Periodically most continuous running plants must schedule a shutdown to perform the maintenance activities which cannot be done while the process is running. The process of managing this period while the plant is shut down is commonly known as a turnaround.
Turnarounds are very expensive in terms of lost production and the expenses associated with the maintenance activities performed so it’s critical to plan and execute these activities as efficiently as possible.
I spoke with Mark Coughran, whom I highlighted in an earlier post, about the planning role the Emerson control performance group can play in a process manufacturer’s turnaround planning process. Based on the experience the team has gained working with process manufacturers across many industries, they have collected their best practices into a Pre-Shutdown Automation Service.
With this service, Mark and other consultants help identify and prioritize the control loops and devices that should be improved including control strategies, tuning, control valves, dampers, drives, process sensors, and transmitters. They pre-diagnose the troublesome control loops and devices which most impact process stability and flexibility and that can only be fixed with the process shut down.
The process begins by working with plant staff to assess the performance of critical loops with the most economic impact on the plant. Using tools like Emerson’s EnTech Toolkit and Entech Valve Tester for loop performance measurements and analysis of process dynamics, control performance consultants provide specific recommendations to optimize controller and instrumentation performance and recommend further improvements to the instrumentation, process design, and control strategy to be implemented during the turnaround. A key aspect of these tools is that they enable performance diagnostics while the process is running in normal operating configuration giving an online holistic view of operating control performance.
When problems are identified that have a significant impact on operational performance, the team makes specific work package recommendations for the turnaround, which may call for follow-on services that Emerson’s Instrument & Valve Services team or local business partners can provide such as offline testing of control valves, dampers, and instruments using tools like FlowScanner and AMS ValveLink.
Typical problems uncovered as a result of this pre-shutdown service include: poor valve trim or positioner performance, excessive loop oscillations, sluggish response, excessive dead band, or loop interactions which can often be solved with advanced control.
By pre-diagnosing and better focusing the control improvement efforts, the pre-shutdown service helps make turnarounds more efficient and results in better control performance post-turnaround.