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HOW TO PREVENT FALSE STARTS WHEN AUTOMATING VALVE BAG FILLERS

20 August 2015

HOW TO PREVENT FALSE STARTS WHEN AUTOMATING VALVE BAG FILLERS

A major concern when automating a valve bagging system is the false start.  A false start is when the bagger is started and the bag is not properly positioned on the filling spout; product can be dumped to the floor and dust can quickly fill the building.  Most false starts are due to variations in bag construction and wrinkles in the bags due to stacking and transportation of empty bags from the manufacturer; quality bags are critical to automated operations.  When a system is manually operated, the operator visually ensures that the bag is properly applied.  If the start is unintentionally tripped, the operator can quickly respond by pressing an emergency stop button.  When a system includes an automatic bag applicator, it is likely that an operator is not readily available to respond to a false start.  Control methods must be implemented to eliminate false starts where possible and mitigate their effects otherwise.


At Premier Tech Chronos, we take a number of measures to address the concern of false starts due to miss-applied bags.  The first item that must be considered is the start mechanism itself.  As a bag is placed on the filling spout, the leading edge of the bag moves a mechanical plate to trip a non-contact proximity switch.  If the bag jams on the end of the filling spout or is not placed deep enough onto the spout, the auto-start switch is not triggered, the bagger does not start, and the bag is rejected.  Because, on occasion, it is possible to trip this switch when the bag is not properly in position for fill, other measures are employed.

All Premier Tech Chronos baggers used with automatic applicators also include the following:

  • Bag Blow-Off Switch – As the bag fills, it rounds and pulls away from the auto start switch.  The blow-off switch must be maintained throughout the fill.  If for any reason this switch is not made, the packer is immediately shut down.
  • Maximum Fill Timer – If for any reason, the bag takes longer to fill than expected, the packer is shut down.
  • Loss-in- Weight or No-Weight-Gain – This is a feature on all current Premier Tech Chronos weight controllers.  An algorithm evaluates whether the bag is filling as expected.  If the bag has burst or if the product flow has stopped, the weight controller will detect this and shut down the machine.

The three features above all address the problem after the packer has been started.  This is important for bags that burst during fill (weak or poor quality bags), but does not address the problem of a false start until it is too late.  It is much better to prevent the false start than to try to detect it after the fact.  A failsafe mechanism, that detects that the bag is both around the spout and deep enough onto the spout, would be ideal.

Premier Tech Chronos has developed a Bag-on-Spout Sensor (B.O.S.S.), a patented 2-point “Bag-In-Place” detection system.  It is an optional feature on all machines, but strongly recommended for Clean-Pak machines with ultrasonic valve sealing.  It utilizes two lasers to detect the position of the bag in the area of the filling spout (see illustration).  Each laser is mounted in a pressurized enclosure to keep the lens clean and protect the device from dusty environments.  The laser sensors are mounted directly to the packer frame and aimed in the direction of the left and right sides of the filling tube. The B.O.S.S.  is capable of detecting all of the major modes of failure for miss-applied bags.  These lasers are calibrated to detect the presence or non-presence of a bag. This form of detection is unique in that it does not physically touch the bag to determine if the bag is in place. Though there are some conditions that may fool the B.O.S.S., when used in conjunction with the other features, automatic packaging systems can be very safe, reliable and clean.


 Benefits

• Cleaner operation by eliminating filler starts due to misplaced bags
• Eliminates labor cost of cleaning spilled product due to misplaced bags
• Cost savings by eliminating contaminated product on the floor
• Can work II-G-1 or II-G-2 rated areas

Conclusion

•  The B.O.S.S. unit actually looks and measures the bag placement on the Filling Spout, AND won't let the filler start if the empty bag is not placed properly onto the Filling Spout.  Since the product isn't even flowing from the filler, no product spills.

• The B.O.S.S. uses two lasers that point down past either side of the Filling Spout.

• If a bag's top (the bag's valve/sleeve area) blocks the laser somewhere in between the filling spout's diameter (top and bottom surfaces), the B.O.S.S. considers the bag to be placed properly.

• If the bag slides underneath the spout, the laser is blocked "past" the bottom of the spout, and the B.O.S.S. considers this an improperly placed bag.

• If the bag is "above" the filling tube top, the B.O.S.S. also considers it an improperly placed bag. 

• In both "improperly placed" bag cases, the B.O.S.S. keeps the filling machine from starting, and the bag is rejected so another bag can be tried.

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