Intrinsic Safety

SAFA has formed a sub-committee for discussion of matters concerning intrinsic safety. Mr Rowan Humphries of Sasol Technology is currently the chairman of this sub-committee and invites interested parties to contact him at with any suggestions or comments (or contact Gary Friend of Extech Safety Systems (Pty) Ltd at

The group will meet every two months, and has set its objectives as follows:

    * To communicate on a regular basis
    * To gain and exchange knowledge and experience between end users, suppliers, vendors, test houses, and legal authorities.
    * To share and implement best practices
    * To ensure practical IS installations and standardise on IS loops
    * To identify and discuss typical problems and concerns in the industry and solve them.
    * To get feedback from the test houses and trends in the international arena.
    * To fill the gap in the knowledge of role players
    * To provide information on local IA certification & the implications
    * To work towards full compliance with IECEx

Technical Documents

    * AN9003 - A users guide to Intrinsic Safety
    * Cost comparison of Exi vs other techniques
    * Exic/ExnL review
    * ARP0108 review meeting - Actions and clarifications
    * AN9025 Introduction to IEC61508

Exic clarification from IS sub-committee meeting

These questions were raised at the IS meeting on 18 August. Herewith follows the questions and answers.

1)      Where does it say that Exic is for zone 2 only?
Ans.  The relationship is identified in 60079-14 section 5.3 and 5.4
(please click here for 60079-14 section 5.3 and 5.4)

2)      Where does it say that it does not require a barrier/isolator?
Ans.  This statement isn't true, you will need an IS interface - barrier, isolator or I/O card or a device with suitable IS safety parameters declared.

3)      Where does it say that you can run Exic wiring with Exia & Exib wiring?
Ans.  It appears in both 60079-14 and Draft 60079-25
(Please click here for the latter)

4)      What is necessary for loop drawing approvals? i.e. how do you do calcs?
Ans.  It will follow the same process that we have now.  However, as per Chris T note cable parameters are not likely to cause a problem for most installations.

Please click here for the 'Comparison of the techniques of intrinsic safety ‘ic’ and energy limitation ‘nL'


Intrinsic Safety

60079 14 section 5.3 and 5.4.pdf Download
AN9003-9.pdf Download
AN9025 Intro to IEC61508.pdf Download
Draft 60079 25 cables.pdf Download
Ex ic and Ex nL comparison.pdf Download
IccfnL.pdf Download
Summary SAFA ARP 0108 discussion - actions after DME meeting.pdf Download
TP1110 -3 cost comparison.pdf Download