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A Question of Standards

It is a mistake to rely solely on compliance to the European Standard EN 61386 when specifying flexible conduit argues Ian Gibson technical director of Flexicon and chairman of the European and IEC committees that prepare conduit standards.   He explains …



Ian Gibson - Technical Director for Flexicon



It is impossible to set a single standard for flexible conduit that will meet all applications.  Consider what it does, it protects cabling.  The most obvious question is what does it protect it from?  The answer is always going to vary according to the application.


The standard, which is referred to in the new 17th Edition Wiring Regulations, specifies tests and performance criteria to classify a conduit system according to 12 features – see table 1.  Each of these features is classified in up to seven performance levels.


For example, the first digit refers to compression strength in N/50mm.  Level 1 is defined as very light at 125, 2 is light at 320, 3 is medium at 750, 4 is heavy at 1250 and 5 is very heavy at 4000.  This makes sense as long as you can remember the detail.  Even if you can, do you think you can remember such information across 12 different categories?  In fact why should you?


Confused?  Well you should be.  Just to compound this you will almost never see all 12 digits printed on the product, even if you could remember what they represented.  This is because some properties will be changed depending on the type of fittings used with the conduit.


Any one who has taken the time to study the standard will realise that virtually any flexible conduit could pass it.  It is not really an indication of anything other than a base minimum standard.



In fact, even though it does stretch to 12 digits, each with sub categories, the standard does not address all of the properties needed by flexible conduit for all applications. It does not for instance cover low fire hazard, or EMC (Electromagnetic compatibility), UV resistance, chemical resistance or abrasion resistance.  I could go on but potentially the standard could stretch onto 20 digits or more


At this point you may be wondering why I, of all people, appear to be criticising EN 61386.  Well I would argue that I’m not.  What I am highlighting is that the standard should not be the only factor you consider.


In fairness how could it address every possible scenario? There are multiple hazards that conduit must protect the cabling from. 


The critical thing is to realise what the standard EN 61386 is there to do.  Its role is to set standards by which different manufacturers can test their conduit to meet different criteria and enable the end user to compare different products on a like for like basis.


If you are going to use the standard to help specify conduit then the pertinent question to ask is what performance level does it meet for each of its 12 criteria?  Even then depending on the application you may find that other approvals are needed such as the Rail Fire performance standards or the Lloyds register type approval for marine applications.


A better approach is to conduct a risk analysis of factors likely to be important.  Potentially this is a never ending list, but factors likely to be important include:  Compression strength, tensile strength, impact strength, temperature range, fatigue life, bend radius, IP rating, chemical resistance and which chemical, abrasion, UV resistance, anti vibration, fire performance and EMC screening. 


Note that this list is not exhaustive and equally not all of the factors listed will be relevant to all applications.  Generally conduit will need to fulfil 3 or 4 of the above requirements and after that personal preference will play a role.


In some ways selecting the correct conduit for the job is like selecting PPE equipment for health and safety. Cheapest is not always best and is certainly not if the conduit fails to do its job.  Ultimately you could be liable and simply claiming that the conduit meets EN 61386 is not a defence.


It is up to responsible manufacturers to help customers in this selection process.  You should find that they have detailed selection charts and product performance data; they may even have an online product selector on their web site.  Better still pick up the telephone and ask for technical assistance – it is in everyone’s interest to get the specification correct.

For further information please contact:  Flexicon Ltd, Roman Way, Coleshill, Birmingham, B46 1HG.  Telephone 01675 466900.  Fax:  01675 466901.  Email:  sales@flexicon.uk.com.  Web:  www.flexicon.uk.com

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