NA 106 has been revisedfrom 2018-09-06
The document differs from NE 106 edition 2007-02-27 beside editorial adjustments as follows:
- Change from NE to NA
- Change of title
- Separate German and English versions
- Introduction of a proof test plan with sub-sections
- Harmonisation of operator and test requirements
- Increased test flexibility through inclusion of partial and intermediate tests
- Description of generic proof test modules for sensors and actuators
- Inclusion of test record examples
Abstract NA 106 ‘Flexible proof testing of field devices in safety instrumented systems’
Testing equipment in safety instrumented systems helps detect dangerous faults disrupting or even completely preventing the required function of a safety instrumented system (SIS). Such a test is a necessary part of the action taken to maintain the required safety-related availability over the lifecycle of a safety instrumented system.
Often the function of safety instrumented systems is proof-tested at one-year intervals. The requirements of such proof tests are laid down in regulations, ordinances or technical rules such as AwSV, VBG, BetrSichV, AD 2000-Merkblatt A 6, WHG, BGV, VDI/VDE 2180, NE 130.
Performing an end-to-end proof test of a safety instrumented system from the sensor to the actuator, however, always entails an additional organisational effort and often a considerable disruption of production.
Consequently, the demand to make the proof test intervals and/or the test itself more flexible without at the same time jeopardising plant safety is in keeping with ever more stringent requirements in terms of production times and plant availability.
Current risk-based standards, such as IEC 61511-1, open up possibilities to meet this demand.
The aim of the proof testing strategy presented here, i.e. flexible proof testing of field devices in safety instrumented systems, is to ensure the longest possible plant operation, not interrupted by any tests, while at the same time maintaining the necessary safety integrity of the installed SIS. This involves extending the previous fixation on a fixed test interval to include an additional testing method with different test intervals and test steps within a safety instrumented system.