Radiation-based Process Instrumentation

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Contents

Non-contact measurement with PROTRAC 3

Impressive application solutions 4

Support from planning to realisation 5

The radiation-based measuring principle 6

Communication in any system 8

Safety-oriented instrumentation via SIL 9

Level measurement with FIBERTRAC and SOLITRAC 10

Level detection and density measurement with MINITRAC 12

Mass flow measurement with WEIGHTRAC 14

SHLD source holder 15

Application example: level 16

Application example: limit level 17

Application example: density 18

Application example: mass flow 19

plics® – the idea with a future 20

System integration 22

Adjustment and diagnosis 23

Non-contact measurement with PROTRAC

A plus with PROTRAC

VEGA Grieshaber KG has been the measurement specialist for level, limit level and pressure for over 50 years. Measuring instruments from VEGA reliably deliver volume, level and pressure data from all kinds of media. From the finest to the roughest bulk solids, in adherent or abrasive slurries and liquids.

With ProTrac, VEGA has extended the existing instrument line up to include radiation-based process measurement. ProTrac solves any measurement task, no matter how difficult, and sets new standards with regard to safety.

Reliable measurement technology for extreme process conditions

Every measuring technique reaches its limits at some point: extreme temperatures, high pressure in the container, aggressive media or problematic physical features of the product make precise measurement of level, limit level, interface or density impossible.

The good news: the new, radiation-based instrument series ProTrac delivers exact and reliable results with the help of gamma rays even in the most difficult measuring situations. A low activity source – safely embedded in a source holder – emits its radiation in the direction of the measured product. The radiation penetrates through the container wall as well as the measured product, gets damped in the process and is received by a detector. The measurement is external to the process and is therefore maintenance-free.

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VEGA is your competent partner for all aspects of radiation-based measurement:

Technical configuration of the measurement ■pointAdvice about approvals ■Support with logistical processes ■Setup and commissioning ■Return of used radiation sources ■

PROTRAC: typically VEGA!

VEGA is known worldwide for its extensive metrology and instrumentation know-how. For over ten years VEGA has been an international technology leader in radar level measurement. But VEGA has the right instrumentation on hand for other measuring tasks, too: the spectrum of level and limit level instruments extends from capacitive measurement to ultrasonics right through to guided microwave. And for pressure measurement there are instruments that register hydrostatic pressure and process or differential pressure. Since the introduction of the instrument concept plics®, all VEGA instruments can be commissioned and operated in the same way: whoever knows how to operate one VEGA instrument knows how to operate them all. ProTrac, the youngest member of the VEGA instrument family, is of course also a plics® instrument

– with all the advantages that are so typically VEGA.

Consultation and service give confidence

When implementing a radiation-based measurement point, important aspects with regard to radiation protection laws and regulations must be taken into account. But you don’t have to do this on your own. VEGA accompanies you step by step and provides individual consulting. VEGA application technicians plan the layout of the measurement point together with you and recommend how ProTrac should be installed to ensure a reliable measurement.VEGA sends you the licensing application for operating a radiation-based measuring instrument and advises the person responsible in your company about the safety aspects. And although ProTrac is designed to operate completely maintenance-free for many years, VEGA is a partner you can contact any time after installation and commissioning.

Peaceful utilisation of radioactivity

French physicist Henri Becquerel discovered the radioactive emissions of uranium in 1896. We can hardly imagine our world today without the many applications of radioactivity. In medicine it has created completely new possibilities for diagnosis and therapy: we encounter them, for example, in radiograph technology and in cancer therapy. In industry radioactive beams are used, among other things, to check welded seams or analyse materials.

Industrial measurement technology also makes use of the uniform properties of radioactivity. Today, the radiation intensity of radiation-based instruments for determining level, density or interface is so low that only special, highly sensitive sensors, such as ProTrac, are able to pick up this minimal radiation.

Support from planning to realisation

Impressive application solutions

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Well shielded

Radioactivity is a sensitive topic, and there are good reasons for people handling it with extreme care. In radiation-based applications, contamination of the measured products or people is impossible: the radioactive isotope is packed doubly safe in a stainless steel capsule and reliably shielded by additional lead sheathing. And a solid steel housing protects it from mechanical destruction or corrosion by environmental effects.

Radiation-based measurement neither contaminates the measured medium nor changes it in any way – it stays just as it is.

