Bottle burst inspection


Bottle burst inspection

Glass packaging is, without any doubt, the material which allows the highest Quality to the liquid product.  Glass bottles have, however, a fearful characteristic.  

  A bottle burst projects thousands of glass splinters of different size.  Eyes are the most endangered

Part of them shall explode in the Filler machine, as a consequence of:

  • fabrication defects;
  • erroneous handling;
  • erroneous conservation, i.e. in excessively cold ambients;

during the phase in which the bottle is pressurized.

Bottles’ burst let fragments of glass fly several meters far from the valve which tried to fill it. They have been witnessed cases in which bottles of major Bottlers, were so poor in terms of fabrication Quality, to induce on average a single burst each 2000 bottles. If fragments reach places 5 - 7 meters afar, imagine their density in a radius 10 times smaller, say in the 2 - 3 valves adjacent (left and right side) to the one which hosted the bottle which bursted.    

The risk to drink a beverage plus a fragment of glass is low, but the consequences for the health of the final Customer eventually drinking it, may truly reach fatal levels.

The safety sequence

To prevent these scenarios, nearly all Fillers Machines are today including, at least as an optional, the automatic:

  • rinsing of their valves, along a certain number of Filler revolutions;
  • underfilling of the bottles (to force their rejection by a fhe fill level inspector);

adjacent to the valve where a bottle burst, along a pre-defined number of consecutive Filelr Machine revolutions.  

An example in the standard sequence adopted by worldwide fabricants of Filler Machines and by Vendors of Electronic Inspectors:

First revolution                   full            full         burst         full          full

Second revolution                            empty     empty      empty

Third revolution                                empty     empty      empty


When the Filler Machine does not possess such vital options, these may be acquired upgrading the FBI out of the Filler. 

The figure on right side shows one of these sensors, detecting a metal disk part of each one valve, following their position used to know that a:  

  • container exists,   
  • container burst,   
  • Filler Machine Cycle.

The figure below shows the four sensors added to an in-the-Machine configuration: 

  • Bottle Burst inductive 
  • Bottle Burst acoustic, 
  • Machine Cycle,
  • Container Presence.

Not shown below a fifth necessary sensor, named Filler Synchronization, vital to locate what is the Filler revolution angle, implying which Valve is each one Valve.     

Container Presence sensor, positioned closer than possible to the infeed of the bottles under valves, detects the presence of the bottle before its pressurization phase.   Bottle Burst sensor is most commonly positioned closest than possible and prior to the release of the bottle to the starwheel following the filling carousel, so to maximize the probability to detect a burst, by the observation that a bottle detected as present by container presence sensor, is no more existing after pressurization phase.   

This electromechanic logic is the basic one, sensible to the distance existing between the inductive sensor and the metal bodies to be detected.    

  Location of all the proximity sensors in-the-Filler machine

Since a few years the best Bottle Burst Inspections are controlled by a microphone-like acoustic system, sensible to bottles' bursts.  

Forced underfill

It is named forced underfill the standard and minimum approach to prevent that bottles adiacent to the one which burst, may reach final Customers with fragments of glass into.   A very important feature, allowing to consider the Bottle Burst option of the Electronic Inspectors superior in terms of safety to the standard one owned by fillers, is the fact that the Electronic Inspector knows what is the position of the burst in the sequence of the bottles reaching the Rejector, say into its Shifting-Register.

Then, the Electronic Inspector-based solution has an higher probability than filler-solution to reject the adiacent risky bottles, with probable fragments of glass into.   As said, Fillers reject these bottles, forcing their level low, say using the only underfilling level inspection of the following Inspector, when inspectors use that same system plus an additional one deriving by the knowledge of the position of the burst in the sequence of the bottles: locating functions, based on the tracking system co-operate as a further check, to prevent such extremely risky bottles from reaching the consumers.   

In the case of the modern Bottle Burst Inspections, the shower function of the Filler machine  is activated and the glass splinters are removed from the filler valves when it detects a suspicious noise.

A practical example

To make a practical example, we cite a case in which fill level inspection guarantees >99.9 % of that defect rejected, say <1 bottle each 1000 not rejected.

