How does laser spectroscopy work to identify leaks and micro leaks in bottles?
A laser beam is positioned at the same height as the bottles’ headspace, so the total or partial pressure can be measured in line as the bottle passes over the belt. The physical property of certain molecules in the gaseous state to absorb light only from specific, defined wavelengths is exploited to take the measurement, making it possible to identify which molecule to monitor in the headspace of the closed container and to obtain very fast and accurate measurements of total or partial pressure. This also makes it possible to take measurements of diverse types of bottled products with different filling/storage gases.
Applications of the technology
Possible applications include the following:
- Products with added nitrogen: Bottled water and other beverages to which nitrogen is added to remove air from the headspace or to keep the container under pressure and prevent PET bottles from damage during palletisation and transport. The presence of water vapour molecules in the headspace is used to control the nitrogen pressure online; this makes it possible monitor the operation of the nitrogen dispenser, stabilise the pressure inside each bottle, and detect under- or over-pressurised bottles (by comparing them to a standard pressure value), which can cause faults on the cap.
- Hot-filled products: The most common application is hot-filled fruit juices in glass bottles with twist-off caps. The degree of vacuum in the headspace is measured directly inside the closed container, making it possible to detect products with imperfect closures.
- Carbonate products (CSD): All carbonate products can be measured using the presence of CO2 molecules in the headspace. The solution is placed immediately after the pasteurisation phase (for beer and other pasteurised beverages), or away from the filling machine.
