Instrumentation Portfolios - mi-wea.org · PDF file27-Jun-01, Slide 8 The Right Technology for...

[File Name or Event] Emerson Confidential 27-Jun-01, Slide 1

Instrumentation Portfolios

Level


Agenda

Level Measurement Overview

– Technology Overview

– Selection Criteria

– Installation Guidelines

Level Measurements for Municipal Applications

– Sump Level

– Open Channel Flow

– Differential Filter Screens

– Lime Storage Silos


20%

Radar

Ultrasonic

Technologies for Continuous Level Measurement

Submersible

Level

PR

ICE

Accuracy, maintenance and

Application Difficulty

Float

Switch

Bubbler System


The Right Technology for your Application

Inventory tank gauging

Guided

wave

radar

Differential

pressure

and

hydrostatic

Point

level

detection

Non-

contacting

radar

Ultrasonic

For liquid tank

levels including

wide temp. and

pressure

requirements

For level &

interface

measurement

of liquids and

solids inc. wide

temp. and

pressure

requirements For liquid or

solid tank levels

including wide

temp. and

pressure

requirements

For simple tank

levels and open

air level

For high and

low alarms,

overfill

protection and

pump control

For steam/water interface

gauging, condensate

protection & turbine water

induction protection

Complete tank gauging for tank terminals

and refineries


Float Level Switches

Tough, rugged design for long life in aggressive environments

Operates in almost any liquid at high pressures and temperatures

Wide range of mounting options to meet site standards

Side or top mounting on existing vessel connections

External bridle mount option allows isolation while plant is live

Widely used and certified for marine applications

Applications

• High and low alarm

• pump control

• Maximum and minimum level detection

• Independent high level alarm


Point Level Detection

Flexible mounting

Appropriate for high and low alarms, overfill

protection, pump control including wide

pressure and temperature requirements,

including hygienic

Suitable for most liquids

Immune to changing process conditions


Bubbler Tank Level

SPM Variable Logging Advanced Process Alerts

Challenge

– Incorrect tank level readings due to issues such as:

• Improper adjustment of air flow

• Loss of instrument air

• Plugged or blocked sense tube

– Operator is unaware of the problem as the PV may not change

Solution

– Standard deviation provides a clear indication of bubbler level process issues

• Stdev increases with over adjustment of instrument air

• Stdev decreases with loss of instrument air or plugged sense tube

Plugged sense tube or

loss of instrument air

Over adjustment of

instrument air


The Right Technology for the Application

Process Condition Submersible Hydrostatic

Ultrasonic Guided Wave

Radar Non-Contacting

Radar Aeration

Agitation

Ambient Temp Changes

Corrosion

Density Changes

Foam

Internal Obstructions

Coating

Vapors

Viscous, Sticky


Indicator

9710 Hydrostatic Level Transmitters

Hydrostatic Level - head pressure of a liquid which is proportional to

level in a vented tank or open to atmosphere application. Accuracy

usually +/- 3% of full scale. 20 foot well +/- 6 inches


Ceramic Capacitive Sensor

• As the applied pressure changes, the ceramic wafer flexes.

• Changes the distance between the capacitance plates

• Sensor’s electronics convert deflection to 4-20mA

• Rugged, Ceramic Sensor Face

• No oil-fill, very low deflection for low hysteresis

Capacitive Plates Force (pressure)

Surface mount electronics


Submersible Level

Technology Advantages

Flexible mounting, typically suspended

Unaffected by conditions in the vapor space or on the liquid surface

Useful Features

Ruggedized sensor made of ceramic or protected by external cage

Vent tube protected with Teflon filter or sealed bellows

Cost under $1,000.00

9700

Submersible

Hydrostatic Level

Transmitter

Process Condition Submersible Hydrostatic

Aeration

Agitation


Corrosion

Density Changes

Foam


Coating

Vapors

Viscous, Sticky

Vent tube


The old dinosaur

The original sonic level

transducer

Used Dip switches to set

programing.

