Emerson Process Experts

I had the opportunity to visit with Emerson's Tom Wallace who was here in Austin recently. I like to joke with Tom that a post I had done with him comparing and contrasting HART and Foundation fieldbus caused such a stir, that it produced one of this blog's highest monthly visitor totals to date.

So let's see what we can do this month! Tom takes a comparative look at some of the swirl that surrounds EDDL and FDT/DTM in a new paper, FDT/DTM, and Enhanced EDDL, what's best for the user. These are both technology enablers for field devices, automation systems and asset management applications.

If this is all acronym soup to you, here's Tom's brief description of these technology enablers:

Device functionality is invoked using Electronic Device Description Language, EDDL or DTM's [Device Type Manager]. The DD or DTM tells the host what functionality the device has, and how the functionality is invoked. It also tells the host how to do common maintenance functions such as calibration, trims, tests, and other device activities.

I'll start with Tom's conclusion and then highlight some of his supporting points. He concludes:

In my opinion, there is a better technical implementation based primarily on ease of implementation and support. That solution is to use EDDL for all devices where EDDL is technically capable of delivering complete device functionality, and to use a DTM or a snap-on application to handle only the exceptions. I make this recommendation because it is simpler to implement a single solution than a combined solution. EDDL is a single solution that will work for the vast majority (95%) of HART, Foundation fieldbus, and Profibus PA devices.

Tom's point for commissioning Foundation fieldbus devices contrasts installable programs versus data files:

Commissioning Foundation fieldbus devices on most control hosts require DD's [device descriptions]. Most control hosts have a set list of applications that are considered safe to install on the host engineering or operator station. Each DTM is an application, and the testing required to ensure hundreds, or potentially thousands of DTM's are compatible with a control host user interface is not practical. EDD's are files, not application programs. Therefore there is no program installation risk loading EDD's on a control host.

On data availability, Tom writes:

…EDDL is the path for data availability that originates from a device, or is going to a device. The OPC Foundation support for the enhanced EDDL will broaden the use of EDDL for applications such as ERP, maintenance management, and other applications.

For the display of data in field devices, Tom notes:

EDDL is supported in the host by DD services. DTM is supported in the host by a frame or FDT. For many applications and hosts either EDDL or DTM can be used for data display. For hosts that are not based on a windows operating system, EDDL will be used as DTM requires a windows operating system. EDDL has defined display objects such as charts, graphs, etc. DTM is more of a free form environment using a variety of programming languages.

The choice for the enabler technology to use is EDDL or a combination of EDDL and DTM. Tom lists some considerations for your discussion based on operating systems, operating system version management, functionality and complexity of the device and if a custom display needs to be created.

Tom sums all this up with the following recommendation:

The final recommendation is to use EDDL as the required standard since each device must have a DD. Allow the use of DTM's on an exception basis where the functionality is required, and EDDL cannot provide it. Make sure that all the functionality to replace a failed device, or place a new device in service is available in EDDL. This will simplify implementation and maintenance, mitigate operating system migration issues, and provide a lower risk more error free working environment.

Update: Welcome readers of Gary Mintchell's Feed Forward blog! Join the conversation and add your comments below or on Gary's post.

Tags: EDDL | FDT | DTM | HART communications | Foundation fieldbus | FF | Profibus | device description |

May 14, 2008 in Asset Optimization, in Enterprise Integration, in Foundation Fieldbus, in Interoperability, in Profibus, in Technologies | Comments (0)

Courtesy of Emerson's VP of wireless technology, Bob Karschnia, I received a draft copy of a whitepaper circulating about redundancy in WirelessHART device networks. It's not yet finished so I don't have a link, but here are some of the key thoughts I gleaned from it.

Redundancy, in this context, is defined as a duplication of critical system components to reduce the probability of a failure caused by a single component. This redundancy is available at three levels including the network of wireless field devices, the access points and the gateways to the control and/or asset management systems.

Starting with the wireless field devices, the WirelessHART standard supports communications redundancy through multiple paths (spatial diversity), multiple transmission frequencies (frequency diversity) and multiple timing possibilities (time diversity).

