Maximizing the advantages of electric actuator diagnostics

B. Gundaboina and A. KMITTA, Emerson, Houston, Texas

Driven by stringent greenhouse gas (GHG) emissions regulations and technical improvements, electric valve actuators are becoming increasingly common in applications throughout the process industry. Significantly reduced power requirements, spring-return and fail-safe features, and a host of embedded diagnostics have driven the installation of these actuators in an ever-expanding range of processes.

Unfortunately, diagnostic and equipment monitoring software has historically been unavailable for this market segment. Despite adding many actuator diagnostic features, data monitoring and analytic products have been largely unavailable for electric and electro-hydraulic actuators until now.

This article focuses on recent software developments that empower users to monitor these devices, enabling them to detect and proactively respond to developing issues before failures occur, and to integrate valves equipped with these actuators into traditional maintenance asset monitoring networks.

Electric actuating options. Until recently, electric actuators saw limited use in process industries. Typically, actuators were only utilized in remote areas, had limited torque and were prone to failure. They also had rudimentary diagnostics that provided little information beyond indicating if the valve was working. Remote monitoring and connectivity options were largely non-existent.

A global focus on reducing methane and GHG emissions spurred many users to transition from natural gas–actuated pneumatics to electrical and electro-hydraulic actuators (FIG. 1). Actuator designs and technology have improved significantly, allowing some actuator models to achieve zero-emissions performance, and now include integrated spring-return, fail-safe technology. These new designs are suitable for safety integrity level shutdown applications and operate with a fraction of the power required by previous models, while generating far more torque.

These technical improvements have also made electric and electro-hydraulic actuators increasingly attractive for applications where pressurized air is expensive or unavailable. As a result, these actuators are becoming common in many new capital projects, and they can be retrofitted to existing valves when needed.

Electric actuators incorporate significant processing power and advanced diagnostics to operate efficiently and reliably. These features can be helpful to a technician addressing a problem at the valve. However, unlike most pneumatic actuators and positioners, few data access options have existed to connect electric and electro-hydraulic actuators to existing asset monitoring software networks.

Electric actuator connectivity solutions. Fortunately, the information gap is being closed with the introduction of software applications specifically focused on the electric and electro-hydraulic actuating market. These software applications offer various useful features, including the ability to access device information—along with current status and alarms—and execute basic functionality and test commands (FIG. 2).

More advanced applications provide extensive features, including the ability to perform local partial stroke tests, upload and download valve configurations (remotely or locally), and capture and store stroke curves for analysis, troubleshooting and side-by-side comparison (FIG. 3).

While all these features are invaluable to technicians, the transformational improvements come via advanced data analysis, analytics and predictive maintenance. Only recently have these data applications started to utilize the information in the valve’s historical performance, stroke curves and alarm logs to identify current and developing problems, and to offer specific suggestions for troubleshooting and repair (FIG. 4).

Data analytics can identify potential issues as they develop, allowing maintenance personnel to plan outages and avoid unexpected downtime, which typically translates into significant operating improvements.

Evaluating potential options. Each software application has different capabilities, so users are advised to evaluate available options and determine the best alternative for their specific application. Here are some key features worth considering:

1. If the company already has asset management software, does the new software integrate with it? Obviously, a fully integrated package that seamlessly works with the existing software will be easier to configure and maintain, and it will be familiar to plant personnel, lessening training requirements.
2. What capabilities does the software offer? It should include at least these basic features:

1. Access and configure the actuator key parameters
2. Upload (and store) and/or download configuration parameters
3. Allow continuous access to real-time data for remote monitoring and storage
4. Allow access to device logs and historical data
5. Capture torque and performance curves, and then compare stored values to current values to detect variations
6. Allow technicians to stroke test valves and/or perform partial stroke tests
7. Provide an easy-to-comprehend interface for basic data and alarms, with a means to “drill down” into the details as necessary
8. Diagnostic help screens to identify problems and offer potential solutions, leading to shorter repair time.

1. Connectivity options can be a strong differentiator among offerings. Some key protocols that should be supported include:

1. Bluetooth
2. A wired highway addressable remote transducer
3. Modbus
4. Infrared data association
5. Foundation Fieldbus
6. RS-232 serial.

1. Communication options should include remote and local access. The software should be PC-based and available on a laptop, smartphone or tablet.
2. Ideally, the software should utilize an open architecture and/or integrate digital terrain model data files to access multiple vendor devices from a common platform.

Recent case studies. A chemical plant's maintenance personnel installed electric actuator monitoring software^a in their existing asset maintenance system. They began capturing and comparing torque curves using the existing Foundation Fieldbus network. Over time, they noticed some valves were developing a spike in the closing torque, ultimately attributed to product buildup within the valve. By monitoring the valves for this spike, they could readily identify problem valves and then pull them for cleaning before the valve was damaged or production was affected.

In another application, the remote valve monitoring software detected consistent under-voltage alarms on a valve. The valve was working, but the analytics suggested a developing power supply problem. A field check confirmed the power supply was not operating properly, and it was repaired before an outright valve failure occurred.

A third company used a local Bluetooth connection to perform partial stroke tests on their valve monitoring software. This allowed the plant to extend its safety instrumented system interlock testing frequency. The plant also utilized the captured partial stroke test torque curves to identify valves beginning to coat and plug.

Takeaway. Electronic valve actuators have come a long way from the simple, motorized valves that once dominated the landscape. Fail-safe features, low power requirements and electro-hydraulic hybrid designs have rapidly broadened the range of applications, and these devices are becoming increasingly common throughout the process industries.

While initially slower to market, capable data monitoring and configuration software is now available for these devices. With several connectivity options, these new applications offer features that enable technicians to configure, operate and troubleshoot valves and the associated actuators. These capabilities are useful and important, but the gathering and utilization of performance and historical data yields the greatest savings. Advanced data analytics and actionable repair suggestions enable maintenance departments to identify and address issues before production is impacted, improving uptime, reliability and profitability. HP

NOTES

^a Emerson’s DCMlink

BHAVANA GUNDABOINA is a Senior Product Marketing Manager for Emerson. She earned her BS degree in mechanical engineering from Osmania University and has spent 12 yr working in the oil, gas and petrochemical industries, supporting product design and manufacturing engineering.

ANTHONY KMITTA is a Software Engineering Manager for Emerson. He has spent 16 yr working in the steel, process automation and software development industries, supporting operations, controls and manufacturing engineering. Kmitta earned his BS and MS degrees in electrical engineering from Purdue University.