The radiation-based measuring principle

Application areas for PROTRAC

Continuous level measurement ■

Density and concentration measurement ■

Level detection ■

Interface measurement ■

Mass flow measurement of bulk solids on conveyor ■belts or in screw conveyors

Flow-rate measurement of liquids ■

Special application areas ...

… require special solutions. For some applications, no alternative to radiation-based measurement has been found to this day. Extreme temperatures, high process pressures and extremely difficult mounting conditions represent a challenge that only non-contact radiation-based measurement can cope with. Different detector models make ProTrac instruments so flexible, that they can readily be adapted to the most difficult measurement tasks: FiberTrac is a flexible detector for level measurement in round and conical vessels. The PVT rod detector SoliTrac is the specialist for straight sided containers. And the NaI detector in MiniTrac was designed specifically for density measurement and level detection.

A familiar principle

The core element of a radiation-based measurement is a weakly radioactive isotope that emits collimated gamma rays. A caesium-137 or cobalt-60 isotope is usually used as the radiation source. A special detector attached on the opposite side of the tank receives the radiation. The scintillator converts the radiation into flashes of light that are counted and evaluated. Since the gamma beam is damped and reduced by product presence or properties the device can calculate the level, limit level, density or mass flow from the intensity of the amount of received radiation, i.e., from the number of light flashes.

The advantage over other measuring techniques: radiation-based measurement works independently of pressure, temperature, viscosity and all chemical properties of the medium, even under the toughest operating and environmental conditions.

Gamma radiation source and opposing detector form a measurement setup. Damping of the radiation is proportional to the level, to the density or to the mass flow.

Configuration of a radiation-based measurement

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DTM EDD

PLC

HART Handheld-

Simple adjustment and safe operation

With ProTrac, commissioning and operating a radiation-based measurement point is simpler than ever. The on-site adjustment module PLICSCOM can be used to set the parameters of simple level or density applications. For complex measurement tasks incorporating several detectors or additional sensors for temperature or flow-rate measurement, there are high performance DTMs and EDDs with user-friendly assistants for commissioning and analysis.

PROTRAC speaks all languages

Whether Profibus PA, Foundation Fieldbus or 4 ... 20 mA/HART, ProTrac communicates with any process control system currently on the market. The instrument speaks the language of your automation equipment and can be integrated into any process control system with no problem. The universally applicable electronics also provides for smooth cooperation between systems: one relay output, analogue and digital inputs and outputs, as well as a serial multi-gauge communication bus, make a wide variety of applications possible.

Instrument with early warning system

All ProTrac instruments are equipped with a clever Asset Management system. This means that they operate with self monitoring and diagnosis – already before any kind of disturbance or failure occurs.Even when only the tiniest deviations from the optimal state are recognized, ProTrac switches from "green" to "yellow" status according to the traffic light principle. There is thus sufficient time to correct the factors that caused the disturbance.

A high degree of safety

To increase safety, VEGA has set new standards in radiometry: in the sensitivity of detectors and in the quality of source holders.

VEGA is the first supplier to develop radiation-based instruments for continuous level measurement, limit level and density applications that comply with the strict SIL guidelines. The hardware and software, which were both developed according to IEC/EN 61508, fulfil the most demanding requirements. To ensure the safety of employees and production processes, the SIL classified equipment operates redundantly: critical functions and components are often duplicated, so that the device can automatically fall back on the twin function.

Safety-oriented instrumentation through SILCommunication in any system

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FIBERTRAC 31

SOLITRAC 31

For measuring tasks in still hotter environments, FiberTrac and SoliTrac are also available with water cooling.

To enable precise adaptation to any measuring range, the detectors are available in different lengths. Multiple sensors can also be cascaded.

Convincing features

Whether the straight SoliTrac or the adaptable FiberTrac: both sensors operate completely independent of the process, since they are attached to the outside of the container or tank.Various fasteners and holders are available for trouble-free mounting on any kind of vessel. The sensors are maintenance-free and long lasting and work reliably in ambient temperatures from -40 to 60 °C.

FIBERTRAC: a flexible solution

FiberTrac has a flexible plastic detector for level measurement in round and conical vessels. The up to 7 m long detector tube can be adapted to fit the container form. This is made possible through flexible scintillator fibres of plastic. The big advantage: due to the length and flexibility of the detector, one single instrument often suffices where previously several rod detectors had to be connected in series.