To use the additional safety offered by the in-the-Machine Inspectors, implies to reduce such a value not less than 2000 times, when the Tracking System is delivered so to assure a relative percentage of False Triggers <0.05 %.    That is also one of the reasons to be sure that the False Trigger Safety is commissioned and enabled, in the in-the-Machine Electronic Inspectors treating risky products, with inspections in a Filler.

Locating and inspecting bottle bursts  

in-the-Filler Machine

The Electronic Inspector tracks the defective potentially contaminated by glass splinters containers mixed in the flow of the others, by mean of a serie of inductive sensors or optic sensors set in the Filler Machine's carousel, and at-the-Conveyor outfeeding the Filler’s outfeed star wheel.

Into the Filler Machine, the role of basic reference for all distances, there measured in units of Filler’s Pitch, is played by a virtual Trigger.    It is obtained by the falling edge of the Machine Cycle sensor, all times a Container Presence sensor signal is associated, in-the-Filler Machine until the Transfer Point.   As a matter of fact, “How many Filler Machine steps” is a distance value which can be used also out of the Filler.   Be used  in the initial meters (however <2.0 m) of the outfeeding Conveyor, if this is straight and does not present any cause for bottles’ sliding.   One of such parameters exists for each one inspection.

Filler Synchronisation sensor

In the Filler it exists a synchronization sensor indicating the rotary plate no. 1, named Filler Synchronisation sensor.  

 Machine Cycle (green) and Container Presence sensor signals (orange), as seen by an Electronic Inspector in a Filler running at 60000 bottles-per-hour.  Visibly, the Container Presence sensor signal is a short one.  A Container shall be considered “Present” when the signal’s duration (low phase, zero volt, equivalent to a logic “ 1” in this NPN logic) shall result at least 2 ms long.  The scale of the image is expressed in millimetres, because of the presence of an Encoder.  Then, they are millimeters of Distance equivalent to seconds of Time 

Machine Cycle sensor

Then a Machine Cycle sensor, providing a pulse each single pitch of rotation of the Filler’s  tank.   Filler Synchronisation, Machine Cycle and Container Presence are a reference for all the Filler, as seen by the viewpoint of the Electronic Inspector.    

Container Presence sensor

A third one, named Container Presence sensor, is a true inspection and not a synchronization sensor.   It detects the mere presence of a bottle entered in the Inspector’s Shifting-Register.   Machine Cycle and Filler Synchronisation are signals always surely infeeding to the Inspector as a consequence of the Filler's revolution.   But, a Filler can rotate also empty, and that’s why a Container Presence sensor is necessary.   

Transfer Point’s relevance

The number of steps from the inspection to the Transfer Point is programmed.    On the Transfer Point, it terminates the Machine Cycle and it starts the shifting-register area: as yet seen, there lies a virtual trigger.   Transfer point is the point where the Filler Machine outfeed starwheel starts to leave the container on the outfeeding Conveyor, part of the inspector shifting-register.    More precisely, it corresponds to the vertical projection, onto the conveyor surface, of the center of a container lying in a position a few millimeters before it starts to be released to the outfeeding conveyor.

How-many millimeters are “a few” ?     

An amount x:                                     x  <  2      

preventing the otherwise progressively increasing False Triggers, accumulated due to wearing of the Filler Machine starwheel vans and of its axial fixing and bearings.

Tracking in-the-Filler and at-the-Conveyor 

Why Containers' Triggering is a vital subject

“It makes no sense to speak of the “defective status of a container” in presence of ambiguity about “what container” is defective”

“Pharmaceutical Industry, ...with few exceptions discards as dangerous the rejection over an external Conveyor of the containers detected “defective” in-the-Machine… both detection and rejection have to happen in-the-Machine

To let the Reader of these notes fully understand why all of the Triggering subject is developed in so many pages in this web site, there is to remark that:

  1. the identity of whatever object is its most fundamental information.   It makes no sense to speak of the “defective status of a container” in presence of ambiguity about “what container” is defective.   In other words, containers’ Tracking, is much more important than whatever inspection, say whatever measurement of one of the physical properties of these objects;
  2. when comparing Food and Beverage Packaging Industry with the Pharmaceutical Packaging Industry, we discover that the former with few exceptions discards as dangerous the rejection over an external Conveyor of the containers detected “defective” in-the-Machine.    Following Pharma safety standards and customs, detection and rejection have to happen both in-the-Machine.  The rejection has not to happen out of its Shifting-Register, one truly satisfying the requisites of rigidity and impossibility of the containers’ sliding out of the cells them attributed.   Pharma Industry refrains to operate like Food and Beverage Packaging Industry operates following the OEMs and Vendors’ design choices. 

