I have recently attended an informative presentation regarding the recent IEC 62353
recommendations/standards applied to the electrical testing of medical equipment in service as opposed to the IEC 60601-1 type testing standards.

I was impressed with the conclusions and thought it a step forward in standardizing the important issue of electrical safety testing of medical equipment. Unfortunately it is quite meaningless, like most UK standards of electrical testing, since no one HAS to comply with them unlike the standards in many enlightened countries such as Germany or Australia. In practice many Doctors’ Surgeries and Health Centres use IEE type electrical PAT testing of their medical equipment, I would be interested to know the patient leakage currents they measure. Their ignorance of the difference in standards between electricians Portable Appliance Test and the standards regarding testing of Medical Equipment is also shared by the electrical contracting PAT testers; but as they are usually paid per item why should they worry?

On the subject of electrical testing my hospital’s management clearly encourages the electrical testing of medical equipment but does not apply any importance to the testing of the individual IEC leads, this I find very strange.

I suppose I am one of the ‘old boys’ that can remember when Britain was indeed Great and was not afraid to uphold ‘standards’ in which they believed. Although I am vehemently opposed to unwarranted regulations I believe this was an opportunity missed in not making it mandatory for all medical equipment to undergo regular testing to reduce dangers to users and patients.

What are other members thought?

Regards

Barney

I reckon you need to spend an evening trawling through earlier threads that have touched on this topic, Barney. They are myriad!

Employers have a "duty of care" and can be prosecuted if they fail to exercise it. It's all down to the H&SAW Act (off the top of my head), or something like that. Some sort of legislation, anyway.

If electrical safety testing of medical equipment was made mandatory as you suggest, the first thing that would happen is that engineering managers would be howling for the extra resources that this would entail!

Enjoy your homework, Mate. We all look forward to your summary sometime tomorrow (or the day after). Ha, ha.

Believe me Geoff, the work is already being done by electricians doing PAT tests on Defibs/ECG machines etc at Surgeries, and we as tax payers are paying for a test that was only intended for fridges,vacuum cleaners and kettles not for patient connected medical equipment.

Barney

Yes, I've seen it for myself, Mate (many times). I was at a vet's doing some servicing on ultrasound kit a couple of months back, and enquired why the staff there allowed grubby local sparkies to put their stickers (and, supposedly, carry out their test) on "my" nice equipment. All I got was shrugs, and mumbles about how the two young chaps just came in and "checked everything". I think I frightened them a bit when I mentioned the word "warranty" in relation to our (expensive) kit (well, it belongs to them really, but I expect you know what I mean).

By the way, they apparently always go around in pairs. Plus and minus, I suppose.

To make testing mandatory under legislation, i.e. meaningful in law, a period between tests would have to be specified, explicitly (as well as the use of a testing standard, e.g. 62353), for devices based on the risk presented by devices, their likelihood of failure and the environment that they're used in.

In any case, given the diversity of devices and the risks presented, if testing were not performed at "regular intervals" that're considered acceptable under law, enforcing "reasonable testing intervals based upon risk" for a particular devices would be difficult. The problem is that individuals' idea of reasonable test interval varies in practice - usually heavily influenced by the resources that're available for testing.

To make the requirements of legislation easier to implement hence enforce, perhaps, there would have to be a mandatory test on all devices at an interval that's fixed and, ultimately for many devices and applications, the interval between testing would not be realistic given the number of devices in a typical general hospital and the complexity of tests associated with a significant proportion of the high-risk devices.

Visual inspection, basic functional checks and electrical safety checks would be necessary whatever the medical application or electrical device involved. The basic testing methods indicated in 62353 are, in fact, almost identical to those indicated in 60601-1 under normal conditions except that IR tests are now specified, explicitly, lower earth bond currents appear to be encouraged, plus there are some other relatively minor changes in allowable earth-bond figures, etc.
The tests now formally specified in 62353 but not 60601-1 consist of stuff that most individuals have considered good practice for years when performing 60601-1 tests, anyway; most of which have already been included in many electrical safety testing products already on the market.

One thing that 62353 is very useful for, even if its use is not mandatory, is that manufacturers and service agents can use it as a benchmark for stating, more explicitly than 60601-1 does, good practice in routine safety testing in much the same way as manufacturing standards are used by manufacturers to illustrate to notified bodies/competent authorities, etc, that good or "state of the art" engineering/design practices, essential safety aspects and performance considerations are being applied.

Therefore they have a good argument when specifying the requirements of servicing/testing, including safety testing which was previously out of their "control" and the domain of EBME/Medical Physics, etc, based upon selection of tests that were not previously specified in writing - hence somewhat open to interpretation.

