Dewatering systems


Refer to the figure on right side, where a green colour scanning line intercepted a water drop scanning, and measured its distance to the bottle’s plastic, greater than toward the closure top surface: a wrong distance.   When nearly all of the bottles are damped, the effect is a systematic error superimposed to the uncertainty of the measurement system. If closures are damped, because no drying system is applied, the losses due to water drops amounts to 0.02 %.


At right side:  green colour scans intercepting water drops emulating cocked closures, increasing false rejects. A single water drops is the equivalent of several pixels. Implying an additional false reject, added to the value we’d have had if all closures should have been dry



“To prevent these false rejects the inspection’s sensitivity could be decreased, but then we’ll have an optic closure inspection no more capable to reject what guaranteed by the Vendor of the electronic inspector and requested by the bottling factory Quality Control Dept.”






0.02 % of false rejects becomes a huge loss on Production under today’s common assumptions:

  1. Bottling Line is an high-speed one (> 30000 bph);
  2. We integrate false rejects over the entire life-time of the Line (> 10 years).



Nearly inertial dewatering solution

To prevent these false rejects the inspection’s sensitivity could be decreased, but then we’ll have an optic closure inspection no more capable to reject what guaranteed by the Vendor of the electronic inspector and requested by the bottling factory Quality Control Dept.    Still today: 

  1. no Inspector has an “intelligence level” adequate to fully compensate water drops;
  2. trying to assure themselves Bottlers’ new orders, when questioned during pre-order phase about the performances in presence of water drops, many Vendors of Electronic Inspectors guarantee nearly whatever.
dewatering caps

The solution has to be pre-emptive.  The video above shows a commercial solution (“Mistral" model by SECOMAK Ltd., based at Elstree in the Hertfordshire, United Kingdom) for a dewatering system.    A 1 year long deep and extensive testing in tens of high-speed Aseptic Beverage Bottling Lines ranked it the best of six different commercial and non-commercial competing solutions.  The production speed always as high as 1.5 m/s, 52 000 bph.  The key point is the fact that this system acts by mean of two rows of needles, thus consuming little of air, and does not influence bottles’ own dynamics. Meaning that the total displacement (or, sliding) of the bottles along their journey in those ~400 mm where the needles dewater necks, under-caps and caps’ all-around surface, is limited.   Thorough and statistically significative tests over ~ 1 billion of bottles and the availability of data given by the Inspectors’ false triggers counters menu and distributions, allowed to set a precise boundary to the induced sliding, for > 99.5 % of the unstable 500 ml capacity bottles resulted < 20 mm.   Front of bottles’ diameters ~58 mm, we have a maximum sliding which the Inspector shifting-register may recover of 29 mm.   The remaining 0.499 % of the bottles’ slides in the range (20 - 29)mm, still completely recovered by the shifting register system of the Inspector.   And only 0.001 % of the bottles slided over 29 mm then prone to become a container without any identity. 


In presence of water drops, multiple light refractions, diffractions and reflections define the superior limit to the size of the defect we can detect by a camera system and an inferior limit of the losses (false rejects) along the Inspector's lifetime



Non-specific systems

Unproper system

Alternative systems are the blowers like the one on side and below, commercialized by Vendors in different sizes until 15 kW of power: power choice is function of the area to de-water and of containers’ speed.  They are commonly visible nearly wherever and it’d be imagined that they are adapt for the special application we are referring to: dewatering systems.   The tunnel solution is thinked for bottles not having any associated identity in a Shifting-Register.   It is a satisfactory dewatering system only for standalone electronic inspectors and not the actual in-the-machine whose Shifting-Registers is extend tens of meters along Conveyors and Machines.

