Fundamentals of Industrial Control WEEK 4

1. Fundamentals of Industrial Control WEEK 4 This week : Temperature Measurement Terminology Temperature Sensing Technology

2. How was it last Week? Recap of last Week: Remember the terms? Types of Pressure Sensors When and Where to Use What We Need to Use Did we miss any? Did You Read Up?

3. Pressure Measurement • Pressure can be created either compression( pumping) • Or Expansion in a closed vessel • Or by Gravitational exertion in a vessel

4. Force Exerted By Liquids • In a vessel , force exerted on the walls of the vessel have three contributing factors: • Height of the liquid • Specific gravity of the Liquid • Temperature of the liquid

5. Gas Laws: • Boyles Law: P1V1=P2V2 works as long as temperature is kept constant • Charles Law:V1/T1=V2/T2 works as long as pressure is kept constant • Idela Gas law: P1V1/T1=P2V2/T2 works on the day to day applications!

6. Pressure Measurment Basics • Manometers: U tube and Inclined designs • Great for low pressures • Still used for low pressure <10 psi applications

7. 27.8” of H2O=1 PSI U -Tubes No. 246 solid plastic inclined style stationary gage with 0-6" w.c. range.

8. G and A PSIG vs PSIA Pounds per square inch Gauge = reference to atmosphere on earth Pounds per square inch Absolute = Reference to “Space Vacuum” PSIG= PSIA+ 14.7

9. Types Of Primary Sensors • Elastic Deformation(means they move with very little pressure) • Diaphragm type • Metallic and Non Metalic • Primary use is Low Pressure • 10 Psig and under • Typical is inches W.C. and 0-5 psig

10. Bourdon Types • P43 deflection of solid Tube Bourdon tubes are circular-shaped tubes with an oval cross-section. The pressure of the media acts on the inside of this tube which results in the oval cross section becoming almost round. Because of the curvature of the tube ring, the bourdon tube bends when tension occurs. The end of the tube, which is not fixed, moves, thus being a measurement for the pressure. This movement is indicated by a pointer. Bourdon tubes bent at an angle of approx. 250° are used for pressures up to approx. 60 bar. For higher pressure, bourdon tubes are used which have a number of superimposed coils of the same diameter (i.e. helical coils) or helical-shaped coils (i.e. helical springs) at one level. Bourdon tubes can only be protected against overload to a limited extent. For particularly difficult measuring operations, the Wika pressure gauge can be provided with a chemical seal as a separation or protection system. The pressure ranges are between 0...0.6 and 0...4000 bar with a reading accuracy (or accuracy class) from 0.1 to 4.0%.

11. Spiral Type • P44 • Same idea as bourdon except very expensive to make and lower pressure capabiltiy • Also known as a helical element

12. When to use what!!?? • From 0-10 PSI use Diaphragm • Bellows elements are low pressure as well but are no longer used in gauges • From 5-30 psi Helicals are offered but are not price practical. • 15 psi and higher Bourdon tubes are the clear choice.

13. Dual Scale RangeGraduations Inner ScaleOuter Scale Inner ScaleOuter ScaleFigure IntervalsMinor Grad.Figure IntervalsMinor Grad. 0/9 oz./in.2 0/15 in. H2O 1 0.2 5 0.2 0/20 oz./in.2 0/35 in. H2O 5 0.5 5 0.5 0/35 oz./in.2 0/60 in. H2O 5 0.5 10 1 0/60 oz./in.2 0/100 in. H2O 10 1 10 1 . Standard Ranges

14. Type number1008A/AL Size63mm (2.5"), 100mm (4") Case304 stainless steel, dry (1008A), or liquid filled (1008AL) Fill fluidGlycerin Ring304 stainless steel, crimped WindowPolycarbonate DialBlack figures on white background, aluminum PointerBlack, aluminum Bourdon tube"C" shaped bronze (vac.-600 psi and compound) Helical bronze (1000 psi-6000 psi) Helical stainless steel (10,000 psi-15,000 psi) MovementPatented PowerFlexTM with polyester segment SocketBrass, with O-ring case seal RestrictorBrass throttle plug 0.013" orifice in all ranges (except vacuum and 15# psi ranges) Connection.25 NPT lower and back RangesVac. thru 15,000 psi and compound. Equivalent metric ranges available AccuracyASME B40.1, Grade B, 3-2-3 Operating temperatureDry gauge: -40° F to 150° F Glycerine filled: 20° F to 150° F Silicon filled: -40° F to 150° F Gauge Options CaseSealed case, field-fillable (LJ) Silicone filled (GV) Mounting hardwareU-clamp (UC), front flange (FF), retrofit flange (RF) SocketThrottle plugs 0.007", 0.02", 0.063"

15. Process gauges are .5% accuracy Pressure psiCompound psi 0/15 30" Hg/15 psi 0/30 30" Hg/30 psi 0/60 30" Hg/60 psi 0/100 30" Hg/100 psi 0/160 30" Hg/150 psi 0/200 30" Hg/300 psi 0/300 0/400 Vacuum 0/600 30/0 in. Hg 0/800 34/0 ft H20 0/1000 0/1500 0/2000 0/3000 0/5000 NOTE: Equivalent standard kg/cm2, and kPa metric ranges are available. 0/10,000 0/20,000 0/30,000

