2010 HART Plant of the Year
08 February 2011
The 2010 HART Plant of the Year 2010 is the MOL Danube Refinery near Budapest. The company is committed to the operation of a predictive maintenance system. In developing its long term strategy the application of devices based on HART technology have a major role to play.
Beginning in 2002, the Instrumentation and Electrical Department at MOL Danube made two major decisions, says Gábor Bereznei, who heads the group. First, going forward, firstly, the department would purchase intelligent field instruments that support the HART Communication Protocol.
The second decision Mr. Bereznei’s group made was far more strategic, and is in fact the basis of this article. The MOL Group issued an internal directive to encourage its engineering departments to develop and use the in-depth and sophisticated communication options embedded in the HART instruments.
What is the significance of this second decision? Overwhelmingly, the greatest number of HART instruments communicate directly with handheld devices, such as Emerson’s popular 375 HART Communicator. In fact, it’s part of their plant welcoming ceremony: when the instruments arrive at the factory and are taken out of the box, they are connected with such a device for their initial set up and calibration.
For millions of HART devices, this is the first and last time they engage their communications in a digital HART conversation. After this, the device is sent off to lonely isolation somewhere in a manufacturing plant, never to communicate again—unless a technician takes the handheld out into the field, where the instrument is installed, to do some maintenance work on it a year or two later. And then, once again for a brief few moments, its HART electronic circuits are energised and it communicates using its protocol with the handheld interrogator. Then it goes silent again.
That’s under-utilising a valuable asset, decided Mr. Bereznei. The HART electronics embedded in the instrument in the first place enables it to communicate over its 4-20mA signal line, which is the standard pair of twisted wires that connect it with the control system. These HART digital signals contain a rich set of valuable diagnostic information that can enable engineers to monitor the health of equipment on the factory floor. Much like heart monitors in a hospital connected to a central nursing station allow technicians to keep an eye on dozens of patients, HART monitors in plant equipment allow factory technicians to ‘see’ what is happening in the equipment on the floor of their plants.
“Let’s get connected and put these HART instruments to work,” said Mr. Bereznai, and this became the Instrumentation and Electrical Department’s directive. And so today at the Danube Refinery there are over 30,000 HART instruments installed and engineers have connected 3,707 of them - mostly the valves and instruments in critical control loops - directly into computerised maintenance management systems (CMMS). The majority of these, 2,874, are in an Emerson Asset Management Systems (AMS) that uses ValveLink software for diagnosis. (There are another 437 instruments in this system connected via a Foundation Fieldbus network.) Another 833 instruments are similarly connected in Yokogawa Plant Asset Management (PRM) systems.
MOL Danube uses MTL and Pepperl & Fuchs multiplexers to connect the HART-based instruments to its control systems, which are mostly supplied by Honeywell and Yokogawa.
Beyond these 3,707 instruments, all HART instruments in the refinery are in the database of the AMS calibration support system. Where there is no electronic maintenance programme, field diagnostics is performed using handheld communicators. Used daily, these instruments are used to reconfigure the field devices’ measurement range, detection of communication defects, and changing the configuration. Conveniently, the communicators can be connected to the signal wires at any point in the control loop, which means the technician only needs to go to the control cabinets. This usually saves the technicians from going into remote and possibly dangerous areas of the plant.
MOL Danube has developed a two-way connection between AMS and the Enterprise Resource Planning (ERP) systems, SAP. SAP has its own preventative maintenance software, SAP-PM.
How they got started
Maintenance systems have been used in refineries for a long time, and by the late 1990s MOL Danube had its own home-grown version in place. Initially, there were separate computer systems for the various maintenance systems but in 2005, a project was launched to combine as well as expand these systems. During the amalgamation project, centralised systems were developed in a client/server architecture. The objective of the project was to develop a standard maintenance strategy, in other words, to have these systems operate according to a strategy developed in a uniform way, rather than in isolated islands.
