Namur highlights 'proven-in-use' safety issue

Leverkusen, Germany – Namur is warning process operators that simply purchasing a “proven-in-use” device – as described by the IEC 61511 standard for safety instrument systems – does not discharge them of their responsibility to ensure suitability of the equipment for any particular process application.

Namur also urges operators to follow its own recommendation NE130, which describes general requirements to be met for devices to be “proven-in-use”. Up to now this NAMUR recommendation was available only in German, but may now be obtained in a bilingual (English/German) version from the NAMUR office.

NE130 is intended to “concretise” the requirements of IEC 61511. It defines an equipment class “which is both suitable and, simultaneously, practical for operating, monitoring and safety equipment in process industry,” said a statement from the automation end users group.

According to Namur, such devices can then be utilised in a single-channel configuration for SIL 2 applications and at least in 1oo2 redundancy for SIL 3 applications. At the same time, it said, a simplified mathematical SIL verification may be applied, as detailed in the NE130 recommendation.

Measurement categories temperature, pressure, flow and level and associated actuators are addressed in the NE 130, though the methodology described can, in principle, also be employed for other measurement principles, Namur pointed out. Howevr, it does not apply for safety-related programmable or hard-wired programmable systems and their I/O modules, nor is it suitable for complex process analyzers.