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these editorial articles or for further information, please contact:

Tom McDougall
Land Instruments International
Infrared Temperature Measurement
Dronfield, S18 1DJ, England

Tel: +44 (0) 1246 417691
Fax: +44 (0)1246 410585
Email: infrared@landinst.com
 
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'Infrared linescanning systems' (PDF 468KB) published courtesy of Glass Worldwide - 3rd issue 2006

'Float and automotive linescanning' (PDF 1540KB) published in the July/August 2004 edition of Glass International

'Linescanner can take the heat on the float line' (PDF - 1389KB) published in the September 2004 edition of Glass

'Thermography aids chiropractic diagnosis' (PDF - 101KB) published in the August 2004 edition of Vision Systems Design.
For a printable version of this article click here

PR020577 - INFRARED LINESCANNER IMPROVES CEMENT KILN PERFORMANCE

The Landscan LSP 62 improved kiln performance at a factory in Cameroon.

A maintenance engineer at the cement factory in Cameroon.

A thermal map of the live feed from the Landscan LSP 62.

A linescanner from infrared temperature measurement specialist Land Instruments International has improved the monitoring of kiln shell temperatures at a cement factory in Cameroon.

Mounted in a robust, air purged and cooled stainless steel enclosure at a distance of 27 metres from the kiln, the Landscan LSP 62 infrared linescanner continuously scans almost the entire 55-metre length, relaying a thermal map to the control room so that staff can adjust process variables accordingly. It also gives immediate warning of worn or missing refractories in the kiln lining.

Monitoring was previously limited to manual checks using a hand-held Land Compac 3 infrared thermometer. Only 20 metres of the kiln shell was accessible for checking in this way, but it took a full hour to take the readings at 1-metre intervals - which were then entered onto a PC for evaluation.

With the kiln operating at up to 500 degrees C and an ambient temperature of around 45 degrees C, collecting readings was an extremely difficult task for the operating and maintenance engineers.

The factory, which is operated by the Lafarge subsidiary CIMENCAM, is in Figuil, close to the border with Chad and 800 km from Yaounde, the Cameroon capital. The semi-desert location was chosen because of the local availability of limestone and other raw materials and the proximity of the border with Chad, to which much of the 275 tonnes produced each day is exported.

Three metres in diameter and 9.10 metres in circumference, the kiln makes 4.5 revolutions per minute at a speed of 750 mm per second. It is scanned through an angle of 80 degrees with a field of view of 100:1 (95% energy), and each revolution triggers an encoder that saves the completed scan and displays it in the control room alongside the live data from the next.

The Landscan LSP 62 is one of Land's LSP6 series of linescanners which, although they have many other industrial applications, were developed with monitoring the shell temperature of rotary kilns very much in mind.

Damage to the kiln shell and its lining due to excessively high temperatures and thermal shock results in high repair costs and irrecoverable loss of production.

The refractory-lined lower end of the kiln can be subjected to temperatures of up to 2,000 degrees C, not to mention the effects of abrasion from the product itself. If the refractory is damaged, localised heating of the kiln shell may occur, creating a hot spot that, unchecked, will seriously damage and even warp the kiln.

But much of this can be avoided if - as now in Cameroon - the plant operator has a detailed knowledge of the degree to which the lining is worn (and therefore the likelihood of premature failure), along with the presence and magnitude of clinker-ring build-up.

Conversely, monitoring the condition of the kiln refractories and stopping production for relining or repair only when necessary may lead to an extended campaign life with associated cost savings.

An infrared linescanner contains a high precision thermometer module, a rotating mirror and associated electronics. Linescanning heads are normally used to monitor the shell temperature of a cement kiln, scanning a section from a distance of around 30 to 40 metres. Up to 1,000 measurements can be taken with a single scan - the equivalent of having the same number of conventional fixed infrared thermometers mounted in a line down the length of the kiln.

Output signals are transmitted to a PC containing data acquisition electronics and software, which displays a colored thermal map representing the distribution of temperatures along the kiln shell, making the location of hot or cold spots very evident. Cooling fans can then be positioned accordingly.

Central to the LSP6 concept is the scanner head, which can generate high speed temperature profiles at up to 100Hz in the measurement range 20 to 600C with an accuracy of +/-3C. It also has a wide scan angle of 80 and a field of view of 100:1 (95% energy) maintained at all target distances.

Of the three versions offered, the LSP62 is the most appropriate for kiln applications, covering temperatures from 100 to 600 degrees C. It is sufficiently compact to be installed where space is limited, and has a sapphire protection window for added durability. A built-in Class 2 laser to define the scan plane and sighting angle is supplied as part of the package, making the initial set up quick and simple.

A complete range of mounting assemblies, water cooling and air purging options are also available - and the scanner head can be de-mounted for maintenance and put back in position without the need for realignment.

Completing the system is the new 19in rack mounted Landscan Control signal processor, which generates serial and Ethernet temperature data outputs that can interface to local process control or the new Landscan Configuration Professional and Landscan WCA software.

Top of pagePR020432 - ARE YOUR PROCESS TEMPERATURES UP TO SPEC?..

..and can you prove it to your customer? Norman Fisher, sales manager at Land Infrared, has some cautionary tales to tell.

In times of recession when orders are hard to come by, companies inevitably look for the benefits of their product that will give them an edge over their competitors.

Quality and reliability are often the chosen themes - which naturally leads to questions being asked about their suppliers' manufacturing procedures.

