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 rowan.humphries@sasol.com with any suggestions or comments (or contact Gary Friend of Extech Safety Systems (Pty) Ltd at garyf@tempcon.co.za).
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'