Hazardex 2019 Conference Presentations - Eliminating explosion risks through properly sealed cables
20 November 2018
This report was commissioned in order to establish the correct type of cable gland for a particular type of cable construction when used in Zone 1 and Zone 2 hazardous areas. This resulted into an investigation and testing program to establish if selecting cable glands using the guidance from IEC 60079-14 Electrical installations design, selection and erection - is in fact safe for flameproof applications using cables typically used in marine and off-shore.&nb
The applicable standard which dictates if a barrier type or non-barrier type cable gland should be used, IEC 60079-14, proposes criteria to make this selection, which is a point of contention in the industry, and it is believed by many that it is possible to meet the requirements of the standard with a cable / cable gland combination that is unsafe for use in the intended Flameproof type ‘d’ (Ex ‘d’) application.
Several varied cable/cable gland assemblies were put through the following tests to collect data on how non-barrier cable glands, employing an elastomeric sealing ring, performed in the prevention of flame transmission and gas migration under test conditions:
* Test 1: Flame non-transmission of an internal ignition. IEC 60079-1:2014 Cl 15.4.4
* Test 2: Restricted breathing test. IEC 60079-14:2013 Annex E (Informative)
* Test 3: Gas migration test (Bespoke)
These test results were then assessed against the requirements of the installation standard (IEC 60079-14), and the standard itself is examined for its potentially dangerous guidance on the selection of cable glands. For example in the clause 9.3.2 of this edition 5.0, when it states “where there is a likelihood that gas or vapour migration may occur through the interstices between individual cores of a cable, and the cable leads to a non-hazardous area or between zones, then the construction and application of the cable shall be taken into account.” This can be seen as an attempt to pass the responsibility onto end users to use “good engineering practice” and assess each case independently. It is thought however, that this has the opposite effect and is in fact conducive of “bad engineering practice”.
The results of the investigation show that the selection criteria detailed in the IEC-60079-14:2013 (edition 5.0) installation standard, allows for situations where non-barrier type cable glands can be used with unsuitable cables for various applications, and how the standard could be improved to promote safer selection of cable glands for flammable atmospheres.
Presenting Author: Jonathan Hichens- Lead Certification Engineer. IECEx Competent Person (Ex001) Paper Topic: Investigation, Report & Safety Analysis into the suitability of cable and cable gland selection for Zone 1 & Zone 2 hazardous areas when comparing physical test results to the theoretically evaluation and assessments normally undertaken. (Applications were based upon the guidance of the installation standard IEC 60079-14:2013, using marine offshore cables to NEK TS 606 & IEC 60092, which are generally more compact than typical onshore and offshore cables used in explosive atmospheres).
Jonathan Hichens is Lead Certification Engineer for CMP Products Ltd, a market leader of cable glands, cable cleats and accessories. He has been with CMP for over two years where he oversees the team responsible for testing and certification of a portfolio of products for industrial and hazardous applications.
Prior to working at CMP Products he spent several years as a project engineer and project manager for a bespoke fluid handling systems OEM, primarily for hazardous locations applications, and before that was an Aircraft Mechanic in the Royal Air Force.
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