Methods for the inspection Return (Rewash) Bottles
The main problem of checking bottles for foreign substances with a Sniffer is the production
speed of up to 45 thousand bottles per hour (12.5 bottles/sec.). This is why many of the analytical
methods common in chemistry (chromatography) can not be used. Some basic technologies have been
developed to match the necessary speed and sensitivity. These can be divided into different categories:
- Pulse Fluorescence: "Activated" by electromagnetic radiation such as UV light molecules transmit energy to other specific spectra (wavelengths). => Detection of gasoline, diesel, naphthalene, Exxon.
- Spectroscopic Procedures (with
"light"): UV / VIS (visible light)
/ IR (infrared) . The spectrum permits
conclusions concerning structure and
composition. Most of time absobtion spectras
with Gas-specific filters.
-
Microwaves for Ammonia
compounds IR (SOX) => alcohols, volatile
hydrocarbon, acetone, toluene.
-
Photo ionisation:
Ionization with UV => (PID). Measurement of
conductivity of ionized gas. Wide-range
detection of chemical compounds, but
unsuitable for soft drinks and alcoholic
drinks because of missing selectivity.
-
Chemo Luminescence:
Stimulation of molecules by "oxidation" =>
Detection of Ammoniac and similar compounds
and aliphatic hydrocarbons. (KR)
-
Mass Spectroscopy: Analysis of the gas
composition by "measuring" the mass of
molecules and its concentration. => A
universal widely used, reliable procedure.
Analysis of mass spectra, wide-band
detection and identification of all
unwanted, known and unknown substances with
a specific gaseous phase.
-
Residual Liquid Color Measurement:
Complementing the Sniffer, this process
measures the “colour” of the residual liquid
within the visible light spectrum. =>
Detection of foreign substances with no
specific gas phase and detection of perfumed
substances ("PEX" detergents) by measuring
the foam produced after the injection of
carbonate or soda (NAOH).
-
Electronic nose Chips with
semiconductors or thick films with chemical
substances having reactions to certain
gases. Several sensors with different
characteristics form a nose, able of
distinguishing odours. Unsuitable for
alcoholics or soft drinks because of missing
selectivity. Relatively slow.
-
Chemical Sensors in combination with Leak
measurment is very successful. Developed and
protected by Inspecto Automation used in
Canis.
How good are the Sniffers? The sensitivity of
the sensors for solvents, hydrocarbons and
ammonia is usually around 0.1 up to 1 micro
litre per litre of air.(1
ml = 1 Qube-mm).
All these methods have one thing in common: The Sniffer takes a sample
out of the gaseous phase from each bottle. Just imagine what it would
mean for a human nose to have to smell 36'000 bottles! It is clear
therefore that Sniffers cannot be maintenance-free. With each gas sample
some dirt and some sugar will be sucked in, polluting the pipes and
sensors in the course of time. However, this problem has been largely
solved by means of an automatic cleaning device and change parts.
|
