CASS (Conformity Assessment of Safety-related Systems)

​CASS is an open and transparent methodology for assessing compliance to IEC 61508 and related standards.

At its heart, there are a number of tables (assessment templates) that can be used to map evidence of compliance (the assessee’s documentation) to the relevant clauses from IEC 61508 and record the assessor’s evaluation of that evidence. The methodology guides the assessor through the various evaluations to be performed. Each template lists a number of ‘targets of evaluation’ (TOEs) relevant to a particular type of assessment.

The assessment templates are free of charge and are available from the Downloads page. There are a number of supplementary documents that, together with the templates, form the methodology. It can be used in-house to prepare evidence of conformity supporting a Self-declaration, used by external auditors or even for Accredited Certification.

Advantages of using CASS

The CASS methodology has been designed by industry for industry to demonstrate functional safety compliance. It offers the following advantages:

  • Open to all and free of charge
  • Transparency in the assessment method - when complete, the templates show clear links between the evidence of conformity, the requirements from the standard used and the assessor’s evaluation
  • The methodology can be used to support a (self-) declaration of conformity
  • Can be used by certification bodies and is recognised by national accreditation bodies
  • Evidence can be prepared by the duty holder in advance of an external audit
  • Compatibility with industry guidance standards such as IEC 61511

Being able to demonstrate compliance with IEC 61508 (or related standard) is important to many organisations because it:

  • Is required by regulatory authorities for many plant owner/operators
  • Provides assurance to business stakeholders of operating companies managing high risks
  • Enables competitive advantage for equipment and service providers
  • Provides increased confidence in procurement of safety-related equipment and services

Management of CASS

The CASS methodology is owned and managed by The CASS Scheme Ltd, a non-trading company limited by guarantee with a membership of cross-industry institutions. The main duties of the company’s directors are to manage the ownership of the intellectual property and to control the release of new CASS documents for the benefit of industry at large.

New assessment templates or guidance documents are created by technical working groups set up within The 61508 Association under the mutual Memorandum of Understanding signed by the two parties. Thus The 61508 Association provides the main technical resource for CASS.

The Members of The CASS Scheme Ltd are:

  • Association of British Certification Bodies
  • British Computer Society
  • Energy Industries Council
  • Federation of Electronic Industries
  • Gambica
  • Institute of Measurement and Control
  • Institution of Chemical Engineers (Loss Prevention Group)
  • Institution of Engineering and Technology
  • Railway Industries Association
  • The 61508 Association


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