Emerson Process Management Rev AA manual SIL Capability, Systematic Integrity, Random Integrity

Functional Safety Manual

IP101/FSM, Rev AA

January 2012

Horizontal Float Switch

Table 3.

Failure Rates for Level Switch

4-contact Versions – Types D and P

The Mobrey level switch has met manufacturer design process requirements of Safety Integrity Level 2 (SIL 2). These are intended to achieve sufficient integrity against systematic errors of design by the manufacturer.

A Safety Instrumented Function (SIF) designed with the Mobrey level switch must not be used at a SIL higher than the statement without “prior use” justification by the end-user, or verification of diverse technology in the design.

Random Integrity

The Mobrey level switch is classified as a type A device according to Table 2 of the standard IEC 61508-2. Therefore, based on an Safe Failure Fraction (SFF) of between 0% and 60%, a design can meet SIL 1 with Hardware Fault Tolerance (HFT) = 0 and SIL 2 with HFT = 1 when the level switch is used as a single component in a sensor subsystem.

Safety Parameters

The failure rates given here are valid for the useful lifetime of the product, as described in the section “Useful Lifetime” on page 12.

NOTE:

The FMEDA report is available from the Safety quick link at www.mobrey.com. In the right-hand panel, there are SIL documents including the FMEDA report.

(1) FIT is the abbreviation for Failure In Time. One FIT is 1x10-9failure per hour.

Table 4. Failure Rates for Level Switch 6-contact Versions – Types D6, P6, H6, and B6

(1) FIT is the abbreviation for Failure In Time. One FIT is 1x10-9failure per hour.