On right side: closures drying before inspector: blower-controlled air-knives, acoustic insulation and drip accumulation tray



Unproper system

In the reality, what we are here naming tunnel solution, are systems to dewater:

  • bottles external sidewalls, 
  • cans’ tops and bottom before an ink-jet marking system, 

One more time clearly visible difference between the Secomak technology seen above and the one here on side, in the consumption of air and energy, markedly in favour of the Secomak-like solution.  They have to be dry the tops of the closures and the bottles’ plastic rings, say the areas evidenced with red colour in the figure above, then the air-knives have to be carefully directed there.  All times the electronic inspector is configured in-the-machine rather than standalone, air-knives geometry has to be optimized during startup to respect the most fundamental requirement of shifting-registers, limiting bottles’ sliding to  < 1 / 2  bottle diameter. When closures get out damped by the capper, it is mandatory to interpose a dewatering system.  

On left side:  the tunnel solution, as seen by a passing bottle.  Visibly, it is thinked for bottles not having any associated identity in a Shifting-Register.  Then, it can be satisfactory only for standalone electronic inspectors  and not the actual in-the-machine whose Shifting-Register extend themselves tens of meters along Conveyors and Machines



Cap inspection with camera without dewatering system










If the dewatering system is absent, the expensive and intrinsically high-performing optic closure inspection based on 1 megapixel camera, shall be reduced to performances closer to a low-performance single analog sensor optic closure inspection, costing one-hundredth times less.  The reason why a single and simple water drop may affect so much a visual inspection with camera, is hinted by the the Worlfram Interactive animation below (Flash Player necessary).   

Here, a single water drop appears represented as an ellipsoidic object.  Water has a refraction index completely different than air.  More, the same water drop deviates the incident light beams toward different directions, by an angle related to  the wavelength of the photons.  Two parallel beams entering the water drop, shall pass through different amounts of water and, if their frequency is different, this second factor shall add further deviation.  The net visible effect, correspondfing to the original couple of light beams, shall be a pair of blurred dots whose distance is different than the original.  A geometric deformation plus a blurring. 



Links to other pages about Closure Inspection:

Crown-Cork, Threaded Cap or LidUltrasound Inner Pressure Inspection IntroductionIn these web pages we have frequently remarked the necessity to answer the fundamental question:…is it safe, can be sold that bottle?

Plastic Cap Visual Check with 1 Camera. The optic closure inspection is the most modern, comprehensive and satisfactory way to control closures’ status, its only disadvantages being cost and complexity, as seen by the user side. It is devoted to detection of cocked (inclined) closures, broken TE (tamper evident) bands, closures applied too high or absent at all. All these factors implying contamination of the product and extremal risks for Consumers. The basic operation principle implies a single CCD or CMOS-camera, allowing a partial coverage, < 180º, of the closure external lateral surface. The optic system includes 3 mirrors to increase the focal length, minimising optic aberrations due to parallax error.

  Broken Tamper Evident Rings, missing and inclined cap, cap too high or too low are the controls most commonly performed by mean visual cap camera systems Links to other Closure controls pages:…

plastic cap visual check wi med-2

  Links to other Closure controls: Contact

Optic Closure Presence inspection, with analog photosensorsIntroductionThe optic closure inspection, with analog photosensor, is one of the simplest inspections existing. It adopts an analog photosensor, with a projector irradiating passing closures by the top and a receiver giving out to an operational amplifier a signal whose extension, the duration counted in encoder pulses, is proportional to the reflection. …

Laser check of Closure InclinationLinks to other pages about Closure Inspection:    The added value to apply a LASER slantedcap inspection to a Vision cap check Two different configurations exist for the LASER check of slanted caps:…

Inductive Closure or Lid Presence Inspection 4096x3079@1x. Introduction The simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal. The one figured on side shows an example of this basic solution, where the cap sensor is referred to a Trigger photosensor obscured by the container along its passage, before it starts to be detected by the inductive sensor. Disadvantages The system is very cheap but it presents a relevant disadvantage. It can be detected only: cap presence; cap absence; metal caps (e.g., aluminium, steel or tin). This meaning that a container capped by, i.e. a cap inclined 45º, then a container surely open, shall be considered correctly closed and passed to the Market. The signal outcoming by these sensors is normally a quite fluctuating one: impossible to act on the signal duration, when trying to detect mal-positioned closures. Advantages However simple, this system has however several important advantages: capable to reach also the highest production speed, typically > 140000 cph; economy; a sensor like the one partially visible in the image (Pepperl+Fuchs®) or one of the many equivalent by different Vendors, is very cheap (<100 $); is always available wherever in the World.