If the reliability of our product depends on the quality of a certain component, how can we be sure that it is being made exactly as it should be?

It's at this point that the supplier gets a visit from the customer's quality audit team; and if he can't demonstrate conclusively that specified procedures are being followed to the letter, he could find his contract in jeopardy.

The reliability of many engineered products depends on metal components, of course - and in most cases it is accurate temperature control at critical points on the process route that determines success or failure.

When business is booming, the customer's over-riding concern is to get parts so that he can continue to meet demand, and 'minor details' such as process temperatures are of little or no interest.

But when the economic tide turns, the supplier must be able to show that he is doing the right thing at the right time - and in exactly the right place.

The five case studies summarised here show how infrared temperature measurement can often provide a solution - but this is usually not an area where off-the-shelf, 'point and press' portables can do the job, however tempting the price ticket. In fact, as some of these examples show, they can give incorrect and misleading results.

Accurate Temperature Measurement Choosing the right system and integrating it into the production line are crucial to success, which is why it's important to have an equipment manufacturer well versed in the realities on board from the start.

At Land Infrared, we wouldn't claim to have 'seen it all' - because there is always a new challenge around the corner - but we have certainly acquired a great deal of experience over the years in matching our technology to a wide range of production circumstances.

Interestingly, all of these projects are from our order book for 2001 - the year when the manufacturing recession began to bite - and in most instances the need to install accurate temperature measurement systems was a respond to pressure from the customer.

1. Forging

Manufacture of a safety-critical suspension part from 13-25mm diameter bar depends on a bar temperature of at least 950C, to avoid possible cracking or insufficient hardness.

Temperature measurement immediately before forging The customer - a European car manufacturer - was dissatisfied with existing temperature measurement arrangements, which were limited to a single thermocouple inside the furnace in which the bars were heated, supplemented by the ability of operators to judge bar temperature from appearance alone.

Reliance on such subjective judgments is commonplace in manufacturing, but it is invariably ill-founded because - although the human eye is a good and repeatable detector - it is not calibrated and no two eyes are the same, so that quality varies from operator to operator.

The system Land installed measures the temperature of each bar at the critical point - immediately before forging - and activates a warning buzzer if it is below temperature.
2. Rolling

A precious metals manufacturer needed to improve efficiency in response to the recent opening-up of the industry to Europe-wide competition.

Products included blanks from which coins are stamped, consisting of strips of semi-precious and base metals that are fused together by resistance-heating to 450C before passing them through a set of pinch rolls. Process control was limited to the heat setting of the furnace, and metallurgical analysis 'after the event' to determine whether an adequate bond had been achieved.

To reduce scrap rates, the company wanted to use strip temperature as a means of varying strip speed. Land demonstrated that the most accurate measurement position was the 'wedge' formed at the point where the strip and the roll converge - a method it has also used successfully in the continuous annealing of bright metal strip.

3. Fusing

A surgical instrument manufacturer risked losing a long-standing contract to rivals when the orthopedic tools he supplied frequently parted from their plastic handles during use.

The tool was assembled by heating the stainless steel shank in an induction coil, and then inserting it into the handle using a pneumatically operated jig.

Although the company knew that the shank had to be at around 350C to achieve a successful bond, the only controllable part of the process was the heating time - and the portable infrared thermometer used to check temperatures gave inaccurate readings, resulting in a high reject rate.

The system that Land Infrared supplied takes accurate temperature readings from the correct fixed distance - something the portable could not achieve - and activates a light signal for the assembly process to continue if the temperature is within tolerance limits.

4. Heat Treatment

During the manufacture of bandsaws, the saw teeth are hardened by induction-heating to 850C, followed immediately by oil quenching.

As in several of the other cases described here, the only means of controlling quench temperature was to adjust the speed at which the band traveled through the induction coil.

There was a fair degree of 'guesstimation' involved - which was reflected in the proportion of product that had to be scrapped if metallurgical analysis showed that the carbon content of the tooth area was below the specification.

The company wanted to reduce the scrap rate by measuring the temperature of the teeth as the band passed from the induction heater into the quench.

As well as meeting this requirement, Land's system showed that the line speed controls were not as accurate as had been assumed - a deficiency the company has since rectified.

5. Casting

A company casting steel cylinder liners inside a rotating mould were using a hand-held infrared thermometer to check the temperature of the mould's internal surface, which determines the rate of flow of the metal and hence the thickness of the liner.

Land replaced this manual method with an automatic continuous system, eliminating the considerable loss of production time necessary for an operator to go into the safety compound surrounding the casting area to make the temperature measurement.

As a consequence, productivity has increased by almost 100%, achieving the output required by management.


6. A final thought

Several of the companies described here were 'caught napping' with inadequate temperature measurement arrangements when the customer came calling- but there must be thousands of other cases on production lines in all parts of industry that pass without notice.

It's easy to take the short-term, cynical view of course. The thousands who get away with it are the lucky ones. Why spend the money if you don't have to - especially when business is bad? Every little helps to make the bottom line look better.

But there is a more positive (and potentially more profitable) approach. If you spend a few thousands to bring your temperature monitoring arrangements up to standard, you won't just cut your production costs (desirable though that is).

Equally importantly, the facility you have invested in becomes a positive selling point in its own right. Instead of just rescuing the orders that you've got today, it can help you win the multi-million pound contract of tomorrow.

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