EN13849 compared with EN954
Written by: Doug Florence
A brief description of the differences between EN13849 and EN 954 and the effects of the new standard on
The well established standard for safety related control systems, EN954, has been replaced by a new standard
EN13849. EN954 remains as a current standard at present, but it is superceded by EN13849. EN954 has been withdrawn
as a Machinery Directive harmonised standard at the end of 2011.
EN13849 moves towards the functional safety approach used in EN61508 and EN62061. It aims to use an approach
based on reliability calculations to allow for use of modern electronic equipment in safety related control
systems. It also encompasses non electrical control systems such as pneumatic logic or hydraulic components.
EN954 used a rather crude risk assessment chart to define an appropriate control system structure which was
referred to as a category. The basic concept was that the higher the risk that the control system was mitigating,
the more robust was the required structure. EN13849 uses a similar risk assessment to EN954, but assigns a
required level of reliability called a PL to the safety related control systems. The concept of system
structures referred to as categories remains, but the reliability of the resultant control system is calculated
rather than it being assumed that a certain structure will give a certain level of reliability.
For Sistema software see this
This article describes the implications of EN13849 for machinery manufacturers