Head RADIATION EMITTED FROM TARGET B. REAL CONDITIONS PARTICLES, GASES IRCON Head FLAMES STEAM, SMOKE SOLID OBSTRUCTION 42
Review of Key Points Temperature can be expressed in several different scales There are time lags involved with temperature measurement. Application considerations include fluid properties, corrosion, fluid velocity, accuracy required, and control requirements Thermocouples and Resistance Temperature Detectors are two of the primary types of temperature determination. Live Question and Answer Session During Q&A, questions may be asked via your telephone line. Press the *1 key on your telephone key-pad. If there are no other callers on the line, the operator will announce your name and affiliation to the audience and then ask for your question. If other participants are asking questions, you will be placed into a queue until you are first in line. While in the queue, you will be in a listen-only mode until the operator indicates that your phone has been activated. The operator will announce your name and affiliation and then ask for your question. 43
How Many People Are at Your Site? Poll Slide Click on the appropriate number indicating the number of people that are at your site. Sample Exam Question - #1 A tank level is measured using a differential pressure transmitter and a bubbler tube. The tank is vented to atmosphere. The bubbler tube is 1 foot from the bottom of the tank and the tank wall is 20 feet high. A 0-10 psig differential pressure gauge, accurate to.25 per cent of full scale is connected to the bubbler tube connection at the high side of the transmitter. The low pressure side is connected to the tank top. With the tank containing liquid with a specific gravity of 1.2 and the level in the tank at 14 feet, the gauge reading in pounds per square inch (psi) is most nearly equal to: A. 7.8 B. 9.35 C. 13 D. 6.8 44
Sample Exam Question - #2 Assume the output from a thermocouple is linear with temperature from 0 degrees F to 300 degrees F and the element generates the following voltage: 212 degrees F 9.0 mv 50 degrees F 0.9 mv If the thermocouple voltage is 1.9 mv, the temperature indicator reading (in degrees F) should be: A. 20 B. 38 C. 70 D. 88 Sample Exam Question #3 To measure the level of a liquid with a dielectric constant greater than 2 in a horizontal vessel with changing composition and temperature, the device with the BEST reproducibility is a: a. Guided Wave Radar level detector b. Ultrasonic level detector c. Capacitance level detector d. Differential pressure transmitter 45
Sample Question - #4 Which of the following flow meters can be used to directly measure the volumetric flow rate of a fluid? A. Differential Pressure B. Magnetic C. Positive Displacement D. Turbine E. Vortex Shedding Sample Question - #5 The flow of water in a 4-inch pipe is measured with an orifice plate and differential pressure transmitter. At a flow rate of 120 GPM, the differential pressure is 27 inches of water. At a flow rate of 176 GPM, the differential pressure will be approximately equal to: A. 12 wc B. 18 wc C. 58 wc D. 68 wc 46
Related Courses from ISA Industrial Flow Meter Engineering (EI10) Overview of FOUNDATION Fieldbus Technology (FG25C) All ISA courses are available any time as on-site training For more information: www.isa.org/training or (919) 549-8411 Other Related Resources from ISA Flow of Fluids Crane Technical Paper 410 Instrument Engineers Handbook, 3 rd Edition Process Measurement & Analysis (Bela Liptak) Flow Measurement Engineering Handbook (R.W. Miller) McGraw Hill Publishing The ISA5.4-1991 Instrument Loop Diagrams standard National Electric Code Handbook - NFPA 47
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