Twelve points to consider when upgrading your control system

The feedforvard.com article – “It ain’t broke, but it’s obsolete” discussed why it is important to replace or upgrade obsolete control systems. Upgrading process control systems are complex and can prove to be very costly if not carefully assessed and planned. Here are a few questions you should include when investigating different technical solutions.

1. Phased or All at once

Can the upgrade be carried out in phases? If some of the equipment can be upgraded without a shutdown, then this can also provide additional spares for critical equipment that can only be upgraded during a plant shutdown. However, the compatibility of the new hardware and software with the old equipment would need to be evaluated. A common strategy is to upgrade the HMI (Human Machine Interface) or SCADA (Supervisory Control and Data Acquisition) elements of the process control system first, followed by the Central Processing Units (CPU) for the control system and the I/O modules.

2. Standardisation

Should standardisation of control system equipment be considered? This should not be dismissed in cases when you have various control system packages as standardisation can help reduce the total cost of ownership. The operating company may also consider whether they want to stay with the same vendor or consider a new vendor or a system integrator to plan and execute the migration.

3. Expansion Capability

Is the plant going to have any expansion projects in the near future? The expansion capability of the new DCS should be discussed with the vendor. Expansions will also need to consider the existing network infrastructure and upgrades to network equipment like switches and firewalls.

4. Performance Enhancements

What were the performance issues and limitations of the existing system and could these be addressed by the upgrade? A gap assessment can highlight performance benefits obtained from improved HMI interfaces, advanced process control functions, alarm management and asset management tools available with the new platform.

5. Functional Safety

Does the Safety Integrity Level (SIL) capability of the upgraded safety systems meet the requirements in the IEC 61511 standard on Functional safety – Safety instrumented systems (SIS) for the process industry? The Safety Requirements Specification (SRS) for the facility would need to be reviewed and will often need to be updated to address the latest IEC 61511 requirements. This can be a challenging task and is recommended to be done at an early stage when planning an upgrade. The SRS serves as the design basis document for the SIS, defining the Safety Instrumented Functions (SIFs) and their target Safety Integrity Level (SIL) requirements. The upgrade project team should evaluate how the new safety system selected meets the requirements specified in the SRS. Most safety system vendors have certified Functional Safety Management systems, ensuring that systematic capability requirements are addressed when the new safety system is engineered for the upgrade project.

6. Cybersecurity

How will the upgrade address functional safety requirements and mitigate cybersecurity risks? With many vendors offering IIoT (Industrial Internet of Things) services like data analytics and digital twin solutions via the cloud, upgrades should strengthen the cybersecurity of the systems and ensure that IEC 62443 series of standards on cybersecurity of industrial automation and control systems are addressed.

7. Software Porting

If a newer version of the same product is considered, can the software be easily ported from the old to the new product? Porting of the software would reduce the effort required to program the application software on the new control system. Nowadays, most products in the market use IEC-61131-3 standard programming languages for programmable controllers, making it easier to reproduce the software logic on the new platform.

8. Proprietary Code

For package equipment with a unit control panel, the control algorithms may be proprietary and the source code will be protected. This can make the upgrade more challenging, requiring control narrative reviews and the development of new algorithms in addition to rewriting code.

9. Documentation

What is the quality of documentation for the existing control system? This can be challenging on brownfield projects if the documents are not maintained to reflect the as-built details of the control systems. In some cases, documents may not be available in native format or may be entirely missing. This will impact the engineering man-hours required to bring the documentation to as-built status after the migration. The time and resources required to align the operating and maintenance procedures with the new system should also be accounted for in the upgrade plans.

10. Wiring and Terminations

Can the new equipment be replaced within the existing system and marshalling panels? Can any of the wiring and termination arrangements be retained? The new I/O modules and field terminal assemblies may have the same I/O density and form factor as the existing IO modules, providing an opportunity to replace the I/O modules within the existing marshalling panels. The FEED should review the physical condition of the existing marshalling panels and the quality of the wiring, termination and tagging. If the new I/O modules interface differently with some field equipment, the changes to the loop diagrams and any additional equipment to be included within the panels should be identified at an early stage. These details can impact the power consumption, heat dissipation and spare space for the panels.

11. Simulation and Testing

How can we gain confidence that the upgrade will go smoothly? A detailed and thorough factory acceptance test (FAT) is crucial and will often save valuable time troubleshooting integration issues at the site. Most application software can be tested through simulation during FAT to verify the functional requirements. Communication interface testing between the new and existing system needs to be well defined and the existing system hardware should be included in the test setup to perform extensive integration tests during the FAT.

12. Training

Training your operations and maintenance teams on the upgraded equipment should not be overlooked. When migrating the entire system to a new platform, if the “look and feel” of the existing HMI graphic pages is to be retained, then several custom graphical elements (faceplates, indicators, navigation menus, alarm banners, etc) often need to be built and tested as a new graphics library on the new platform, adding time and costs to the upgrade project. If the upgrade is performed in phases, there may be an opportunity to run the old and new HMIs in parallel allowing the operators to familiarize themselves with the new graphic pages and elements. A structured training program to ensure that the engineers and technicians receive the relevant training on the new product, meet competency requirements and gain sufficient confidence to operate and maintain the new system is vital to complete an upgrade project.

The above list provides the reader with an insight into a few topics to consider for a control system upgrade. This is by no means a comprehensive list and each facility will have several other areas that need to be reviewed based on the size and nature of the facility and the type and condition of control system platforms being upgraded.

“It ain’t broke, but it’s obsolete”