Torque Guidelines for Closures & Capping Bottles

A common question that is asked is 'How tight do we screw your closure onto a bottle?'

It is not a simple answer, you can measure the removal force to open a closure, but not the force used to apply it on your filling line.

The important thing to understand is the removal force (opening force) that is required for your consumer when they first open your pack.

Quite often it will be at least 30 days after you have filled the pack.

The type of bottle, the temperature you fill the pack, and the thickness and structure of the liner will all have an effect on the removal torque. 

Here's a breakdown of the important things to know about Torque Guidelines for Closures & Capping Bottles.

Torque is rotational force applied during application or removal of a closure from a bottle.

The rotational force with which a closure is applied to a bottle finish during capping. It affects seal integrity and tightness between bottle and closure. Properly established application torque will provide sealing integrity under expected conditions or temperatures, humidity and shock.

The rotational force with which a threaded closure is removed or unscrewed from a bottle finish. It defines the amount of rotational force necessary to loosen, open, or remove the closure. A properly designed package should have a removal torque range appropriate for its intended use and the consideration of any requirements for child resistant or tamper evident closure needs. A pack with a tamper evident closure will have two separate removal torques. The first is the torque to make the closure start to move, the second torque is the opening force required to break the tamper evidence system on that pack (Generally the second force will be dependent on the type of tamper band being used)

The application torque which is sufficient to cause the closure and/or bottle finish to distort and override the matching closure/bottle threads, resulting in loose caps, no seal, or package component deformation.

Torque is defined in inch-pounds or Newtonmeters and is measured by various types of torque meters. Specific methods for performing torque tests are defined in Technical Bulletin PBI No. 7. The optimum relationship between applied and removal torques and good sealing characteristics under various physical and environmental conditions must be established for each individual package. Application torque requirements also vary according to the closure size being used. The following torque values are listed for use as guidelines only, and are to be used for closure application by hand under controlled conditions. Special conditions may require torque values other than those listed. The actual figure you set will be dependent on many other variables. Bottle material, liner type, filling temperature, capping head and if the pack is passing through an induction tunnel.

*These are generally accepted application torques. Specific closures may require specific application torques which differ from those listed above. Check with your closure manufacturer for specific information.

Immediate removal torque values are approximately 40- 80% of application torque values. Production capping equipment should be adjusted to produce similar immediate removal torque values. It is important you test packs 30 days after application as this will be more indicative of the of the removal force the consumer will experience opening your finished pack. This is very critical for any torque dependent child resistant package.

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