Hold Baggage Screening Systems

The complete integration between the Baggage Handling Conveyor System and the X-ray Machine lies at the heart of a successful HBSS line. The X-ray Machine has the knowledge of the security status of a bag whilst the bag remains on the X-ray Machine belt conveyor.

Once the bag leaves the X-ray Machine conveyor the correlation between the bag identity and bag status is broken and therefore this correlation has to be taken over by the Baggage Handling System Controls. This is essential in providing an automated in-line process allowing screening to be undertaken without stopping bag flow.

Successful HBSS installations thus require the combination of X-ray Technology, Mechanical Design, and an Integrated Control System. For a system to function effectively, the three elements must be designed to work as a single entity.

The Industry standard Five Level Screening Process is based on the following: -

Level 1: Automated evaluation of the X-ray image by the X-ray Machine.

Level 2: Operator analysis of the Level 1 image at a workstation(s), carried out whilst the bag continues in transit.

Level 3: A more in-depth analysis of the original Level 1 image at a separate workstation(s) or subjecting the bag to a separate X-ray process using a different X-ray technology, for example Computer Tomography (CT Scanner).

Level 4: Re-uniting the passenger and bag and carrying out a manual search.

Level 5: In the event that the passenger cannot be found, then the bag is considered a bomb threat and dealt with accordingly.

The process starts at Check-in. An essential parameter is that the X-ray Machine is presented with singulated and separated bags to avoid any confusion between X-ray image and bag identity. If bags enter the Baggage Handling System correctly there is a minimised need for corrective action before the X-ray Machine. The most effective method is to incorporate automatic discharge of bags from the Check-in Conveyors onto the Collector Belt using 'slot allocation' control.

There is a preference for bags to be presented to the X-ray Machine in a flat orientation due to restrictions on the tunnel height and to achieve the optimum image. Many bags will transfer from the Check-in Conveyor onto the Collector Belt in an upright orientation and it is necessary therefore to incorporate bag-toppling devices on the Belt Conveyor System leading to the X-ray Machine.

Prior to the X-ray Machine there is a need for bag size, bag orientation and bag spacing to be checked and corrected. Overhead photoelectric cell arrays can check for overlapping bags or bags, which are positioned too close together. Bag Separation Conveyors immediately prior to the X-ray Machine can automatically separate and correctly pitch the bags. Overheight or overlength detection will stop the bag on a Conveyor prior to the X-ray Machine and provide an alarm to an operator who can correctly re-orientate the bag.

The bag is now correctly orientated and pitched and is presented to the X-ray Machine and it is now the X-ray Machine's responsibility to create the X-ray image and to automatically analyse the image during the Level 1 process. Bags failing the automatic Level 1 process need to have their images forwarded to a workstation for inspection by an operator.

The operator is given a limited time period to make a clear or reject decision and bags failing the Level 2 examination need a more in-depth examination of the initial X-ray image or a secondary X-ray scan utilising alternative technology, both embodied within the Level 3 process, or ultimately Level 4 examination involving a manual search of the bag contents in the presence of the passenger.

If the Baggage Handling System is to function effectively then continuous bag flow must be maintained during the X-ray process. The normal method is to undertake the Level 1 and 2 analysis whilst the bags flow along the Conveyor System to a 'decision point' downstream of the X-ray Machine. At the decision point the Level 1/2 failed bags are diverted from the main bag flow to an area where the Level 3 or 4 process can be completed without any time constraints.

There are many ways to affect this diversion process, the selection of the best method being based on bag throughput and/or spacial constraints. The simplest method is to discharge the bag at a 90o junction onto a reversible Belt Conveyor. One direction to the make up area for all cleared bags, and the other direction to a dedicated Level 3/4-process area.

Other methods involve the automatic diversion from the main Belt System using either a High Speed Motorised Plough or a Pusher. The final option is to use a 'Vertical Sortation Unit', which automatically diverts the bag onto an upper or lower Belt System. On installations utilising multiple X-ray lines it is often common practice to route the Level 1/2 failed bags to a common Level 3/4 area.

At the Level 3 area, different technologies can be incorporated.

i) The original X-ray image can be retrieved at the Level 3 workstation with the operator having more time to manipulate the image and thus reach a decision. A useful feature is the incorporation of a printer at the Level 3 bag presentation area whereby the bag security number can be printed and stuck to the bag. This identification can assist in bag identity for the retrieval of the original X-ray image and can also categorise the bag i.e., 'failed level 1'; 'failed level 2'; 'tracking error' etc.

ii) The bag can be fed through a further stand alone X-ray machine utilising different technology to the Level 1/2 machines and the image interrogated by the Level 3 operator.

iii) Trace technology can be utilised.

