Validation

Safety instrumented systems
Non-configuration of smart instruments presents problems

Smart instruments in safety instrumented systems

Smart instruments in safety instrumented systems


  • When instrument manufacturers provide functional safety compliance certificates, always read the small print.
  • Instrument manufacturers’ ability to produce instrument firmware to IEC61508 standards is variable, immature, or difficult to assess. However, it is improving.
  • KISS (keep it simple stupid) is still excellent advice for design.
  • An extremely interesting article by Tom Nobes of Sellafield was published in the July edition of InTech. It is a breath of fresh air to see that the nuclear industry takes a genuine Good Engineering Practice approach to validation of configurable instruments, and the paper gives good guidance on appropriate methods.

    There are very few pharmaceutical organisation that even record the configuration of smart instruments, let alone validating their implementation. This is not only the case for HART instruments, but also applies to PROFIBUS PA and Foundation Fieldbus. Too often the focus is on GAMP, 21CFR11 and the calibration management system, with a gaping hole surrounding the smart instrument configuration.

    Tom Nobes shows the methodology to be used for smart instrument “substantiation” (i.e., validation) and the difficulties he has had in getting the necessary information from manufacturers goes to show how few customers look for it. Part of this may arise from the fact that under IEC61508/61511 the nuclear industry has quantatively defined the required risk reduction factor, whereas the pharmaceutical industry has skirted this vital metric and remained resolutely qualitative in the case of GMP.

    Nonetheless, it is difficult to justify incomplete recording of smart instrument configuration at a minimum. Paragraph 12.1 of the draft revision of Annex 11 (computerised systems) to the EU GMPs requires that “Alterations to any component of a computerised system should only be made in accordance with a defined procedure within the manufacturing authorisation holder’s Change and Risk Management policies/procedures”.

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