Field-Based Control Changes the Cost of Ownership of Control Systems

By J. Thurman Payne, Dresser Valve & Controls

Field-based control with current technology is very different from control in the past, and yet it is the key to success in the future. It eliminates the non-value-added costs and maximizes the value-based aspects of control. Field-based control is the essential element in the ability to annually generate double-digit returns on investment and generate consistent increases in earnings expected in today's business environment.

Non-Value-Added Costs

To understand the difference between non-value-added costs and value-added costs, it is helpful to understand supply chain optimization. A supply chain is a system through which organizations deliver their products and services to their customers. A supply chain can extend from suppliers to manufacturers to distribution channels to consumers. Supply chains can extend from concepts to market, through product to order, through order to cash, through consumption to reorder. Supply chains can include the acquisition of raw materials from a supplier's suppliers, the acquisition of product from a supplier, and the conversion of the raw material to a higher-value product through the distribution of the higher-value product to the endusers. Supply chains work on the integration and improvement of the many work processes that are part of business today.

A process is anything that has an input and an output and some activity in between. Mowing the grass is a process; driving a car is a process. So a supply chain can be thought of as a string of processes, each taking a raw material and converting it into a product of higher value.

Value can be defined as performance divided by cost. Therefore greater performance at a lesser cost increases the value. Supply chain optimization is the process of increasing value through integration of the supply chain to eliminate non-value-added activities and processes.

The supply chain definition is straightforward and the supply chain process is simple, so how can anything go wrong? If one individual was obtaining the raw material, adding value through conversion to a product, distributing the product to the consumer and then obtaining cash for his or her efforts, things would be simple. There would not be any flow problems in communication, product or funds.

However, one person cannot understand the whole process. In reality, it takes many people and many machines to convert a raw material to a final product. At each step in the process, information, product and funds have to flow forward and back through that process. Problems occur when these items do not flow smoothly, often because steps are interposed that bring no value to the overall process, but seem to be necessary to make that particular process step work better.

For example, if one is making a valve, one needs steel that can be cast into steel bodies. Then the steel bodies are machined into functioning parts. Having an inventory of steel castings can keep the machining equipment going more continuously and produce more product from a inventory makes the machining process go smoother. Inventory may be necessary if there is inadequate communication of what production is needed to ensure that shipments can be met. Inventory may be efficient for the individual process step, but it may not yield the lowest cost product when one looks at the whole value chain. The pressure for lowest cost leadership throughout a business demands elimination of unnecessary inventories designed to cover system inadequacies.

Supply chain analysis

Supply chain optimization is the process of identifying value and non-value steps in the chain and eliminating or reducing the non-value activities. One approach to this analysis is as follows:

1. Identify the costs for each process step

2. Locate the opportunity areas in which to concentrate for an improvement effort

3. In the opportunity areas, compare the value-adding features with the non-value-adding practices

4. Quantify the possible savings in time, cost, or customer satisfaction

5. Improve the processes in the opportunity areas where the greatest savings can be achieved.

A process can be commonly improved by adding communication capability to eliminate time delays or inventories in a process. For example, excess raw material inventory can be eliminated by communicating knowledge of actual orders that will result in actual shipments.

This same principle applies in process control. In the early days (pre-pneumatic control) of the process industries, an operator was needed to manually control a valve. The operator had to read a field measurement device (gauge, flow, level, etc.) and decide how to adjust the valve. The costs for this step included the cost of the measurement device, the valve, the operator, and any necessary support facilities. In today's sophisticated refineries, the current costs of this "manned control loop" for 24-h/d control could exceed $230,000.

In the pneumatic era of control, maybe the measurement signal and output signal to the valve would be transmitted via pneumatic communication to a central control house. In the central control house more information would be available about downstream and upstream situations (customers), and this data could be available for an operator to lower inventory (or flow or pressure) at a particular place in the process. Control of one process control loop had been reduced to $13,000.

Electronic instrumentation reduced the costs, but the control philosophy was very similar. It just was easier to incorporate information from a neighboring electronic instrument into the primary instrument (it was easier and cheaper for controllers to communicate by wiring them together) than it was with pneumatic instrumentation and controllers. Computers began to be used to make calculations from process data (online material balances and yield calculations) and communicate that information to operators who could use this information to adjust setpoints. The cost of control was reduced to $11,900.

The next major jump in instrumentation and controls was the advent of Distributed Control Systems (DCS) and the move of the microprocessor into the sensor measurement devices. The DCS took the electronic signals that were coming into the control room and put them into a computer that would serve as a controller. The computer could be used to display the results, and to interrelate information with output devices such as valves. In this way, various control loops could use information or communicate directly with sensors, measurements, calculations or information a great distance away. With DCS, the cost of one control loop went down to $4,700.

DCS control was a significant improvement in control, but it had evolved over a period of time with no regard to supply chain optimization and no analysis of value and non-value-added activities. There were many non-value-added activities that had increased the cost of ownership. System configuration had grown to become a very complex activity. The various vendors tried to integrate the individual configuration of the field devices, wiring systems, DCS hardware, and PC's or display devices via software, but this simply increased configuration complexity.