Consider a wireless temperature transmitter mounted in your process communicating with other wireless devices—say a pressure and level transmitter. This device creates a self-organized communications path through one of the other devices back to an access point or directly to a wireless gateway. If the path through this device is obstructed, the temperature transmitter will retry at a slightly different time, frequency and path to the other device. If it fails, it will retry—again adjusting time, frequency, and path.

As we discussed in an earlier post, Planning Your Wireless Instrument Installation, it's important that each wireless device have at least two other devices to communicate with to provide alternative paths when needed.

An access point is a specialized WirelessHART device with a high-bandwidth communication interface to the gateway. Multiple access points can be connected to the gateway to provide path diversity and increased bandwidth across the network. There is no limit to the number of access points in the field network.

At the highest level of the field network is the gateway, network manager software and security manager software. The network manager performs scheduling and routing services. The security manager performs security key generation and storage as well as field device authentication services. All three components can reside within a physical gateway or can be distributed in separate gateways.

Using a mechanism similar to redundant controller pairs available in most automation systems, primary/backup redundancy management is being developed and stress-tested for these gateways.

I'll keep a sharp eye out for the finished whitepaper and update this post with a link.

Tags: WirelessHART | sensor network | field network | wireless transmitters | wireless device network | communications redundancy |

May 1, 2008 in Interoperability, in Technologies, in Wireless | Comments (0)

I wrote this post while on a flight back from a meeting in Rome. As an engineer, one can't help but be inspired by the buildings and architectural wonders created by the engineers in the Roman Empire. Talk about built to last!

I think about engineers today who worked on this mobile smartphone I used to compose this post while on the plane. These phones have a life span of a couple of years at best. I saw a colleague with a newer version of my model. It includes a global positioning system (GPS). He downloaded Google Maps and it automatically connected with his GPS. This is not only cool, but also very useful as it gave real-time positioning information as we walked the streets of Rome.

Imagine the contrast of old and new as we used it to find historic monuments like the Pantheon. Here is something with a life span of a few years to find something that has lasted thousands of years.

Thankfully, in our world of process automation our work may live on a decade or two. These systems are not without change as the hardware and software continues to advance. These systems take advantage of the work of really smart engineers who keep advancing the technology.

I tie this all back to a press announcement of four really smart Emerson engineers, Terry Blevins, Deji Chen, Mark Nixon, and Willy Wojsznis receiving an excellence in documentation award from the ISA. The award was for their ISA EXPO 2006 technical paper, Improving PID Control with Unreliable Communications.

As part of the DeltaV technology team, they have played a major role in some of the innovations automation engineers around the world use every day to improve their process operations and their business results.

A sample of the innovations include Foundation fieldbus, OPC, on-the-fly process modeling for real-time control performance, EDDL, embedded MPC, fuzzy logic, neural network with the other common control block.

Congratulations to Terry, Deji, Mark, and Willy on their award and helping to advance the craft automations engineers apply.

Tags: PID | advanced control | advanced process control |

November 12, 2007 in Technologies | Comments (0)

Dr. José A. Gutierrez is Corporate Director of Technology at Emerson. As such, he not only advises our wireless experts in Emerson Process Management, but also across the other Emerson businesses.

At the recent ISA Expo, he presented the paper, Reliable Wireless: Mitigating the coexistence Challenge. His key point is that through a number of communications diversity techniques, high communications reliability on the order of 99.9% or higher is achieved. These diversity techniques are supported the IEEE communications standards and are used in the new wireless field network standard, WirelessHART.

José had quite a bit of expertise to share and has a long history of participating with many standards bodies. Some of these include IEEE LAN/MAN, editor-in-chief of the IEEE 802.15 Working Group-Task Group 4, program manager of the ZigBee Alliance, board of directors' member of the Wireless Industrial Network Alliance, and chairman of the Networking Working Group of the ISA SP100 committee.

He began his presentation by defining the term coexistence from the IEEE 802.15.2-2003 Part 15.2 standard:

The ability of one system to perform a task in a given shared environment where other systems have an ability to perform their tasks and may or may not be using the same set of rules.

Collisions and coexistence issues can happen when two or more packets overlap in both time and frequency with sufficient energy to interfere with one another. Coexistence can be measured by the end-to-end message delivery success rate overall all operational conditions.

