This report relates to the proof testing of safety instrumented systems (SIS). It has been produced as part of a research project funded by the Health and Safety Executive. The contract was placed with Eutech Engineering Solutions Limited. The objectives of the research were to define a set of guiding principles upon which proof tests of SIS should be developed, to provide independent advice to HSE Field Inspectors and to report on current practices, highlighting examples of good and poor practice where relevant. The research gathered data from industry via interviews, workshops and questionnaires and executed searches of data within the public domain. This report presents the findings of the research. The target audiences for the report are industrial end-users of SIS and HSE Field Inspectors. Industrial end users should benefit from the communication and illustration of current practices. The collation of experiences, views and examples give an indication of what is practicable and of the issues of concern to different sectors within the chemical industry. The data generated by the industrial research is presented ‘as found’ in an attempt to provide a genuine indication of the practices, experiences, and concerns within the industry. The data collected during the research was analyzed and the results used to generate and support a set of guiding principles for the proof testing of SIS. Each principle is presented in this report and is supported by the research data and a rationale based on recognized standards and guidance. The current high profile of IEC615081 amongst end-users was evident throughout the research. Its principles have been used to construct the rationales supporting the guiding principles. Detailed recommendations have been generated to provide practical guidance on the application of the guiding principles. The recommendations have been used to create a checklist for use by HSE inspectors. The checklist is presented in Appendix 2.
A set of guiding principles upon which the proof testing safety instrumented systems (SIS) should be based has been developed via research into chemical industry practices, experience, and views and via searches of data in the public domain. Interviews, questionnaires, workshops and searches identified a set of issues relating to proof testing which was of particular interest to a cross-section of the chemical industry. These issues have been used to generate guiding principles, which address the following:
- proof testing practices;
- the content of proof testing procedures;
- the format of proof testing procedures;
- planning and scheduling;
- proof test records;
- competence;
- awareness of hazard and risk;
- management of change.
The research indicated that the proof testing of SIS is common practice but that some organizations take a more structured and focused approach than others. The size of an organization and therefore its ability to deploy engineering resources was significant as was a commonly held view that the reducing numbers of competent, experienced technical personnel are beginning to have an impact on proof testing practices. The research confirmed the existence of a conflict between the need for realistic proof testing and the need to minimize downtime, particularly within high throughput continuous processes such as refining and bulk chemical manufacture. The increasing profile of IEC615081 was a common theme throughout the research with manufacturing organizations expressing trepidation over its potential impact on existing installations, notwithstanding its no retrospective nature. Examples of good and poor practice were encountered and have been highlighted in this report, however, searches of published literature and incident databases provided no tangible evidence that incidents have been directly attributed to issues relating to proof testing. CLICK HERE (pdf) to download this report.