Used dials to set the

range of the unit

Accuracy 3% of span

Fischer & Porter

50US3100


Bottom

reference

Reference

Height

Ultrasonic Level Measurement

Distance

to surface = Speed x (Round Trip Time / 2)

Level = Reference Height – Distance

Accuracy +/- 0.25% of span

Cost ranging from $1,000 to $1,500

for remote display

FM approved Class I Div. I


Distance out = 32 in

External Temperature Input

Why is this important?

Bottom

reference

36 in actual distance 75 deg F

Distance out = 36 in

Electronics Temp = 75 deg F Electronics Temp = 100 deg F External Temp Input= 75 deg F

Vapor Space Temp is 75

deg F, but, we’re

correcting for SoS based

on 100 deg F!!!

If we measure the vapor

space temperature, we get

accurate SoS correction.

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The Transducer design

Transformer

Potting compound

2 or 3 core screened cable

Crystal

Circuit board & temperature sensor

24 Volts

3000 Volts peak to peak

100+ decibels

The Transducers

Measured

Level

All ultrasonic transducers have

what is known as the blanking

distance. This is the distance

from the front face of the

transducer within which valid

echoes cannot be received.

It varies with transducer type.

Typical range is 6 inches to 48

inches (10 & 120 feet range

Transducers)

Blanking


dB Transducers

METRES

5 10 15 20 25

dBM3

dB6

dB10

dB15

dB25

Key Blanking Max Range

40 35 30

dB3

dB40

The Transducers Beam Angles

Most Transducer beam

angles are stipulated at the

half power point. It can

either

be quoted in half beam or

full beam values.

In the past obstacles within

the beam angle have

caused problems with false

echoes, now however with

the latest software beam

angles are less of a

problem, even in the most

severe of conditions

Process Measurement

Although narrow beam angles and careful transducer positioning reduce the

risk of “false readings”…..….it is still necessary to have “echo recognition

software” to ensure reliable readings.


Digital Adaptive Tracking of Echo Movement

Tra

nsd

uc

er

ou

tpu

t m

V

Distance in meters

The red trace shows the raw echo, with a peak from

each of the reflections visible. The true echo in this case,

is second echo, which the software has automatically

recognized as the moving liquid level and will continuously

adjust these dynamic parameters regardless of the

changing conditions within the wet well.


Does it work in cluttered wet wells?

YES


Do I have to lower the transducer due to the Beam Angle?

NO!

Existing ultrasonics

New System


Does it work with poor surface conditions?

YES


Installation Considerations

Avoid mounting very close to the tank wall

Avoid turbulence & splashing (Beam angle)

Align vertically

Do not mount in the center of a tank

Be mindful that most ultrasonics use an onboard temp sensor to compensate for speed of sound

– Protect with a sunshield or use an external temp input to provide more accurate ambient temp compensation.

Optional external temperature input

can be mounted in the shade

Installation Guide

Siting the Transducer..looking down a wet well...

