The digital transformation process typically necessitates the replacement of legacy control systems. These systems run the critical manufacturing processes that typically cannot be shut down or taken off-line for very long without noticeably affecting a plant’s output.
Consequently, many control system legacy replacement projects include extremely aggressive (very short time duration) cutover windows to replace the old gear with the new. This time restriction poses a significant challenge to the integrator or supplier responsible for making the cutover without adversely affecting plant operations.
Superficial project planning can lead to a cutover disaster and cost the plant significantly in lost opportunities for production. Diligent and comprehensive planning can greatly increase the probability of getting through the cutover to the new control system with a minimal number of surprises, headaches, and difficulties. Let’s examine some of the touch points to consider.
Start with existing system documentation
Realize that your control system’s drawings and configuration charts are most likely not accurate and/or not current. Plan to meticulously verify the hardware and wiring against the drawings along with verifying configurations of all communication channels/ports. Expect to find devices mounted in panels or connected to a network that don’t show up on the drawings. Likewise, you should expect to find devices and wiring on drawings or configuration charts that are nowhere to be found in panels or on the plant floor. Don’t panic when this occurs; simply document and move on.
Field verifying the legacy system will most likely reveal inconsistency in device naming and labeling along with wire labeling. For example, a shutoff valve might be labeled CV301 on the P&IDs, labeled V301 on the schematics, and labeled 301 on the metal asset tag on the valve body itself. The corresponding wiring from the controller to the valve’s actuator solenoid might be labeled Y234 at the output module, wire 2 at the marshalling panel or junction box, and no label at the valve actuator itself. It’s much better to find these inconsistencies prior to the critical cutover window to save precious time when it counts. Additionally, upgrading legacy control systems is an excellent opportunity to correct these common labeling and naming inconsistencies.
Understand operational functionality
Critical to a successful short-duration cutover is to have a comprehensive understanding of the operational functionality of the existing system. Changes, edits, or additions to the control code might have been made over the years to improve production but were not adequately documented. Worse yet is when no document of the control functionality can be found. It is unrealistic to expect the integrator to somehow glean all the intricate functionality and nuances of the controls for the new system simply because the integrator is in possession of the control code and HMI application. The stakeholders need to commit to allowing the plant’s operators, maintenance, and supervision to share their tribal knowledge of the system with the integrator.
Design review
Plan for extensive design reviews with the plant’s active participation—the more reviews the better. Also, conduct in-depth factory acceptance tests (FATs) where the operators run the new system under full simulation with mass balance, energy balance, alarms, upset conditions, manual control, and system recovery. Create a living document during these activities that captures the operational functionality and configuration of the new system when it goes live on the plant floor.
Proper planning
Coordinating and meticulously planning the activities and responsibilities of all the participants—including plant personnel, IT, integrator, contractors and even suppliers—prior to a short-duration cutover is paramount to achieving results.
In this planning process, be sure to consider:
- What pre-work will be performed and by whom, such as device or wire tagging, or panel mounting, or conduit installation and wire pulls?
- How extensive will controllers, I/O, networks, servers, and panels be configured and pre-tested and who will do it?
- Will the existing instrumentation be re-calibrated before or during the cutover; who will be performing the calibration and how long of a time window will instrument calibration be given?
- Who will mount and wire any control or network enclosures?
- Will any pneumatic tubing re-work be needed; who will perform the work; and when/how much time will it take?
- Are other projects planned at the plant simultaneous to the legacy cutover during the short-duration time window that could impact or interfere with the cutover, such as repairing/resealing floors in areas where checkout and water-trials need to happen; or plant power taken down to service the main switchgear or unit substations?
- If a device or critical system component fails during testing, who should be contacted at the supplier to expedite equipment replacement?
- What is the plan—how much time should be allocated and who will (specifically) be involved in running dry and wet tests of the new control system with the existing process and utility systems to ensure production starts up on time with minimum impact on quality, efficiency, and output?
Success is better guaranteed when everyone knows what’s going on, precisely who’s doing what, and exactly when during each step of the cutover.
Project managers, plant operations, IT, the integrator, and contractors can greatly reduce the risk and significantly increase the probability of success with extensive planning, copious amounts of communication, coordination with all involved, and then sticking with the plan. Surprises will undoubtedly surface during the short-duration cutover. The key is to only encounter a small number of these surprises by taking the steps ahead of time, to plan the work, then work the plan.
Stephen Malyszko, Chief Executive Officer at Malisko Engineering, a certified member of the Control System Integrators Association (CSIA). See Malisko Engineering’s profile on the CSIA Industrial Automation Exchange.
