EBME Forums Forums Free discussion Free discussion Electric Shocks

W'eve had a couple of incidents where nurses have received minor electric shocks from medical equipment that was not plugged in!!
They got the jolts from touching the live and neutral prongs of the mains plug after removing the plugs from the mains outlet. Our Sherlock Holmes discovered that the culprit was the mains interference IEC connector in the equipment. Some IEC filters have capacitors across L&N whilst others have bleeder resistors of about 1Meg across the caps as well. [see RS catalogue Sept2000 book1 page 361/3 for different types & specs]
Are there any regs governing this?
Has anyone else come across this phenomina?

Yes !

It all depends at which point of the mains cycle the switch was turned off. Switch off when the mains is at a peak, and the caps store about 350 Volts DC which can't get away to anywhere because there's such bl...y good insulation between the live and neutral and the earth.

It hurts, too !

I remember the same scenario many years ago when I was working at Chester EBME. From memory (don't quote me) I think we had the manufacturer replace the mains inlet receptacle/filter - choosing a replacement from the RS catalogue was considered to be a little risky due to "illegal" modifications. Cheers.

WE HAVE JUST HAD AN INCIDENT OF A MIDWIFE RECEIVING ELECTRICAL SHOCK WHILE SWITCHING A MERIDIAN 800 FETAL MONITOR ON. THE SWITCH IS AT THE BCAK OF THE MACHINE. MDA AND HSE HAVE BEEN INFORMED. WHEN WE TESTED THE MONITOR, IT PASSED ALL THE SAFETY CHECKS. WE HAVE LEFT IT FOR MDA TO INVESTIGATE.

HAVE YOU HAD A SIMILAR INCIDENT?

ALEX

most electronic equipment standards place restriction on the accessible voltage across the plug pins - modern equipment ought to comply

for medical equipment, standard 60601-1 requires (clause 15) that 1sec after disconnecting the plug, the voltage between plug pins should be less than 60V
(to test this you should repeat disconnection & voltage measurement several times to try and catch disconnection at different points on the 50Hz cyle - obviously gretaest cahrge will be stored on capacitors if you can catch the cycle peak)


[This message has been edited by ged dean (edited 25-01-2001).]

Alex,
We have 3 Meridian 800 units, would be interested to hear the outcome from the MDA.

Have recived an answer from MDA myself regarding my original post. Will scan the letter in and post on the site presently....

HAVE A LOOK AT MDA SN 1999(19) RE DRAEGER PHOTOTHERAPY UNITS. AS STEVE EDGE SAYS ABOVE WE HAVE HAD THIS HAPPEN AT CHESTER A FEW TIMES ON VARIOUS PRODUCTS.

EG 140 SERIES VICKERS INCUBATORS,

SLIT LAMPS

PHOTOTHERAPY UNITS.

OTHER PRODUCTS OF OLD IN WALTON/FAZAKERLEY HOSPITAL.

AS STATED PREVIOUSLY, LOOK AT BS EN 60601-1
IT IS QUITE CLEARLY MENTIONED THERE.

We have another two on this theme:

(a) EME Infant Flow Driver

(b) SLE 2000 VPM Monitor for use with
their ventilator.

(a) is in the hands of the MDA at the moment.

(b) is about to be in the hands of the MDA.

Usual problem by the looks of it, non medical grade rf mains filters being used, no bleed resistor, etc.

Come on chaps the above kit is in your hospitals, why has this not been picked up before?

Replies please.

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[This message has been edited by JIM GAVIN (edited 19-04-2001).]

LIFEPAK 9 defibs do it too. Physio Control recognise the problem and lack of compliance with 60601 but have decided not to instigate any remedial action.





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Paul Jones
Principal Clinical Scientist

Equipment “incidents” getting you down? Things could be worse. Imagine having to replace the faulty mains leads on 14 million X-Boxes!

Check it out on http://www.chron.com/cs/CDA/ssistory.mpl/tech/news/3045726