I must admit that I do have concerns that it is possible that tests indicated in 62353 could "pass" medical devices with a single fault condition present (that have actually been designed under 60601-1 to protect the patient under a single fault condition) and that some leakage limits (especially compared to those in the in the 3rd edition 60601-1) may not be fully compatible with 60601-1.

Potentially, over the life of the device or system, lowering the "safety margin" designed into new products that're manufactured by companies adhering to the essential safety requirements of 60601-1. However, saying this, I've not had an opportunity to fully study the "ins and outs" of both the standards and compare them properly, yet, plus failures are few and far between so the risk of a scenario where 62353 misses an SFC in a medical device and a second fault occurs is probably very low thus an acceptable one.

Perhaps anyone who disagrees would care to comment?

Thanks Barney for your kind comments on our seminar. I am pleased you found the information useful.

It was very interesting for me to receive many positive comments on the IEC 62353 yet the UK experts voted against the IEC 62353 draft.

Geoff is right about the legal requirements only being driven by the HSE. How can you prove something is save if you do not test. I therefore believe more guidance would be beneficial on testing intervals (shortfall on the IEC 62353)

However, as mentioned in the seminar, the IEC 62353 is published and will further develop over the years (just like the IEC 601 has done over 30 years) to grow to a better document perhaps suitable for making it mandatory (it will be mandatory in Germany next year). This would make matters clear and will get rid of the pat testing "biomed" engineers like you have mentioned in this forum.

As is clear from this forum, the IEC 62353 will provide a more efficient and saver working practice across the UK for those who currently test to IEC 60601 (or pick and mix – see previous forums)

For those who missed the seminars or would like to receive a copy of the presentation, drop me an email (johnb@seaward.co.uk)
We aim to continue with further seminars in the near future. Any suggestions on locations across UK and Ireland or even abroad?

Thanks

John Backes.

A couple of comments come to mind. Why so many standards? IEC-this, and IEC-that. It's all very confusing (except, perhaps, to those making a career out of it all). Why can there not be just the one regulation for routine "PAT" testing of all equipment, with medical equipment in sub-set?

And why are we always in such a state of flux? After all, would you say that the kit itself (ie, the medical equipment to be tested) has changed fundamentally in the last ten (twenty, thirty) years? Why can't we just fix a set of criteria and then get on with it? Bring back HTM-8!

Excuse me, but I thought that the United Kingdom was already part of the European Union. So, if it's to be mandatory in Germany ...? What's the score here (more bloody chaos, by the sound of it)?

I wonder if anyone from the IEC lurks on this forum? I hope so.

Suggestions on locations, John? How about Cloud Cuckoo Land?

Thanks for all your comments.

I attended John’s seminar at Bristol and can highly recommend it to all Biomeds.

Regarding it being mandatory to test, surely it is better to test medical equipment to a medical equipment standard than to allow the electricians PAT test to replace it, which is what is happening outside the hospital environment.

As Richard correctly states the PAT test intervals are also not mandatory the IEE set out a code of practice with recommended intervals, however in the real world this means small businesses calling in the local electricians and they will PAT test everything in sight at a yearly interval. This is of course better than not testing but surely a label on a ECG machine saying it has passed its electrical safety test is misleading if the item has not been tested to a ‘medical equipment’ electrical standard test such as the IEC 62353.

I do not accept the view that it would be difficult to cope with mandatory intervals since I consider that many items could be tested at wider intervals than many hospitals attempt to meet at present. At least having an interval based on evidence of failure and practical achievement would ensure that all medical devises would be tested to a medical electrical standard.

Incidentally having been as Geoff colourfully describes, a ‘grubby PAT tester’ in previous employment, I maintain the most important test of all is the visual inspection and testing of the mains lead, especially the IEC type. It shocks me (excuse the pun) when I see Class2 equipment tested with a Class1 IEC lead without a separate test of the earth resistance of the portable mains lead.

Barney

Taking into consideration the sheer volume of medical devices in circulation, problems in accessing it for routine maintenance and the resources available in your typical Medical Physics/EBME medical equipment maintenance department.

Actually providing "evidence of failure" or failure to access equipment within the mandatory period may be taken as "an admission of guilt" under law if testing were mandatory.


But who decides on the intervals applied and to which devices? What would be "reasonable"? That's what I'm getting at when I say it would be difficult - managing what's, seen in the eyes of the law as, acceptable or not.

