Siemens SIPART PS2 6DR50xx Instrucciones de operaciones Pagina 103

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Functional safety
8.2 Device-specific safety notes
SIPART PS2 with and without HART communications
Operating Instructions, 09/2007, A5E00074631-07
103
The following table shows the achievable Safety Integrity Level (SIL) for the entire safety-
instrumented system for type B subsystems depending on the safe failure fraction (SFF) and
the hardware fault tolerance (HFT). Type B subsystems include analog transmitters and
shut-off valves without complex components, e.g. microprocessors (also see IEC 61508,
Section 2).
HFT SFF
0 1 (0)
1)
2 (1)
1)
< 60 % Not permitted SIL 1 SIL 2
60 to 90 % SIL 1 SIL 2 SIL 3
90 to 99 % SIL 2 SIL 3 SIL 4
> 99 % SIL 3 SIL 4 SIL 4
1)
As per IEC 61511-1, Section 11.4.4
According to IEC 61511-1, Section 11.4.4, the hardware fault tolerance (HFT) can be
reduced by one (values in brackets) for sensors and final controlling elements with complex
components if the following conditions are applicable for the device:
The device is proven-in-use.
The user can configure only the process-related parameters, e.g. control range, signal
direction in case of a fault, limiting values, etc.
The configuration level of the firmware is blocked against unauthorized operation.
The function requires SIL of less than 4.
The device fulfills these conditions.
8.2 Device-specific safety notes
8.2.1 Range of applications for functional safety
The SIPART PS2 positioner is also suitable for control valves that satisfy the special
requirements in terms of function safety to SIL 2 in accordance with IEC 61508 or IEC
61511-1. The 6DR501*, 6DR511*, 6DR521* and 6DR531* variations are available for this
purpose.
These are single-acting, depressurizing positioners with an input from 4 to 20 mA for
installation on pneumatic actuators with spring reset.
The positioner automatically depressurizes the valve actuator on demand or in case of faults,
which thus switches the valve to the specified safety position.
These positioners meet the following requirements:
Functional safety to SIL 2 under IEC 61508 or IEC 61511-1, from firmware version C4
Explosion protection on 6DR5***-*E*** variations
Electromagnetic compatibility in accordance with EN 61326/A1, Appendix A.1
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