Vacuum measurement system is quick to install and use

Established in 1880, Bennett Opie is a family-owned manufacturer of products including pickled walnuts, cocktail cherries, lemon slices, bottled fruit and organic sauces. Most products are packed into vacuum-tight jars with metal lids.

There are three main filling lines, which between them run continuously for 10 hours a day, four to five days per week. Empty jars are fed into each line, where they first pass through a jar cleaning station. Next, the jars are fed to a spice dosing system (if the product requires this) and then through a solids filler, where the jars are filled at high speed with fruits or other solid foods. The jars are filled with a liquid preservative, then transferred to a metal detector system that checks each jar for traces of metal. Towards the end of the line, a metal lid is screwed onto each jar. The final stage on each of the three filling lines involves the jar lids passing through a vacuum integrity check (dud detector) station, with the check performed by a vacCONTROL non-contact eddy current measurement system supplied by Micro-Epsilon.

James Jennings, Engineering Manager at the plant, comments: "Each filling line at the plant processes up to 150 jars per minute. We manufacture in relatively small batches for all major supermarket chains and specialist retail outlets and so typically we need to changeover a filling line four to five times every day. Minimising set-up times on the filling lines is therefore critical."

Vacuum checks

A key issue with regard to set up times is the vacuum integrity check on each jar lid. This inspection is necessary to ensure that the jar is correctly sealed and that no bacteria have entered the product during production. Jennings explains: "Before installing the first two Micro-Epsilon systems in 2005, we had to use special compressed air blasters to remove water from the jar lids before they could pass through the original dud detection machine. This machine used optical sensors to check the tightness of the jar lids. However, we soon realised that the machine could not measure accurately if the colour of the lid was black. As most of our lids are now black, we needed to look for an alternative measurement solution that could handle up to 200 jars per minute."

At that time, says Jennings, manual intervention and inspections were required on each filling line. A batch of jars with defective lids may build up until a stop button was pressed or the jars would be left undetected. There were no automatic stops or alarm systems in place to detect 'bad' jars.

During the Christmas shutdown period in 2005, Bennett Opie installed two vacCONTROL measurement systems from Micro-Epsilon. A third system was installed in August 2010.

Jennings states: "We installed the first two dud detector systems from scratch within just three days. This work included mounting the vacCONTROL systems on some stainless steel tables that we had designed, and fitting an ejection table for each line. The systems were up and running with few engineering issues. In fact, since installing the first two dud detectors, we have only had to recalibrate the systems twice in five years, which is pretty impressive."

About the vacCONTROL system

Micro-Epsilon's vacCONTROL system uses a non-contact inductive sensor that is unaffected by water or by the colour of the jar lid. The inductive sensor, which is positioned approximately 3mm from the target (lid), measures the lid deflection caused by the vacuum inside the jar. The sensor scans the lid shape while the individual jars pass the measuring point. The microprocessor records the measurement values and uses these to calculate the lid deflection as a function of the internal pressure. The system then compares the values with a pre-set deflection value to determine the tightness of the jar lid. If the lid deflection is not large enough, an eject pulse of adjustable length is generated. This pulse controls a sorter, which separates the jars into 'good' (sealed correctly) and 'bad'.

Bennett Opie no longer requires compressed air blasters to remove water from the jars, so cost savings have already been made. Jennings says: "Micro-Epsilon's measurement system has a statistics program and counter, which means we can see exactly how many jars each filling line has produced within a certain time period. We have display boards at the end of our filling lines with production targets on. We can now easily check the performance of a certain line or its average throughput over the last hour, as well as monitoring production and quality trends."

Furthermore, the system will automatically shut down a filling line if it detects more than three lids in a row that are incorrectly sealed. This is a huge benefit to the plant, as these defective jars can then be removed and re-processed later. There is also no need for manual inspection checks, so labour savings have also been made here.

Rapid payback

Jennings continues: "As well as making savings on compressed air, the new dud detectors have made our products 100 per cent customer-compliant, with fewer quality issues or rejects coming back to us from customers. The vacCONTROL systems are also easy to use and it takes us no more than one hour to train an operator from scratch. It helps that menus and navigation are intuitive and familiar.

"In terms of payback, I would say that we have achieved this already. For example, since installing the new dud detectors, we have reduced set up times on each filling line significantly. Our original dud detectors took around 10 to 15 minutes to set up, whereas the new systems take four minutes, a reduction of at least 60 per cent."

Follow the link for more information about Micro-Epsilon's vacCONTROL and other non-contact measurement systems, or call the Micro-Epsilon sales department on +44 (0)151 355 6070 or email [email protected].