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Product category: Fieldbus systems, Fibre-optic systems
News Release from: ARC Advisory Group | Subject: Profibus in the Process Industries
Edited by the Processingtalk Editorial Team on 27 June 2005

The value of Profibus in the Process
Industries

ARC reports that the value proposition of Profibus lies in its ability to address the needs of multiple manufacturing domains, running on a common communication layer

The adoption of fieldbuses in manufacturing continues to grow rapidly, especially in the heavy process industries such as oil and gas and chemical where the penetration of fieldbuses is still small Manufacturers are realising the benefits of homogeneous fieldbus architectures that enable industrial networking across domain boundaries from simple sensors to complex field instrumentation

Profibus, with its common communications layer, many application profiles, and breadth of media alternatives, offers manufacturers a solid long-term value proposition to help protect their automation investments.

The value proposition of fieldbus has changed from the initial perceptions of the marketplace.

Benefits such as reduced wiring and installation costs are apparent, but often mask the long-term benefits of fieldbus and device networks.

According to ARC research, the greatest benefits of fieldbus and device networks are realised in the areas of maintenance and operations, long after a plant has been commissioned.

In other words, fieldbus itself is often not the cost-saver, but merely an enabler to a new level of asset management effectiveness that can significantly reduce operating costs and help manufacturers achieve operational excellence.

Many of the benefits of fieldbus are still being discovered as users gain more experience with these technologies in real world plant settings.

In typical process industries such as oil and gas or bulk chemicals, fieldbuses can contribute significantly to the achievement of operational excellence by enabling the sharing of critical information about the condition of devices.

A fieldbus simplifies the gathering of data for Plant Asset Management (PAM) systems that watch over devices, tracking their "health", and even detecting problems before they occur - a process known as predictive or proactive maintenance.

Profibus, which conforms to the international IEC 61158 standard for fieldbus, is the most widely used industrial network to connect control systems with field devices.

To meet the special needs of the process industries for intrinsic safety and bus power with two-wire technology, Profibus offers MBP-IS (Manchester Coded, Bus Powered, Intrinsic Safety) transmission technology as well.

All variants of Profibus share a common communications layer; the differences are a function of the required network media and application profile.

This single communication layer simplifies network configuration and diagnostics in all areas of the plant by providing a seamless link between all manufacturing domains.

Profibus DP is used to network I/O and intelligent devices due to its fast response time and may also serve as the fieldbus "trunkline".

With data rates up to 12 Mbps, more devices can be connected to the network than with other fieldbus solutions.

For hazardous areas, Profibus PA employs an intrinsically safe physical layer that provides bus power to devices on two-wire technology.

Field instruments such as pressure or temperature transmitters, flow meters or control valves are networked using Profibus PA.

Because DP and PA share a common communication layer, PA segments can be coupled as extensions to a Profibus DP backbone network via segment couplers that are transparent to the bus protocol.

The HART protocol has become a de facto standard in the process industries, and ARC estimates that the majority of intelligent, microprocessor-based field instruments installed today are HART-compatible.

Unlike other fieldbus solutions, Profibus allows for direct integration of HART devices.

In view of the large number of installed HART devices, the Profibus HART specification was developed to enable the mapping of the HART client-master-server model on Profibus.

Installed in the engineering or asset management stations, a communications channel allows transparent remote access to diagnostic information and parameters.

Profibus Targets Process Industries.

Fieldbus technology is gaining traction in the process industries not only due to perceived benefits such as lower installation costs, but also other benefits such as enabling sophisticated tools like predictive maintenance through the use of intelligent asset management.

Profibus in particular offers a unique value proposition to various process industries.

Chemicals and Petrochemicals.

The chemical industry produces a wide range of products for consumer use as well as preliminary products for other industries such as automobile and building materials.

These industries employ a variety of different manufacturing processes - from batch processes in fine and specialty chemicals to continuous processes in bulk chemicals.

In addition, discrete applications such as filling, packaging and labeling are often integrated into these processes, especially in the manufacture of consumer products.

Chemical plants tend to be large, centralised facilities that place special demands on automation equipment and machines over lifecycles often in excess of 15 years.

A single plant may employ thousands of simple actuators and sensors in addition to a wide range of more complex field instruments and analytical devices.

These devices produce and consume large numbers of analogue process and control variables that are communicated between controllers and devices.

Many plants also employ smart motor control centres to provide controlled motion for mixers, pumps, valves and transportation equipment.

Plant equipment must be designed to operate in dusty, corrosive and often explosive environments.

High availability of automation systems means employing redundant control systems and networks and is critical in chemical manufacturing, especially in continuous processes that may run for years without stopping.

To meet these requirements, Profibus offers a large number of redundancy options such as two redundant, separate copper lines or fault tolerant optical ring structures.

