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Emerging Trends in Asset Maintenance
Sarita Patel Solution Architect, Solutions Group Emerson Process Management The continuous wear and tear of assets in process plants create a major challenge for the plant operators to maintain high production levels. Keeping 1000s of equipment up and running is seen as a complicated process and requires critical data across the plant. The article discusses how digital architecture is emerging as the game changer in asset maintenance.

In a perfect world, a plant would produce at its maximum output forever! Now we all know that it is a ¬Blue Sky  dream. The plant (represented with grey in Figure 1) does start out pretty close to perfect, but then reality sets in and time brings process changes and wear and tear to the equipments causing performance to deteriorate, at times to the point where production stops completely due to an unplanned shutdown (note the first break in grey). Then the production recovered and the natural deterioration is addressed by another plant shutdown. The result of all this is significantly lower financial performance. Time, friction, process parameter changes (dynamic nature of plant), the basic laws of physics are all the enemies of a perfect plant. Moreover, the difficulty of keeping 1000 s of equipments up and running is seen as a very complicated process and requires critical data across the plant. Typically, a plant has 20-40 per cent control loops in manual control because loops are tuned for a ¬perfect plant . But the conditions change and they do not perform according to the changing conditions, the operators start moving the loops in manual mode to ¬line out , stabilise and to compensate the fact that variability has been introduced in the process. 80 per cent of control loops show extensive variability for the same reason as above. It is also found that many loops were never tuned properly since the beginning. Many potential advantages of PlantWebTM (Advanced Process Control) are being missed, because PlantWebTM sits on top of regulatory control and if conditions mentioned above happen, operators turn off their advanced control as it is dependent on feeding set points to a well tuned regulatory control system. 86 per cent of maintenance is Reactive (too late) or Preventative (Unnecessary) (from Reliability Magazine 2002). Best practice is that only 40 per cent maintenance should be reactive or preventative, with other 46 per cent to proactive maintenance.
Since plant live on statistics, there is no other solution but the digital plant architecture that brings us to the next level of automation infrastructure.
It started with pneumatic/electronic analog panel boards for regulatory control and was state-of-art until 1976, the era of DCS started from 1976. The first fully digital plant architecture was introduced in 1998.
The digital plant architecture is specifically designed for new wealth of information, that comes from the 1000 s of intelligently transmitting field devices. It basically imbeds and deploys Predictive Intelligence to the plant. It is networked, unlike DCS whose ¬brain  is centralised in the control system. PlantwebTM is developed around the fact that there s intelligence everywhere and it is integrating the intelligence and getting the right information to the right person which is important today. Standards are what allow us to implement a technology in most cost effective way, by integration of best available products. The above features of digital plant architecture enables us to do more than just process control, and that is what changes the game/. the fact that the asset data and control data are being integrated in the same architecture and doing asset management, hence leads to better process control and then integrating all this with ERP system is where the business profit comes from.

As mentioned in the beginning that, friction, fouling, wear and tear and dynamic nature of plant are impacting all the equipments and unfortunately it is not visible at the early stage. Let s say, if a line is plugged and the reading on the screen or the reading which is being controlled is actually wrong because of freeze or blockage in the line. A bearing which is wearing and that is going to cause a major piece of equipment to shutdown, can be a sensitive issue. A digital plant architecture can tell all this information well on time enabling to take maintenance action proactively. It also generates significant and measurable reports for reference.

As it is said that, more and better information means more opportunities for reducing operational costs and improving quality, throughput and availability. In addition, new environmental and safety requirements have been established after many of today s facilities were built, and plants have struggled to get access to measurement and diagnostic information that could ease compliance. Too often, the cost or difficulty of adding new measurements has over weighed the perceived benefits. With traditional ¬wired  technologies, distance and complexity can make, connecting the measurement point to the control system, impractical or cost prohibitive.

WirelessHART technology removes the barriers of traditional wired field solution and gives unprecedented access to data that was previously out of economic or technical reach. Lower installation costs, due to reduced wiring and labor expenses, are only part of the equation. Estimates vary, but when we start to tally these up-front costs - including design, procurement, installation, and startup, as well as the infrastructure to support a typical wired analog measurement point - the total cost can far exceed the cost of the measurement device itself. The cost can go even higher if wiring-related infrastructure - cable trays, junction boxes, marshalling panels, and rack rooms - is at brim of their capacity and must be expanded to accommodate more measurements. The same is true for automation infrastructure such as I/O cards, controllers, and software licenses. In contrast, a smart wireless measurement point can be added for only a small fraction of the cost for wired installations.

Even more important is what can be done with the additional information. WirelessHART also empowers mobile workers to do their job more efficiently by getting remote access to the information they need. Most plants already collect data from hundreds - if not thousands - of stand-alone measurement points. It s all done manually, by operators making ¬clipboard rounds  to check gauges, sight glasses, chart recorders, or other indicators once per hour, shift, day, or week.

Now WirelessHART can be used instead of clipboards to bring that data back to the control room. The lower cost for adding wireless devices makes it feasible to do so for many of those hundreds or thousands of measurement points. It terminates the need for operator to collect data manually. Because the wireless devices can collect and transmit the information automatically at frequent intervals, we can get a more accurate, more up-to-date picture of what's happening in the plant - while operators reduce their exposure to hazardous conditions and get more time for higher-value work.

Millions of smart HART-based devices in the field today have some level of diagnostics capability. Unfortunately, many plants don t have the infrastructure to receive HART data in the control room. Since only a fraction of these devices are digitally monitored, the potential for accessing ¬stranded  diagnostics information in existing plants is significant.

Existing wired smart devices can be upgraded with a wireless adapter to transmit diagnostics information back to the control room or maintenance shop, where appropriate personnel can take corrective action as needed.

Process control signals continue to be communicated over the wired connection, while diagnostic data is simultaneously transmitted wirelessly to an asset-management application. This additional information opens the door to improved maintenance productivity.

The possibilities are almost limitless. They range from process control, equipment monitoring, environmental monitoring, asset management, device diagnostics, and energy monitoring/management to asset tracking, improving productivity of mobile workers, and security applications.

PlantWebTM can improve the plant overall efficiency by 2 per cent or more. Predictive intelligence in embedded in process gives new insights to improve performance and reduce costs. WirelessHART in the veins of PlantWebTM can definitely take the controlling and maintenance of the plant to the next level.