Radiation-based sensor for continuous level measurement

Flexible plastic detector for round and conical vessels ■Measuring range up to 7 m ■Cascadable for larger measuring ranges ■Simple retro installation without interrupting process ■Signal output 4 ... 20 mA/HART, Profibus PA, Foundation Fieldbus ■

Measuring range: 1 ... 7 mProcess temperature: anyAmbient temperature: -40 ... +50 °CProcess pressure: anyMeasuring precision: ± 0.5 %

Radiation-based sensor for continuous level measurement

PVT rod detector for cylindrical vessels ■Measuring range up to 3 m ■Cascadable for larger measuring ranges ■Simple retro installation without interrupting process ■Signal output 4 ... 20 mA/HART, Profibus PA, Foundation Fieldbus ■

Measuring range: 1 ... 3 mProcess temperature: anyAmbient temperature: -50 ... +60 °CProcess pressure: anyMeasuring precision: ± 0.5 %

SOLITRAC: solid performance

The robust PVT rod detector of SoliTrac is the specialist for cylindrical vessels. The sensor with straight plastic scintillator is available up to 3 m long on request and can be simply mounted on the outer wall of the vessel. PVT detectors work with a precision of 1 % in a temperature range of -40 to +60 °C.

State-of-the-art sensor technology

The special feature of ProTrac: every ProTrac instrument can be equipped with the most suitable detector type for the particular application. But all the sensors have one thing in common: they contain a high-quality NaI or plastic scintillator, a photomultiplier and of course the signal processing electronics. The scintillators are highly sensitive materials with special nuclear/physical properties: even the smallest quantities of gamma radiation trigger flashes of light inside them. The photomultiplier converts these light flashes into electrical impulses and amplifies them. The signal processing electronics then calculates the exact level of the medium from the electrical impulse rate.Two sensor types are available for continuous level measurement: SoliTrac and FiberTrac.

Level measurement with FIBERTRAC and SOLITRAC

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MINITRAC 31

Full or empty

MiniTrac is also used when the minimum or maximum level in a vessel has to be monitored. This serves to avoid overfilling or protect pumps from running dry.

Mounted at the height of the desired minimum or maximum level, MiniTrac delivers a reliable switching command when the respective level is exceeded or underrun.

MiniTrac is equipped with a sodium iodide crystal scintillator that measures with a precision of 0.1 %. Just like its larger colleagues made of PVT plastic, MiniTrac is highly sensitive to gamma radiation and delivers reliable measurement data.

Radiation-based sensor for level detection and density measurement

NaI detector integrated in sensor housing ■Simple retro installation without interrupting process ■Signal output 4 ... 20 mA/HART, Profibus PA, Foundation Fieldbus ■

Process temperature: anyAmbient temperature: -40 ... +60 °CProcess pressure: anyMeasuring precision: ± 0.1 %Thin or viscous

Radiation-based density measurement is gaining more and more importance in the chemical industry. Since products in this sector are often highly corrosive, the only reasonable alternative is non-contact measurement. The food and pharmaceutical industries depend, for hygienic reasons, on measuring instruments that can “see through things”. But radiation-based density measurement is especially important in petrochemical and offshore applications: knowing the consistency of the drilling mud and being able to recognize different types of oil in a pipeline are absolutely essential in these sectors.

A very big little sensor

MiniTrac is a real all-rounder. It is employed everywhere where the density or limit level of liquids or bulk solids has to be monitored. It can be mounted on any kind of vessel: on simple tanks and bunkers as well as stirring vessels, on sluices or on high-pressure reactors. Due to its small dimensions, MiniTrac finds room almost anywhere – for example on pipelines or in the narrow corners of feed hoppers.

Level detection and density measurement with MINITRAC

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WEIGHTRAC

The SHLD source holder can be mechanically, and if required also pneumatically or electrically, closed. This “turning off” of the radiation is necessary, for example, when servicing work on the container is carried out.

A safely packaged radiation source

ProTrac is equipped with SHLD, the new generation of source holders. The source holder fulfils two important functions: on the one hand, the lead casing protects the surrounding area, secondly it also protects the capsule containing the radioactive isotope from mechanical or chemical damage. The inner core of the source holder consists of several seal-welded stainless steel capsules which completely enclose the radioactive isotope. This core is then cast into a thick layer of lead in the steel housing. Only a narrow slit remains open, which allows the radiation to escape in a focussed collimated beam in the direction of the measured medium and the detector.

