ASTM D3198-97 (2002) Standard test method for application and removal torque of threaded or lug-style closures
Measuring the application and removal torque on threaded containers
NOTE: Withdrawn standard, no replacement (2016)
This ASTM test method describes the procedure for pre-conditioning containers and their closures before measuring the torque needed to close the container, and then open it again. The results can be of use for rating the performance of automatic capping machines, observing the tendency of closures to loosen during storage or shipment, or the force required to break hard plastic and overturn or “strip” soft plastic and metal closures.
Representative specimens of a threaded or lug-style container are held in a torque-measuring device and either the predetermined amount of torque is applied to its closure, or the amount of torque necessary to loosen the closure is determined, or both.
A calibrated torque meter capable of indicating clockwise and counter-clockwise torque. The meter should have a means of securely holding the container without distortion. A special cap mandrel may be used to hold the closure to facilitate application and removal without distorting the closure.
Separate, unused containers and closures are pre-conditioned at a specified temperature and relative humidity for 48 hours.
The container is secured in the torque meter grips so that the axis of rotation of the cap is concentric with the centre of the moveable plate on which the container rests. Avoiding any contact with the container, the calibrated torque meter is used to observe the application torque as the closure is smoothly screwed onto the container. The digital torque meter records the maximum torque, this is application torque. To measure removal torque, the assembled container and closure are secured in the torque meter grips so that the axis of rotation of the cap is concentric with the centre of the moveable plate on which the container rests. Without touching the container, the closure is rotated counter-clockwise. The digital torque meter records the maximum torque, this is the removal torque.
This overview is intended to provide a basic understanding of the test procedure and suitable equipment to meet the standard. Please refer to the latest official ASTM test method D 3198-97 (2002) standard for more detailed information.