Explains methods and provides guidance for the evaluation of Process Control Systems (PCS) during the phase of selection between different proposals.

This International Technical Specification describes methods and provides guidance for the evaluation of Process Control Systems (PCS) during the phase of selection between different proposals.

The methods of evaluation proposed in this technical specification are intended for use mainly by users, engineering companies, or independent test laboratories, to verify manufacturers’ proposals during the tender (as described in IEC 62603-1) or the provided Process Control System during the FAT procedure.

The specification and test procedures specified in this technical specification apply to a large variety of automation systems, both based on conventional technology (e.g. 4 mA to 20 mA field devices) and based on Intelligent Field Devices (IFD) with serial communication of any kind. For this reason, the tests specified in this technical specification are not necessarily sufficient for automation systems specifically designed for special duties. In such cases, user and manufacturer should define additional tests for assessing specific functions or performances.

The procedure for specifying the PCS technical requirements, evaluating the different offers, and carrying out the tests on the chosen PCS differs from one company to another and from one project to another, but some common steps exist, as Figure 1 shows. The IEC 62603 considers this process divided into two steps: definition of the PCS technical requirements (in the scope of IEC 62603-1) and test of the chosen PCS.

The first step of the specification of a PCS is to define the process requirements, in terms of required performances to achieve a satisfactory control of the process. Normally these requirements are defined with a joint effort of process engineers, automation, and instrumentation experts. From the process requirements, the automation engineers derive the PCS technical requirements, that is the functionalities the PCS should offer to achieve the required goals. Based on the process requirements and the PCS technical requirements, suppliers prepare their technical offers, and the evaluation procedure starts. IEC 62603-1 suggests a possible procedure for assessing the fitness of a proposed PCS to the specifications, based on a simple algorithm that considers the weight (importance) of each single required function.

After the selection of the PCS maker, the implementation stage starts. When the PCS is ready, prior to shipping the PCS on site and sometimes even during the implementation stage, the user/engineer may perform a set of Factory Acceptance Tests.

The technical evaluation of the tenders (IEC 62603-1) is mostly based on the evaluation of documents and data-sheets, and it may require simple calculations, e.g. for performance calculation. These verifications are based on general data of the proposed automation systems, not dedicated to any specific piece of hardware of software.

On the contrary, the FAT is mostly based on testing activities in laboratories or factories on a specific PCS including both the physical devices and the application software.

Figure 2 shows the typical process of PCS evaluation in an automation project.

The first evaluation is needed to select one supplier from a number of proposals. The reference document is the PCS technical requirements provided by the user or by a delegated engineering company. Scope of the evaluation at this stage is to verify if the proposed systems support the specified functions and performances. Evaluation is mostly based on the documents supplied by the supplier, such as technical data-sheets, manuals, conformity declarations, and so on. The PCS technical requirements should include the description of the required FAT procedure.

After the supplier\'s selection, the detailed engineering stage starts, and the user (or the delegated engineering company) produces a document that describes the software requirements in details. The PCS supplier assembles the PCS and implements the logic. After the completion of in-house tests, the Factory Acceptance Tests starts.

Several aspects of process control systems are in the scope of existing IEC standards that are to be considered together with the present document. This technical specification reports abstracts of the cited IEC standards based on the revisions available at the date of submission. Users should consult the most recent versions of the referenced standards for the actual requirements.