Protective container for the radiation source

Best possible shielding with low container weight ■Simple exchange of radioactive source ■Fire-resistant for 30 minutes at +800 °C ■Optionally with pneumatic or electrical shutter ■

Process temperature: anyAmbient temperature: -50 ... +100 °CProcess pressure: any

Radiation-based sensor for mass flow measurement

PVT rod detector ■Precise bulk solids measurement on conveyor belts or screw conveyors ■Simple mounting by means of measuring frame ■Signal output 4 ... 20 mA/HART, Profibus PA, Foundation Fieldbus ■

Conveyer width: 0.5 ... 1.6 mProcess temperature: anyAmbient temperature: -40 ... +60 °CProcess pressure: anyMeasuring precision: ±1 % measuring range end value

Contactless measurement makes WeighTrac wear and maintenance-free.

With the help of MiniTrac the mass flow of freely falling bulk solids can also be determined, for example in pipes or shafts.

Everything flows

The ancient Greeks already knew it: everything flows. But how big the flow really is, is often not that easy to determine. WeighTrac is the radiation-based alternative to the mechanical belt weigher: when implemented on conveyor belts or in screw conveyors, WeighTrac delivers reliable data on the throughput quantity of bulk solids. In the process, the radiation source sends its signals through the bulk solid, which damps the gamma rays more or less depending on material quantity and density.

Mass flow measurement with WEIGHTRAC SHLD source holder

SHLD source holder

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Reliable level detection in cellulose pro-duction

Cellulose is the basis for the production of paper, tissues, wadding and dressings.

In cellulose production, wood chips are broken down chemically with the help of cooking liquor. After the cooking process is finished, a part of the raw wood material is dissolved in this medium. To be able to use the lye (cooking liquor) again, it must be regenerated.

This is carried out in special reactors in which the lye is cleaned through oxidation. The oxidation process takes place at a temperature of around 160 °C and a pressure of 10 bar in an oxygen atmosphere – aggressive process conditions in which previous measuring techniques quickly reached their limits. But to ensure the safety of the plant, monitoring the maximum level of the reactor is extremely important.

Without a doubt, this is a job for continuous radiation-based level measurement with the ProTrac sensors SoliTrac or FiberTrac.

Practically everywhere in the world, radiation-based measurement has proven to be the optimal measuring method for polyester melt: the measuring equipment, mounted on the outside of the vessel, delivers reliable process data – without touching the product or the vessel. The isotope caesium-137 is used as the radiation source. Since it has a half-life of 30 years, the source usually never has to be exchanged and is therefore virtually maintenance-free.

Polyester melt: level measurement despite rotation and heat

It’s hard to imagine life without polyester. It can be found in beverage bottles, in clothes, in varnishes and in circuit boards. This versatile synthetic material is created in a polyester melt reactor, in which terephthalic acid is esterified with monoethylene glycol.

The process conditions in such a reactor place heavy demands on a level instrument: the process temperature climbs up to 280 °C and there is a vacuum inside the vessel. The vessel itself is completely enclosed by a heating jacket. In addition, a disc agitator causes rotational movement of the contents.

The ideal solution: the radiation-based level switch MiniTrac. This instrument is completely external to the vessel and is thus independent of the process conditions that conventional measuring techniques cannot handle. Pressure and extreme temperatures are no problem at all for MiniTrac.

Application example: limit levelApplication example: level

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temperature of the clinker, WeighTrac determines the flow rate without touching the medium. Production can thus be optimally monitored and controlled.

Another advantage of the radiation-based mass flow measurement: WeighTrac can be integrated into existing conveying systems with no problem. But the instrument can do even more: if, in addition to the flow rate, the density of the clinker material needs to be determined, ProTrac can measure the bulk density of the clinker.

To achieve a high flow velocity – and thus a slower settling out of material – pipes with diameters less than 100 mm are usually employed.

The required measuring precision is reached by sending the radiation through the pipe at an angle of 30°. MiniTrac can be easily installed in this position with the variable mounting accessories.

Emission protection: density measurement of lime water in flue gas desulfurization

To lower their emission values, coal-fired power stations operate expensive systems for flue gas desulfurization. Many of these systems use the so- called wet method, whereby lime in the form of a lime water suspension is used as a “detergent”: the lime water suspension is sprayed into the untreated flue gas in the scrubbing tower. The sulfur dioxide con-tained in the exhaust fumes is largely absorbed by the ensuing chemical reaction. Gypsum is the end product.