ladder

pumps

inflow

guides & chains

Transducer

mounting

position

1st

3rd

2nd

Pump Stations

Installation Guide

Installation-tipsSolution #1

Aim transducer near the point of inflow where the foam

may be broken up by the falling water

inflow

“clear” area

Pump Stations

• Pump station solution

• Sonic level transmitters were installed

New Sonic Transmitter Solution

Fixed Obstructions True level

New Solution


Standpipes & Spiders Webs


Web 1m down – DATEM in action

• dB40 in position in shaft

150 Foot Pumping station he Cavern”

• dB40 in position in shaft- “Birds eye” view

150 Foot Pumping station “The Cavern”


Ultrasonic Technology Advantages

Non-contact, no moving parts

Unaffected by fluid density or viscosity

Widely-compatible materials of construction for chemical tanks

Useful Features

Submersion-rated to withstand occasional flooding

Signal-processing done at the device for highest integrity and reliability

External temperature input for more accurate speed of sound compensation

Rosemount 3107

Submersion-rated

Ultrasonic Level

Transmitter

Process Condition Ultrasonic

Aeration

Agitation


Corrosion

Density Changes

Foam


Coating

Vapors

Viscous, Sticky

Rosemount 3102

Ultrasonic Level Transmitter

with integral keypad and

display


So where will some RADAR give

advantage over Ultrasonics

WHY USE RADAR


1. Long range measurement of small granular size materials, e.g. 60 Foot grain silos

Ultrasonics RADAR

WHY RADAR


3. Liquids with steep temperature gradients in the air space, e.g. food industry storage and blending tanks

20o

C

45o

C

70o

C 100oC

WHY RADAR


4. Liquids with layers of foam, e.g. soaps and detergents

WHY RADAR


5. Solids or Liquids with Gases other than air

e.g. fermentation vessels in Breweries

Closed Digester tanks must use Radar

WHY RADAR


6. Powders with high airborne dust levels particularly pneumatically filled silos

e.g. lime silos and cement silos

WHY RADAR


Where Radar is better than Sonar


Guided Wave Radar Level Measurement

• The microwave pulse is

guided down a probe

• Energy is reflected from the

product surface

• Distance is calculated

• Some of the pulse may

continue past the product

surface

• Allows for interface

measurement (e.g. Oil

and water)

Distance = Speed x Time of Travel / 2


Guided Wave Radar Technology Advantages

Highly reliable and robust measurement

Excellent choice for solids applications

Useful Features

Ability to handle difficult applications with a single probe

Useful software interface for ease of configuration

Coated probe diagnostics

Cost $2,500.00

Rosemount 5300

Guided Wave

Radar with Single-

Lead Probe

Process Condition Guided Wave

Radar

Aeration

Agitation


Corrosion

Density Changes

Foam


Coating

Vapors

Viscous, Sticky

Single-lead flexible cable ideally

suited for solids applications


Full Range of Probes for Highest Application Flexibility

HTHP/HP: SST HTHP/HP:

Not Available

Std: SST or PTFE covered Std: SST, Alloy 400, Alloy C-

276, or PTFE covered Std:

SST

Std:

SST

Std: SST, Alloy 400, or Alloy C-276

Flexible Single Rigid Single Twin Rigid Twin Coaxial

Ma

teri

als

of

Co

nstr

uctio

n



A single-lead probe is the best choice where possible

Mount the probe away from inlet pipes

A shorter nozzle helps prevent the probe from shorting

Anchor flex probes to the tank bottom in turbulent applications

For tanks with internal obstructions such as agitator blades, non-contacting radar is a better choice


For Difficult Applications, Choose non-Contacting Radar

View from inside the pumping station

Here the customer

wanted a non-contacting

technology, but had very

restricted “view” from

above.


Non-Contacting Radar

• Microwave pulse emitted from

antenna

• Microwave pulse reflected from

product surface

• Distance to the product surface is

calculated

Distance = Speed x Time of Travel / 2

~ 12 Inches foam layer

~ 0.5 inches foam layer

60

dB

25

dB

The reflection from the water level is noticeably attenuated with 100 mm foam.

Foamy Application

~ 6 inches foam layer

24 inches foam layer

Device confused by thick foam layer and reported foam face as the water level.

Foamy Application

24 inches foam layer

Actual level Locked level

Foamy Application

From test results we can see that 0 to 6 inches of foam have little to no affect on Radar. But 2 feet of foam depending on foam density can cause major level issues


Non-contacting Radar Technology Advantages

Non-contact, no moving parts

Unaffected by fluid density or viscosity

Tight, focused beam helps avoid false reflections from internal tank obstructions