Don't worry, Lads, all this will change over-night (and who knows, perhaps resources will magically be made available), if the Health and Safety Tsars ever find the time to cast their hawk-like gaze over medical equipment!

Need I remind you that we exist in a State where even our finest police force, in the execution of their duties, does not escape the all-embracing Health and Safety laws?

I wonder if anyone from the H&SE lurks on this forum? I hope so.

Hi Geoff,

Being part of the EU does not mean that each member country has identical laws. This would be nice, lets all adopt the German laws. Mandatory PAT testing on non medical equipment (VDE0701/0702), medical equipment (VDE0750/0751), laws on fixed installations (VDE0100) and perhaps, remove the speed limit on our motorways and whilst we're at it, lets adopt the Euro before the Torries come back in power. I'm up for it.

The IEC62353 is aimed to deal with all different IEC's / VDE's EN's MDA's, AS/NZ's, AAMI's, NFPA's, CSA's and so forth. Looking at the UK, there is no single approach to routine maintenance, yet as you correctly state, Medical Equipment has not changed much over years let alone by geographical area.

So I concluded in the seminar that the IEC 62353 is a welcome standard for all involved in the medical sector, not just the professionals working in the UK but far beyond.

Anyway Geoff, you wouldn't know the nearest airport to Cloud Cuckoo Land so I can check the venue?

This argument should focus on the effectiveness MHRA who seem to be a toothless organisation. Barney mentioned how standards are enforced more riourously in Germany and Australia, but the FDA in America are the "daddies" of regulatory bodies. All American equipment manufacturers live in fear of the FDA. Perhaps our MHRA should take a leaf out of their book. I can imagine a squad of black jacketed troopers with MHRA logo on their backs decending on an unsuspecting Biomed department for using the wrong safety test standards. But seriously, why go to all the trouble to write the standards if they are not mandatory or enforceable?

I think I can answer that one, Bill. This is Britain, Mate. The land of muddling through, making do, and doing it on the cheap!

There's your answer, John, you're already in it!

No - not a missed opportunity but possibly mis-directed and possibly being used as a springboard to develop and sell a product which I totally disagree with if it is the case.

This aside it's a more prescriptive approach to testing and could be used to make the applicability of tests, for those technically less competent or less knowledgeable, less ambiguous than the current standards for routine purposes.


I'm left wondering why the UK experts voted against 62353 if, as a standard for routine safety testing, it has significant benefits over and above the tests that are specified for 60601-1?

More guidance, i.e. a standard that's not mandatory, is not what's needed, it's more prescriptive routine testing legislation that is needed from the HSE, MHRA and DoH based on evidence plus a standard for routine testing that's acceptable to UK experts.

IEC 62353 appears to follow identical tests to 60601-1 except that it specifies IR testing (which, as it happens, is performed on most if not all of the automated/semi-automated "pick and mix" "60601-1 compliant" electrical safety testers that I've ever used).

IEC 62353 specifies the MINIMUM earth bond test current of 200mA - higher test currents can be used.

An important factor is that IEC 62353 does not include the single-fault tests that ensure medical devices are capable of remaining electrically safe under SFC.

IEC62353 also applies limits from earlier revisions of 60601-1 that may no longer be consistent with the 3rd edition 60601-1 standard.

On balance IEC62353, as it stands, may potentially add to confusion and does not necessarily make safety tests (that are generally perfomed using automated/semi-automated safety testers) easier, safer or significantly faster. Not for Engineers that apply the tests after re-manufacture of systems, during evaluation or acceptance checks, anyhow.

My view is that IEC62353 may not be suitable for anything but routine test purposes hence I'd be inclined to continue testing using a "60601-1 compliant" with IR tests and earth-bond test current that is capable of overcoming poor contact resistance and surface contamination, for accetance, evaluation, re-manufacture and after repairs.

Accepting the fact that we cannot possibly perform testing to all of the requirements in the 60601-1 standard, since some are destructive - that's not what we try to achieve with safety testing in the field and this has been the case for years since BS5724 was published in the 70s.


As well as the Rigel 288 if you want a safety tester that can be used as a versatile bench instrument for Engineers used in evaluation, acceptance-checks and tests after re-manufacture of stuff like video endoscopy stacks, etc, then I'd suggest the highly portable (mains operated) Gossen Metrawatt Secutest SIII .

This includes IEC62353 (VDE0751) and a host of other standards/limits for British/European Standards IT/ Telecoms, Laboratory, PAT, Household, etc. Internal printer, 4-wire kelvin Ohms measurement, in fact some nice "instrumentation" features with some useful accessories.

