EBME Forums Forums Maintenance Technical Assistance Class I electrical safety test on Class II equipment

Jerry,

If I received a letter like the one you have then I wouldn't be satisfied with the answer. Personally speeaking I would contact the MHRA for advice - I don't think it's beyond a biomedical engineering graduate to find their contact details.....

Marcel,

The references are the general, collateral and particular BS standards. I have found problems in the past with the classification of new devices and stated leakage limits on applied parts. I have found earth and enclosure limits close to the maximum values. Without knowing what you're testing and why then you can't pick upon this sort of thing in my opinion.

Geoff,

In my opinion it's easier to do applied parts tests than enclosure, earth leakage and insulation resistance between enclosure and mains parts, for example. Once the applied parts have been selected, connected and the safety analyser has been configured appropriately then it does all the work - only real concern is whether to do mains on applied part SFC for BF/CF. No probing required.

Admittedly, looking at proposed standards, in future it may not be necessary to routinely test applied parts nor perform some leakage tests under SFC, e.g. enclosure leakage. But items may fail routine tests if the leakage of devices can be shown to be within 10% of the maximum allowed leakage - thus limits may not need to be exceeded for a fail.

Safety testing is not the be all and end all really but we need to know what's being tested and why. Lose that knowledge and some manufacturers will try to get away with fobbing us off with any old excuse for equipment. The example above may be an illustration of this if Jerry has his facts right.

Hi all,

just for interest. I am not sure, if you know a B.Braun´s Perfusor compact. But the whole machine is ClassII clasified (marked on its bottom).

When you get the new perfusor from B.Braun, the "PC mains cable" is enclosed. And Mr. Braun says: Just do a whole cable measuring for protective earth conductor resistance. So you "disintegrate" the machine and measure just a part of that.

Isn´t it wonderfull?

Hi All,

I've found the MDA (now MHRA) DB9801 Supplement 1 December 1999 Device Bulletin Update "Checks and tests for newly delivered medical devices" In annnex 2 Background - Pre-Use Tests, page 20 there is a long discussion concerning electrical safety testing of medical devices. After extensive studies the final paragraph of page 21 states (quote):
"There is little evidence that electrically-powered medical devices are a special hazard and no justification for a disproportionate allocation of resources to test them - as compared to non-electrical products with similar risk levels. This document presents a compromise position, recognising that some electrical testing is legally necessary (see Section 3), and that the decision to eliminate some of the tests currently in use is a difficult one to take."

The paragraph before this talks about "one hospital clincal engineering department that had conducted 13000 electrical safety tests on new equipment without finding a single electrically unsafe device."

It seems to me that it would be useful if the MHRA were to publish a definative guide concerning electrical safety testing of medical equipment "applied parts", particularly those such as SPO2 finger probes, blood pressure cuffs, IV sets etc which don't have a normal conducting path to the patient.

Some manufacuturers do advise that you test patient leakage current for their probes. For example, Toshiba recommend that their ultrasound probes used with their diagnostic ultrasound machines such as the Powervision 6000 are tested by immersing them in saline with a small stainless steel plate connected to the applied parts of the safety tester. It's normal to get 2 -3 microamp leakage current per probe when you do this.

Ian

I too read that comment in DB9801 about the department that ran 13000 tests on new items without a single failure and suspected that either the engineers worked for the richest hospital on earth (13000 new bits of kit?) or they were checking electric toothbrushes, hairdryers etc as well as medical stuff.
Even I don't test those.

Marc

Marc,

You may be right, who knows what people use as "medical" equipment in their hospitals and I agree 13000 items are a lot of medical equipment. Our hospital has only some 2000 items. However, I'm inclined to agree with the conclusion that electrical safety is no more important than that the equipment functions properly when "attached" to the patient.

Clearly, testing for electrical safety of medical equipment is very important, especially where there is an electrical connection to the patient.
However, it seems to me that we must be sensible about this. In our unit we try to test all medical equipment at least once per year for electrical safety and we always test it if the equipment has be "opened up" for repair or service irrespective of its due test date.
We use an automated electrical safety analyser (Bio-Tek 601) to save time, as I'm sure that many EBME's and MEMU's use. However, it's important that the technicians who are performing earth bonding, insulation tests, enclosure leakage, patient leakage etc understand why these tests are carried out and the danger to the patient if any test fails.I always explain to trainees why and how these test are performed. But I don't think that we should go overboard and spend hours testing an individual item of equipment, unless engineer's have got time on their hands with nothing better to do, that's fine.
In my view, it's important that everyone in the department follows the same protocol so that all testing is consistant whether it's electrical safety or functional testing.

I think you chaps are missing the point; By electrical safety testing all equipment held within a hospital, simply ensures that technicians ascertain a true servicability state of all equipment by carrying out visual, functional and electrical safety checks.

Otherwise, the vast majority of equipment would simply be left to rot until it actually breaks down. So it effectively becomes a safety blanket. Any minor bumps and bruises found can then be nipped in the bud as opposed to acumulating damage over time.

It comes as no supprise that very few items are ever found to be faulty. It again does not supprise me when some technicians take electrical safety testing to the extreme and perform build standard tests.

So in truth electrical safety tests beit BSEN60601-1, HEI95 - 98 MDADB9801 etc etc are used by managers to cover a multitude of sins.

DB9801 requires NHS departments to do tests that include applied parts leakage where applicable. BS EN 60601, etc, etc are manufacturing standards.

We use safety tests to establish whether equipment is safe on installation, i.e. acceptance, and to give an idea of whether a combination of equipment used in a medical system is safe to use, i.e. baseline insulation resistance, earth-bond and leakage measurements for example.

Leakages vary as interconnected components are changed so we also do standalone and system tests to determine whether we need to fit seperating transformers to medical systems or assess the risk they may present in certain applications.

Devices with Type B applied parts are an example of an applied part that can present a more significant risk when used in certain environments. It's not as cut and dry as implying applied parts tests are "type-tests" thus uneccessary.

Safety testing using a safety analyser shouldn't be used as an excuse for doing basic maintenance checks, i.e. visual and physical inspection, including functional verification.

Hello Rob,

I'd be interested to know in what way that "I'm missing the point" (that's if you are refering to myself?)
I thought that it goes without question that when you check and test all medical equipment you carry out:
(1)A visual check of case, leads, connectors, plugs, sockets,etc.
(2)A mechanical check of any moving parts.
(3)A functional check
(4)Checks that the equipment is within manufacturers spec.
(5)An electrical safety check.
You also carry out any other tests that the manufacturer recommends or is in the test protocol for your department. These tests are either carried out annually or at any other interval that the manufacturer recommends or that your department has decided is appropriate for the equipment concerned. We call this Planned Preventive Maintenance (PPM's) and any EMBE unit or MEMU who doesn't do this isn't doing its job properly.
My point was, how much time and to what degree you devote to No. (5). It all depends on the equipment and the likly risk involved. Clearly, with interconnected systems there is much more of a problem when your looking at patient leakage currents than when your looking at a "stand alone" device.
Ian

There is a place for electrical safety testing even if some see it as a means of justifying routine inspections.

EST can be visual or electrical according to the Health and Safety Executive (HSE).

As the risk presented by the equipment becomes greater the more essential the requirement to ensure it is safe.

The point is that unless you actually perform an electrical safety test and document it you can't categorically state that a piece of equipment is electrically safe.

But Rob's point is worth summarizing:-

Electrical safety testing is part of PM (and not the other way around).

This issue has been threshed over endlessly on this very forum, and I doubt that anyone is labouring under any misunderstanding here.