Useful Features

Physical design that sheds water condensation

Rosemount 5400

Non-contacting

Radar

Process Condition Non-Contacting

Radar

Aeration

Agitation


Corrosion

Density Changes

Foam


Coating

Vapors

Viscous, Sticky

37° 9° Beam angles with 4” antennas

26 GHz 10 GHz

High-frequency option (26 GHz) for tanks with obstructions

Low-frequency option (10 GHz) for foaming applications



Maintain a clear and unobstructed view of the level surface

Mount away from product inlets

Avoid mounting above internal tank hardware (e.g. ladders and baffles)

Do not install in the center of the tank

Generally ok to mount close to the wall if the surface is smooth

Cost $4,000.00

• Larger Diameter Seal

• No Dirt or Condensate accumulation

Rosemount 5400 has a large diameter seal


W&WW Measurements

Sump Level

Open Channel Flow

Differential Filter Screens


Sump Level

Monitor level in sumps and lift stations

Transmit level to a PLC or Local Display

Trip high level alarms to prevent overflow

Typical Level Technologies

Submersible

Hydrostatic Ultrasonic

Because the signal processing is performed in

the transmitters, a separate control box is not

required, though it can be useful…….


Sump Level Control

Requires a PLC or Controller

Pumps are activated when level reaches set point

Large wells may have more than one pump

– Multiple pumps in series provide assist and/or standby for heavy loads

Rosemount 3490 Universal Controller

Relay 1—Pump 1

Relay 2—Pump 2

Pump 1 Pump 2

The controller has onboard pump-

control algorithms and serves as an

intrinsically-safe power supply for the

transmitters. It also features local

display and integrated keypad for

configuration.


Open Channel Flow—Application Overview

What is measured?

– Flow is inferred by measuring the level of water flowing through a restricted channel

Typical Level

Technology

Ultrasonic


Open Channel Flow Measurement W

AS

TE

WA

TE

R T

RE

AT

ME

NT


Open Channel Flow—Flumes & Weirs


More Flumes & weirs


Open Channel Flow

Channel has a built-in flow restriction with known geometry

– Flow rate can be determined by measuring level upstream of the flow restriction

Rosemount 3100 Family of Ultrasonic Transmitters with

Onboard Configurable Flow Geometries


Flume & Weir Flow Calculations

Basic equation for rectangular flume :-

Q = (2/3)3/2

(gn)1/2

CvCdbh3/2

gn = acceleration due to gravity

Basic equation for “V” notch weir :-

Q = 8/15 tan a/2 (2gn)1/2

Cehe5/2

(Kindsvater Shen)

These formulas

embedded in all sonic

transmitters


Parshall Flumes Standard sizes & geometry

– 1”, 2”, 3”, 6”, 9”, 1ft, 1.5ft, 2ft, 3ft,4ft, 5ft, 6ft, 8ft,10ft to 50ft

Self cleaning at critical flow conditions

Easy to maintain

Support for Parshall

Flumes embedded in all

3100’s and 3490’s!!!


Open Channel Flow—Equipment Selection

Ultrasonic Level Measurement

– Flow calculated in the transmitter

Equipment Considerations

– Level accuracy makes a big difference

• Consider that a V-notch weir may have only a 6-inch span!

– For best accuracy, use an external temp sensor mounted in the shade

– Application typically uses a submersion-rated device

– Easy configuration with built-in equations for flow geometries

– Flow totalization (daily and/or cumulative)

– Make it easy to verify the calibration

Rosemount 3493 Universal Control Unit for Totalizing

and Logging Flow

Rosemount 3108 Ultrasonic Level Transmitter with

External Temp Sensor


Differential Level Across Filter Screen

Downstream level subtracted from upstream level to indicate when screen needs to be cleaned


Guided Wave Radar for Lime Storage Silos

– No moving parts

– No maintenance

– No exposure to lime dust

Replaces mechanical measurements


Point Level Detection & Pump Protection

Pump Protection High Level Alarm Limit Detection

Vibrating Fork

Level Switches

Level Solutions for W&WW

Instrumentation Portfolios - mi-wea.org · PDF file27-Jun-01, Slide 8 The Right Technology for...

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