The important factor in this procedure is the concentration, i.e. the density, of the lime water – it must be correct. The fine particles in the lime water are very abrasive, making a non-contact radiation-based density measurement and the best and most reliable solution.

Belt weigher: how much clinker is on the conveyor belt?

Cement is produced from the raw materials limestone, clay, sand and iron ore in a continuous process in cement plants. Clinker is the cement ingredient that is responsible for hardening when water is added.

Clinker is burned in a rotary furnace at about 1450 °C and then cooled down to around 200 °C. The still red-hot clinker is transported to a temporary storage location by a cell conveyor.

Here, the most suitable way to monitor the mass flow of the hot product is with a radiation-based measurement: completely unaffected by the

Application example: density Application example: mass flow

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plics® – the idea with a future

Simpler is better

plics® makes everything simpler – from selecting to ordering, right through to setup, maintenance and service. In this modular system, you combine exactly the performance features you need to solve the measurement problem – both technically and economically. Whoever has once worked with plics® can apply the setup, wiring and adjustment concept to any other application, and even to other measuring principles. Because of the broad range of the technology and the “easy choose, easy use” concept, plics® brings a plus in security and reliability to every application.

Easier for user and planner

plics® offers individual selection and combination of sensors, process fittings, electronics and housings. For the engineering department, this translates into easy, straightforward planning and instrument selection. For the plant builder, it means short delivery time, uncomplicated connection and quick setup and commissioning, and for the user, operational reliability, simplified maintenance and reduced inventory costs.

Radiation-based measurement with new values

VEGA has greatly simplified the world of process instrumentation with plics®. Now, with the introduction of the new ProTrac sensors, all the advantages of the plics® instrument concept are also available for the radiation-based measurement of level, density and mass flow as well as radiation-based level detection.

VEGACONNECT

4 … 20 mA/ HART

PVT scintillator

AluminiumDouble chamber

Indicating and adjustment module

Electronics

Housings

Sensors

Functional safety

PLICSCOM

Profibus PA FoundationFieldbus

Flexible plastic

scintillator

NaI crystal

Stainless steelDouble chamber

Explosion protection

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System integration

All current standards for measurement data transmission

VEGA offers practice-oriented solutions: from the proven 4 … 20 mA measured value transmission with superimposed HART communication technology to fieldbus technologies like Profibus PA or Foundation Fieldbus to wireless transmission. When it comes to interfaces for level detection, the selection ranges from non-contact electronic switch to relay, transistor and NAMUR signal to current jump signal.

Communication at all levels

VEGA supports all leading standards that make uniform, centralised field instrument operation possible. If the measuring instruments are integrated in primary management or control systems, they can be accessed via the corresponding infrastructure for purposes of adjustment, servicing and diagnosis. The DTM as well as the EDD description language are supported.

Adjustment and diagnosis

PLICSCOM: the multifunction talent

With its new adjustment philosophy, PLICSCOM offers a lot of practical advantages. It can be mounted on any instrument in four positions 90° apart. Adjustment is carried out via membrane keys. The clearly structured menus make setup and commissioning as easy as child’s play. PLICSCOM also serves as an indicating display on the instrument. Status messages are displayed in plain text. In addition, all device data, such as measuring range, process fitting and seal material, can be called up. When an instrument is exchanged, PLICSCOM ensures that the measurement point is quickly up and running again: all sensor data are saved in PLICSCOM with a simple keystroke and copied later into the new sensor.

Instrument adjustment via PC and control system

DTM/FDT technology is the manufacturer-independent, innovative description technology for field instruments. With it, even highly complex field instruments can be operated with mobile laptops and PCs as well as the usual engineering and operating environments of control systems. With the help of DTMs the sensors are configurable in every detail and important adjustments can be carried out quickly and easily.

As a system-independent operating system for DTMs, PACTware is the first choice for many field instrument manufacturers. VEGA also delivers appropriate field instrument descriptions for system environments that depend on EDD description technology.

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VEGA Grieshaber KGAm Hohenstein 11377761 SchiltachGermanyPhone +49 7836 50-0Fax +49 7836 50-201E-mail info@de.vega.comwww.vega.com