ContentsDefinition of instrumentation & Process Control P&IDs & Instrument symbols Process Measurement n Transducer (Temperature-Pressure- Flow-Level) n Transmitting and Switching Elements Definition of Instrumentation & Process Control System Instrumentation: n A collection of instruments for the purpose of observation, measurement, protection or control. Process Control n Regulation or manipulation of variable influencing the process to achieve desire quantity/quality in an efficient manner Block Diagram of Process Control Loop Measuremen t Controller Final Control Element Process Set Point P&ID and Instrument Symbols P&ID stands for Piping & Instrumentation Diagram n Definition:diagram where it will show the process piping and instrumentation connections with Process tanks and vessels, reactors, exchangers, …etc. in order to produce particular product or perform specific task. n The P&IDs contains detail connections for the instrumentations where defined by graphical symbols and identification letters. Instrumentation Identification Example of instrument Identification n FIC4003 (Flow indication and Control) n FI4002 (Flow Indication) n FT4003 (Flow Transmitter) n FV4003 (Flow Control Valve) n PIC4002 (Pressure Indication and Control) n PV4002 (Pressure Control Valve) n PDSL1234 (Pressure Differential Switch Low) Control Loops FT-1 FV-1 FIC 1 SV PV MV FE-1 FY 1 Vent AFC FSL 1 IA i Process Measurement In this lecture we will cover the measurement instruments: n Temperature Elements n Pressure Elements n Flow Elements n Level Elements I. Temperature Definition: n It is the Degree of Coldness or hotness or in other word related to the kinetic energy of molecules. n Temperature generated by heat energy. n Heat energy has unit of BTU (Brithish Thermal Unit) or Calorie Temperature (Cont.) Units: n Fahrenheit (ºF), Centigrade (Celsius) ºC, Kelvin ºK, Ranklin ºR F= 5/9 x C + 32 C= 9/5 (F-32) K= 273.15 + C R= 459.7 +F Temperature (Cont.) ºF ºC ºK ºR -459.7 32 212 -273.15 0 100 0 273.15 373.15 0 459.7 671.7 Water Freezing Water Boiling Absolute zero Temperature (Measurement) n Thermocouple: Consists of two dissimilar metals joined at one end and other end connected to meter. When joined end (Hot junction) heated, voltage will be produced at the other end (Cold Junction). Temperature (Measurement) Temperature (Measurement) Resistance Temperature Detector (RTD) n Heat Sensitive element prepared with carefully made electric resistance. n Used material: Platinum, Nickel, Iron, Salver w In our plant most of RTDs used are Pt100 platinum resistance= 100 ohm at 0 degree C n As temperature rises, resistance increases. Temperature (Measurement) Thermostor: n Very small Solid thermo-electric devise made of solid semiconductor of various metal oxides. n The electric resistance of thermostor decrease with an increase in temperature. II. Pressure Definition: n Defined as the normal force per unit area acting on surface of an object. n P=F/A Units: n Pa, psi, inches of mercury, inches of water, BAR, atm, Kg/cm2 Pressure (Cont.) Scale of measurement: n Gauge Pressure Scale n Absolute Pressure Scale n Vacuum Pressure Scale Pg= Pa - Atmospheric Pressure Pressure (Cont.) vacuum Gage pre.Range Barometric Atm.Range Zero gauge Zero (Absolute) Abs. Pressure Pressure (Measurement) Manometers: n Used for the direct measurement of pressure and vacuum. n U-Tube Manometer w A glass of U- tube shape, partially filled with liquid. w The zero is connected to the scale when both ends of the U-glass opened to atmosphere. P1 P2 h U-Tube Manometer Pressure (Measurement) n U-Tube Manometer (Cont.) w When applied pressure at one end of the tube, difference in level will occur: w P2-P1=p. n p : Arvoitv (iþ/iv3) n : nriynt (iv) H2H1: Hprooupr (roiy) Hprooupr (Mroouprµrvt) n Well Manometer (Single Leg): w Used for low pressure application with higher accuracy from the U-Manometer. w P2-P1= p (1+A1/A2) n P1 P2 h zero line A2 A1 Pressure (Measurement) n Iv)iivrôTuþr Movoµrtrp w Yorô oop rctprµr iou rprooupr orrii)otiov w H2H1· p (1+A1/A2) A. oiv o P1 P2 zero line A2 A1 h L Pressure (Measurement) Pressure Element n Mechanical devices changed its shape when pressure is applied n The pressure elements sometimes called elastic deformation pressure element n Each type has its range of operation pressure. Pressure (Measurement) Pressure (Measurement) Pressure Transducers n Elastic deformation element joined to electrical device. n Changes in resistance, inductance, or capacitance Pressure (Measurement) Strain Gauge: n Fine wire in form of grid. n When the grid distorted, resistance of the wire will change according to: R=K. L/A K : Resistively of the metal L : Length of wire A : Cross sectional Area Pressure (Measurement) Grid Wire Ceramic or paper backing Lead wires Strain Gage Pressure (Measurement) Strain Gage (Cont.) n As Strain Gage is distorted by the elastic deformation length will increase and area will reduced. n Resistance will increase accordingly. Pressure (Measurement) Inductance Type n Consists of Coil, Movable Magnet core, and elastic deformation element. n AC