SOMMAIRE
LOREME
12, rue des Potiers d'Etain - 57071 Metz
03.87.76.32.51 - Fax 03.87.76.32.52 - Email: [email protected] - [email protected]
E 8
4-20mA signal isolator, signal splitter with 2,3,4 outputs
SIL2 / SIL3
CAL4/100ig CAL4/100igM
FMEA summary
Overview
This document summarizes the results of the Failure Modes, and Effects Analysis (FMEA) of the isolator
CAL4-100ig from LOREME manufacturer.
In addition to the characterization of information required for the operational safety ( especially for the availability and
storage of spares parts ), this study fulfills the requirement of IEC-61508 by indentify and quantify the dangerous failures
of the component, thus allowing to interact on design for reduce this risks.
Purpose of analysis
This study was made in order to verify the suitability of the isolator CAL4-100ig to be used in SIL2 or SIL3 safety
applications.
Scope of analysis
The dedicate device embedded a set of electronic components for acquiring a 4-20mA current input signal from a
sensor and reproducing two analog output signals (4-20mA), image of input.
Generally, a transducer is taking place between a sensor and a protective equipment, designated as "Logic Safety
Equipment"
Sensor
transmitter
CAL4-100ig
PLC /
Logic Safety Equipment
Analog output 2
Analog output 1
PLC /
Logic Safety Equipment
Specification of device
The converter CAL4-100ig is a subsystem of type "A" according to [CEI61508-2-§ 7.4.3.1.2] :
The failure modes of components required for the safety function are well defined.
The behaviour of the converter in fault conditions is fully defined.
The converter benefits from a experience feedback in many safety application.
Safe failure
[CEI61508-4-§3,6.8] Failure that does not have the potential to put the safety system in a dangerous or fail to function
state. A safe failure it is not dangerous failure.
SFF
[CEI61508-2-§7.4.3.1.1-d] The Safe Failure Fraction is the proportion of non-hazardous failures. It describe the frac-
tion in percent of safe failures
S and detected dangerous failures
DD related to the total failure rate (sum of safe
failures
S and dangerous failures
D).
D
S
DD
S
SFF
Dangerous failure
[CEI61508-4-§3,6.7] Also designated as unsafe failures. It is failures that have the potential to put the safety system in
a dangerous or fail to function state.