A straightforward maintenance strategy yields improved plant performance

Moving from reactive to preventive maintenance helps Monsanto improve output and reduce costs at its Muscatine plant. Smart field devices and control valve positioners provide critical diagnostic data to reliability engineers, guiding their efforts.
By Peter Welander May 4, 2013

Monsanto's Muscatine plant in Southeast Iowa earned the 2012 HART Plant of the Year award. Courtesy: Control EngineeringIn many situations, a straightforward and consistently applied maintenance strategy can have results that attract positive attention as production and plant availability increase while maintenance costs decrease. Such is the case at Monsanto’s Muscatine manufacturing facility. The combination of technical solutions with corresponding work processes has had measurable positive results and earned the facility the 2012 HART Plant of the Year Award.

The Monsanto Muscatine facility is located in southeast Iowa along the Mississippi River. It manufactures Roundup herbicide along with acetanilide select chemistry products, including Harness Xtra, Degree Xtra, and Warrant. The facility covers 150 acres and employs around 450 individuals to operate and manage eight individual process units. These include waste treatment and plant utilities along with the product manufacturing process areas. The majority of the plant operates continuously, year-round, and the oldest parts of the facility date back 50 years.

An inherited maintenance platform

Monsanto's Muscatine plant in Southeast Iowa earned the 2012 HART Plant of the Year award. Courtesy: Control EngineeringThe processing units are controlled by a mix of Emerson DeltaV and Provox DCS (distributed control system) platforms tied to more than 3,200 instrument assets, including transmitters and control valve positioners. Of this total installed base, there are currently over 600 HART and 125 Foundation fieldbus instruments within the facilities AMS Intelligent Device Manager. The outstanding instruments not yet in the AMS Intelligent Device Manager are in large part either not terminated to smart I/O or are simply non-smart devices. One of the pivotal changes in Muscatine’s operation happened in 2006 when Joel Holmes, site electrical reliability engineer, received a standalone Emerson AMS unit from another Monsanto plant. Having access to that unit enabled him to explore some of the capabilities of a more sophisticated maintenance strategy using diagnostic information gathered from field devices using HART Communication and Foundation fieldbus protocols.

Given the facility’s extensive population of maintenance-intensive valves and instrumentation, this was an area where Holmes felt that improvements in reliability would have the largest impact on overall plant performance. Part of the process of integrating his new maintenance tools with the work processes involved assigning a criticality value to the instrument assets in each process unit. Those that could impede production were given the highest priority for monitoring.

As Holmes described the process, “We utilize an A, B, or C letter designation to denote asset criticality. The highest criticality ranking is an A, with the lowest criticality ranking being a C. Keep in mind, A-ranked critical devices will receive the most attention since their performance is crucial to the on-stream time of the production system whereas C-ranked devices may, in many cases, be allowed to run till failure since their impact to the production system is minimal or they have in-line spares.”

Electrical reliability technicians Mike Chaney (left) and Thad Witte follow-up on alerts from AMS to track down problems in the process units before they cause downtime. Courtesy: Control EngineeringAs Monsanto gained experience with AMS, use within the plant became more sophisticated with improvements in overall effectiveness. The Alert Monitor became the primary predictive tool integrating the plant’s asset criticality measure with the Device Manager. The respective device group assignment in turn directly impacts its polling rate, or the frequency at which the Alert Monitor extracts the devices status, health, and diagnostic information from the field.

Over time, Holmes created three groups of devices: transmitters, control valves, and vapor sensors. This helped balance the loading of the Alert Monitor since having too many devices poll at the same frequency overloaded the system, resulting in extremely slow update rates or no response at all. Each device group has a set series of polling rate values dependent upon its criticality ranking.

Working in a legacy environment

This control valve positioner communicates with the process unit’s controller using conventional analog I/O, so there is no capability to read the HART data. Adding the wireless THUM allows the diagnostic information to be visible within the AMS Device MaWhile some of the process units have relatively new control systems with HART-enabled I/O, there are other areas where the system is still plain analog. These will be upgraded as the plant moves through a series of migrations to DeltaV control systems with CHARMS I/O, but in some areas that is still years away. The work-around that the plant has developed to gather diagnostic information involves either WirelessHART THUM communication for critical tags, or HART/Foundation fieldbus handheld communicators for devices that require less frequent monitoring.

The WirelessHART deployment is growing with about 25 devices currently in operation. Holmes expects that number to grow, and each process unit will soon have its own wireless gateway.

A case in point

As the Glyphosate Technicals unit was anticipating a scheduled shutdown for catalyst regeneration, Holmes and his team addressed a planned and scheduled deficiency work order with a two-inch eccentric ball control valve that had been identified as suspect through a prior control valve reliability PM route. The AMS Intelligent Device Manager along with its ValveLink Snap-On application had measured increasing friction as the valve moved through its full span of travel. This indicator suggested a problem was developing and triggered a failure when performing the diagnostic scans on the control valve assembly. While the valve was not exhibiting any issues that would be visible to the operators, the valve signature indicated that the amount of force required to open and close the valve had increased substantially. It was still able to perform its control function for the moment, but comparisons with historical signatures revealed that a more drastic situation was developing.

Operators were unaware that there was a friction problem with the valve since the step response test results were performing normally. The valve was performing its control functions, but it was only a matter of time before the valve would malfunction. Cou

Holmes recommended that the electrical reliability technicians change out the valve during the outage; therefore, the reliability technicians proceeded to remove it from service during that time. When they pulled the valve body free from the flanges, they found a 1/4 x 4 in. bolt stuck in the valve that had apparently come off one of the clamps holding a filter element designed to capture the catalyst. It had been carried down the pipe by the flowing process stream. Had that bolt remained in the valve, at some point it could have initiated flow control issues up to and including the valve refusing to close which would have caused additional problems.