It doesn't include any "gimmicks" plus, to be fair and balanced, I'd say that its database connectivity/data storage and retrieval is not really setup for high volume tests, like the QA90 or Rigel 288, for throughput, and it's not quite as configurable when it comes down to mixing applied parts (unless this has now been addressed in later software) but it is a decent bench instrument for engineers (Voltmeter, Ohmmeter, Ammeter, Power-Factor, Functional tests, etc).

Very competitively priced with a 25A, 10A/200mA earth bond tests and, more importantly, specified tolerances and errors that are more meaningful than many of the technical specifications and performance metrics that're given by the competition. Perhaps this is because it's manufactured for the German market and has to comply with legislation.

Although the high current pulse followed by 200mA earth bond test of the Rigel 288 is novel it only has single wire, i.e. Ohms needs to be zeroed, earth bond resistance measurement, plus the accuracy of measurement appears to be outside those generally specified in IEC62353 due to a combination of display resolution and basic accuracy, for example.

I'm of the opinion that NO electrical saftey tester, including the Rigel 288, can avoid presenting potentially injurous voltages or currents to the operator or even the equipment under test. That's in the nature of electrical safety testing unfortunately.

I wouldn't be surprised if there are disclaimers and warnings about the potential for damaging or injurous voltages and currents during testing in the operator manual - just like all the other EST manuals.

Well, my two cents on the subject...

I think that the main problem with IEC 62353 is that, as it is related to the second edition of IEC 60601, it does not take into full consideration the aspect of risk management.

A lot of people tend to think that the tests and limits of IEC 60601 are "rigid", meaning that they can´t be changed, but the truth is that the standard always had a "safeguard" clause (it´s clause 3.6 in the second edition) which says that the construction of the equipment could be different from the standard if it was demonstrated that the risk level is the same as would be if the clause of the standard was met (nowadays it would say - if the residual risk is acceptable). This was not used much because there´s was some difficult in applying the concepts of risk management without a defined framework (and this was one the reasons of the development of ISO 14971 and it´s incorporation as a regulatory requirement in the new edition of IEC 60601).

What it means is that the equipment could be constructed in a way in which the tests of the standard would not be aplicabble, or would be, but in a diferent way - change in test method or limit values, or both or whatever. Or new tests would have to be developed to test the risk controls - and safety standards, in a risk management framework, are nothing more than a collection of agreeded risk controls and tests to verify that these risk controls, which are not always the best or cheapest ones, are effective.

This mindset could make the life of people testing equipment in a post-marketing environment really hard. But that´s the way it is, as the regulatory requirements of manufacturers are risk management-based.

The truth is, there´s no way for this to function correctly if manufacturers do not declare the tests that need to be performed on their particular equipment to mantain them safe. That´s because the risk management information is not available to the end-user.

All in all, i think the standard is a great step in one direction, but i´m not sure that is the right one.

I'm not going to get into discussing standards and clauses in standards since nobody wants to wade through that but I think that problems are likely to be caused by the application of 62353 that may be inconsistent with current 60601-1.

Without thinking about it too deeply I think that it is possible to fail a device using the leakage limits in the 62353. For example when some of the current leakage limits are greater in 60601-1, e.g. current earth leakage requirements.

62353 tests may be performed that do not take into acccount the single fault failures that medical devices are intended to be tolerant of. Thus a 60601-1 compliant device under SFC may pass a 62353 EST. Is this a safe medical device?

For example I suppose it's possible for a SFC to be present under 62353 testing, e.g. enclosure leakage, earth O/C, and still pass leakage tests on a device designed to pass 60601-1 under SFC with accessible conductive parts. How would we detect this was the case?

This device could still have a fault on it and pass enclosure leakage tests and earth leakage tests, obviously, since earth is O/C, with enclosure leakage from accessible conductive parts limited by adequate construction to 60601-1. Could we tell the difference?

My personal view is that 60601-1, itself, should include its own requirements for routine testing or 62353 should be tied even more closely to it, to be amended concurrently with it, or even incorporated into 60601-1.

Whatever happens in the future people like us, in maintenance, are going to need to make references to 60601-1 when acceptance testing and evalutating medical devices. Even if we apply a routine medical electrical testing standard.

We need a clear and concise rationale, that is uncluttered by risk-assessment approaches, and one that outlines a suite of non-destructive tests that can be used to give pass/fail criteria when rotuinely safety testing medical electrical devices.

All we want to know, Richard, is:-

Does this mean we have to bin all our old (and existing) electrical safety testers?

