Intrinsic safety in hydrogen/oxygen mixtures

Background
Occasionally it is necessary to make measurements in hydrogen/oxygen mixtures. The increased use of fuel cells and the use of hydrogen as a vehicle fuel have increased the frequency with which this requirement occurs. The requirement occurs usually within process vessels since when the mixture is released the problem becomes a mixture of hydrogen/oxygen /air [...]

Cable parameters and all that

The intrinsically safe [IS] system standard [IEC60079-25] discusses in detail how to draw up the system documentation and in particular how to calculate the permitted cable parameters. Unfortunately the standard has to take into account all the possible variations and hence the process looks quite complicated. In the majority of applications the simple precaution of [...]

Intrinsically safe multicores

It is an opportune time to review the use of multicores containing more than one IS circuit because of the introduction of the ‘ic’ concept. [For the uninitiated ‘ic’ is intrinsic safety without faults intended for Zone2 use and will replace the ‘nL' concept of the type ‘n’ standard in time] A further factor [...]

The use of mechanical tools in hazardous areas

Purpose of note
From time to time concern is expressed about the possible risk of frictional sparking caused by the use of steel tools in hazardous areas. This note attempts to put this risk in perspective and make a positive proposal on acceptable practice.
Background
It is recognised that frictional sparking between certain materials can ignite a flammable [...]

The future role of the humble paper clip in Hazardous Areas

Apart from their traditional use of holding the multiple sheets of paper that one is required to have with them when performing inspections on equipment in hazardous areas, what are the other uses for the humble paper clip these days ?
The first one that came to mind was a piece of test equipment for [...]

Earthing –bonding and all that

The perennial problem of earthing and bonding is raised from time to time. The basic principles that are applicable to all bonding problems is that it is potential difference that causes problems and explosions and that all currents should be provided with a well defined low impedance return path. Within Europe there is a strong [...]

A non-progress report

My apologies for the long interval between entries on this blog, but my contemplating time has been taken up preparing papers for a seminar in Australia, which I rashly promised to provide. If you are involved in Intrinsic Safety now is a good time to get involved in rewriting the standards, which you [or is [...]

ATEX instructions- a paper chase

There exists an ATEX working group/ standing committee, which promulgates interpretations of the ATEX apparatus directive. Quite what its powers are and how binding its decisions are is not clear but if we assume they are significant, then its latest decision is a nuisance. At a recent meeting [November 06] under “Any Other Business”, [...]

The Three Day Expert

It is generally acknowledged that there is a lack of expertise in defining and installing electrical equipment in hazardous areas. In the last few years the facilities for the training of technicians has improved, in Europe this has been largely due to the EEMUA initiated courses but supplemented by some other organisations. The problem of [...]

Ex d – a non solution to a hot problem

Background
Very occasionally someone notices that the IEC apparatus standards usually only consider ambient temperature conditions of  -20 °C to + 40 °C. This range can be extended when this is considered desirable and noted on the certificate and by marking. The usual limits are –40 °C and + 75 °C. Some concern has recently been [...]