TECO HK Series Microwave Consistency Transmitter Technical Review

Solution Providers for Process Industries

Thompson Equipment Company, Inc. 125 Industrial Ave., New Orleans, LA 70121

HK Microwave Consistency Transmitter

Technical Review 2.0



TECO Products & Services

• Stockrite™ consistency transmitters• Drainac™ freeness transmitter• Brainac™ refiner control systems• BrainDrain™ refiner/freeness control• Silica free heatless air dryers• Instrument and valve repair, remanufacture & calibration

• Flow meter expertise and sales



Today’s Presentation

• How Microwave Measurement Works• The HK Series Microwave• Points on Installation• Calibrating the HK• Things to think about



Consistency Measurement

• No direct measurement of consistency–Must measure something else which has a relationship to consistency

• Mechanical Transmitters–Respond to apparent viscosity or network strength

• Optical Transmitters–Respond to absorption, reflection or transmission of light



How does Microwave work?

• Measures the bulk dielectric constant “ε” of your process

• This is a measure of how fast EM energy can travel through a material

• Usually expressed as a ratio relative to speed of light in a vacuum




• Water has a high dielectric constant –About 80

• Cellulose Fiber (and most mineral fillers) have a low dielectric constant–About 4




• The bulk dielectric constant of your process is a function of how much water and not-water is in the process

• A higher dielectric means there’s more water and a lower dielectric means less water



0 20 40 60 800

20

40

60

80

100

Dielectric

%C

sDielectric vs Consistency

Pure Water

Pure Fiber




• You measure the dielectric constant by measuring the phase shift of a signal transmitted through the process

• As the dielectric changes, the phase shift of the signal will also change



Dielectric vs Phase Shift

100 150 200 250 300 350 4005

10

15

20

25

30

Phase Shift

Die

lect

ricMore Water

More Water




• To get consistency, you build a calibration between the measured phase shift, Φ, and your lab’s consistency evaluations



• The Compact System• Single piece construction with flange-mounted insertion-pin sensors

The HK System



• Modular System• Remote Electronics • Available in insertion or non-insertion configurations

The HK System



The HK System

Insertion PinsAvailable in different lengths



The HK System

Non-Insertion PinsNon-Invasive Transmitter Bodies



Notes on Installation

• Choose a vertical pipe as close to a pump discharge as possible–maximizes turbulent mix in the pipe and avoids laminar flow

–Avoid horizontal runs• Ensure minimum pressure of 15 psi

–Higher line pressures are desirable–Reduces the impact of entrained air




• Choose locations with stable process temperature

• Avoid locations subject to large variations in conductivity/salinity

• Insertion pins should be angled–Promotes shedding of trash and avoids stock buildups




• Minimize distance from the transmitter to the sensors

• Protect Cables and Connectors–Don’t over tighten connectors–Avoid water or dirt contamination of coax connectors

–Don’t bend cables



Intro to Calibration

The Basic Calibration Equation is

Cs = A1*Φc + A0

Cs = calculated consistency valueA1 and A0 are linear coefficientsΦc = temperature-corrected phase shift




Temperature corrected phase shift Φc is calculated:

Φc = + Φraw + Tk1*(T-Tref)

Tk1 = linear temperature coefficientT = measured process temperatureTref = reference process temperatureΦraw = measured uncorrected phase shift

Note that this is a delta or deviation calculation




Finally, Φraw is itself a delta:

Φraw = Φm - Φref

Φm = measured phase shift

Φref = reference phase shift




• Put it all together and the whole thing looks like:

Cs = A1* {Tk1*(T-Tref)+(Φm–Φref)} + A0

• The meter measures red parameters• We define green parameters during setup and calibration




A1 is the slope of the line

A0 is the y-intercept of the line

%Cs

Φ Phase Shift

Temperature correctionadjusts Φ



Performing a Calibration

• Successful calibrations consist of several steps–Setup Operating Parameters–Perform the Reference Measurement–Refine Calibration Offset



Set Initial Operating Parameters

1) Define the linear coefficients A1 and A0

–The initial value of A1 depends on sensor configuration, e.g. -0.235

–The initial value of A0 is 0.0–There is a table in the manual that defines the coefficients for various sensor configurations




2) Define the linear temperature correction coefficient

Tk1

–Again, the initial value of Tk1 depends on the sensor configuration. e.g. 1.0




3) Define the output 4-20 mA range–i.e., what %Cs produces 4mA and 20mA

4) Optional–Some exteriorly-mounted meters may require that you define ambient temperature correction coefficients because of temperature-induced cable effects from seasonal temperature shifts. This procedure is rare.



Reference Measurement

• Establishes normal operating regime (Tref & Φref) for the meter– All subsequent measurements are based on deviations away from the normal regime

• Must be completed properly for a successful application– Ensure that total system attenuation falls within the acceptable limits of 5 – 55dB



Reference Measurement• Process must be stable

– Signal attenuation variance less than 0.5dB– Phase Shift variance less than 20 degrees Phi

• Process sample must be collected and analyzed during performance– Use proper collection procedures & analysis methodology for the best results

• Perform the Reference Measurement Procedure twice for best results



Reference Measurement• Establishes reference parameters Tref and Φref

• Eetermines nominal signal attenuation for the application

• Useful for diagnosing system behavior if the unit develops problems in the future

• Attenuation changes indicate shifts in the process or in instrument function.



Reference Measurement• Finally, input the Lab Evaluation of the process sample collected earlier.

• This will adjust the value of A0



Reference Measurement• Complete Reference Measurement by initiating Measurement Range Computation–software procedure that sets the meter’s limits for consistency.

–These limits are not accessible through the operator interface

–can be calculated manually–process consistencies outside limits will not read correctly



Refine the Calibration Offset

• Collect several process samples• Analyze the samples and determine the average meter deviation from the lab values

• Adjust A0 accordinglyA0 new = A0 old + 1/n Σ (Lab-Meter)

• The Meter is now calibrated and measuring consistency



Notes on Calibration• This methodology produces a single point calibration

• Occasionally, better performance is possible by tweaking A1 and A0

• Use Excel to regress a number of process sample-meter data pairs– Use the resulting linear coefficients to adjust the meter’s operational parameters using the technique illustrated in the manual



Notes on Calibration

• The HK meter supports a linear calibration model only

• To implement non-linear models, you will need to use your DCS– Set to output uncorrected phase shift only– Set A1= 1.0 and both Tk1 & A0= 0.0



Things to Think About

• Application success requires consideration of these factors:– Temperature– Conductivity– Salt Content – Entrained Air– Fillers and Additives




• Temperature– The dielectric constant of water is a function of temperature, which is why we compensate for it

• Conductivity– Changes in conductivity will change the bulk dielectric constant of the process. These shifts will look like changes in consistency, but they’re not. Severe variations may require compensation for best accuracy




• Salt Content– Like conductivity, salt content will change the bulk dielectric of the process. Shifts in salt will also look like shifts in consistency

• Entrained Air– Air has a dielectric of about 1.0 and will look like fiber to a microwave signal

– Higher line pressures make big bubbles into little bubbles and minimizes the impact of entrained air




• Fillers and Additives– Most fillers and additives have high dielectrics and look like water. Some, like TiO2, have low dielectrics and will look like fiber

TECO HK Series Microwave Consistency Transmitter Technical Review

Engineering

Transcript of TECO HK Series Microwave Consistency Transmitter Technical Review