Validation for Safety
Since December 31st 2011, it is no longer acceptable to use the EN 954-1 standard for a safety related part of machine control systems; this venerable standard has been replaced by EN ISO 13849-1. The new standard brings many changes, but one that seems to have received little attention from plant engineers and, indeed, many others is the requirement for validation.
Section 8 of EN ISO 13849-1 states “the design of the SRP/CS (safety related parts of the control system) shall be validated” and goes on to state that details of validation are given in EN ISO 13849-2. But what does validation involve? Fortunately, EN ISO 13849-1 spells this out very clearly, as follows:
“The validation shall demonstrate that each safety-related part meets the requirements of ISO 13849-1, in particular:
- the specified safety characteristics of the safety functions provided by that part, as set out in the design rationale, and
- the requirements of the specified category [see ISO 13849-1, clause 6].
Validation should be carried out by persons who are independent of the design of the safety-related part(s).”
It might be tempting for plant engineers and managers to think that meeting the requirements of EN ISO 13849-1 and EN ISO 13849-2, and in particular validation, is a problem for the equipment supplier. In part, this is true, but don’t forget that almost all plant is subject to routine PUWER assessments and that PUWER assessments always reference the latest standards, even if these came into force after the equipment was put into service. In other words, EN ISO 13849-1 and EN ISO 13849-2 are definitely the concern of plant engineers and managers.
However, ensuring that validation is in line with the standard is no trivial exercise. F or this reason, many companies are finding that the services of an expert consultant, like TÜV SÜD Product Service, to assist with this process is an excellent way of saving time and money, as well as ensuring that the requirement for independent validation is met.
