With regard to plugs and their reliability, ever wondered how the brand name MK originated?

Regards

BOD

Appalingly bad spelling BOD - although there was a sound engineering reason as well

OMS

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Failure is always an option

Re spellig:

Socket contacts are self-adjusting as to pitch and contact making and have a non-expanding and size-limiting entry to protect the contact tongues from over expansion and permanent distortion: a feature of the original 'Multy-Kontact' spring grip patented in 1919.

Socket contacts are screened by MK 'Anti-Flash' shutters and the design is based on the original MK patent of 1927.

Regards

BOD

The BS committee responsible for BS1363 did not take that view with regard to mis-use of safety socket covers (despite the "general public" in question being children).

I'd be interested in why you think we MUST make things "foolproof"?

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Eur Ing Graham Kenyon CEng MIET

Foolproof as far as possible where cost will allow! It's the responsibility of designers to take a holistic view on whatever they're designing as far as I'm concerned. To design, then market any product or commodity, without a proper macroscopic viewpoint in regard to social engineering and the consequences of injuries, being sued or prosecuted is irresponsible, - if it can happen it will.

Regards

But that is not the view taken by Standards Committees all of the time.

Whilst it's a "Designer" and "Manufacturer" responsibility to ensure a reasonable level of safety, it's not immediately transposed to the "Standard", from what I've seen.

However, there's a circular argument here. What's the "reasonable level of safety" - it may well be cited that the accepted "reasonable level of safety" is the "Standard" (although that does absolve the manufacturer of designer of their responsibilities).

Back to the socket covers. If a common product is open to clear mis-use by children as well as adults, it's not "foolproof". Take a look at this site:

http://www.fatallyflawed.org.uk/


What do you propose is done about the issues discused on the site, given that there are apparently no reported injuries or deaths? Yet it's clear that there is something awry and injury or death may result?

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Eur Ing Graham Kenyon CEng MIET

Hi for what its worth I think it would be a mistake to do away with the fuse in the plug as this alows individual protection to appliances . without having a dedicated the socket

Would agree, but IEE CoP for In-Service Inspection says, and BS1363-1 and Plugs & Sockets (Safety) Regulations imply, that the fuse protects the flexible cord, not the appliance.

In addition, with the prevalence of mcb's, I often find that the mcb (even B32 and C32) operate on appliance faults, either in addition to, or instead of, the BS1362 fuse (5A or 13A, sometimes 3A).

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Eur Ing Graham Kenyon CEng MIET

Children are a special case, especially when at the crawling stage and/or at an age where the danger is not obvious to them. There was an article somewhere, where a young lad was fatally electrocuted because he had tried to power his toy using wires/pins pushed into a 13A socket, I can't recollect the source though. How many near misses have occurred with 13A sockets?
It would be feasible to design an interlocking system with the switch/plug, so that the switch is in the OFF position before a plug is withdrawn; and to ensure a plug is inserted before the switch can be placed in the ON position. Motivation would be required though for an individual manufacturer to adopt such a design and risk losing market share, this would have to be adopted in the standards.

Regards

Is this really proportionate to the risk?

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Ross Currie TMIET

Are the statistics to be believed? What price a human life? Could it happen? Will it happen?

Regards

This seems to have drifted a little from the original topic, however:
The question is who are you trying to protect from what?

A socket outlet fitted with shutters, especially the type that require equal force on the L and N pins to open will protect against the random poking with a metal object problem.

Sleeved pins (or a recessed socket like the Schuko) will protect against a metal object being pushed behind the plug.

It is much harder to protect against a 'planned' attack of the type mentioned above where the person wishes to gain access to the electricity. From an early age I would have been capable of removing the top of a 13A plug with the (uninsulated) screwdriver from my Mechano set and then attempting to push it into the socket. There were always other means for the inventive mind! Kettle connectors (old and new) are not shuttered. The old style also made a useful adaptor for 5A round pin plugs which I used in later life from time to time as an emergency shaver adaptor.

Best regards

Roger

Good point. But are the connectors inherently unsuitable for fixed installation? or is it just a case of only being tested/certified for a lower duty simply because that's all that is currently required of them? We probably want a modified design for wall mounting anyway (suitable for a back box rather than clipping into a chassis) so presumably more rigorous testing/certifying could be done then.
- Andy.

Not to be confused with "Multi Contact" who appear to make connectors for the DC side of PV arrays.
- Andy.

I think it's a bit of both. Doesn't mean we can't make an IEC-320 compatible outlet, shuttered (as some are now anyway), that's got suitable creepage and clearance distances for a "better" grade of Insulation Withstand and more suitable terminals for "solid" and lower-stranding class of cables.

Maybe even different type tests.

Maybe just requires another "part" to the IEC320 standard (there are 5 at the moment).

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Eur Ing Graham Kenyon CEng MIET

Then again, why are we even considering IEC320 outlets, when it's a flawed design?

We all know that when you move the lead too much, the "free-part" falls out of the "chassis part" !



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Eur Ing Graham Kenyon CEng MIET

I disagree - engineers only have limited duties to thier clients generally.

If we take you comments literally then we wouldn't design anything.

What is your view on engineers working in the defence sector - good engineers design good guns - but they may have apalling social implications and result in many injuries when used as designed

Regards

OMS

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Failure is always an option

Depends who the "engineer" and the "client" is, if the designer/engineer is taking a selection of items that all are type tested and have independent standards, to design an installation say, that's one aspect, (he can still get it wrong and should be held responsible). The designer hasn't too many choices in the design of a system, he has to use what's in the market place for that application.
A bit different to designing individual items, there is a responsibility to ensure the safety of whoever is dealing with the end product, the Toyota fiasco is testament to that, who would be held responsible if there were major incidents, as a result of the maldesign of the braking system?


Design has to embrace all the potential factors that can occur for lifetime of that product, whether environmental, compatability, mishandling, abuse, ageing etc etc., not to consider all the factors is poor design. When doing university we were required to study design failures, a classic example was the Comet jet plane, fatique and the griffith crack theory, another - the Japanese who designed the foundations for a H.V. transmission line but didn't consider galloping lines, the pylons were simply plucked from the ground, could such incidents have been foreseen and prevented - Yes, the technology was available then.
If there was a new design for a domestic small power installation and there were no pre-conceived ideas, would you go for ring finals, 13A sockets, square pins, fuses in plugs or a system more continental or American?

What is your view on engineers working in the defence sector - good engineers design good guns - but they may have apalling social implications and result in many injuries when used as designed

This is a design for a specific purpose - to maim or kill; and a red herring, does the design meet the objective safely without causing accidents to the user?

In summary, I think there are pro's and con's for the 13A ring, I'm not convinced on the design/safety of the accessories though.

Regards

Jaymack - how can you be that innocent

Designers produced the grid systems for a client - but the jury is still out on the health effects of putting HV lines adjacent to centres of population

Designers came up with the mobile phone - but the long term impacts of induced brain cancers are still not known.

To take you back to university you must remember the ethics dilema of being appointed to design the gas delivery system for a certain establishment in Poland.

All of this undertaken by engineers - so no, I tend to disagree that we have this "duty" to all and sundry - we have duties to our clients and that's generally about it. We may think we have duties to a wider society but that covenant was broken many years ago

Regards

OMS

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Failure is always an option

Too glib!

Regards