Plant maintenance managers set out the following ambitious goals:
- To create an online analysis, transmitter, and assembly diagnostics system;
- To automatically forward measurement results and diagnostics alerts to the ERP system, specifically the SAP-PM system;
- To improve plants’ availability and cut maintenance costs; and
- To reinforce CAPEX project support: ‘appropriate assets to the appropriate place.’
Where HART Communication came in
Connecting 3,707 instruments into an on-line diagnostics system has changed the way the MOL maintenance department runs its operation. On-line device diagnostics—signals coming from the instruments in the field directly to the plant maintenance and control systems—makes it possible to prevent plant shutdowns and slow-downs. It does this by allowing the engineers to detect small problems that are growing in time. Plant shutdowns caused by the potential overall failure of a given asset can thusly be avoided.
The system works so well and has proved to be so beneficial the company has set up a separate unit to operate the applications and systems. Staffed with three engineers, their main task involves monitoring asset defects and carrying out any necessary repairs. They are called the FIMS team, where FIMS means Field Instrumentation Management System.
The FIMS team has learned that, using the supplementary information provided by HART communication, it is possible for the field devices to post a large number of diagnostic reports concerning their operation at the time. Based on this information, it is easy to determine the type of actual breakdown and the method of repair.
The team also developed a statistical application to exploit HART information deeper and follow up alerts sent by AMS to the CMMS, and CMMS work orders received by AMS. Using this application they are able to evaluate the mean time before failure (MTBF) and most frequent instrument failures.
“This allows the targeted repair of assets, which, in turn, enables us to save time and dispense with unnecessary parts procurement,” said Mr. Bereznai. Maintenance performed subject to an accurate technical scope and in a timely manner reduces the number of breakdown events and the duration of downtimes.
The Alarm Management System for devices was developed for more efficient operation in this area. Staff engineers examined the various devices according to type and manufacturer, and set priorities for device alarms provided by HART communication according to severity. The objective of this system is to have only those alarms forwarded to the enterprise resources planning system (SAP) which require physical intervention at any given asset.
Priority is also the principle for grouping alarms according to their severity. The engineers put the alarms into two general groups: alarms associated with actual defects, and alarms serving to prevent actual defects.
This makes the implementation of preventive maintenance possible, which results in substantial cost-saving. The fundamental notion is that it is always less expensive to eliminate a defect as it develops than to purchase new assets to replace malfunctioning ones.
More stable operation
On-line diagnostics provided by the HART instruments does something more than preventive maintenance, according to József Bartók, automation engineer at MOL Danube. “It ensures the stable operation of the system and increases the precision of control.” This is an aspect of the technology that comes directly to the bottom line, increasing the profit generating capability of the unit.
The Instrumentation and Electrical department team learned that the loss of profit arising from inaccurate control is easily recaptured using HART technology.
“In a given unit, the inaccuracy of the loops controlling the applied separation processes—which can typically be traced back to the de-tuning of the control valves—could not be identified without the use of intelligent valve positioners supporting HART technology,” says Mr. Bartók. “With the application of this technology, valve failures can be screened out and the corresponding loss can be minimised by repeated calibration.”
Commissioning and shut downs
HART-enabled instruments help streamline the installation and commissioning of control loops, because newly installed transmitters can be checked without ‘driving’ them with the 4-20 mA signal in the field. Engineers say that, thanks to this option, they generally spend 20 per cent less time in commissioning. All the results are stored automatically in AMS.
HART-enabled diagnostics has another important role to play in plant maintenance, but this opportunity only comes once every four years when the plant shuts down for maintenance. This is a good time to remove troublesome valves from the system and have them repaired or replaced. Obviously, such a large scale event is very costly and requires a great deal of advance planning.
The perplexing question facing engineers at shut down time is “which valves should be removed for additional work?” The labour is so costly and critical the decisions must be made with high confidence.
In the past, without the benefit of HART communication and computerised maintenance systems, the only way to make these decisions was on the basis of good, old-fashioned operating experience. So, the defective valves usually got discovered and repaired, but unfortunately an unavoidable consequence was that some valves were dismounted that required no repair at all.
What has HART technology provided? Before the implementation of HART, about 60% of the control valves were selected for repair. So, while it was assured that all faulty valves were likely corrected, there were probably many other valves removed that didn’t need attention. Following the introduction of HART diagnostics, how many valves are selected for repair? It has fallen to about 5% !
Yet, it must be admitted that the number of defective valves has not decreased since the introduction of the system; valve construction hasn’t improved that much. Now, however, because it is not necessary to disassemble and send to the repair workshop failure-free control valves, the maintenance department estimates the company saves on average €54,600 per unit during one shut down.
HART technology is widely used in other areas of the plant, such as in the calibration laboratory. There, calibration data are automatically recorded in an AMS computer, which generates test reports and certificates in electronic format, which is then handed over to the SAP-PM system. The company has performed nearly 3,000 instrument calibrations and has acquired an extensive database on its transmitters.
WirelessHART transmitters may be the next big thing. MOL has equipped two units with WirelessHART instruments (four temperature transmitters and five control valve positioners with Wireless extender (adapter), plus one gateway.) These are integrated into the plant maintenance system. This is a whole new technology for instruments, and promises to bring many new benefits for large scale process operations.
Summing it up
“Our company is committed to the operation of a predictive and proactive maintenance system,” says Mr. Bartók, “and in view of realising these objectives, in the Refining Long Term Maintenance Strategy the use and development of maintenance systems, and the application of devices based on HART technology play an important role.”
HART technology is widely used, both off-line and on-line, at MOL Danube for carrying out daily maintenance tasks. “It provides a lot of help, making our maintenance processes faster and more efficient,” says Mr. Bartók.
“Our company is committed regarding the use of this technology. We intend to leverage the benefits it provides to the greatest degree possible. MOL Group is committed to disseminating and utilising the benefits the HART Standard provides in the broadest possible scope, and this includes the other refineries in the MOL Group.”
Their extensive use of HART communication as part of their overall operation and maintenance strategy has earned MOL Danube the 2010 HART Plant of the Year Award. This award is given annually by the HART Communication Foundation to recognize the people, companies and plant sites around the world that are using the advanced capabilities of HART communication in real-time applications to improve operations, lower costs and increase availability.
When Mr. Bartók was asked how he would describe the benefits he has seen from using HART communication, he selected the words “availability and available” indicating that for MOL HART communication contributes to increased plant availability, the availability of critical information for field devices and the availability of standardized information available in the system. It is this availability that has helped them achieve their objectives.
MOL Danube refinery at-a-Glance
There are 1,200 workers at this 162,000 bbl/day capacity petrol refinery which uses HART technology in almost every control loop. The communications technology has been set up in strategically important refining units, to make operating and maintenance works more efficient. HART communication is available on 30,000 of the plant’s 40,000 instruments, and about 3,707 of those HART instruments are connected into on-line maintenance systems.
Example case study of Gas Oil Hydrotreater
K-803 tower KFV8017 head pressure control valve was very slow in motion, and this was causing a serious effect on the control loop. The managers of the unit assumed it was a stuck valve and ordered it removed for repair. Unfortunately for the service technicians, the by-pass valve wasn’t good enough to isolate the stuck valve so they had to take a different approach.
By using their on-line diagnostic tools the technicians made further investigations into the intelligent positioner in the valve, and as a result concluded the valve was in good condition, but the current-to-pneumatic (I/P) part of the intelligent positioner was damaged. The unit operational staff put the valve in manual and, after half an hour of instrumentation work, eliminated the problematic item.
Thus, removal of the valve was avoided, which saved the company a very costly two days of unscheduled downtime (a minimum time estimate) which would have a projected cost of €637,000.
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