Different country's governmental regulations address the sharing of the radio frequency (RF) spectrum in different ways. The common approach has been in assigning different bands for applications such as TV, AM and FM radios, cell phones, toys to name but a few. You can get an idea of how these frequencies are divided with the U.S. frequency band allocation chart. A personal aside—it also makes for a great eye chart!

José discussed the unlicensed bands referred as ISM bands, short for industrial, scientific and medical bands. These bands are allowed for usage in a variety of applications and in some cases with worldwide availability. Only device certification is required for use in this band. Limits are imposed on the radiated power of devices transmitting at these frequency and they require governmental certification for the country in which they operate. These bands include 900MHz (902-928 MHz), 2.4GHz (2.4-2.4835GHz), and 5.7 GHz (5.725-5.875Ghz). For you non-electrical engineers, an Hz or Hertz is one frequency cycle per second. These unlicensed bands are very crowded.

The good news for process manufacturers is that the responsibility rests with automation suppliers to get their wireless devices certified for use.

The presentation covered the various ways information could be transmitted on these frequencies. It's enough for a future post, but I'll list some of the methods here: narrow band, frequency hopping, direct sequence spread spectrum (DSSS), orthogonal frequency division multiplexing (OFDM) and ultra wide band (UWB).

Tying all this back to coexistence, the IEEE 802 standard committee is the authority on wireless coexistence and ensures that these technologies will effectively coexist with all previous technologies.

José posed the question about what wireless suppliers can do to eliminate the coexistence challenge. The solution is to apply techniques that create diversity to mitigate this coexistence challenge. These diversity techniques include:

• Path Diversity: Mesh Networking
• Frequency Diversity: Channel Hopping
• Time Diversity: Time Division Multiplexing
• Power Diversity: Power control over multiple communication links
• Space Diversity: spatial location of sensing devices (not practical for WSNs)
• Coding Diversity: Use of advanced DSSS technology

The key for wireless field networks is to use a combination of these techniques to deliver the necessary high end-to-end message delivery success rate for reliable wireless operation. These diversity solutions used in IEEE-based standards applied in industrial applications including DSSS, OFDM, and UWB and used in the WirelessHART standard help eliminate coexistence issues as one of your considerations.

You can learn more about wireless basics, the technologies, cases for how they can be applied in plant applications and IT considerations by visiting the on-line wireless courses at PlantWeb University.

Tags: WirelessHART | wireless coexistence | wireless field network | ISM band | narrow band | frequency hopping | direct sequence spread spectrum | DSSS | orthogonal frequency division multiplexing | OFDM | ultra wide band | UWB |

October 31, 2007 in Interoperability, in Technologies, in Wireless | Comments (3)

At last week's ISA Expo 2007, Emerson's Gary Law received the Douglas H. Annin award. This award is award is in recognition of Gary's outstanding technical achievements in the design, development and application of automatic control systems. The ISA describes this award:

The Douglas H. Annin Award recognizes an outstanding achievement in the design, application, or development of the components in an automatic control system from the input measurement through the final control element. The award is in honor of Douglas H. Annin, a pioneer in modern-day control valve actuation and control valve body design.

I've known Gary for many years in our work advancing the DeltaV system. He is now a technologist with the DeltaV architecture team. He is responsible for the system architecture, and future developments of DeltaV system and PlantWeb architecture.

Gary was instrumental in the design and introduction of the DeltaV SIS (safety instrumented system.) He was a part of eight different patents for this development and holds more than a dozen overall through his career. This Douglas H. Annin award was recognition for this innovation. Specifically:

For design and development of a safety instrumented system logic solver that is built into a basic process control system input/output card.

DeltaV SIS was the first SIS to take advantage of smart instruments (sensors and final control elements) used in safety applications communicating via the HART communications protocol. The diagnostics from these instruments can be used to monitor continuously the health of each safety instrumented function (sensor + logic solver + final control element.)

In earlier posts, I've discussed some of these innovations and their application. These include performing partial stroke tests automatically within the safety instrumented function, separation between control and safety systems, and the ability to do complex safety shutdown sequences.

Scalability is another key aspect that was brought to safety instrumented systems with the design of DeltaV SIS. Logic solvers are added in small increments (16 I/O channels) for process manufacturers' SIL 1-3 safety instrumented functions. The hardware, software, and communications running in the logic solvers are different from the DeltaV automation system, but the configuration software is the same. This design provides the separation proscribed by the IEC 61508 global safety standard.

