EBME Forums Forums Maintenance Technical Assistance Recording,Storing and Analysing Electrical Safety

Let’s hear it for Mark of Taunton, for there speaks an experienced, practical bloke! The “drive”, though Mate, probably comes from a) Companies wanting to sell the latest safety testers, and b) Biomeds who prefer playing to getting the real work done! Just because it’s possible to do clever things, it doesn’t automatically follow that they’re worth doing. I have been in places where the guys emphasized electrical safety to the “nth degree”, but didn’t even keep a stock of lamps (had never even surveyed the kit to see which lamps were needed … hear what I’m saying?). In these days where everything is technically possible, we need to be selective, thoughtful even, about how we use technology, surely?

Having just re-read the above post ... all I can say is that I'm impressed by this guy's incisiveness!

When you conduct tests do you just go by a pass or fail indication on your tester after it has run through all the tests? If so you, like many others I have seen, may have missed the fact that the leakage (mains or applied part) had been increasing over time which would indicate a possible fault occurring. This is especially true of ECG probes who may pass a test to the required limits but may have high leakage indicating imminent failure (or at the least a bio hazard).

In IEC 62353 a reduced set of tests are conducted to save time and simplify things but in order to add a reasonable level of safety there is the requirement to compare test results to enable one to see trends and investigate before the unit poses a danger.

Without suitable records (paper or electronic) there would be no to prove legally that a device was maintained correctly.

We should not knock the recording of test data just because some do not see the point in doing it. The amount of data is not that high, especially if IEC 62353 is adopted. After all if we go by what many are saying that equipment never fails electrical safety tests then why bother testing at all?

Mike.

OK, here we go ... Biomed 101. Come on, Granny ... get sucking on those eggs!

First of all, let’s agree terms. By biomed I am referring to the in-house technical support of medical equipment, carried out by resident technicians employed by (or closely allied with) the hospital. As we all know, there are other ways of supporting in-service equipment, but let’s stick with the in-house biomed model for sake of argument.

As I never tire of repeating, the raison d'être of the biomed department is PM. From the dawns of biomed time, we have always done our regular "inspections" aimed at ensuring that the kit is kept in good shape. Myself I like the terminology (that originated from ECRI):- I/PM. Inspection(s) and Preventive Maintenance. After all these years, if biomeds are still not wholeheartedly on board with the notion of I/PM, and indeed actively engaged in carrying out an I/PM program, then (quite frankly) they may as well shut up shop, as they’re not doing any good.

(And I am aware that some biomed shops see things somewhat differently. Basically they just hang-out in the workshop waiting for jobs to come to them. They are wrong, the management is wrong, and the service they provide is sub-standard. To paraphrase John Sandham, they are being reactive, but not proactive! This is not the way!)

Secondly, electrical safety testing is (and always has been) part of I/PM. If anyone disagrees, then they’re also just plain wrong! And it has also always been standard practice to carry out EST following a repair. It’s all just a matter of common sense after all.

If you don’t document the work you have carried out, then as far as "the record" is concerned it was never done! That’s why biomed also needs a decent database system to log, record and control the work.

So, there you have it. Three easy steps to true enlightenment:-

1) Embrace I/PM
2) Carry out EST as part of I/PM
3) Record your work in a database system

Folks, this stuff is not rocket science!

A quick word about "standards". It doesn’t really matter much which one you follow. In real terms, they are all much of a muchness, and even if you look closely you will be unlikely to distinguish between them (in terms of the rationale behind them, allowable leakage currents etc.). To my mind, you may as well use the latest one, which happens to be IEC 62353. There is no need to go to the nth degree of esoteria. Just stick to the basic tests, because that is all that’s required at first line. And ... I would suggest always following the latest equipment management "guidelines" too. As far as I’m aware, in the UK that would be DB 2006(05). It’s there, and it’s an official document, so why not use it? (and section 4.4 even lays out, in reasonably clear terms, the legal requirement for electrical safety testing, and goes as far as to say "these include pre-use testing of new devices in addition to subsequent maintenance tests").

But finally, take a look through John's articles ... they are generally well-reasoned, and up to date.

If kit never fails, maybe it's because it's being well maintained.

But I'm interested in the where's and how's of recording EST results. Primarily in the tester itself, I should imagine ... but then what? Downloading into a PC? Which software? What is the (file) format? Can the data be analyzed easily, and retrospectively, etc., etc.

Also, if a guy doesn't have the latest tester, how does he check against the earlier results (if indeed this is worth the effort ... personally I doubt it ... it kit passes it passes, if it fails it fails, regardless of what was going on at the previous I/PM).

Comparison of present to previous test results would probably be quite futile given almost all the kit nowadays has a detachable IEC mains lead. Variations would be bound to occur on mains side results due to swapping of leads. The danger is then that a considerate techie will waste precious time investigating something insignificant, causing time pressures elswhere on significant risks. Also since it's the mains lead itself that's the point of failure, tracking them would be more usefull than fretting over 35 microamps higher earth leakage on the latest test.
Several years ago I tried serial numbering IEC leads and had to drop it because it took too long! The only way it could be made practical would be to instigate it as part of the acceptance procedure so numbers are phased in. Haven't tried that yet.
As regards patient leakage. I have never seen a "failing" isolation circuit. It either works or (typicaly post defib pulse) doesn't. In which case you will also have no patient signal on that parameter. I haven't had an isolation breakdown in the last 18 years the kit is so well engineered these days.
Marc

... so why are we talking about retaining EST results, then?

In order to PROVE; 1. your tests were passes 2. the test was the correct one for that type of device 3. there were some leakage values to indicate that the IUT was connected during test 4. that there was a current drawn by the IUT to demonstrate that it was turned on during test etc etc etc.
Downloading tests takes less than 15 minutes per week. No one should be deleting results these days.
Marc

The fact that most medical electrical equipment never fails an electrical safety tests is testament to the good design of modern equipment.

It does not mean we don't need to test and it certainly doesn't remove the need to compare previous results to see if there is an upward trend in leakage values, which would indicate a potential imminent failure, especially in the case of ultrasound transducers. Simply using the test limits (60601 or 62353 etc.) as a guide is not really acceptable for routine field testing as it could lull you into a false sense of security (again especially true when testing US probes).

Test equipment manufactures should be encouraged to produce test gear and software that makes the task of testing and recording, including previous test comparisons, as simple as possible so there is less room for error. This can only increase the level of safety already designed into the equipment which surely must be a good thing?

Yes, but the real issue here is the recording, storing and analyzing of EST results. What we want to discuss is how to go about that. How's it done, the best way of doing it, how to refer back (it needs to be easy, or else it will be skipped), how to analyze previous results (if, indeed, this is actually worthwhile). That sort of stuff ... bearing in mind that not every body has access to the latest testers (eg, Rigel 288's).