Induction Cap Sealer Troubleshooting: Causes & Fixes

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Problems on this page:

Foil not sealing Burnt liners or melted caps Seal incomplete around the rim Missing foil not detected Sealer tripping on temperature Foil hard to peel or tearing Sealing head struck by containers Leakers despite a good foil Seal quality changing through the shift

Foil not sealing

Hits OEE: Quality

Symptoms: The inner foil peels off easily or is not bonded at all.

Power too low for the line speed

Raise the power or slow the line, then confirm with a peel check.

Sealing head too high above the caps

Set the head height for the cap size.

Cap torque too low

Check the capper torque so the foil is pressed against the neck.

Wrong liner type for the container

Check the liner specification for the container material.

Prevention: Seal checks on samples at start-up and set intervals.

Burnt liners or melted caps

Hits OEE: Quality

Symptoms: Liners show burn marks or caps deform after sealing.

Power too high

Reduce the power for the line speed.

Line slowed or stopped under the head

Make sure the sealer drops power when the line stops.

Head set too low

Set the head height for the cap.

Settings not changed for a new cap size

Use the recipe for each cap and container.

Prevention: One recipe per cap and container, with power and height recorded.

Seal incomplete around the rim

Hits OEE: Quality

Symptoms: The foil bonds on one side of the rim and not the other.

Cap not centred under the head

Check the conveyor guides keep containers centred.

Cap torque uneven

Check the capper chucks.

Defects on the container neck

Inspect the neck finish for flaws.

Head not parallel to the conveyor

Level the sealing head.

Prevention: Peel checks look at the whole rim, not only whether the foil holds.

Missing foil not detected

Hits OEE: Quality

Symptoms: Containers without a foil reach the end of the line.

Missing foil detection not enabled

Enable missing foil detection and set its reject.

Detection sensitivity set wrong

Test the detector with a cap that has no liner.

Reject device not working

Check the reject device with test containers.

Caps without liners in the supply

Check incoming caps.

Prevention: Missing foil detection challenged with a test cap at start-up.

Sealer tripping on temperature

Hits OEE: Availability

Symptoms: The sealer alarms on over temperature and stops.

Cooling water flow low or too warm

Check the cooling flow and temperature.

Cooling fans or filters blocked

Clean the filters and check the fans.

Hot room around the power unit

Improve ventilation around the power unit.

Running at maximum power all the time

Check whether the line speed and caps need that power.

Prevention: Cooling checked on the maintenance round.

Foil hard to peel or tearing

Hits OEE: Quality

Symptoms: Customers find the foil hard to remove or it tears in pieces.

Power too high for the liner

Reduce the power to the validated range.

Liner type wrong for an easy peel

Check the liner specification.

Cap torque too high

Check the capper torque.

Container material changed

Check the liner suits the container material.

Prevention: Peel strength checked on samples.

Sealing head struck by containers

Hits OEE: Availability

Symptoms: Containers hit the head, damaging it or knocking containers over.

Head height not changed for a taller container

Set the height at every changeover.

Containers tilting on the conveyor

Check guides and conveyor transfers.

Caps loose and lifting

Check the capper.

Head mounting loose

Check the head mounting.

Prevention: Head height on the changeover checklist.

Leakers despite a good foil

Hits OEE: Quality

Symptoms: Containers leak even though the foil looks sealed.

Container neck damaged

Inspect the neck finish on leaking containers.

Container wall too thin

Check the containers against their specification.

Foil seal weak in one spot

Check peel along the whole rim.

Cap cracking

Check caps for cracks after capping.

Prevention: Leak test on samples after sealing.

Seal quality changing through the shift

Hits OEE: Quality

Symptoms: Seals start good and get weaker or stronger as the shift goes on.

Line speed changing without a power change

Link the sealer power to the line speed where the unit allows it.

Sealing head warming up

Check the cooling of the head.

Cap torque drifting

Check the capper torque during the shift.

Different cap or liner lots

Record lot changes and check seals after each one.

Prevention: Seal checks at set times through the shift.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: capping machine · filling machine · labelling machine · checkweigher · bottle unscrambler

Stop the same fault coming back

Recurring induction cap sealer stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover