During the Emerson Exchange EMEA 2024, Chand Basha Chittoor, staff engineer E&A at the SABIC Centre of Excellence in the Kingdom of Saudi Arabia, informed delegates how the company optimized turnaround planning and execution using control valve diagnostics.
Turnarounds at SABIC petrochemical plants are performed approximately every five years, with 15 days typically maintenance window available to undertake the required maintenance and repairs. Plant downtime costs millions of dollars per day, so turnaround planning and execution is critical. A typical plant can have over 300 control valves. To complete all work within the turnaround timeframe, prior analysis of control valve condition is required.
Emerson, which has been a preferred automation services provider to SABIC since 2020, utilizes its Connected Services to perform control valve analysis and provide the information needed to properly prepare for a turnaround. Emerson personnel work with SABIC plant staff to analyze control valves prior to a turnaround, starting about six months before the shutdown. These analyses, especially control valve signatures, provide the data required to ascertain which valves need servicing and which do not, thereby greatly improving turnaround planning and execution. Chittoor explained that for those valves requiring servicing, the analysis helps to determine what type of work is needed and what spare parts need to be ordered; to ensure that the right staff are available; and to deal with any unexpected issues. The analyses also provide valuable data to increase uptime during operation after a turnaround.
Chittoor explained to delegates that multiple workshops were initially held with Emerson to formulate the plan. Emerson introduced its valve connected services program and the two companies aligned their approach. The scope of the project was established, with a list created of over 300 control valves, ranging in size from 2 inch to 60 inches, for diagnostics. Most of the valves had an Emerson Fisher™ DVC6000 Digital Valve Controller, from which diagnostic data about the valve was retrieved during a site walk-through. These diagnostics were then reviewed to establish appropriate work requirements.
Within the maintenance window of just 15 days, the selected valves were removed, overhauled, tested, reinstalled, and a function test was performed. A valve signature test was run both before and after the repair activities. This provided plant staff with the information needed to secure the necessary budget for ordering spares and performing repairs. It also could be used to clear a valve for service after a positioner replacement, which helped avoid the need for a complete valve overhaul. The functional test was performed after the valves had been reinstalled to ensure smooth start-up.
In terms of performing the diagnostics, Chittoor explained that starting early was key, with the valves monitored online during normal operation. That included monitoring the status and performing friction analysis. The data was evaluated during the review stage and the valves were categorized into 3 categories (red, yellow & green) and the results revealed that 23% of the valves had a poor seat profile, packing leak or extremely low/high frictional values that need to be dropped for overhauling (Red Category). About 54 % of the valves required tuning, calibration or positioner replacement and it can be repaired in line (Yellow category). The final 23% had normal frictional values, and no gland leaks or tuning or calibration issues, which are healthy, and no action is required (Green Category).
By establishing which valves needed overhauling, there was a significant reduction in the number of cranes, amount of scaffolding, manpower, transportation, spare parts, and overhauling and testing work required. This helped to reduce costs by 30% and time by 10%. Chittoor said the key lessons learned were that starting early was essential to finishing early. A condition-based maintenance strategy provides obvious benefits and having an asset management system in place, such as Emerson’s AMS, can help to save time and reduce risk.