Sliding conditions

One time a bottle is released by the Filler Machine out feed starwheel to the outfeeding Conveyor, all of the information regarding the bottle contained in its accompanying data sheet, is received by one or more Tracking Triggers.   Just one Trigger, in this case named Trigger 1, if the Electronic Inspector main cabinet and related Rejector are close to the Filler Machine out feed starwheel's Transfer Point.   How much close ?     No more than 2.0 m from the Transfer Point.   A distance which could be 1.0 m longer, if the fastest container format expected to be treated is a relatively slow one, e.g. <0.8 m/s.   At least six conditions make a container prone to slide, during its release by the Machine starwheel and along its journey through the Conveyor.   

Each one of them is sufficient to let a container slide that much (>1/2 container diameter) which is enough to clear its identity in the Inspector Shifting-Register:

  1. distances >2.0 m,
  2. curves between the Inspector main cabinet and the Rejector, 
  3. speed is >0.8 m/s, 
  4. light containers (<0.8 kg),
  5. equipments (e.g., air blowers, twists, etc.) whose action perturbates containers’ motion, exists along the Conveyor, interposed between Machine’s Transfer Point and following tracking Trigger,
  6. Conveyors’ cross-overs,

If any or more of these reasons conditions the installation’s layout, a serie of Triggers becomes vital to assure the conservation of the original data written in the container’s accompanying data sheet.    

Tracking Triggers prospectus in an in-the-Machine Inspector

Containers’ Tracking Triggers 1, 2, 3, 4, 5 correct setup   

[Similar menus for the Tracking Triggers exist whatever the Vendor of the Electronic Inspector, however with differences in their motives, colours or logos].   

Setup of “additional containers not accepted” and “loss of containers not accepted” has mandatorily to be identical to that in a red colour box.  Be wary of setups you may discover presenting “additional containers accepted” and/or “loss of containers accepted”.    Particularly in a Full Bottle Inspector equipped with inspections in the Filler, like the Bottle Burst and the necessity to control the critical Forced Underfill outfeed signal.  They'd correspond to a deliberate decision to send to the Market also bottles having glass splinters into.  Have you ever requested or authorised in a written way to leave disabled Machine Safeties and/or to counter Vendor's Technical Dept. written design recommendations like these ?    

Food and Beverage Companies managers’ triadic quest for: 

  1. minimum losses, 
  2. minimum  downtimes, 
  3. maximum rejection of defects and safety. 

implies that all Quality Control equipments have to be at least as performant as they were declared by the respective Vendors in the Technical Gurantees part of that Offer which had been accepted by the Bottler. 

But, the Electronic Inspectors’ Shifting-Register is the most complex kind thinkable.  It joins rigid and banal Shifting-Registers, like those of the rotary machines (Filler, Labellers, Closers, Cappers, Seamers) to the anelastic deformable Shifting-Registers (Conveyor’s belts) where containers can freely move themselves, rather than be firmly kept blocked in the Shifting-Register’s cells.   

Have you seen macroscopic defects passing through the Inspector, not detected ?    

We refer ourselves to bottles:

  • semi-empty,
  • without closure,
  • without all of the labels.

Missing rejections made strange by the fact that, simultaneously extremely smaller defects are correctly detected and rejected, as an example:

  • 2 mm underfilled bottles,
  • closure inclined or too high for a few millimetres,
  • bottles rejected because one of the labels is misplaced (but present) for 1-3 mm.

Rules of commissioning

If your answer to the question above is positive,  it hints to a parameterisation (or, setup) violating basic rules of Commissioning of the Inspector’s Shifting-Register and of the positions of the Inspector’s detectors in-the-Machines.    

