We have CMMI processes at CL3; does that help us get IEC 61508 certification for SIL 3?

Companies that deliver a product or service do so by following a sequence of processes.  High quality deliverables are a result of high quality processes and continuous improvement in those processes.  Improving the business processes improves the process capability (more predictable results with less variance).  As capability increases, the organization reaches higher maturity levels which usually lead to competitive advantages.  Capability Maturity Model Integration, (CMMI ™) is a way to measure and improve the capability and maturity of such processes.  Although it can apply across the broader product development and maintenance cycle, it is still mostly used for software engineering.

CMMI is a process-improvement-based, goal-oriented framework.  Several levels of capability and maturity exist, ranging from chaotic (Level 1) to optimizing (Level 5).  Its capability and maturity levels are measured against goals and objectives of various process areas. IEC 61508 is a well-known international standard for systems and instruments that implement safety instrumented functions and systems, including development of hardware and software.  The basic philosophy of the standard follows the pattern of planning, execution, validation, and documentation. Its Safety Integrity Levels (SIL 1- SIL 4) yield a level of risk reduction needed to prevent and avoid hazards.  There is not a direct correlation between CMMI capability and maturity levels and Safety Integrity Levels, however there are similarities in the requirements of the CMMI Process Area goals and practices that correlate to requirements of IEC 61508.  Demonstrating compliance to CMMI levels 2 or 3 may help with functional safety assessments showing that the organization has processes in place for many key assessment areas.  This can better prepare an organization for functional safety assessment, but lacks one-to-one correspondence of the rating levels between CMMI and IEC 61508.  Further work in safety assessment must be considered for the areas that are not addressed by CMMI.