Leaking and seal failure
Updated
In a still product a leak is a mess. In a pressurized one it is the closure telling you it was about to be a bottle bomb.
A seal under load
A carbonated or live bottle has internal pressure pushing outwards at the closure continuously, and that pressure rises with temperature.
So a seal that is adequate cold and at filling can be inadequate in a warm van three weeks later, which is exactly where leaks appear.
Why seals fail
Torque outside tolerance. Under-torqued does not seal; over-torqued distorts the liner so it does not seal either. Both fail, and the second surprises people.
The wrong liner for the product or the closure, which is a component nobody specifies and the one that actually does the sealing.
A damaged bottle finish. A chip or a molding flaw on the sealing surface, invisible until it leaks.
A poorly set crimper, for crown caps.
Pressure, simply exceeding what the closure was chosen for.
What a leak costs
The unit, obviously. Then everything in the carton with it, because a sugary liquid ruins labels and cardboard.
Then the consignment, because a leaking case arrives sticky and is refused.
And the information, which is the part worth having: a leak is a pressure warning, and a batch producing leaks is a batch to pull and test rather than to replace and continue.
Catching it
Torque checks through every run, on a gauge rather than by feel.
Inverted bottles held for a period and inspected.
Retained bottles held warm for the shelf life, which is the only test that reflects the condition in which seals actually fail.
And inspect the bottle finish on incoming stock, because a supplier's molding problem arrives as your leak.