Environmental Limits; Application Limits; Design Verification - Emerson Fisher 1052 Safety Manual

1052 Actuator
October 2017
Designing a SIF Using a Fisher 1052 Actuator
Safety Function
When the 1052 actuator is de­energized, the actuator and valve shall move to its fail­safe position. Depending on
which configuration is specified fail-closed or fail-open, the actuator will rotate the valve control element to close off
the flow path through the valve body or open the flow path through the valve body.
The 1052 actuator is intended to be part of final element subsystem as defined per IEC 61508 and the achieved SIL
level of the designed function must be verified by the designer.

Environmental limits

The designer of an SIF must check that the product is rated for use within the expected environmental limits. Refer to
the Fisher 1052 Diaphragm Rotary Actuator Product Bulletin for environmental limits.

Application limits

The 1052 actuator materials of construction are specified in the product bulletin. A range of materials are available for
various applications. The serial card will indicate what the materials of construction are for a specific actuator. It is
especially important that the designer check for material compatibility considering on­site chemical contaminants and
air supply conditions. If the 1052 actuator is used outside of the application limits or with incompatible materials, the
reliability data provided becomes invalid.
Diagnostic Response Time
A 1052 actuator does not perform any automatic diagnostic functions by itself and therefore it has no diagnostic
response time of its own. However, automatic diagnostics of the final control subsystem may be performed such as
Partial Valve Stroke Testing (PVST). This typically will exercise the actuator and valve over a small percentage of its
normal travel without adversely affecting the flow through the valve. If any failures of this PVST are automatically
detected and annunciated, the diagnostic response time will be the PVST interval time. The PVST must be performed
10 times more often than an expected demand in order for credit to be given for this test.

Design Verification

A detailed FMEDA report is available from Emerson. This report details all failure rates and failure modes as well as the
expected lifetime.
The achieved SIL of an entire SIF design must be verified by the designer via a calculation of PFD
architecture, proof test interval, proof test effectiveness, any automatic diagnostics, average repair time and the
specific failure rates of all products included in the SIF. Each subsystem must be checked to assure compliance with
minimum HFT requirements.
When using a 1052 actuator in a redundant configuration, a common cause factor of at least 5% should be included in
the Safety Integrity calculations. This value is dependent on the level of common cause training and maintenance in
use at the end user's facility.
The failure rate data listed the FMEDA report is only valid for the useful lifetime of a 1052 actuator. The failure rates will
increase after this time period. Reliability calculations based on the data listed in the FMEDA report for mission times
beyond the useful lifetime may yield results that are too optimistic, i.e. the calculated Safety Integrity Level will not be
achieved.
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