IntroductionThe simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal. …

Inner Pressure Inspection by Induction. Oscillograms deriving by the induction analog measurements of two different lids. Each oscillogram composed by the sequence of hundredths of individual samplings operated by a single-channel analog sensor. A symmetric one representing an actually closed can. An asymmetric one, representing a leaking can whose inner pressure is low. Passing one and the same can closed by a lid through one and the same Inner Pressure Inductive Inspection, a statistically significative number of times, i.e. 1000 times, results in 1000 slightly different oscillograms. From a layman point of view, differences representing the superposed effect of physical properties of the object, measurement instrument and medium, changing during the 1000 tests. Differences making sense of the way IGUSes (further details about IGUS, here) observe the state space where the entire description of the object exists.

Inner Pressure Inspectionby InductionOscillograms deriving by the induction analog measurements of two different lids. Each oscillogram composed by the sequence of hundredths of individual samplings operated by a single-channel analog sensor. …

Ultrasonic fobbing systemsWhy the ultrasonic fobbing systems ?Common disadvantages of the closure optic inspection systems: Optic, with 1, 2, or 3 CCD-camerasTamper evidence band Missing closure, inclined and high closure…

3-D cap colour space. To perceive the rationale for the inspection of the caps’ colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap. In this conditions the production face the risk of: Operators errors in the special sort bottle + cap: entire cartons of wrong caps reaching the Capper; caps of the wrong colour mixed in the lot of the caps of the correct colour. A solution pass thru the control of the colour of each one cap applied by the Capper Machine. Colour control made illuminating with a source of known spectrum (a halogen lamp) the cap. Part of the light reflected by the cap enters the lens of a trichromatic detector. This is a device with three separate channels, referred to the familiar fundamental colours red, green and blue. The signal in the outfeed of each one channel is separately amplified and later digitised and processed, comparing the digitised value with upper and lower limits set during the commissioning. The signals incoming by three separate channels, each one corresponding to a fundamental colour, are processed to deduce the cap colour. The couple of yellow colour vertical lines are the inspection window, the range of distances measured in millimetres equivalent to Encoder pulses. In the vertical axe of the diagram they appear, digitized in a scale of 4096 bits, the signals’ amplitudes. In the example shown, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production As an example, refer to the graphic on right side: a couple of yellow colour vertical lines represents the inspection window, the range of distances in the Inspector's Shifting-Register, where the three chromatic channels are evaluated; red colour the red chroma signal, whose grey level is normalized (0 - 4096); blue colour the blue chroma signal amplitude, whose grey level is normalized (0 - 4096); green colour the green chroma signal, whose grey level is normalized (0 - 4096); white colour their superimposed amplitude, whose grey level is normalized (0 - 4096). Caps whose tri-chromatic mix is out of each one of the three allowed ranges, shall be rejected. In the example, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production In the video above it is visible ad addition to the standard configuration of this kind of devices, namely a stainless steel curved screen, opposite to the source of light and trichromatic sensor. The Sun in some special times of the day, gets into that PepsiCo Bottling Hall, infeeding the thrichromatic sensor. Knowingly, Sun’s spectrum is continous and centred on yellow colour. The screen allow to overwhelm these phases, preventing Electronic Inspector’s systematic errors: huge false rejects stopping the entire 50000 bph PET Bottling Line.

Caps' Colour InspectionTo perceive the rationale for the inspection of the Caps’ Colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap. …

Unproper system

Dewatering systemsRefer to the figure on right side, where a green colour scanning line intercepted a water drop scanning, and measured its distance to the bottle’s plastic, greater than toward the closure top surface: a wrong distance. …


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