Valve World Americas | March 2017 • www.valve-world-americas.net6

SPECIAL TOPIC | Control & Smart Valves

By Sandro Esposito – Setpoint Integrated Solutions

An Ounce of Prediction Prevents a Pound of RepairsThe control valve is where the rubber meets the road (or more literally, where the fluid meets the steel). Adequate and timely control valve maintenance is therefore an area processing facilities can make a big impact on their business because the failure or poor performance of a valve may shutdown operations, affect production output or lead to an unsafe situation.

It is estimated that about 18 million control valves are handling fluids in facilities around the world. This final control element is for most processes the component with greatest impact on plant performance and safety. The fact that control valves must manage flu-ids flowing at high velocities and often operate in severe service conditions, it is essential that they perform properly so that facilities, people and the envi-ronment remain safe. And with ever-increasing pressure in a competitive market to keep facilities running with little or no downtime, end users are demanding longer intervals between maintenance activities and greater abil-ity to complete maintenance tasks with-out shutting the plant down.

Add daily wear and tear to the equa-tion, and it becomes clear why control valves are high-profile assets that com-mand a significant portion of a plant’s maintenance resources. It is essential, therefore, that this budget and time be spent wisely.

The key is to detect valve performance issues early, before they become big problems that impact the process and to surgically intervene at the right time. This article describes enablers for a predictive maintenance program that can help plant personnel reap at last, the benefits of digitally enabled control valves. This article outlines key techno-logical, data integration and workflow factors that must be considered in im-plementing successfully and effective-ly, an asset maintenance program for control valves.

The Better Approach to MaintenanceBy definition, a reactive maintenance program results in unscheduled – and costly – downtime. Because mainte-nance is not completed until the valve is malfunctioning, the process must be stopped until repairs are made.

Preventive maintenance reduces down-time but is also inefficient. Because maintenance is completed according to a preset time- or use-based schedule, rather than being dictated by actual con-ditions, tasks may be completed sooner than is necessary and parts may be re-placed before their useful lives are over.

There is a better approach – predictive maintenance, in which valve health is continually monitored, allowing plant personnel to maximize uptime by de-tecting and correcting minor issues quickly, easily and cost-effectively with minimal disruption of the process.

Detecting Control Valve Problems Before They Impact the Process

The Benefits of Predictive MaintenanceThe benefits of predictive maintenance add up quickly in preventing downtime, reducing compliance costs and stream-lining maintenance processes.

Like virtually any problem, valve issues are far easier to fix, and less costly, if addressed at the first sign of trouble. Take, for example, a valve that is stick-ing slightly due to process deposits on the internal guiding parts; if the issue is detected early, it can be addressed before the guiding surfaces are dam-aged to the point that the valve seizes in place, upsetting the process and re-quiring a major overhaul. Another ex-ample is the detection of inadequate actuator force to shut the valve against operating pressure. In such cases, a simple adjustment of the actuator spring (spring-to-close application) or increase in air supply (air-to-close appli-cation) may solve the problem and pre-vent seat leakage that can damage the expensive internal trim components. Other problems, such as positioning performance degradation, can also be addressed before they cause variability in process output.

The costs of complying with today’s more stringent environmental regula-tions have become significant, but pre-dictive maintenance practices can help end users control them. For example, digital valve positioners (DVPs) can monitor the cycles and accumulated movement of the stem within the pack-ing. Such information is needed to en-sure that a control valve’s stem packing is adjusted adequately and maintained in a timely manner to prevent or mini-mize fluid emissions to atmosphere.

And when maintenance tasks must be completed, a proactive approach will streamline the process. Maintenance can be scheduled around the produc-tion cycle, minimizing any disruption. Logistics can be mapped out and parts ordered in advance, helping ensure a smooth process with no surprises.

Three Keys to Predictive Maintenance – Technology, Data Integration, WorkflowPredictive maintenance requires a three-pronged approach consisting of technol-ogy, data integration and workflow.

Technology

Technologies used to detect valve per-formance issues can be divided into two categories: “direct” technologies that are determinative for the type of

problem detected and “indirect” tech-nologies that infer a problem based on indirect measurements or periph-eral symptoms. Each category includes tools that can detect problems with-out disturbing operation of the control valve (“real-time” tools) and those that are intrusive and cannot be used while the process is running (“offline” tools).