Written rules diffused by Vendors’ Technical Departments.   Rules clearly defining what is the most basic “inspection” in whatever Electronic Inspector: the constant control and cross-check of each container’s identity in the Shifting-Register.   

If the identity, the identification of an object is ambigous, how and why could we consider it non-defective and ship it to a Customer ?    This can be obtained forcing determinate “bits” to do what Vendors’ Technical Dept. and rationality do not want be done. 


No “Statistically-significative” Bottle-Burst or Locator

If the: 

  • Design, 
  • and/or Integration, 
  • and/or Commissioning, 

of a Bottle Burst inspection and rejection system are inadequate to the purpose, the location of the Filler's valve no. 1 will not be correctly attributed, not it’ll be possible to correctly and always reject the desired sequence of bottles around the one which exploded.  

To understand the point, we can imagine a rotary reference system whose angular velocity ω is constantly changing in nearly random way.  

 Easy to recognise the typical footprint of an erroneous or missing commissioning for the joint set of in-the-Machine functions underlying also the Bottle Burst and Forced Underfill.   The location of the Filler's valve no. 1 will not be correctly attributed.  Meaning that the reference system in the Electronic Inspector is rotating with respect to the real system in-the-Machines

Be wary and suspectful of arguments trying to convince you that in-the-Machine functions (like all those described before) inherent to:

  • Filler Valves' or Closer heads' Locating;
  • Filler Valves' or Closer heads' Sampling;
  • Bottle Burst attribution;
  • Forced Underfilling;

should be only statistically-guaranteed.   

Below an example of the difference between deep and poor knowledge of the status of a system defined in a bidimensional space.   X and Y are values measured for physical properties related to the system status.   In an ideal-world case, the sharp observed distribution of the measured values (right side graphics) is a vertical line of infinitesimal thickness, infinitely thinner than what here depicted.   These infinities correspond to 100 % of information about the true value of one of the physical properties characterising a system.  

In our practical cases, distributions can only be spread and then the key point becomes the answer to a single question: how-much spread ?  

What a variance to consider “acceptable” to say that we have enough knowledge about a system ?   

 3-D sharp (spiked) and unsharp distributions for the Probability of a status of an objects. Status derived by the informations arising by physical measurements of its properties X, Y.   Electronic Inspectors' physical measurements, kept apart extremely rare exceptions, are based on electromagnetic interactions between a sensor and the object (e.g., a container)

“...only if the design, integration, installation or commissioning are erroneous let the in-the-Machine functions become statistical, say generally wrong”

To say that the knowledge available at a given time for a physical property, as an example, the couple of angles of revolution of the Filler’s Valve no. 1 and of the Capper's head no. 1 is statistical, means an unsharp distribution like that one above, at left side.  In the reality, only if the Design and/or Integration and/or the Installation and/or or the Commissioning are erroneous, the in-the-Machine functions surely become statistical, say generally wrong.  

A way to quantify if all is correct lies in the observation of the Electronic Inspector’s False Triggers Counter.   This has always to be < 0.5 %, thus assuring correctness to > 99.5 % of the Locating and Sampling operations.

Is it fiducial the False Triggers Counter ?  

Can the False Triggers Counter: 

  • protect you completely ?  
  • be always evidence of the Truth about what really is operative front of you, in the Electronic Inspector ?  
  • prove that an Electronic Inspector really is wired and commissioned as the expensive in-the-Machine you paid ?

No.   They have also be Audited installations where a brown-coloured wire had been connected where someone else suggested, exactly and only to let the alarm red colour traffic light of the Electronic Inspector deprived of its in-the-Machine functions, be showing a calming green colour traffic light.   Thanks to the complex sabotage designed by someone else, definetely too complex for the incompetent Service Technicians sent to the Bottling Site, the False Triggers Counter menu, looked stellar with its 0.00 % of False Triggers.  