16. Grades of gauge Accuracies 3-2-3 rule!

17. Diaphragm Seals P46 • Primary use: to Isolate the process from the gauge Allowing thick process and toxic chemicals;erosive;corrosive to be read accurately • Automatically derates to 1% BFSL • Types of Fills: • Glycerine:$ Freezes,Common and inexpensive • Silicone: more $$ but temperature stable • Fluorolube: $$$$ food Grade and Stable

18. Diaphragm Seals

19. Diaphragm seals

20. Accessories • Siphons: to isolate water/vapour from high temp steam.

21. Snubbers • Throttle the flow into and out of the gauge • Oversnubbing can block the flow and gauge will not move!! • Subject to plugging! • Use only on clean fluids..no solids.! • Throttle screws can plug up too...

22. Electronic Measurement • Strain Gauge P53 • Capacitive element P54 • LVDT inductance P55 • Piezo Crystal P56 • Capacative and Strain Gauge=90% market share!!

23. Strain Gauge:

24. Capacitive: Requires more movement to sense .But is reliable technologyRosemount first ot come out with it.

25. Piezo Crystal

26. Variations of gauges and switches

27. Differential pressure Measurement: • With orifice plates principally • used for flow detection and signal transmission • differential in Filters;room pressure • equivalent of two sensors interacting to one another.

28. Thermometers P96 • Liquid In Glass Type: Prinicpally used for Commercial Services Expansion of An Alcohol based susbstance to expand within a fixed volume area in a direct correlation to a fixed mechanical scale

29. Alcohol Basics

30. Filled Systems • Have higher volume of volatile liquid • Changing volume compresses gas /liquid to make a pressure exert on a Bourdon tube,identical to a pressure gauge! • Good accuracy at limited small ranges • Inaccurate at large ranges

31. Different Class & Grades • All operate the same • Class 2A,B,C,D different ranges and voltile liquid fills are used…but in the end • They all do the same function..expand and generate pressure!

32. Mechanical Gas Operated Thermometer • 2 1/2”(63mm), 3 1/2”(90mm), 4”(100mm), 4 1/2”(115mm), 6”(150mm), 8”(200mm) dials • 1/2”(12.7mm) x 6”(150mm) bulb is standard • Double braided copper capillary or stainless steel capillary • Numerous options: armour, duct flanges, compensated capillary, longer bulbs etc. • Other dial sizes available • Other bulb sizes available • 2% accuracy Vapour actuated

33. Pro / Cons List • Pro: Provide reliable indication and can be remote located away from process. • Pro: No Power required to operate process I.e. Temperature Switch/Recorder/Controller • Con: Expensive to manufacture, no longer mass produced • Con: Impractical if Gauge is located below Bulb,Need to be recalibrated.

34. Bimetallic Thermometers • Taken over Vapour filled market • Economical and Mass Produced • Vibration Sensitive • Accuracy 1%

35. Bi-Metallic Construction Similar to a spiralhelic pressure gauge in its Construction

36. Is It Break Time Yet ?

37. Thermocouples • Basic Principle: Seebeck Effect • 1821… when two dissimilar wires are joined they generate a very small current/voltage potential

38. Types Of Thermocuples

39. Thermocouple Extension Wire

40. Thermocouple Management • All connectors must be of the same type • All joints to be done with connectors that are rated fro the thermocuple type or else dissimilar metals will falsify the reading • Runs of less that 200 feet recommended

41. Types of thermocouple design • Grounded type: Wires are welded to the casing. High (fast) response time but…susceptible to noise and eMF countershock. • Ungrounded type: Tip is electrically isolated by thin insulation so as not react electrically with any field power systems • Pro: less prone to burning out equipment • Con: slower reaction time( nominally)

44. Internal Construction • Tubular : typical 1/4” diam to 3/8” • Micro tube 1/16” tube grounded • Standard is 1/4” with MgO filling inside the tube to prevent breakage of wire joint • P109 p120

45. RTD’s • Typically design is ceramic rod with platinum wire wound around it. • Nominal resistance =100 ohms @0 Deg C. • Nominal accuracy= .1% !! • Does not require special “extension wire” • Overall much less installed cost. • Travel long didtance with 3rd wire • Self heating is minimal problem

46. 100 deg c. =185.51 ohms Standard DIN Curve Most Common

47. Thermistors P127 • Same idea but a lot higher ressitance range. • Works inversely of RTD ..decreases resistance as temp. increases • not as linear as RTD • Typical = 1000-10000 ohms • inexpensive = mass produced=everywhere in industry • I.e. motor windings

49. Infra-Red Sensors • Based on the principle that all objects radiate energy…. • Intensity of radiation increases as temeperature increases • Emissivity is best with blackened surfaces

50. Pro : NON contact Safety:no risk relavent accuracy inexpensive Con: innacuracy from surface finish 1% at best!!