The ideal choice, of course, is a technol-ogy that is direct and real-time – able to detect problems determinatively dur-ing normal process operation. Vibra-

tion monitors and acoustic sensors are two such tools. Monitoring vibration of a control valve can flag mechanical problems related to the stem and plug. Acoustic sensors can uncover such is-sues as cavitation, flashing and leakage to atmosphere. These technologies are costly, however, and highly specialized training and extensive experience are required to correctly interpret the data they provide. As a result, implementing them on a permanent basis is impracti-cal for most facilities.

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SPECIAL TOPIC | Control & Smart Valves

DVPs, however, are an effective, budget-friendly and easily implemented direct/online tool. They have become the dominant brain of control valves and therefore, already found in many facili-ties. The built-in sensors (input signal, position, pressure and temperature) combined with analytical software mea-sure operating performance and will de-tect performance problems. Their ability to capture and trend historical runtime data also provides leading indicators of valve performance degradation.

DVPs can help detect a wide variety of common control valve performance

problems, including shutoff of up-stream pressure, damage of internal parts from cavitation and flashing phe-nomena, fluid leakage to the atmo-sphere, high friction, actuator spring failure, air leaks from tubing or the ac-tuator diaphragm, positioner contami-nation and positioner feedback.

Data Integration

No matter which technology is used, it is crucial to aggregate the data collected and with analytical software, transform the data into actionable information for real-time asset management. The data also must be presented not in its raw state, which requires interpretation by plant personnel, but as information that can be readily used to assess the vital signs of a control valve’s health.

The integration can be done using digi-tal communication protocols such as HART™, FOUNDATION™ Fieldbus or PROFIBUS™, or using wireless signals such asTWireless HART or ISA100.11a. Because these protocols and signals are open standards and are omnipres-ent within a plant’s infrastructure, they

allow valve diagnostic information to be seamlessly integrated into the facil-ity’s asset management software.

Workflow

Einstein said “The world we have creat-ed is a product of our thinking; it cannot be changed without changing our think-ing.” When it comes to control valve maintenance, technology can certainly make a difference, but work practices must also simultaneously evolve.

For plants that have traditionally fol-lowed reactive maintenance practices, this requires a paradigm cultural shift. Personnel must move from a mindset of waiting for problems to occur to one of proactively monitoring asset health.

Recent technological advances have made this cultural change easier.

Technological Advances Ease the WayMany of the technologies used to di-agnose control valve health have been available for years, but they did not pro-vide data in a user-friendly manner and were based on the incorrect assumption that end users could analyze the data and make correlations or fault models on their

own. As a result, they gathered dust.

For example, many plants invested in asset management systems with the belief that they would offer signs of control valve degradation and provide some level of predictability of when the valve would require maintenance. In practice, however, these systems would pick up alerts from a device without correlating them with other data from the control valve. They sig-naled significant failures that needed to be reacted to, rather than helping plant personnel be proactive.

Since then, control valve vendors have invested in data modeling so the user can act proactively on determinative in-formation without having to be expert number-crunchers. In addition, the wide adoption of integration standards such as FDT-DTM and the evolution of the “in-ternet-of-things” using data exchange technologies for sensors such as OPC (OLE for Process Contro,), the integra-tion of diagnostics with asset monitor-ing systemss are now much simpler.

Plant personnel now have access to the information and user-friendly tools they need to implement predictive mainte-nance practices.

From the advent of the wheel to the in-vention of the computer, humans have used technology to accomplish tasks more efficiently. The same holds true today in process control. By adopting a proactive approach to maintenance and taking advantage of digital valve posi-tioners and open softwaresstandards, plant personnel can detect and address control valve performance problems before they impact the process.

ABOUT THE AUTHOR

Sandro Esposito is the director for digital technolo-gies & innovation at Setpoint Integrated Solutions, a leading process automation and valve automation supplier in the gulf coast. He graduated from the Ahuntsic College in Montreal,QC, Canada with honor-ary academic mentions. He has worked for 23 years in the control valve and process automation indus-tries where he managed the development and com-mercialization of smart valve positioners and valve

diagnostics software. He holds several patents and has published multiple papers in leading industry publications.

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Digital Valve Positioner (DVP) with integrated sensors Technology integrated with workflows

DVP’s raw sensor information plotted vs time. Useful but no actionable information

Transforming with analytics raw sensor data from DVPs into actionable and usable information