This past week I had the pleasure of attending the IEC 60079 committee meetings in Seattle. I found that the meeting was very valuable, and went a long way in harmonizing all of the safety standards and technical reports surrounding functional safety in the process industries. Basically, the IEC 60079 committee is involved with the standardization of gas detection systems. Their latest “standard” (and I am using the term very loosely here), is related to using gas detectors in safety critical applications. At first, I was very concerned, as a member of the ISA 84 working group 7, that the scope of this standard would conflict with the technical report we had just written regarding the application of performance based fire and gas detection and suppression systems. I was further concerned about overlap with IEC 61511.
After meeting with the team members and explaining the contents of the ISA technical report to the IEC committee, I am now happy with the direction of all of the work. After a a rewrite of the IEC 60079-29-3 draft standard the focus of the document is really more related to specific requirements that one should be concerned with when applying the gas detectors in safety applications that supplements IEC 61511, as opposed to replacing it. If course I was still concerned that the document being generated was a standard as opposed to a technical report. I found out at the meeting that the document being generated is essentially equivalent to a “technical report”. When IEC issues documents they can be either normative requirements (i.e., shalls) or guidance documents (i.e., shoulds). The IEC 60079-29-3 document is being written as a guidance document, which makes all the sense in the world. Furthermore, some proposed changes that were incorporated into the latest draft refer to the ISA TR84.00.07 when the issue of detector coverage and mitigation effectiveness come up.
On the ISA side, I clearly took to heart the message that TR84.00.07 is very offshore oil and gas slanted, and that there are a large number of gas detector users for whom the approaches in the technical report are unnecessary overkill. There are a large number of gas detection applications where a direct measurement of gas concentration is being made (such as pulling a sample out of a vessel vapor space), and where mitigation effectiveness is 100%. The next revision of the technical report needs to make clear that a detailed coverage and mitigation effectiveness analysis is in many cases not required, and include some examples of where a gas detection function can be treated just like any other traditional SIF.
Thanks to all the IEC 60079 committee members for their gracious hospitality at the meetings.