 By mean of this cable some Service Technicians bridged a constant GND (0 volt) to give to the Bottler just the sensation of a correct Container Presence Signal.  In the reality, before they disconnected the Container Presence Sensor and all others devoted to in-the-Machine Locating functions.  This sabotaging cable had been months in that Electronic Inspector.  Enough to let the Brewery's most skilled Electronic Engineers suppose that an Electronic Inspector is complete, corresponding to the Contract and correctly functioning.   Removing the sabotaging cable, the Truth immediately revealed itself front of many Witnesses and cameras.  The worldwide second Beer Group discovered that just <35 % of the price paid for that Machine was commissioned and operative.  

Removing the sabotaging bridge, the Bottler discovered that:

  1. the in-the-Machine electronic inspector’s Bottle Burst inspection and rejection system was totally bypassed;  
  2. the expensive Inspector reduced to a standalone;
  3. since months glass splinters into the beer bottles were proceeding unrejected to the Market, exposing people to illnesses and the Brewery to claims

Disconnecting the brown-colour sabotage cable, immediately the Truth gots out with the opposite reality: 

  1. nearly 100 % of Falsely Triggered bottles;
  2. the in-the-Machine electronic inspector’s Bottle Burst inspection and rejection system was totally bypassed; 
  3. the expensive inspector reduced to a standalone;
  4. since months glass splinters into the beer bottles were proceeding unrejected to the Market, exposing the Brewery to claims related to Product Liability.

Readers will try to imagine the rational for such actions: “Why to behave this way ?”.  Reason is always and only the Principle of Maximum Profit.   A skilled Service Technician need over 10 years to be slowly built over stratified experiences.   More, the Technician has to be one who really studied and operatively understood Math, Electronics, Mechanics, etc. and not just someone with a piece of paper.   

Then, you understand that the maximum profit is reached when a someone, just camouflaged to look like a Service Technician, costing 50/day is resold to the Beverage Bottler for 750/day.   The Bottling Company's Maintenance electronic engineers specialization closes the circle.   Because they are highly specialized to assure Production, they are typically highly skilled in Machinery Automation.    But, …..but the Electronic Inspectors are not “Machinery Automation” !    And that’s why the sabotage briefly described above, passed undetected to several Electronic Engineers who tried to assess the operation of that Electronic Inspector. 

If who installed or started or commissioned or however guaranteed you a Sampling of Locating system, part of an Electronic Inspector, emits any statement sounding like “statistically guaranteed only” then he:

  1. has no idea of what is speaking;


  1. under-evaluates your know-how;


  1. knows that his/her Staff did not synchronised the system (it operates standalone and not in-the-Machine) and tries the easy way to get rid of the fact you have discovered a hole in the Commissioning whose huge economic value may had yet been paid by your Company.

With the time, you’ll discover that very strangely, there is something like a hole in the technical literature made public about this special subject.   A huge hole, when considering that if a standalone Electronic Inspector costs X, then its in-the-Machine variant shall be always paid by you:  (2 - 3) times X.     So much more because you’ll be paying a great difference in the hardware, installation and commissioning activities.    

To the date, the Writer of this notes audited ~70 Electronic Inspectors in worldwide Food and Beverage Bottling Lines guaranteed in-the-Machine to the Bottling Companies.   Companies who paid the correspondingly higher price (two-three times more expensive) than an Electronic Inspection equipment configured with the same inspections, installed and commissioned Standalone.   Equipments Audited typically because the Food and Beverage Bottling Company technical staff, with the time started to feel that something basic was wrong or missing.   The Audits revealed an amount of missing functions yet paid.  

Machine-Conveyors-Inspector synchronisation

Whatever the case, then also for relatively slow speed Fillers (<1.0 m/s), it is vital to synchronise the ramp-up and ramp-down phases of the Machine and of the out feeding Conveyor, so that their speed difference results always <0.1 %.    

0.1 % is a value knowingly close to the nonlinearity limit of the commercial Frequency Converters.   Say the equipments regulating the speed of the motors in the Filler and in the Conveyance systems.    As an example, 0.1 % of divergence between bottle in-the-Filler and same bottle at-the-Conveyor, at a speed of 1.5 m/s are 1.5 mm.    1.5 mm may appear a small divergence.    But it is the maximum which can be allowed to be, keeping apart the today rare cases where containers’ speed is relatively slow (<0.8 m/s).   

