A Modification to the SISSafety Instrumented System is anything that is not like-for-like replacement. “Like for like” here means the same component (hardware and firmware version), from the same supplier.
The “same” product from a different supplier (or even a different version of the product from the same supplier) should trigger the Management of Change (MoC) process for the SIS.
As Modifications come in many different shapes and sizes, the approach defined in IEC 61511 is designed to be flexible and is a “one size fits all” approach. While the level of effort to approve the use of a new variant of a device from the original manufacturer would be quite low, and the effort to approve the introduction of a new SIFSafety Instrumented Function to a SIS would be quite high, the approach is flexible enough to handle both.
IEC 61511 requires a 2-stage FSA process to be carried out on Modifications. The first stage confirms that the proposal of implementing the change is fit for purpose, prior to the start of the work. Once the Modification is completed, the second stage of the FSA confirms that the work was done correctly (as per the proposal).
=Method can help you manage MoCManagement of Change for SIS (which is often not straightforward) and deliver Stage 5 Functional Safety Assessments.
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