Picking a DCS: Who Decides and How

Then we go to the long, short and final list phases, the thing to keep in mind about selection is that in a selection phase, there are actors with influence or power, and there are criteria with a certain weight factor or priorities. The results of this combination will be a shorter list of vendors in the next phase, where this process starts again, sometimes with other actors and a new set of criteria. The goal of our research was to define the core selection criteria and their priorities for the purchase of a DCS in the chemical industry, and to design a decision-making model, so  the decision-making process for new systems was more balanced, more transparent, more consequent and faster.

Actors and Criteria

The main actors during DCS-selection phases are the control engineer, purchasing manager, project manager, consultant from headquarters, plant owner and maintenance manager. Other actors at the short list phase are engineering firms. The role of operators—the ultimate end users—is minor in the selection process. 

An in-depth study inside and outside the academic world, inside and outside the DCS world, and company evaluation models provided 24 models. From these, I extracted 12 main criteria:

• Supplier vision
• Supplier's ability to execute
• Supplier's guarantee of the business case
• Functionality
• Interoperability
• Technology
• Implementation
• Documentation
• Training
• Service and support
• User experience and costs, including the initial costs, on-going expenses and exit costs.

The four most important criteria for end users are functionality (11.5%); technology (10.73%); service and support (10.65%); and business case guarantee (8.97%). On average, the highest priority is given to initial costs when buying a system, and the lowest to exit costs. Exit costs (switching costs) don't play a significant role in changing a DCS system. Lifecycle costs don't play a major role; the longer the period, the lower the given priority by the respondents.

At the long phase of the prioritization process, the business case guarantee (9.34%), interoperability (6.88%) ability to execute (5.05%) and exit cost (2.99%) are the most important criteria. Using a mathematical model, I calculated the influence from every actor for every phase, in which zero is no influence and five is a veto on every aspect. The control engineer (2.31), consultant from headquarters (1.68), project manager (1.49) purchasing manager (1.31) and plant owner (1.31) are the most influential actors.

At the short phase, the functionality (11.50%), technology (10.42%), implementation process (8.08%), user experience (6.66%) and vendor's vision about automation (5.60%) are the most important criteria. User experience is the feedback the actors will get from reference visits to other end user sites. The control engineer (2.34), consultant from headquarters (1.88), purchasing manager (1.82), plant owner (1.75) and engineering firm (1.58) are the most influential actors.

At the final phase, service and support (10.57%), initial cost (9.57%), training (4.86%); documentation (4.39%) and on-going cost (4.13%) are the most important criteria. The purchasing manager (2.41), plant owner (2.40), the control engineer (2.25), project manager (2.17) and plant manager 2.03) are the most influential actors.

It's not that certain criteria are important only in a certain phase. But, vendors who lack scoring on these criteria will not proceed to the next stage in the process (Figure 2).

Figure 2. The importance of specific criteria will vary, depending on the selection phase of the process.

Between the various industry sectors is a remarkably wide variance in the weight factors for the initial costs. For greenfield projects, over 90% of all respondents find that they are only interested in the pure system price or the initial installation price when they select a DCS. Life-cycle costing (LCC) considerations play no role. The initial costs get the highest weight priority from the group's headquarters consultant (often an internal engineering group) and an engineering company/engineering procurement contractor (EPC) (Figure 3).

Figure 3. When buying a system, the initial costs have the greatest weight. Exit costs have the least. 

Improving the Method

To improve the selection method, I propose using a multi-criteria analysis, analytical hierarchy process (AHP) method (Figure 4), and the presented selection criteria provide a reliable method for an objective system and partner selection. The application of an AHP model improves the decision making, and the AHP's systematic approach reduces the time needed to select a supplier.

Figure 4. Using an analytical hierarchy process (AHP) concept selection model improves the decision-making process when selecting a DCS, and the AHP's objective and reliable approach also reduces the time needed to select a supplier.

Purchasing a DCS system is a balance between costs, returns and risks of migration and replacement projects. The goal is to choose a supplier that offers the lowest risk in the long run and best added-value services during the DCS's life cycle. By combining the lowest risk to the highest (satisfaction) score on the selection criteria, and by keeping the costs as low as possible, it's likely to result in a recommendation for that particular supplier. The AHP method provides an objective, systematic approach to achieving this goal. 

Willem D. Hazenberg, MBA, MIM, EUR, ING RI, is a senior process control consultant, Stork Industry Services, the Netherlands.

For more information on this subject, including a PowerPoint summary of Mr. Hazenberg's thesis, go to www.controlglobal.com/0912_DCS.html. See also the following LinkedIn group: www.linkedin.com/groupRegistration?gid=142172b