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Continuous On-Line Measurementof Liquid/Solid Interface

AM845 Thickener

Interface Gauge (TIG)

AM845 Thickener

Interface Gauge (TIG)

Analyze Detect Measure ControlTM

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INTRODUCTIONThe Thickener Interface Gauge (TIG) provides

continuous on-line measurement of the level of the

liquid/solid interface in thickeners and counter-current

decantation (CCD) washers. Unlike other interface level

measurement systems the TIG also measures the span

and positioning of the transition zone. The transitionzone is the region between the clear liquid and the

solids compression zone. A narrow transition zone

indicates a well defined liquid/solid interface while a

broad transition zone indicates a poorly defined bed

due to slow or impeded settling of the solids. This

information can be used for better control of flocculant

addition rates.

The TIG determines the level of the liquid/solid

interface by either measuring the natural gamma

TIG 1Suitable for a process with low levels of naturallyoccurring radioactivity (Th, U or K-40) in the slurry(such as red mud in alumina plants or monazite inthe mineral sands industry). This unit has a detectorarray which is immersed in the thickener or CCDwasher. The gauge is specifically ruggedised totolerate high temperature and corrosiveenvironments.

emissions from the product (TIG 1), or the attenuationof gamma emissions from a reference standard (TIG 2).The information from the array of detectors isanalysed and processed by a sophisticated algorithmwhich outputs continuous level measurements.

TIG 2Suitable for a process with no naturally occurringradiation in the slurry. The TIG detector array ismounted in parallel, 200mm away from a referencestandard rube which is filled with mineral sands. Thegauge measures the level of the zones in the tank bythe amount of radiation that is absorbed by theslurry at different densities. No radiation licensing isrequired for any version of the gauge.

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SPECIFICATIONSThickener Interface Probe Assembly (AM204)

Probe Dimensions

Probe lengths depends upon application,

12 metres maximum. Probe diameter is 50mm.

Probe Material

316 grade stainless steel, other materials availableon request

Number of Detectors

Application dependant

Operating Temperature

Power Interface Probe Assembly (AM274) 0-110C

Probe Head Unit (AM284) 0-60C

Options

Teflon, Halar or Linotex sheath ro reduce the rate of

precipitation onto the probe and assist with cleaning.

Radio modem for remote communications

Processor Transmitter Unit (AM542)

Operating Voltage

Mains input voltage continuous range from 110

to 240 volts AC, 50 to 60 Hz, 30 watts, 24 volts

DC option.

Outputs

Two 4-20 mA individually isolated outputs (one for

the level of the liquid/solid interface and the other

for the span or position of the transition zone).

Isolated 2 wire RS-485 or 4 wire RS-485(downwards compatible with RS-422) multi-drop

serial data link.

Two user selectable alarm outputs (eg. high and

low level alarm) via voltage-free contacts rated at

110 volts DC, 125 volts AC, 1 amp maximum).

Resolution

Typically 5mm

Update Time

10 to 900 seconds (user selectable), with rolling

average over last 1 to 10 measurements (user

selectable)

Distance between Probe and Transmitter

Up to 1000 meters. 20 meter cable supplied as

standard.

Operating Temperature

0-50C

Enclosure

316 stainless steel, wall mounted with IP66

environmental rating.

400 H x 300 W x 195 D (in mm)

The Thickener Interface Gauge (TIG 1) ismanufactured under license from the CSIRO.

Specifications are subject to change without notice.

INSTALLATIONThe Thickener Interface Probe is mounted

vertically either inside the vessel or down the

outside (refer sketches).

If the bottom of the probe is above the level of the

rake then the probe is normally fixed in position.However, if the bottom of the probe is below the

rake then the probe can be mounted on a support

which allows the probe to tilt when it comes in

contact with the rake. Alternatively, the probe may

be mounted on the front edge of the rake assembly

with power provided through sealed slip-rings. As an

option, the probe can be supplied with a radio modem

to enable remote transmission of the output signals.

TIG 3In applications where high temperature and internaltank access is prohibitive, a detector array may bemounted on the outside of the vessel, to measurenatural radiation through the vessel wall.

The system is suitable for applications where theprocess contains elements emitting low levelradioactivity as per TIG 1.SPECIFICATIONS.

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Thermo Electron Corporation

Australia11 West Thebarton Road, Thebarton

Adelaide, South Australia 5031AUSTRALIA

PO Box 292

Torrensville Plaza 5031AUSTRALIA

Telephone: +61 8 8150 5300Facsimile: +61 8 8234 5882

email: sales.pid.adelaide@thermo.com

USA Office5788 Pacific Center Blvd

San DiegoCA 92121

USA

Telephone: +1 858 458 1700Facsimile: +1 858 452 9250

Chile OfficeSan Crescente 448

Las Condes, SantiagoCHILE 755-0315

Telephone: +56 2 335 3388Facsimile: +56 2 335 1590

Analyze Detect Measure ControlTMTIG 4/2006