Instrumentasi dan kontrol (MS312)

Instrumentasi dan kontrol (MS312) Minggu ke 7 & 8III, 2011/2012Liman HartawanMateri Pembelajaran/Pokok BahasanMetoda-metoda & Alat-alat ukur temperatur.Metoda-metoda & Alat-alat ukur tekanan.Metoda-metoda & Alat-alat ukur aliran fluida.Sub kompetensiMahasiswa mampu menjelaskan pengukuran temperatur, tekanan, dan laju aliran fluida.Referensi Utama4. Michael D. Whitt. 2004. Successful Instrumentation and Control Systems Design. The Instruments Systems and Automation Society (ISA).Continuous fluid flow measurementPressure-based flowmeters

Orifice plates

Most popular tap locations for orifice plates

Other differential producers

Other differential producers

Proper installationNecessary upstream and downstream straight-pipe lengthsBeta ratio (ratio of orifice bore diameter to pipe diameter: = d/D)Impulse tube tap locationsTap finishTransmitter location in relation to the pipe

Flow conditionersUntuk menghilangkan turbulensi atau menyeragamkan kecepatan fluida

Pressure-based flowmetersVenturi tubes and basic principles

Proper mounting position

High-accuracy flow measurement

Velocity-based flowmeters

Vortex flowmeters

Magnetic flowmeters

Ultrasonic flowmeters

Ultrasonic flowmeters

Positive displacement flowmeters

Positive Displacement MeterTypical Principle of OperationSchematic of a nutating-disk meterSchematic of a rotary-vane flowmeterSchematic of a lobed-impeller flowmeter

23Instrumentasi & KontrolCoriolis flowmeter24Coriolis flowmeterThe meter operates on an application of Newton's Second LawF = m.a (Force = Mass x Acceleration)A mass element m is moving with velocity v in a rotating tubeThe tube rotates with angular velocity Coriolis acceleration ac = 2 ( v ) acts on the mass elementCoriolis force is F = m .2 ( v )

Principle of the Coriolis flowmeterOne or two U-shaped tubes are the basic element of the flowmeterMotion of rotation of the tube is replaced by oscillation around axis U-shaped measuring tubes oscillate by electromagnetic force and oscillate periodically with harmonic frequency Tubes on the pictures are at zero flow rate of medium

Design of the Coriolis sensorU-shaped tubes is vibrated at the its natural frequencyThe flowing fluid is forced to take on vertical movement of the vibration increasing as it flows towards the bend and decreasing as it flows away from the bend and towards the outlet of the meter

End view of sensor tube showing fluid forces and twist of tubes

The mass flow rate can be derived by measuring the deflection angle using the two sensorsThis measurement is accomplished by measuring the relative times that each sensor detects the midpoint crossing of the respective legThe time difference at zero flow is nullAs flow increases causing an increase in the twist angle, the time difference between signals also increasesThe time interval is proportional to the mass flow rate

Design of the Coriolis flowmetersFor practically all kinds of fluids including slurries, two-phase products and liquids with high viscosityHandles temperatures from -200 C to +200 CChemical and petrochemical industryPharmaceutical industryFood and beverage industryPulp and paper industry

Animated