The use of a fieldbus in chemical manufacturing offers users a number of tangible benefits.

In most cases, networking field devices via a fieldbus can cut documentation, installation and material costs substantially.

As a rule of thumb, the larger the application, the greater the benefits from a fieldbus, which is why many new projects or "bulldozer" revamps are planned around a fieldbus architecture.

Start-up costs can also be lowered due to a reduction of the time needed to perform loop checks, while non-fieldbus legacy devices can be networked via remote I/O blocks that connect to the fieldbus.

Finally, field devices can be calibrated more conveniently over the fieldbus rather than on-site, both during start-up and at regular calibration intervals during normal operations.

Profibus architecture is especially suited to meet the demands of chemical manufacturers.

Data transfers rates of up to 12 Mbps allow a fast exchange of large data quantities between controller and devices, while the typically long distances between devices in a chemical plant can easily be bridged using repeaters and a fiber-optic bus medium.

Profibus offers wide range of application-specific profiles to meet specific needs, such as PROFIdrive for motion applications or PA Devices for intelligent field instruments that can take advantage of the network's high data rate while allowing a larger number of devices to be connected to the network than other fieldbus solutions.

PROFIsafe is profile for safety components that allows safe communication up to safety level SIL 3 according to IEC 61508.

Users can also protect their investment in existing 4-20 mA or HART devices by directly interfacing these to Profibus.

By far the most important advantage of Profibus for chemical manufacturers is its single communication layer, which allows integrated communication across all network media from the field level to the control level.

This seamless communication provides the basis for asset management software to monitor the performance of field devices, helping to predict faults in advance and reduce maintenance costs.

Oil and Gas.

The oil and gas industry will see steady growth over the next five years as oil and gas exploration and production continue to expand worldwide.

Many oil and gas companies are spending increasing capital in pursuit of new oil and gas reserves.

A large percent of spending continues to go towards meeting environmental, safety and other statutory regulations.

Maximising the availability of control systems is absolutely critical, as systems are kept in operation around the clock over many years.

Another top priority is the protection and safety of personnel and the environment.

In a typical refinery, for example, 15 to 20 percent of the process signals are safetyrelated.

Finally, keeping lifecycle costs down to a minimum, especially costs of raw materials, energy and labor, is crucial to remaining competitive.

In the long term, using Profibus can contribute substantially to lowering the Total Cost of Ownership (TCO) of refining assets by lowering maintenance costs through intelligent asset management, which has become a prerequisite for the oil and gas industry.

Moreover, feeding predictive maintenance solutions with accurate real-time field data can head off catastrophic equipment failures by allowing the user to study and analyse subtle, gradual decay in asset performance long in advance of a potential failure.

High availability and integrated safety are a must in these processes.

Typical safety applications in the oil and gas industry include fire and gas, burner management, emergency shutdown and critical process control systems.

Other important system requirements include sophisticated asset management solutions to help end-users keep maintenance and operational costs down to a minimum.

"High availability" refers to dual redundant control systems with redundant industrial networks.

In a redundant control system, every element, from the operator station to field devices and including the fieldbus, is backed up by a duplicate.

The Profibus advantages for oil and gas users derive from its ability to seamlessly connect all types of plant devices without having to isolate process instruments from discrete devices with a second bus.

In particular, Profibus DP can be used to easily and reliably integrate motor control centers (MCC), variable speed drives and switching gear to control systems.

Profibus PA, which integrates seamlessly to DP, is used to network and provide power to field instruments.

Both media types support the PROFIsafe profile for process safety, which allows the use of distributed fail-safe I/O.

Power Generation Investment in power generation assets are growing moderately at about 5 percent annually worldwide, due in part to the exploding need for energy in emerging markets while established power plants in other parts of the world are revamped and upgraded.

Electrical power plants vary by the methods used to generate power, ranging from hydroelectric, nuclear, fossil-fired, and "waste to energy" plants to alternate energy sources.

Although power generation is a classic continuous process, power plants have a surprisingly high "discrete" character.

Hard-wired I/O points can account for two-thirds or more of the total hardwired signal count.

This is due to the complex logic control structures employed in sequential operations like start-up and shut down of systems such as generator auxiliary systems, unit and boiler sequencers, fuel systems, auxiliaries, feedwater systems, turbines, turbine auxiliaries, vacuum systems, lubrication systems, and circulating and cooling water systems.

Fieldbus solutions offer a variety of benefits to power industry users.

Automation assets in power plants account for only about 7 percent of all plant-level capital expenditures, according to ARC research.

Despite this, lower wiring costs typically associated with using a fieldbus can still have an impact on reducing engineering and installation costs.

ARC is aware of a 600 megawatt pulverised coal power plant that was able to reduce its overall costs by 40 percent and its cost per I/O point by 35 percent using a fieldbus.