I don't think so Geoff. The most significant difference I can see between the direct method of 62353 and 60601-1 is the explicit application of IR testing and there's not much in that to be honest since most 60601-1 compliant testers include 2 out of 3 of the IR tests described in 62353 I think. The problem is inconsistency between current 62353 limits and applicable 60601-1 limits, I think.

The 62353 standard introduces some concepts that, in my experience, have been used by skilled, experienced and appropriately trained technicians without having it written down in a standard. Saying this I think 62353 formalises some useful ideas relating to what should be inspected on a PM. Some are just plain common sense in my view.

I've never come across any "60601-1 compliant" commercial medical electrical testers, intended for maintenance rather than manufacturing, that have ever applied destructive or stress tests to devices so the argument about 60601-1 tests being destructive is one for test houses, tester manufacturers and sales-persons to worry about not us.

Ooops, correction (or should I say clarification?):


For example I suppose it's possible for a SFC to be present under 62353 testing, e.g. enclosure leakage, earth O/C, and still pass leakage tests on a device designed to pass 60601-1 under SFC with non-accessible earthed and accessible non-earthed conductive parts. How would we detect this was the case?

Hello all

It could be a surprise, but 99 of 100 manufacturers and hospitals in Brazil seem to apply the 4KV dielectric strenght tests, which are destructive, on post-marketed equipment. This is the kind of untrained people i think would benefit more from the standard.

Anyway, i don´t think there´s need to scrap any safety tester. In fact, someone who knows what he´s doing can always make the tests with simpler equipment (a True RMS Multimeter and some resistors for the leakage tests? It surely work - i remember one colum from Rich Nute in the IEEE PSTC Newsletter in which he advised the use of a normal multimeter to make the tests, because the results would be acceptable anyway - just remembering that the objective of the post-market tests is not the same of the pre-marketing one).

I think in Europe that most purchasers and operators of electrical safety testers intended for routine electrical safety testing would be deterred from purchasing instruments with a dielectric withstand test unless they're manufacturers; given the risk of damage to products and injury to operators.

I'm not certain if these functions wouldn't be disabled by OEM sellers if being sold into certain markets.

Perhaps this is down to an awareness of the health & safety implications and H&S legislation as much as the electrical test standards that are applicable. It doesn't make sense for manufacturers of medical electrical safety testers to provide a product that damages devices and potentially makes them unsafe.

Just a tip: the discussion on leakage current measurement i said before can be read at
http://ewh.ieee.org/soc/pses/Downloads/newsletters/88v01n8.pdf

There´s also an interesting discussion on the pitfalls of pass/fail test in http://ewh.ieee.org/soc/pses/Downloads/newsletters/90v03n1.pdf

In the Technically Speaking column.

Well, the problem is that people buy a separate hipot.

Thanks for that - actually it was a bit of a rhetorical question just to illustrate what I'm getting at RE: 62353 versus 60601-1 and the potential for not necessarily achieving comparable safety tests, using different standards intended to ensure safety of medical devices, in all cases.

Not that I have anything against individuals posting others opinions or information, rather than expressing their own ideas or opinions, or technical understanding.

Unless the operator is fully aware of what's being measured and typical values that are expected plus the maximum limits under NC and SFC then 62353 may not be equivalent to or compatible with tests undertaken by 60601-1, under all circumstances, in my opinion.

I think to be credible then 62353 must have comparable leakage limits to the 3rd edition 60601-1 standard for example - it uses the same patient equivalent load doesn't it?

By a definitive pass/fail what I'm getting at is that an IUT may pass under one standard and not necessarily in another, under certain circumstances, if limits, etc, are not fully compatible and given the different methods and limits used to test devices.

This is bound to lead to confusion at some point when routine testing, if devices manufactured to 60601-1 fail 62353 for example, when changes in leakage limits are not aligned between standards, concurrently.

My point previously being that this is only required if they're a manufacturer since Hi-pot is potentially damaging, i.e. stresses, the IUT. Otherwise if they're routine testing then this is not required.

That surely will lead to confusion. Now imagine devices tested according to the new 60601, in which manufacturers have the option to reduce or increase the limits as needed and if the risk remains acceptable.

The truth is,they´re trying to fix a problem - the lack of a strong link between pre and post production, that in reality can only be solved by one player - the manufacturer.

I think we're at crossed purposes here - we're discussing routine testing of medical devices, i.e. 62353, not manufacture, and I'm comparing aspects of the standard we use for routine tests, a subset of 60601-1, with aspects of the 62353 standard and thinking about the possibility of incompatibility between them if a department uses both standards for acceptance, evaluation and routine tests.