When the AMS Intelligent Device Manager ValveLink Snap-on scan failed, it was clear from the valve signature that there was a serious problem developing. This prompted removal of the valve during the outage.That type of valve normally has a valve signature like this one, where the opening and closing pressures are in a tight group along with the ideal standard performance indicator.

The bolt had damaged the valve’s ceramic plug and seat, so once the valve body was removed and separated from the actuator, it was sent out for rebuilding. A new valve body was mounted on the actuator in the shop. Prior to reinstalling the assembly, it was calibrated and then tested with the use of the ValveLink Snap-On application to make sure the valve signature and additional diagnostic scans indicated normal operating parameters using HART. All scans including the valve signature were recorded in AMS so that results can be compared to future analysis in trending for degradation. When approved, the valve was returned to service without delaying the scheduled startup of the process unit.

Changing plant mindset

Throughout the plant there is a large variety of instrumentation types and manufacturers. Most communicate via 4-20 mA/HART but Foundation fieldbus is also installed where cable routing infrastructure has been a problem. WirelessHART devices are growing iAs workflow processes change, so do individuals’ mindsets. The reliability team members have enjoyed seeing some of the traditional barriers within the company between operations and maintenance crumble as a growing sense of common purpose and cooperation develops.

Holmes described one of the changes: “Along with the reliability programs and some of the efforts related to how we monitor and look at our deficiency backlog, we’re also getting into AEM (asset effectiveness management). This method looks at the process units, what they have to make per our sales, and tracks their process downtime. We want to make sure that we’re not only looking at it from a predictive and preventive standpoint to see what’s causing downtime, but to also have those operating units telling us what their biggest pains are. In the past, maintenance was addressing things that they were seeing failing and having problems, but it wasn’t always the same issues or biggest problems that the process units felt they had. So there was a kind of disconnect there. With us transitioning and now focusing on AEM, in addition to all of our predictive and preventive efforts, we’re getting a better grasp on what needs to be addressed and handled to ensure that we have the manufacturing availability we need.”

Electrical reliability technician, Mike Chaney, has also seen positive effects as he works with operators. “Being in a sold-out state as we are, we get a two day window in some cases to find problems and get them fixed within that window,” he said. “If we can avoid downtime down the road—that’s big. Causing downtime right now is not a good thing. So if we can prevent that from happening, it saves the plant lots of money in the long run. Production sees what we’re finding using this technology. So when we say something to them, they’re not so quick to respond, ‘We aren’t going to do that.’ They’re more willing to say, ‘We’ll get this valve ready for you to pull out and then see what you’ve got.’ They know we’re saving them headaches. If we can keep things running, it makes their day nicer.”

Measuring progress

When this whole program began, Holmes said that they had no good way to distinguish, track, or analyze reliability work performed in the plant. To remedy that, Monsanto created order codes to work within the SAP CMMS. In order to track labor and material costs to specific equipment, individual deficiency notifications are entered from any findings arising from the facilities preventive (PM) or predictive (PdM) maintenance reliability programs. Each issue identified during PM routes or PdM triggers will have a separate deficiency notification / work order created. This allows for predictive vs. reactive work cost analysis to be performed and KPI’s to be generated and tracked.

The code analysis data helps quantify planned versus reactive work. In turn, the system generates bad actor lists and provides for a dollar figure that indicates how much of a cost avoidance reliability program initiatives are providing. An average of 12 AMS deficiency orders are entered each month. With a cost avoidance of over $1,600 per work order, it correlates to over $200,000 saved in time and materials annually. However, Holmes points out that this is strictly an out-of-pocket cost avoidance savings and does not reflect increased income from gains in plant manufacturing availability.

One big effective family

There is more work to do within the plant, but Holmes and his plant management see the direction clearly. “The big hurdle that we have is that operations doesn’t always know what the reliability programs are doing,” he said. “So there’s a constant effort to share and communicate, not only with production but our other maintenance workforce. We continue to share what these guys are doing, their successes, findings, and training. That’s imperative as we try and grow the relationship. It’s very apparent to our upper management, so it’s one of our goals to keep that communication going to tie the three together: maintenance, production, and reliability as one big family.”

Peter Welander is a content manager for Control Engineering. pwelander@cfemedia.com

Key concepts

  • The technical elements of an effective maintenance program are not complicated.
  • Procedural and cultural changes within a plant are critical to ongoing maintenance management success.
  • Many tools are available to support such programs, they are not difficult to implement, and the payoff can be huge. 

ONLINE

Search “HART plant” at www.controleng.com to read Plant of the Year stories from earlier years.

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HART Plant of the Year Award—Celebrating ingenuity and innovation 

Receiving the award, left to right, Thad Witte, electrical reliability technician; Ron Helson, HART Communication Foundation; David Penn, plant manager; Joel Holmes, site reliability engineer; Mike Chaney, electrical reliability technician.The HART Plant of the Year Award is presented annually by the HART Communication Foundation to recognize people, companies, and plant sites around the world for their ingenuity and innovation in applying and using HART Communication. A HART Plant of the Year takes the capabilities of HART instruments beyond configuration and calibration, or uses real-time diagnostics and process variables of HART-enabled devices integrated with its control, information, and safety systems. Each is a powerful example of how to utilize HART Communications better, and to realize even greater benefits for their company. To nominate your plant, go to www.hartcomm.org