Calculations without the headache Software tool verifies the functional safety of protection devices on machinery

Canton, MI – Pilz Automation Safety’s software tool, PAScal, verifies the functional
safety of protection devices on machinery in light of current standards. The Safety
Calculator supports manufacturers in the calculation of failure limit values, as required by
standards IEC 62061 and prEN ISO 13849-1. The software tool enables a reduction in
costs and the amount of time spent on the task, particularly as figures need to be
recalculated each time the safety functions are modified.
The PAScal Safety Calculator separates the safety functions into their component parts,
calculates the overall probability of a dangerous failure per hour (PFHD value) and
verifies the data with the prescribed performance level or safety integrity level. The
software tool also takes into account potential architectures and variations if subcomponents
are connected together and parameterized.

Division into sub-systems
According to the approach of IEC 62061 (sector standard from IEC 61508 for safety in
machine control systems), safety-related functions are divided into sub-systems such as
sensors, inputs, logic, outputs and actuators. So the architecture for each sub-system can
be specified separately. The sub-systems can be combined as required.The Safety Calculator not only considers the factors listed in prEN ISO 13849-1 for
evaluating the common cause failure (CCF), but also takes into account the parameters
that depend on logic or electronics, which affect diagnostic coverage (DC). These include
detection of shorts between contacts or synchronicity monitoring on multi-channel
sensors, for example.

Based on a database
The basis for the Safety Calculator is a comprehensive database that already contains
details of Pilz products. Users can also define their own components and store them in the
database, provided the necessary numeric values are known. The Safety Calculator uses
this data to calculate the PFHD value.
The PAScal Safety Calculator provides support to manufacturers when designing safetyrelated
control elements. For new design procedures are required now that EN 954-1 has
been replaced by prEN ISO 13849-1 for the design of safety-related control systems and
standard IEC 62061 has been published.
The software tool also allows for the flexibility that engineering requires. Safety
functions can change from machine to machine, so that calculations need reworking
again and again. The Safety Calculator absorbs the associated costs.