That is exactly my argument. My problem with 62353 being an independant standard having the potential to have different limits for leakage compared to 60601-1 is that we are testing the same devices using the same methods hence I expect the leakages to be the same under NC at least. Have you looked at 62353 and compared to 60601-1 3rd edition?

When one standard changes limits then the other must surely have compatible limits considering leakages at least? Also earth bond, IR, etc, etc. If you look at the 62353 standard are all the leakage limits equal to those for 60601-1 3rd edition under NC at least? If not then why not? Are earth bond limits the same under all conditions?

Yes 60601-1 is a manufacturing standard for medical devices but, de-facto, it has become established as a standard whose non-destructive tests and limits are used for routine testing of medical devices in the field. One feature that is not usually included in such devices (I've used many) is Hi-pot testing; this is generally reserved for use in manufacturing since it's a requirement to test assemblies during development/manufacture and not generally in the field.


Essentially I agree but it would go some way to fix the problem if basic leakage and earth bond limits were unified for the same type of tests. Also if both standards were updated concurrently or 62353 were a subset of a 60601-1 standard that included aspects of servicing/maintenance provision generally.

I'd like to see the manufacturers test every device out there - it's got to be done with the cooperation of those performing testing in the field, 3rd parties and purchasers servicing organisations. All interested parties in fact - not a range of manufacturers trying to sell products on the back of standards, in my opinion.

Well, the limits are different simply because they do not have to be too strict or because they cannot be too strict (for example the earth resistance adding 100 mOhm, as explained on the annex to 62353). I understande your point when you say that it can be confusing having different limits for the "same" tests, but this is the point..the objective of the tests aren´t the same. And yes, i know that IEC 60601-1 is used for routine tests, and this was the main motivation for IEC 62353, for people to stop using 60601 as it´s not "fit" for routine tests.

Your comment about cooperation i just what i tried to illustrate with the third edition risk management comment - manufacturers, as the experto on the devices, should make it clear what tests are needed and should inform and cooperate the other interested parties.



I think you got to the point, at least in my view of things. This standard was published in a bad time, a transition from the old standard which a lot of people used in a fixed way, and a new standard which is as open as it can get.

If this is the case then why does IEC62353 use the 2nd Ed 60601-1 leakage limits then? Limits for leakage under NC and SFC become particularly important when considering potential for micro-shock. Medical devices and standards that test for them should be consistent if the standards are to be compatible and conducive with patient safety - seeing as the patient load and risk of micro-shock remains the same at similar currents irrespective of the different standards.

Wow, the limits are the same? Are we talking about the same document?

I think the tables giving 60601-1:2005 limits in Annex E and multiple references to IEC60601-1:2005 give it away somewhat. No dc or SFC measurements but generally limits appear to follow the 2nd edition 60601-1 standard.

Dear Mr Ling

Why do we believe that IEC 60601 is better then IEC 62353?
More often than not people pick and mix from IEC 60601 (see previous forums), make there own tests up (within the limits of safety analysers), do not test on TN systems (mainly outside UK) or power the safety analyser from an isolated supply.

For this reason, IEC 62353 does not follow the new limit in IEC 60601 3rd for earth leakage. This is a safety concern with the 3rd edition when the test is not performed as per the standard conditions.

IEC 62353 refers to the enclosure / touch leakage (for Direct and Diff. method);

The 3rd edition Earth Leakage limit of 5mA (NC) and 10mA (SFC) are potentially dangerous and can only be tested safely on an isolated supply. This is not always possible when testing “on location” as carrying such transformer would require a decent trolley. The new pass/fail limits on normal non-isolated supplies are potentially fatal (macroshock) within the limits of IEC 60601.

The European Directive EN 50191 (guideline for test environment) calls for maximum leakage to earth of 3.5mA. Any potential greater leakage must be supplied through an isolated supply.

I would like to know why the limit went from 0.5 and 1mA (SFC) to 5 and 10mA (SFC)??, when enclosure leakage open earth is still at the 2nd edition limit. Surely in those cases where this is possible and acceptable, you would handle this under a specific standard (ie 601-2) rather than under the general?

The IEC 62353 specifies direct leakage (as per IEC 609601) current limits under SFC only (open earth and mains in applied parts) and are identical to IEC 60601 2nd and 3rd edition.

Equipment leakage (Direct method) is equal to enclosure leakage open earth (SFC) and Applied Part leakage is equal to Mains on Applied Parts and has equal limits to 2nd and 3rd edition.