The configuration and wiring complexity and inflexibility made the systems hard to design, averse to expansion and devourers of space. A system was needed that could accomplish the control needs with less of the non-value-added costs:

• Lower wiring costs

• Lower checkout costs

• Fewer terminations

• Less I/O hardware

• Simpler configuration

• Smaller control building footprint

• Easier expansion

• Better diagnostics

• Ability to control more points

• Lower maintenance costs

These non-value activities will be reduced if not eliminated through the use of field-based control. It is estimated that the cost of field-based control will be reduced to $1,200 per loop. Field-based control is the result of the movement of the microprocessor out to the field in control applications (smart control systems). Examples of smart control systems are in evidence in HART and Fieldbus products. But before describing these products, it is significant to discuss the changes occurring in the business environment.

Fieldbus

Engineers will expect smart field devices to perform many of the functions they do not have the time or means to handle in a conventional mode. Ease of information integration between field instruments and control and business systems is a key benefit of smart field devices. Using the older technology of chart recorders, for example, requires manual evaluation to determine trends and other pertinent analysis. Smart devices with the capability to record data histories over a long period of time greatly decrease the time needed to gather and analyze process data.

Fieldbus will only expand the window into the process and expand the ability of smart field instruments to store, report, and analyze data from the process. Bi-directional digital communications between the control room and field devices will make data access easier, faster and more robust. The all-digital communication capability of Fieldbus will mean a seamless integration between the field device and the control room for the exchange of all types of information and documentation.

Many users are eagerly awaiting the introduction of the Fieldbus products. Despite the potential threat from other protocols (Profibus [led by Siemens], LonWorks [initially used in building automation], DeviceNet, Seriplex and ASI), the Fieldbus Foundation protocol has the potential to offer the most functionality and interoperability, and is the best way to get the most out of microprocessor-based smart field instrumentation. However, the Fieldbus communication standard is not yet harmonized; therefore, commercial availability of Fieldbus products has only just begun this year.

HART

HART has often been touted as an interim solution to Fieldbus technology. Even after the introduction of Fieldbus-compatible devices, suppliers will continue to offer HART devices to users who do not have the capital to invest in new installations of Fieldbus-compatible systems.

Many users will also use HART as a migration path to Fieldbus. HART offers many of the same characteristics that will be available in digital Fieldbus. Users can gain experience with remote communications and other features available with HART. They can judge for themselves if a digital field communication system such as Fieldbus is right for them.

One limitation of HART is that it does not use a digital control signal and, therefore, does not offer the benefits of increased accuracy and bi-directional communication that come with the a digital control signal. This will be a drawback to users who are interested in current forms of digital integration and future applications for Fieldbus. HART is also not supported in the control systems of major suppliers such as Honeywell, Elsag Bailey, and Foxboro.

Change Happens Faster

This trend is accelerated by the convergence of increased computer processor capability and communication. The power of development after development in computer technology (Foxboro's 9.4 billion lines of code for control systems will run on a laptop computer). The power of communication technology is that, by using Intranet technology and unlimited computer bandwidth, a board of directors could see a product loading valve opening in Singapore and its immediate impact on their financial spreadsheets in their boardroom in New York City (sensor to boardroom technology).

Standards such as Fieldbus standards cause a more rapid adoption of technology. Over the past 100 years, control has evolved from one person controlling a manual valve, to DCS systems that control thousands of valves, to movement of the microprocessor out to the valve and control in the field. The microprocessor is the technology that moves the control technology from a central control room to the field.

In the process industries, engineers are searching for more efficient ways to improve process quality and increase plant throughput. Control valves have been singled out as one of the most critical components in accomplishing this objective. The microprocessor is quickly becoming a required component of the control valve solution. Applying microprocessors to valving components such as positioners is generally dubbed making a device "smart." The Smart Valve Interface (SVI) is the first step by Masoneilan toward migrating the company into the realm of smart technology. The SVI is a smart valve positioner. It is applied to conventional valving of Masoneilan or another manufacturer, providing increased performance, enhanced diagnostic capabilities and the ability to manipulate the valve functionality on the fly using electronic rather than mechanical components.

An additional feature of the SVI is the ability to perform process-variable control within the device. With the emerging market need for control solutions applied on the valve platform, Masoneilan will enter markets where it has never before participated. For Masoneilan (or other control device manufacturer) to be successful, it must take responsibility for the application of the control function. Masoneilan currently takes responsibility for the valve application, yet it has never taken on the responsibility for the control function. In today's market, the valve is but one part of a triad of measurement, control and the valve acceptance or undertaking. This additional responsibility has far-reaching effects for Masoneilan.

SVI technology thrusts Masoneilan into an emerging techno-market of control. Concurrent with the requirement to enter the control market are the requirements to compete effectively with established control vendors in certain sectors.

The market opportunity is enormous for those organizations whose goods and services bring value to the consumer. Yet, as with any opportunity, there is substantial risk. Those who attempt to selectively participate in the market without a complete complement of control equipment and services face a significant risk of failure.

This shift is already underway, and the trend is expected to accelerate steadily over the next ten years. Virtually every large capital-project sales opportunity being pursued today is based on smart technology.

For more information: Dresser Valve & Controls Div. 85 Bodwell St. Avon, MA 02322. Tel: 508 586 4600, fax: 508 427 8971.