IEC 61508 Functional Safety Assessment Emerson Process ... - Exida

Table 1 gives an overview of the different versions that were considered in the FMEDA’s and
assessment of the Fisher Controls DVC6000 SIS Digital Valve Controller - DETT.
Table 1 Version overview
Application Safety Function
1 4-20 mA Operation, Double-Acting (Relay
A), De-Energize to Trip
2 4-20 mA Operation, Single-Acting (Relay
C), De-Energize to Trip
3 4-20 mA Operation, Single-Acting (Relay
A), De-Energize to Trip
4 0-20 mA or 0-24 VDC Operation, Double-
Acting (Relay A), De-Energize to Trip
5 0-20 mA or 0-24 VDC Operation, Single-
Acting (Relay C), De-Energize to Trip
6 0-20 mA or 0-24 VDC Operation, Single-
Acting (Relay A), De-Energize to Trip
Output A ≤ Output B (with 4 mA input signal)
Output A ≤ 1 psi (with 4 mA input signal)
Output A ≤ 1 psi (with 4 mA input signal)
Output A ≤ Output B (with < 1 mA input
signal)
Output A ≤ 1 psi (with < 1 mA input signal)
Output A ≤ 1 psi (with < 1 mA input signal)
For the 4 – 20 mA operating mode, the fail-safe state is defined as the input signal being 4 mA. The
DVC6000 SIS Digital Valve Controller is classified as a Type B 1 device for these applications
according to IEC 61508, having a hardware fault tolerance of 0.
For the 0 – 20 mA operating mode, the fail-safe state is defined as the input signal being < 1mA.
This will ensure that the electronics are no longer capable of driving the I/P module. Therefore the
DVC6000 SIS Digital Valve Controller is classified as a Type A 1 device for both applications
according to IEC 61508, having a hardware fault tolerance of 0.
© exida Certification SA. EFC 07-07-41 R002 V1R2 IEC 61508Assessment.doc, March 13, 2008
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