Only differences are;

o The way in which the current is limited (3ma in IEC 62353 vs 5mA in 60601)
o Compensation of measurement; ie no compensation in 60601 for voltage drop over current limiting resistor which causes the actual voltage on the Applied PArt to drop significant.
o Mains on Applied Part Voltage is 230V vs 253V in 60601.
o CF Patient connections are shortened instead of measured individually.

I am interested in your views on this.

Those interested in EN 50191 guidelines, email me for a free booklet. (same for IEC 62353)

Thanks
John

It just "appears" to follow. As the test methods are different (for example, not using the +10 % voltage) it means that, even if numerically equal to SOME of the values of the second edition, the resulting value will have a different meaning.

The standard let´s you use the values of the second edition, but just if the measurements are done according to the second edition, not this standard.

Also, as the rationale states for the alternative method:



So, disregarding the values for the alternative method, there´s just the EQUIPMENT LEAKAGE CURRENT and the PATIENT LEAKAGE CURRENT in the differential. But the equipment leakage current dos not have the same values as the earth leakage current of the second edition, so we disregard this too. This means that the only values that "follow" the second edition are for patient leakage current.

Hello Mr. Ling, you asked in some previous post why the UK experts voted against the standards, i finally found the voting document. FYI:



Sounds a lot like your vision. Are you sure you´re not one of these experts? :-)))

Never seen that documment Mantunes - must admit I worked it all out by myself - I'm not any any expert panels.

Thanks for that JB,

As you've indicated 62353 uses the same leakage limits but there are important deviations from the standard that can cause confusion when moving between 60601-1 and 62353.

I think it's useful to discuss the real issues rather than just skirt around them. I think I have an idea why the UK experts were unhappy with 62353 - and that's my opinion coming from a hands-on perspective and not academic or regulatory.


I don't believe I've ever made that comment. Neither have I suggested that there isn't a place for 62353. All I want is less confusion RE: safety testing standards, not more. Actually I think the introduction of explicit IR testing is a good idea for workers at the coalface like myself.

I think the changes you've described are significant RE: patient safety, however I'll need time to have a think about it. Remember I'm not involved with developing standards just trying to apply them to my day job in the real-world, rather than voting on my preferences.


I notice the Rigel 288s I've seen are enabled for 3rd edition 60601-1 limits for 62353 direct tests 1). does this mean that unsafe practices are being encouraged when using this device 2). does this device then comply with the 62353 standard itself?


Users like myself are somewhat captive when considering the tests that manufacturers of electrical safety testers provide built into their devices. The majority of operators probably just use automated tests built-in by the tester manufacturer. Are you saying that Rigel, for example, have previously manufactured testers that are not up to routine testing or that they perform non 60601-1 compliant tests?

I think you're forgetting that we do not aim to type-test devices and this is not what medical electrical safety testers on the general market try to achieve - we are looking for reassurance that safety of devices we tests after repairs/routinely, whatever, is acceptable.

Irrespective of this, however, we need to ensure that routine safety testing methods ensure an equivalent level of safety for the patient. That's why I'm reticent about endorsing a method that doesn't necesarily agree with the general standards RE: basic leakage limits (forget the relatively insignificant variations in mains that are required during some type-testing activities) nevermind the more complex stuff.

You came to an interesting point. What is or would be an equivalent level of safety?

I'll leave that to the experts.

Hum, but that´s the whole point of this discussion, isn´t it? As the example from the UK comment shows, it seems that the UK experts think that an "equivalent level of safety" would just be met if the tests and limits were the same as the standard the products "were" based (by the way, this opinion was also shared by the Italian NC).

My view is that the problem with this argument is that equipment are not obliged to comply to IEC 60601-1, or any standards for that matter, in most of the regulatory schemes (CE Mark and FDA for example - strange enough, here in Brazil the IEC 60601 series is obligatory). They have, in fact, to comply with the Essential Principles of Safety and Performance Of Medical Devices,and the principles can be resumed as: the risks related to the device must be managed and kept acceptable. In this case, the equivalent safety can only me defined by the manufacturer, as the equipment can use other forms of construction different from the standards (and altought people use the standards, as they´re the easiest mean of demonstrating compliance to some of the essential principles, they usually use just parts of standards).

Dear Mr Ling,

I respect your opinion (and that of others). Especially on the subject of electrical safety. Judging by your posts, you obviously know what you are talking about. Never the less, I have different views on some matters which are based on spending lost of time in continental Europe, where people also know what is best, based on years of experience. There will always be a difference in opinion between parties who have developed their own best. All, I am sure are in the best interest of the end-user, the patient, employee, member of the public etc.

