What is Water Hammer Phenomenon ?
During distribution of filled glass bottles packed in a carton case, when a carton falls from above of double-stacked cartons, the bottom carton gets crushed. The bottles inside a carton on the crushed carton drop down corresponding to the crushed amount of the carton. However, the filling content remains at the same position for a short period due to the inertia. After a small fraction of time lag, the content starts dropping, and gives an impact on the bottom heel of the glass bottles, which can cause bottle breakage.
This is usually called the “Water Hammer Phenomenon”. Also, in rare cases, a partially cracked by this Water Hammer Phenomenon but unbroken glass bottle whose inside is negative-pressured is delivered to a consumer.
When the bottle is opened by the consumer, the negative pressure inside the bottle is released, and the filling content pushes the bottle out from inside. The crack on the inside surface of the bottom heel part is promoted, and finally leads to breakage of the glass bottle. This may dirty the consumer's clothing by the content or hurt the consumer by the shards of glass.
Process of glass bottle breakage caused
by Water Hammer Phenomenon
- (1) A filled glass bottle rapidly falls down.
- (2)-1 The liquid content remains in the same position inside the bottle by its inertia force.
- (2)-2 The volume of the head space above the filling point is reduced.
- (2)-3 To compensate the reduced volume of the head space, cavities are generated between the liquid content and the bottle bottom.
- (3) When a cavity collapses, it engulfs its surrounding water and a microjet arises, and then tiny cracks (impact traces) are formed on the heel and bottom of a glass bottle.
- (4) The liquid content falls down due to the high pressure in the head space and gives a strong impact on the bottle bottom.
- (5) Stress is concentrated on the inside surface of the bottle heel and the glass bottle starts to break from the tiny cracks on the bottle heel.
Images of actually-occurred cavites
The actual generation time of cavities is approximately 0.001 seconds.
They can not be seen with the naked eye.