23 August 2002

Beet auto grader all set

It has taken no less than

three years to develop, but

CTM Harpley says its

automatic sugar beet

grading system is now

ready for commercial

launch. Andy Moore

discovers how the system

has progressed

CTM Harpleys automatic beet grading system – designed to separate quality beet from deteriorated crop, stones and trash – will be commercially available next year.

Developed and tested over three years, the Intelligent Data Acquisition (IDA) system has been built for use with the companys 544 cleaner loader.

"We tested the system last season and it was 87% accurate in removing bad beet from quality crop and 98% accurate in separating stones," claims technical project manager Robert Toulson.

"The plan is to fine-tune the system this season and iron out any teething troubles so it will be ready for sale next year."

The key to the system, says Mr Toulson, are three electronic sensor arms positioned on the final web which follows CTMs Spiral Roller cleaner.

Individual pre-cleaned beet slot into 30cm long pockets situated in three lanes where each one strikes a sensor arm at the top of the web.

"The sensors work similarly to a piano tuning fork and relay the vibration level produced by individual beet. This is measured in frequency and analysed by a computer," he adds.

"A hard impact over a short period indicates the sensor has met a stone or soil clod, while a soft impact over a longer period indicates that deteriorated beet or trash have been detected."

Mr Toulson says the system assumes all material passing through the cleaner loader is quality beet, unless high vibration readings indicate unhealthy beet and trash which is removed. On this basis, the system has a fail-safe element and will not inadvertently remove healthy crop.

Once the computer realises sub-standard beet or stones are working their way up the web, it sends a signal to a rejection mechanism.

In one-fifth of a second, a wrap spring clutch is engaged which causes a gate to close, directing trash through a cavity in the web, so that material falls on the ground.

"One of the biggest challenges has been to ensure beet sits on the sensing web in an orderly and even fashion," says Mr Toulson. "The faster the beet jumps about on the conveyor, the more the system is likely to take inaccurate readings."

Improvements to ensure an even crop flow could include a timing control on the reception hopper and changing the angle of the front conveyor.

Maintaining grading accuracy requires the cleaner loader to run slightly slower than a standard machine. Outputs of about 500kg/min are achieved, but over a 1t/min is the target.

"The machine more than makes up for the drop in throughput because of its high separation efficiency," says Mr Toulson. "British Sugar is clamping down hard to eliminate crop contamination, and reduce rejections, penalties and dirt tares at the factory."

A reduction in dirt tares, he says, also fits British Sugars intention to curb the amount of dirt moved around the country, cutting transport costs and potential damage to the environment.

He points out that automated cleaning could also reduce the number of pickers required to sort crop on cleaner loaders and, as a result, labour costs.

Adding £10,000 to the price of a standard cleaner, Mr Toulson believes beet growers could see the system pay for itself over a few years through its ability to reduce crop rejections at the factory and provide a better sample overall.

CTM Harpley also has plans to develop a system to work with its 9000 series cleaner loaders for use with six-lanes or more. &#42

&#8226 Higher quality crop.

&#8226 Less dirt tare.

&#8226 Reduced rejections.

&#8226 Less crop spoilage.

The automatic beet grading system will be eventually developed for use with CTMs 9000 series machines.

Three sensor arms are employed to monitor whether beet is healthy, deteriorated or stones and trash.