Company > Newsletters > Newsletter No.16

OMNIfacts eNewsletter
 
  News from Omniflex
 EndUser Electronic Edition
http://www.omniflex.com		 2007-04-26 00:00:00
No.16

 

Omnifacts is published by Omniflex Pty Ltd. This newsletter is designed to inform and educate in the areas of monitoring and control.
This publication may be freely redistributed if copied in its entirety.  Portions of this newsletter may be reprinted with permission
Omniflex leads the way with Safety Systems IEC61508
Ian Loudon

Safety Integrity Level (SIL) explained

Four safety integrity levels (SIL) are defined by IEC 61508 to statistically represent the integrity of the SIS (Safety Instrumented System) when a process demand occurs. The SIL takes into account device integrity, architecture, voting, diagnostics, systematic and common cause failures, testing, operation, and maintenance. A SIL establishes an order of magnitude targets for risk reduction. This target failure measure is the intended probability of dangerous mode failures to be achieved in respect

of the safety integrity requirements, specified in terms of either the average probability of failure to perform the safety function on demand (for a low demand of operation); or the probability of a dangerous failure per hour (for a high demand or continuous mode of operation). The higher the SIL, the greater the impact of a failure and therefore the lower the failure rate that is acceptable.

SIL 4 Disastrous Impact on the Community

SIL 3 Employee and Community. Multiple injuries.

SIL 2 Major Property and Production. Potential individual injury.

SIL 1 Minor Property and Production

Unfortunately applying this numbered system to a process opens much debate. How do you determine if production protection is “major” or “minor”? At what point could a potential injury occur? The method used to derive the SIL designation, must be carefully documented using well established methods.

The first step to determine or designate a SIL, is to conduct a process hazards analysis (PHA). PHAs range from simple screening analysis to complex evaluations such as a Hazard and Operability Study (HAZOP) which employs a multi-disciplinary team to methodically examine a process design and determine if hazards or operability problems exist that could result in an accident or other unsafe condition. A requirement of IEC 61508 is that a target SIL must be assigned for the SIS for any process in which the PHA has concluded that the mechanical integrity of the process and the process control are insufficient to alleviate the potential hazard.

The HAZOP should clearly define the risks associated with a process in terms of likelihood of the hazard occurring, as well as the severity.

It should be noted that the methodology of IEC 61508 extends far beyond the HAZOP process of defining the incident in terms of loss of containment, explosions, or hazardous chemical releases.The standard focuses most of the actual evaluation on the potential injury, fatality, or other risk to

individual persons.

 

 

Omniflex cannot give its products a SIL number but it can say that it may be applicable in a SIL ‘n’ application. Calculation of Safety Integrity Level (SIL) is a complex issue of reliability and availability of the individual components within the safety loop but also the environment that they work in, the test and inspection procedures, and the whole operational environment. This means that a manufacturer cannot claim they have a SIL numbered product as the SIL is determined by the whole loop in which it is operating.


Omniflex first with IEC61508 Annunciator

The Omni16C Annunciator is suitable for use in safety related applications meeting Safety Integrity Level 1 in accordance with IEC 61508: 2000.  Full details as to SSF and PFD Data are available from Omniflex as well as advice for safety related applications.

Omniflex product development and design now incorporates the criteria related to IEC61508 and SIL 1 related functional safety applications.

Omni16 products are also available in Intrinsically Safe or Non Sparking variants. EX I and EX N.


Omni30 replacement for Legacy RIS UC 30

The Omni30 annunciator series is designed as replacement for the RIS UC30 series products. Based upon the field-proven Omni16C technology, this product range provides state-of-the-art annunciation to fit existing  installations.

Available in panel mount or 19-inch Rack mount configurations, the Omni30 series annunciator can be fitted with incandescent lamp or solid state LED displays. These standard modules can be wired together to form an annunciator system of up to 128 points.

Inputs accept potential free contacts and are individually configured for N.O. or N.C. operation by a combination of wiring and externally accessible “DIP” switch. All wiring terminals are plug-in for easy system maintenance.

Any one of 27 alarm sequences can be selected for each alarm module on the externally accessible DIP switches. Window legends can be created by the user using a standard Laser or Inkjet Printer using the software template provided. When wired together as a system, all alarm modules will be flash synchronised, and can share a common set of pushbutton controls.

 


Modbus I/O Modules connects Legacy Omni16 systems to SCADA or PLC

The MIR module as a general purpose digital input module on any Modbus ASCII or RTU RS232/485 network. Input termination is by 20 way ribbon cable header compatible with Omniflex products such as the Omni16 alarm annunciators.

  • Simple DIP switch settings for Modbus Slave operation provides ultimate simplicity.

  • Fully isolated RS232/485 communications gives best noise immunity.

  • Compatible with Omni16 alarm annunciator repeat outputs and other Omniflex products.

  • Multi drop up to 32 units to a single Modbus Master.

    The MOR module as a general purpose digital output module on any Modbus ASCII or RTU RS232/485 network. Output termination is by 20 way ribbon cable header compatible with many Omniflex products such as the Omni16 alarm annunciators.

    • Last Month:

    Last month we talked about several important topics including:
     

    • Omniflex leads the way with Safety Systems IEC61508
    • Omniflex first with IEC61508 Annunciator
    • Omni30 replacement for Legacy RIS UC 30
    • Modbus I/O Modules connects Legacy Omni16 systems to SCADA or PLC

    If you missed these or other key discussions,
    you can find the back issues on the newsletters page of our website:

    Subscribe/Unsubscribe

    Subscribe to Omniflex News

    Unsubscribe from Omniflex News

    This publication may be freely redistributed if copied in its ENTIRETY.  Portions of this newsletter may be reprinted with permission.

    (c) Copyright 2003 OMNIFLEX PTY LTD 

    		  
    In this Issue
    Omniflex leads the way with Safety Systems IEC61508
    Omniflex first with IEC61508 Annunciator
    Omni30 replacement for Legacy RIS UC 30
    Modbus I/O Modules connects Legacy Omni16 systems to SCADA or PLC
       
    Last Month's Issue
    Subscribe/Unsubscribe

     IEC61508 - Annunciators from Omniflex suitable for SIL 1 Applications

     

    Omni16 Alarm Annunciator

    Omni-16 Series Annunciators

    Implement cost effective independent alarms as part of your risk reduction strategy

     

    OMNIFLEX Alarm Annunciators provide reliable notification when things go wrong - FAST!

    Omni16

    Trusted in thousands of major installations 

    Omni30 (UC30 replacement)

    Omni 30 RIS UC30 Replacement

  • Panel or19" mount

  • Plug-in terminals

  • Omni16C features

  • Choice of Backlit or LED display

  • All "DIP" switch settings externally accessible

  • 24Vdc powered

  • Optional ModBus Slave Serial Port

    • Omniterm MIR 16ch Modbus Digital Input Module (Ribbon Header))

     

    Modbus I/O Modules

    Connects Legacy Omni16 to SCADA or PLC via Omni16 Ribbon Header Expansion Ports.