current pass through coil. n As the pressure varies the elastic deformation, the magnet core will move through the coil. n This will change the inductance. Pressure (Measurement) Movable Iron Core Coil Non Conductive Tube Capacitance Type n Consists of two conductive plates, dielectric, and diaphragm. n As the pressure increases diaphragm will move the plate changing the capacitance. Pressure (Measurement) Pressure (Measurement) Flow (Measurement) Flow rate and flow quantity of materials is made primarily for determining the proportions of materials introduced to the process. Method of measurements: n Head Elements n Area Elements n Quantity Velocity Elements Flow (Measurement) The following properties are important for the flow measurement: n Pressure: Force applied on Area n Density : Weight divided by volume n Viscosity : Resistance to flow n Velocity : Speed of the fluid. It determine the behavior of the fluid. Flow (Measurement) Flow Types: n When the average velocity is slow, the flow is called laminar, i.e fastest layers at the center and the slowest at the edges n When the average velocity increases, the flow is called turbulent. n The measurement of laminar, turbulent flow is as per Reynolds Flow (Measurement) Laminar Flow Turbulent Flow Flow (Measurement) Most Flow are design to work in turbulent flow Units of Flow: n lb/Hr, Kg/Hr, T/Hr: mass flow n cfm, M3/H, KNM3/Hr: Volumetric Flow Flow Measurement Head Flow Elements n When the liquid flows through a restriction, the energy converted kinetic energy. n The pressure will drop and velocity increases. C: constant AH: Aioorprvtioi rprooupr o)pooo Flow Measurement Head Flow Elements n Orifice Plate: the loss in the pressure is more that other type of flow measurement. w The selection of orifice plate based on ratio of bore diameter to (d) to inside pipe diameter (D). þ · ô/A w þrot o))upo)v io unrv: 0.2 < þ < 0.6 w Toro uorô : n 4iovyr tor n Hirr toro n crvo Xovtpo)to tor Flow Measurement n Venturi tube: expensive and the most accurate type þ>0.75 w Hprooupr pr)oTrpv io rc)riirvt Upstream Tap Downstream Tap Flow Measurement n 4iou NoCCir: )nrorrp tnov Trvtupi, w o))upo)v iroo tnov Trvtupi w þ>0.75 w rprooupr pr)oTrpv io vot oo yooô oo Trvtupi Upstream Tap Downstream Tap Flow Measurement Variable Area Flow Meter n Rotameter: consists of tapered, vertical glass consists of float. n Flow will carry the float from bottom to top through variable area glass. A: cross sectional area of the glass g: gravitational acceleration constant h: the height of the float. Variable Area Flow Meter In Out Float Flow Measurement Quantity Flow Measurement n Positive displacement w Measure the total quantity of the flow w separate the liquid into discrete volumes w Total of these volumes in time period will give the total flow amount n Mass Flow meter: w measurement of the weight per unit time. w Continuous measurement of density Level There is two ways of measuring level n Direct level measurement w by varying liquid will get the level n Indirect level measurement w by using a variables which changes with the liquid level changes. Level Measurement Float n special material designed to follow the level or the interface level of a tank n The specialty is the density of the float shall be always touching the desired measurement level. n As the level increases/decreases, float will follow and causing a connecting tape to change its length. Level Measurement Displacer n Archimede’s Principle: a body wholly or partially immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced. n The level is measured by detecting the buoyancy force of an immersed displacer n The major difference between float and displacer is that displacer is partially or totally immersed, while float is always floating in the surface of the level. Displacer Flexible Cable Float Level Measurement Differential pressure n n · AP/p (Bpition uvit) iv)nro n n· AP/(g.p) (LI uvit) µrtrpo n oo irTri )novyro ôioorprvtioi rprooupr uiii )novyr o))opôivyiv. L T Instrument Signal Types All measurement elements are sent to DCS/ESD/PLC Either for alarming, interlocking or controlling. Measurement Instrumentation consists of two parts n Measurement elements (Transducer)- Covered in the previous sections n Transmitting elements n Switching elements Instrument Signal Types Transmitting Elements n Transmitting element will convert the Transducer signals into either electronic or pneumatic signals n Transmitting elements are commonly used for indication and control n Electronic transmitter will send 4 ~ 20 mA w 4mA : min. range w 20mA: max. range n Pneumatic transmitter will convert the transducer signal into 3~15 psi w 3 psi = min. range Instrument Signal Types Switching Elements n Switching elements will convert the transducer signal into a switching contact n The contacts are used commonly in alarming and interlocking processes Conclusion Definition of instrumentation & Process Control P&IDs & Instrument symbols Process Measurement n Transducer (Temperature-Pressure- Flow-Level) n Transmitting and Switching Elements ??QUESTIONS?? THANK YOU