LHR Terminal 4 OPC Server Upgrade

Project Background

This project was driven by a need for change arising from the deployment into the Terminal 4 Production environment of a new model of PLC. Heathrow Airport Ltd. (HAL) mandate that for components of the Baggage Handling System, manufacturer technical and product support must be available over a minimum specified period of time. This is to avoid the need for replacement of failed defunct components with non-like replacements, which would result in delay and compromise operations.

Consequently, suppliers were no longer able to install Siemens’ S7-400 PLCs as the remaining manufacturer support period did not meet the required minimum. The product chosen in place of S7-400 PLCs was the much newer S7-1500, also manufactured by Siemens and with sufficient remaining support lifetime. The choice to use this range of PLCs gave rise to a new challenge; to provide communications between S7-1500 PLCs and the existing HAL Eastern Campus FactoryLink baggage SCADA application, whilst maintaining communications with all existing PLCs of various models via their relevant interfaces.  

Solution Delivered

On investigation AAC found that works had taken place under a previous project intended to deliver OPC server upgrades to the baggage SCADA systems in LHR Terminals 1/2 and 4. The project completed successfully in Terminals 1/2 but had been abandoned in T4 due to technical constraints. AAC use the same models and generations of SCADA servers as those used in the Heathrow Production and Pre-Production environments so were able to investigate the constraints and propose several options.

The most straightforward solution would have been to upgrade one of the existing OPC servers to a newer version which caters for S7-1500 communications, however we found that the newer versions were not compatible with the Operating System of the SCADA servers. We also found that all Siemens S5 PLCs in T4 interfaced to the FactoryLink SCADA via a bespoke application written by a third party, and that this application was not compatible with Operating Systems more recent than that of the SCADA servers. The third party who originally provided the bespoke application were not able to commit to a modification in line with the required delivery dates.

Given that our key considerations were;

  • To enable communications between the legacy SCADA and a new type of PLC
  • To maintain all other existing interfaces with no disruption, degradation or loss of resilience
  • To maintain or improve the availability of the overall baggage SCADA as specified by HAL
  • To provide a solution favourable to O&M providers in terms of reliability, functionality and familiarity
After consideration of many options we proposed that the most robust solution would be to deploy a newer version of the existing OPC server software to enable communications between SCADA and S7-1500 PLCs. We proposed that this newer version be deployed in a Virtual Machine with suitable recent Operating System, hosted in HAL High-Availability servers. This meant that existing interfaces would be maintained and FactoryLink SCADA could interface to S7-1500 PLCs via an OPC server over a network connection, avoiding the dependencies between the SCADA server Operating System, the bespoke S5 interface and the existing OPC server version.

AAC Added Value as Control System Integrators

As a responsible and established SME and HAL supplier AAC was acutely aware of the need to seamlessly maintain existing operations functionality during the implementation of the OPC server upgrade solution. The project was centred around the deployment of a first-of-type component and associated modifications to both the controls and network architecture of the baggage system. There was also a very limited timeframe in which to examine options, run preliminary tests, determine the most suitable solution, test it fully in the Pre-Production environment and deploy it in the HAL production environment – all to be completed in c. 10 weeks to align deployment with the roll-out of the first two S7-1500 PLCs.

With the above borne in mind AAC proactively kept both our client Beumer and the end customer HAL fully informed at all stages of the process. We reported all options explored, their pros and cons and why we chose to discount or take each one further. We also shared all preliminary test results and findings without bias or favour in order to secure customer buy-in for the most suitable solution.

During the FAT period AAC adhered to the HAL-specified test cycles and procedures using approved documentation, and reported progress and test outcomes to the customer daily.

Following successful FAT, authorisation to proceed to deployment in the Production environment for testing was gained. The scope of change under this project was significant, involving;

  • First deployment of a new OPC server application
  • First deployment of new server hardware
  • Modification of network architecture
  • Deployment of a full HAL T4 FactoryLink SCADA Build

As the baggage system is in daily use, changes can only be made during the nightly maintenance window between 23:00 and 03:00. Over six nights AAC deployed the changes each night, carried out testing and then reverted the changes, re-tested and handed the system back to the Operations team at 02:30 ready for use.

On completion of testing of the changes, with approval from HAL the changes were left live in the Production environment and AAC provided go-live support and familiarisation training for the Operations team and HAL support providers.

The OPC server implemented under the project has proven a robust interface and remains so following the addition of a further c. thirty S7-1500 PLCs. The OPC server upgrade was delivered on schedule and no impact to existing baggage system functionality was experienced during the deployment, testing or handover.

This high-profile project was an important enabler for future T4 baggage PLC and SCADA projects and succeeded through the diligence and stewardship of the team.