Perhaps, we can drive the forum to suggestions on how to make the IEC 62353 better than it currently is (to this who have their concerns).


In answer to your question 1) and 2)
1) Default limits are set to the latest standard applicable. We do advocate safe practises hence we are (as a group) actively involved in safety standards committees. Limits can be set by users to reflect other standards or requirement (ie set a limit at 90% or much lower typical value or as per 2nd edition).
2) IEC 62353 and IEC 60601 are treated separately in terms of measurements. Following IEC 60601 limits does not impact on the IEC 62353 tests (or did I misread your question?)

A note on the Alternative Method(main reason for UK to vote against); This test is identical to the dielectric Strength test in IEC 60601 however at a saver voltage (ie 230V instead of 1500V)

By using mains (current limited), a better indication is provided at the insulation at the expected frequency rather than the 500VDC which might give readings subject to caps. Perhaps those who were against this test could see it as a quick (and save) pre test prior to switching on the EUT instead of an insulation test.

regards,
john

I'm not and have never intended to suggest that I know best - only what my views are. Only that 62353 introduces some confusion RE: equivalent level of safety, i.e. applicable maximum leakage limits, decision when to apply different tests, etc, etc.


Isn't that what the experts on the 62353 panel should be discussing and voting on?


So, if I have read your meaning correctly the leakage, e.g. earth and patient leakage measurements obtained and the limits intended to ensure they are acceptable, are not as important as the methods used to measure them?

One of the biggest points that most seem to miss or not realise the significance of, is the need to compare the test results with previous results.

This is not done in 60601 as all that matters is whether it passes or fails the limit values.

In 62353 you have to look at previous test values to see if there has been a significant change which would indicate a potential failure. In fact many manufactures set limits as to how much a value may change from the initial factory or acceptance test value. As an example a Siemens ultrasound unit is only allowed an increase in any leakage value of 1.5 times the initial value or 10uA whichever is the greater! This would never be picked up in an IEC 60601 test!

Would you want a probe used on your family if it displayed a leakage value of 4500uA? This is a pass for 60601 but would 100% fail a Siemens ultrasound safety tests as the initial value would have been about 4uA!

I understand there are those that don't like change and may see performing fewer tests (as required by 62353) as somehow unsafe but in fact if performed correctly they are in fact much safer that those of 60601 as they will pick up faults that 60601 would miss.

Open your eyes and your mind and embrace the new standard.

I particularly like the Alternative test method as, where it is suitable for use, it works really well and saves lots of time booting up and down PC based devices between tests. Many don't accept the equipment leakage values it reveals but in fact they directly correlate to the 60601 open neutral tests!

I suggest those who dislike the new standard actually obtain a tester that works to 62353 and go back to basics and conduct some tests of their own.

You also need to look at the MHRA DB2006(5) document (which supersedes all others) and note that it says to use an appropriate standard but not 60601. As the only appropriate standard in the UK is BS EN 62353 I suggest al get on board as soon as possible.

Since when does a tech need to be told when to compare suspicious results with those of earlier tests?

And, are you suggesting that techs should apply special care and attention on equipment that may be "used" on members of their family? I hope that users of this forum can rise above nonsense like that!

"Preaching to the converted" is the phrase that comes to mind.

Well although you may diligently compare results you may be shocked and surprised that many do not! I have seen many technicians simply connect a device to test and press the start button on the meter and walk away. As long as they get a tick box at the end then they are happy and move on to the next job. This is probably the way >75% of those conducting an electrical safety test work.

You may be one of the "converted" but many are not and still need some preaching!

Interesting you made no comment on the points about the use of 62353 over 60601? That is my experience on this matter as it seems to descend into a non technical war of words trying to put down anyone who upholds the new standard. Some even feel they can come up with a better standard of their own which can only lead to a worsening of the current situation.

IEC 62353 is not a 'Missed opportunity" if all adopt the standard and interpret it correctly, recognising the points that will increase the safety of testing medical electrical equipment.

After all a common standard can only help in ensuring a consistent approach to safety testing and record keeping.

I am rarely shocked, and never surprised, but I imagine that the "missed opportunity" heading arose from a feeling that IEC-62353 did not go far enough. So called "harmonized" European regulations often end up this way, it seems.

Common standards are nothing new. We have had them since at least the days of HTM-8.

But when any new regulation comes into force, no doubt it will be adopted.

PS: I wonder what next year's version will bring (apart, that is, from the need to purchase yet another tester)?

Well if people have purchased the right tester then I am sure it will be fully upgradable to any minor changes in standards.