One path in digital transformation programs is to drive reliability improvements of plant assets by moving from reactive maintenance to condition based maintenance of the equipment.
I caught up with Emerson’s Saurabh Pathak who shared a case study with me of a large, Middle Eastern natural gas transportation & distribution company. This company had a continuous improvement program to improve asset performance and optimize the process. One big area of focus is this shift from planned maintenance to predictive maintenance using online condition monitoring technology.
The scope of this online condition monitoring effort includes wireless vibration sensors for motors, ultrasound sensors, and digital valve controllers monitoring control valve performance. There are also plans to do condition monitoring on gas chromatographs and ultrasonic flow meter measurements on custody transfer systems.
The asset condition data comes from field staff, process data from the control system, and these online condition monitoring sources. It is fed into a closed-loop asset performance management (APM) process which provides for failure reporting, analysis and corrective action management that is connected with their computerized maintenance management system (CMMS).
One objective of this program was to enhance the reliability and availability of the control valves in the process and extend the time between plant turnarounds. To address this objective, they wanted to shift from reactive alert monitoring to condition monitoring. Their vision was to perform remote monitoring of all critical assets, beginning with the control valves, from a central office.
A key technology to enable this remote monitoring were the Performance Diagnostics (PD) in the Fisher FIELDVUE DVC6200 digital valve controllers. These diagnostics include the In-Service Online and Out-of-Service diagnostics tests. Some of the early valve problems that can be detected In-Service/Online thru the diagnostics include improper stroking speed, excess or reduced friction leading to stiction or process leak, insufficient air supply, poor throttling performance, seat integrity, oscillation due to loop tuning or instrument or accessories degradation, erratic performance, pneumatic leaks, regulator degradation, actuator degradation, worn valve components, online trending and alerts. These diagnostics allow early identification of most hidden valve failure modes supporting a predictive maintenance vs. reactive approach.
In addition, the associated online alerts include travel cutoffs and limits, minimum opening and closing times, input characterization behavior (linear, equal percentage, quick opening, and custom), trending and the following alerts: travel deviation; supply pressure, travel alerts; drive signal; cycle counter. Travel accumulation can be monitored continuously for early identification and notification.
Coupled with the ValveLink software, the online diagnostics are complemented by the Out-of-Service/Offline diagnostic tests (dynamic error band, drive signal, step response, and valve signature), providing comprehensive electronics and mechanical integrity checks, and overall valve asset performance health condition.
Issues with the prior time-based plant maintenance practices were that some valves pulled for service did not require repairs, those that were not planned for repair required it, spare parts management was uncertain, and not addressing these issues could delay start-ups.
Once the objectives and vision were established, the company staff met with members of the Emerson Valve Connected Services team to define a scope and key performance indicators (KPIs) accompanied by a site walkdown and shutdown/turnaround/outage (STO) plan review to establish a plan to execute the valve condition monitoring project. The plan included identification of the critical valves across the site and information shared with Emerson valve experts to data analysis in order to provide actionable recommendations to the staff.
Once the digital valve controllers were installed and the Emerson Connected Services team engaged, Saurabh shared some examples of valves that were identified with abnormal closing profiles, leaks beyond the class shutoff ratings, and ones with excessive friction. Through early notification of these issues, the repairs could be scheduled when possible. Other issues identified included stuck valves, gland leaks, and feedback linkage misalignments.
The company estimated the ROI from this Valve Condition Monitoring program at 40% of overhauling cost and expansions of the program to other sites and valves within this site are on the project roadmap.
Visit the Valve Condition Monitoring and Connected Services sections on Emerson.com for more on the technologies and solutions to improve the asset reliability at your organization. You can also connect and interact with other valve experts in the Valves, Actuators & Regulators group in the Emerson Exchange 365 community.
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