Much of the innovations in the DeltaV hardware and its interactions with the configuration software are thanks to Gary's efforts. You can see some of his enthusiasm in the digital bus videos created several years ago.

Congratulations to Gary for this recognition of his work to advance the state of technology in our world of process automation.

Tags: IEC 61508 | ISA | safety instrumented system | SIS | logic solver | sensor | final control element | HART Communications |

October 10, 2007 in Safety, in Technologies | Comments (0)

For those attending the ISA Expo 2007 this week in Houston, Texas, there is quite a number of Emerson experts presenting papers. Topics being presented include: safety, analyzer integration, statistical analysis, EDDL, wireless, applied Foundation fieldbus, project justification, building automation, mesh networks, and predictive maintenance.

I'll be coming in to listen in on some of these and meet with some members from our automation blogging community.

I had a chance to catch up with ModelingAndControl.com's Terry Blevins who will be co-presenting, Keeping Systems and Communicators Up-to-date using EDDL. Here's a quick preview if this standard is something you want to learn more about. Terry also chairs the ISA104 committee that is working to advance this standard.

This tutorial explores the history of the Electronic Device Description Language (EDDL) developments, how the technology works, the benefits of the approach taken, recent advancements, how systems and communicators are changing because of these advancements, and demonstrations. EDDL, or IEC 61804-3, is an international standard and is endorsed by four major interoperability foundations: Fieldbus Foundation, HART Communications Foundation, Profibus Nutzerorganisation e.V (PNO), and the OPC Foundation.

EDDL is a text-based language that is used to describe the characteristics of field devices. Following the EDDL standard, device suppliers create Electronic Device Description (EDD) files for their smart field devices. These files provide a standardized form and structure for automation systems and handheld communicators to access and display information, independent of communication protocol or operating system.

The goal of this technology is to provide an interoperable environment where automation systems and handheld communicators for the purpose of configuration, calibration, diagnostics, and operating data and alarms for display can access information available in smart field sensors and actuators. There are more than twenty million smart devices installed in the world that have EDDs. These first began to appear in the early 1990s in HART devices, and was adopted into the Foundation fieldbus and Profibus standards in 1994. The EDDL.org site provides much more on the history and activities in the advancement of this standard.

Recent enhancements to the standard include better parameter organization, support for charts, graphs help better visualize the information in the smart field devices, and persistent data storage to convey historical information. These enhancements were approved in 2006 as a part of the IEC 61804-3 maintenance cycle.

The next phase of enhancements includes additional support for devices connect to the process including the ability to pass procedures like device setup and maintenance. Other enhancements include increase data access to databases and lookup tables, extended product information access, OPC UA information model, and support for modular devices.

The common threads through the demonstration of EDDL in action is the versatility in support from simple to very complex field devices, the independences of operating systems and control platforms, the common look and feel from an information visualization standpoint, and the ability to add devices on the fly without affecting the running automation system.

The ISA104 committee is meeting at the ISA Expo, so stop by to speak with Terry and the committee members at booth 1356 to find out more first hand.

Tags: EDDL | electronic device description language | EDD | ISA Expo | ISA104 | 61804-3 | Foundation fieldbus | Profibus | HART communications |

October 1, 2007 in Foundation Fieldbus, in Interoperability, in Profibus, in Technologies | Comments (0)

Earlier I mentioned Emerson's Dean Taggart's work with complex sequences in safety instrumented systems, based on an ongoing oil sands gasification project. John Kingston, from Emerson local business partner Spartan Controls, is presenting on this topic along with Emerson's Chuck Miller at the upcoming ISA Expo 2007.

I received a copy of the submitted paper that, among other things, explores the separation between basic process control systems (BPCS) and safety instrumented systems (SIS). Historically, the SIS was a separate entity, but with technological advances, this has begun to change. The authors note that the IEC 61508 international safety standard does not provide a definition of separation. It does mention physical separation as a highly effective technique. Given that the standard is much more performance-based than prescriptive-based, they note that there are few statements defining separation.