In the long term, using fieldbus technology can contribute substantially to lowering the Total Cost of Ownership (TCO) of big-ticket assets such as steam or gas turbines by lowering maintenance costs through intelligent asset management.

More importantly, feeding predictive maintenance solutions with accurate real-time field data can head off catastrophic equipment failures by allowing the user to study and analyze subtle, gradual decay in asset performance.

The particular Profibus advantage for power plant users derives from its ability to seamlessly connect all types of plant devices without having to isolate process instruments, such as flowmeters and control valves, from discrete devices like remote I/O and motor control centers.

The benefits for the user include lower operation costs, improved equipment efficiency, reduced engineering costs due to simplified design and construction, lower lifecycle costs and reduced spending for training and service.

Water and Wastewater.

Water has always played an essential role for human beings and has lost none of its importance up to the present day.

In developing countries, establishing and ensuring a steady supply of clean water is the most critical part of an expanding infrastructure, both for residential and industrial use.

Essentially, there are two typical processes in the water industry: water treatment with the goal of supplying drinking water in highest quality, and waste water treatment to recycling waste water into a usable resource.

Water and sewage treatment plants are ideal candidates for Profibus due to the harsh operating environments and the long distances between controllers and devices.

Either DCSs or PLCs are used to monitor control functions, while field devices range from pressure, flow and level meters to motor control centers driving pumping stations.

Profibus offers particular advantages here due to its wide support from process and discrete controller suppliers, as well as its architecture that allows for seamless connectivity of both process field instruments and discrete devices.

Costs along the entire lifecycle of water and sewage treatment plant assets can be reduced by a centralized approach to collection and evaluation of field information.

Cement and Glass.

Profibus has been used in the cement industry since 1997, when the technology was first applied in cement works in Asia.

As in the chemical industry, cement works are known for their harsh environments and the heavy demands they place on automation equipment.

A fieldbus can greatly reduce the number of possible points of failure in such harsh environments by replacing complex and costly wiring harnesses with a single cable.

Should a problem occur, faults can be located much more quickly with a fieldbus thanks to built-in diagnostics.

Redundancy options for Profibus DP mean that backbone availability is also not a problem.

Cement manufacturers will appreciate the ability to configure field devices remotely from a central control room via Profibus, as instruments such as pressure transmitters and flow meters are often installed in difficult to reach locations.

Gaining access to level measurement devices in homogenisation and cement silos can be particularly cumbersome.

Once devices are networked with Profibus PA, for example, all programming or calibration can be taken care of from a single location using access tools such as the Siemens Process Device Management tool (PDM) or the ABB Control Builder F (CBF).

Electrically controlled motors and drives are an integral part of the logistics automation in cement plants.

One unique advantage of Profibus is its ability to connect all field devices - whether process or discrete - to a single network.

Other fieldbus solutions would require the use of a separate bus to network discrete devices like drives, requiring the user to invest in separate wiring, software and employee skill sets to accomplish the same task.

The glass industry shares many of the harsh environmental demands of the cement industry, but adds a few more challenges.

Glass employs applications common to both process and discrete industries in every stage of production, from the batch house through the furnace, float bath and annealing lehr up to the cross cutters and packaging units.

To fully integrate these processes means to network pressure transmitters, control valves and flow meters on the batch side of the process with complex motor control centers on the handling side.

Hybrid Industries.

Few industries are "pure" process industries.

Even heavy process industries like oil and gas or chemicals employ motor control centers and discrete sensors that are networked with discrete device networks.

Many, such as food and beverage and pharmaceutical, are made up of a distinct process side, complemented by a series of purely discrete applications.

Beer brewing, for example, is a classic process application in which control loops are programmed to maintain process variables at fixed values over long periods of time.

Once the beer has fermented, however, the pace picks up.

Glass bottles whir at high speed around the carousel of a filler, are then capped and labeled, and finally packaged and palletised.

These last few steps are classic discrete applications involving highspeed, often asynchronous coordination of bitlevel signals.

Pharmaceutical is another hybrid industry that employs a blend of process and discrete applications.

Manufacturing the substances used to make liquid, pill or powder-based medications involves continuous or batch applications, while the packaging and handling of final products is typical for high-speed discrete applications.

The hybrid industries have recognised the advantages of using a single fieldbus, Profibus, across all of these applications.

The advantages of a single fieldbus strategy include lower operational costs due to less training, faster troubleshooting, and fewer spare parts.

Using just one bus also means that asset management software and engineering tools only need to deal with one fieldbus tool to access data from both process instruments and discrete devices.

Further information and case studies about Profibus in the hybrid industries are available in the ARC white paper "The Value Proposition of Fieldbus in the Hybrid Industries".

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