Bags clearing the Level 3 examination need to be returned back to the Baggage Handling System and a suitable Conveyor System or simple ball table input point needs to be incorporated downstream of the decision point.

The route for Level 4 bags needs careful consideration, as a failed Level 3 bag is clearly a security risk. If the HBS System is at mezzanine level then a dedicated route to a secure pick up point is needed.

Whilst the bag is inside the X-ray Machine the X-ray image and bag identity link is intact. As soon as the bag leaves the X-ray Machine amongst other bags to flow along the Conveyor System to the decision point and to be diverted to the Level 3/4 area if necessary, it is essential that the X-ray image and bag identity is linked 100% accurately.

It is the responsibility of the Baggage Handling Control System to provide this 'tracking control'.

The interface between the Baggage Handling Control System and X-ray System is based on both digital and dual channel serial communications providing a single autonomous system with the high level interface transparent to the end user.

Each bag on entering the X-ray Machine is provided with a unique bag security number by the Baggage Handling Control System. This number then enables the respective tracking information for each bag to be identified and updated with the corresponding level 1-2 decision as and when instructed by the X-ray Machine whilst the bags remain in transit.

Security checks are undertaken, involving continuous monitoring throughout the tracking zone based on the information of each bag being transferred between shift registers. This is implemented via the use of encoders and photoelectric cell devices verifying that each bag is detected at pre-defined locations along the Conveyor System within set distances of belt travel, that the same physical dimension of the bag exist in each position, and that the bag remains in the correct sequence.

The HBS tracking functionality within the Conveyor System enables up to 1200 bags per hour to be processed per machine with a mistrack rate of less than 1% as a standard requirement to mandatory DETR regulations.

Due to the stringent performance criteria, reliable and fault tolerant software is a necessity to ensure the identify of each bag whilst eliminating spurious signals arising from variables associated with bag weight, shape, texture and the ancillary fixings such as handles, straps, and wheels.

An alternative solution is to utilise 'track and trace' technology. This system requires the adoption of 10 digit bar code reading within the Baggage Handling System.

As part of the Check in process, bag labels are printed at Check in via ticket printers forming part of the CUTE system. The information on the ticket includes a 10-digit IATA bar code detailing specific information relating to the airline, passenger, destination, and delivery location within the Baggage Handling System.

This information is entered into the Airports Sort Allocation Computer database (SAC).

Prior to the X-ray Machine, Bar Code readers diagnose the IATA codes on the printed tickets, the Control System reconciles and verifies the bag specific information from the SAC in terms of a valid bag being entered into the X-ray System.

As part of the HBS tracking functionality the level 1-2 decisions and unique Bag identity are transferred between the X-ray Machine and Baggage Handling System Control System enabling the respective decisions, bag tracking identity and IATA specific information to be aligned.

This has the advantage of enabling: -

• The positive identification of the X-ray security status of each bag and the ability for alignment with the specific information of the IATA bar-code to provide information that aids the Level 3/4 operators ability to achieve quick and effective reconciliation of passengers with failed bags
  
• The facility to re-process bags via manual entry or to re-print tickets of no read bags at manual coding stations.
  
• Verification of bag delivery/sortation to the respective Baggage Handling System final destination.

Bar Code reading alone does not provide full HBSS integrity therefore tracing technology via barcode reading alone cannot be used. However, when applied with HBSS tracking control it ensures 100% integrity within the system.

The Hold Baggage Screening System can be enhanced by the incorporation of a modern PC based Management Information (MIS) or Supervisory Control And Data Acquisition (SCADA) System.

MIS or SCADA systems provide an interactive PC based operating system offering a powerful and user-friendly interface for the supervisory control of the system and providing specific information on the Baggage Handling System performance.

Configured from standard software packages, a scheme specific solution is provided controlling the system from a dedicated control station(s), configured with multiple user levels for Operator route selection and start/stop functions, Engineering diagnostic information and Management Information related to performance data is available, the specifics of which can be summarised as: -

• Route Selection
  - Ability to select and de-select conveyor routes
  
  
• Conveyor System Graphical Representation
  - Available, Healthy, Running/Stopped, Die-back, Automatic/Manual, Out of service etc.
  
  
• Alarm Listings - Fault Diagnosis
  - Specifics of nature of fault, current status and plant item.
  
  
• Event Log - Historical
  
  
• Statistics / System Performance
  - Throughputs, Level 1-2-3 Clear/Reject figures, System Availability, (Hourly, Daily, Monthly)

The MIS-SCADA workstations are usually installed remote from the BHS process in a dedicated control room and often local to the level 1-2 consoles.

To summarise, if the most efficient, fully automated Baggage Handling System with Hold Baggage Screening is to be achieved, then the combined integration of both X-ray and Baggage Handling Systems are essential, often combined with SAC technologies.