The paper refers to a few specific clauses in 61508-1 such as 7.5.2.4, where when the control system places a demand on one of the safety-related systems, then it "…shall be separate and independent" from the safety-related systems. In order to satisfy this clause the control system must be proven sufficiently independent from the SIS. Certification agencies like the various TÜV organizations and other third-party testing labs help provide this proof for SIS suppliers per the IEC 61508 performance standards.

61508-1 Clause 7.6.2.7 addresses common cause failures by requiring functional diversity, technology diversity, diverse parts, services, and support, and that the BPCS and SIS not share common operational, maintenance, or test procedures, and that they be physically separated. Safety instrumented systems like DeltaV SIS address these in the authors' words:

Those factors [governing independence] include diversity, which essentially means that the BPCS and SIS should have different components, operating systems, chip sets, central processing units, etc. When looking at sharing parts, services, and support systems, once must ensure that the BPCS and SIS have different power sources, and that a safety network dedicated to safety related communications is used. They should not share test procedures, which means that if you are testing either the BPCS or the SIS, that those tests should be able to be run completely independently of each other. Finally, physical separation applies to how the architecture of the system is laid out, and how cabinetry is designed; in essence, this is where one would look at separating DCS cabinets from SIS cabinets, and perhaps maintaining the SIS from a different workstation than the one used for the BPCS.

A final clause that is discussed, 61508-2 Clause 7.4.2.3 explores how non-safety functions implemented in an SIS need to be treated as safety-related unless it can be shown it is sufficiently independent (that the failure of any non-safety-related functions does not cause a dangerous failure of the safety-related functions.) This implies that control and safety functions can exist within the same system as long as sufficient care is taken in design and throughout the IEC 61511 safety lifecycle.

The authors summarize the implications of separation well:

Essentially, everything all boils down to good engineering designs and practices. One must consider the standards carefully, and understand the implications before going down a certain path. One cannot simply look at a system and know if it satisfies these requirements, because almost every system has a different level of independence. One must look at the specific details of a system to verify that it satisfies the requirements.

Dean summed up how these applied to the asphaltene gasification project:

The complexity of the process led to a need for integration as well as separation. Integration brings the benefits of integrated development and operating environments, less training cost, simpler architectures, faster and more reliable communications, reduced integration time, better handling of status information, and improved fault handling. The safety requirements of gasification focus on preventing damage to the burner, reactor, and syngas cooler, as well as operator safety. The process itself leads to the need for an intricate startup, as well as multiple methods of shutting down the process depending on the current state. An integrated but separate solution can provide several advantages while still providing the required amount of separation.

Tags: IEC 61511 | IEC 61508 | safety instrumented system | SIS | BPCS | asphaltene | gasification |

August 24, 2007 in Gasification, in Oil & Gas, in Safety, in Technologies | Comments (0)

Austin, Texas is where I call home and is home to some of the leading technology providers in the world. I recently had lunch with a colleague at Freescale discussing life and business here. The brains in much of the DeltaV hardware is powered by Freescale microcontroller chips. For those not close to this industry, Freescale is a 2004 spinoff of Motorola's semiconductor business.

I spoke with some of Emerson's DeltaV technologists responsible for hardware design and they described the history of working with these microcontrollers all the way back to the early 1980s with the Motorola 6801 and 6802 chips. Around this same time, I was working with the 6809 microprocessor chip in my days as an electrical engineering student at the University of Texas. The 6809's assembly language is now only a distant memory.

As Moore's Law predicted, the rapid exponential advances in performance over this twenty-five year span have certainly helped increase the capabilities within automation systems and have reduced the need for many separate host computer-level applications. These applications have migrated into the automation systems where they can run in robust, industrially hardened and redundant environments.

Some of the current generation of microcontroller chips like the Freescale MPC8360E can provide the processing capabilities to handle even more complex model predictive control algorithms, adaptive control, sophisticated phases/operations/unit procedures/procedures for batch processes, and other complex applications. These innovations continue to find there way into each new DeltaV release.

Over the years, it has been beneficial to have DeltaV technologists located in the same city as the Freescale design team. When issues arise, they can be discussed people who have met and gotten to know one another. These relationships can help improve the quality of future designs and supporting tools and documentation.

Tags: Freescale | DeltaV | semiconductor | microcontroller | MPC8360E |

August 15, 2007 in Technologies | Comments (0)