Containers’ speed, being related to the containers’ kinetic energy following a quadratic law, enhances the slidings’ occurrences and then their negative effects.   

False Triggers and Data Sheets

The Trigger controlling the Rejector, say the last one immediately before the Rejector, shall be exposed to count False Triggers, corresponding to bottles whose identity is unknown because lost.   False Triggers which, in your own full interest, have to be absolutely be rejected by the Inspector, because they could have glass splinters into.

The mere existence of the Container Presence sensor shall force this rejection.   Do not forget what seen above about the Transfer Point of the Filler Machine's out feed starwheel.    

  False Triggers Reject Definition.  Similar menus for the Tracking Triggers exist whatever be the Vendor of the electronic inspector, however with differences in the colours, logos and motives.   The icon indicating a deviation out of the Production flow (a rejection) has to look like in the red box “enabled”.   This way, the falsely triggered bottles shall be rejected.  In a Full Bottle Inspector with Bottle Burst inspection  in-the-Filler, whatever different setting you could encounter is a deliberate decision to send to the Market also bottles detected defective with glass splinters inside.  Have you requested or authorised this ?     

We refer to the necessary synchronisation of the Transfer (or, release) Point better than possible and with a positional error <2 mm.    A difference between Filler and of the out feeding Conveyor >10 mm, say a divergence >0.67 %, implies well visible false rejects caused by falsely Triggered bottles.    The only case where it’s admitted a divergence > 0.1 %, is during the Labeller’s emergency stops.    Special and not frequent cases when to reject some correctly labelled bottles is the best action we can take.

Containers’ tracking starts under the control of a virtual Trigger based in-the-Filler Machine and has to continue over the following Conveyors, until after the Rejector and the Reject Verification Trigger set immediately after the Rejector.    A problem today widespread is that the relative porcentage of the Electronic Inspectors in-the-Machine (Label, Fill level or Cap Inspectors) really operating like in their Order and their Design, is reduced to minimal porcentages, never seen along past two decades.    

A synchronisation respectful of the contractual superior limit given to the False Rejects (False Positives) and to the defective and not rejected containers (True Positives), whatever their nature, implies a limit also on the False Triggers.   

False triggering causes

Falsely Triggered container, is a PET- or glass-bottle, a can, keg, crate or case, which lost its “identity” due to several causes and between them:

  1. outfeed too early or too late by the precedent Labeller-, Filler-, Capper-, Closer-, Seamer-Machine:
    1.  typically indicating a commissioning error in the synchronization Machine-Inspector, 
    2.  rarely due to a hardware fault of one of the detectors,
  2. slided forward, anticipating its arrival front of the following Trigger,
  3. slided backward, posticipating its arrival front of the following Trigger,
  4. manually 
    1. introduced in the flow of containers,
    2. removed out of the flow of containers,
  5. arrived so inclined front of the following Trigger, that it terminated to occupy a precedent or following cell in the Electronic Inspector’s Shifting-Register,
  6. flagging label or foil, emulating a container neck arrival front of the following Trigger,
  7. defective Tamper Evident Ring of plastic caps, emulating a container neck arrival front of the following Trigger,
  8. broken splinters, whose passage is registered front of a Trigger.

“Identity” originally attributed in the data sheet, later accompanying each one of them along their journey through the Electronic Inspector’s “Machines” and “Shifting-Registers”.   

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This website has no affiliation with, endorsement, sponsorship, or support of Heuft Systemtechnik GmbH, MingJia Packaging Inspection Tech Co., Pressco Technology Inc., miho Inspektionsysteme GmbH, Krones AG, KHS GmbH, Bbull Technology, Industrial Dynamics Co., FT System srl, Cognex Co., ICS Inex Inspection Systems, Mettler-Toledo Inc., Logics & Controls srl, Symplex Vision Systems GmbH, Teledyne Dalsa Inc., Microscan Systems Inc., Andor Technology plc, Newton Research Labs Inc., Basler AG, Datalogic SpA, Sidel AG, Matrox Electronics Systems Ltd. 

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