The Cove Business Standards Discussion Forums
Go Back   The Elsmar Cove Business Systems and Standards Discussion Forums > > >
Forum Username

Elsmar Cove Forum Visitor Notice(s)

Wooden Line

Defib Protected Applied Parts: 4mm clearance/creepage? - Page 2

Monitor the Elsmar Forum
Courtesy Quick Links


Links Elsmar Cove visitors will find useful in the quest for knowledge and support:

Jennifer Kirley's
Conway Business Services


Howard's
International Quality Services


Marcelo Antunes'
SQR Consulting, and
Medical Devices Expert Forum


Bob Doering
Bob Doering's Blogs and,
Correct SPC - Precision Machining


Ajit Basrur
Claritas Consulting, LLC



International Standards Bodies - World Wide Standards Bodies

AIAG - Automotive Industry Action Group

ASQ - American Society for Quality

International Organization for Standardization - ISO Standards and Information

NIST's Engineering Statistics Handbook

IRCA - International Register of Certified Auditors

SAE - Society of Automotive Engineers

Quality Digest

IEST - Institute of Environmental Sciences and Technology


Some Related Topic Tags
creepage distance, iec 60601 - medical electrical equipment, medical device electronics and electrical equipment, safety (general)
Reply
 
Thread Tools Search this Thread Rating: Thread Rating: 1 votes, 5.00 average. Display Modes
  Post Number #9  
Old 16th April 2018, 10:27 AM
MedMartin

 
 
Total Posts: 33
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

Hi,

as I understand it, the 4 mm is also required within one applied part.
To use your example between ECG leads are also requirements for differential mode testing and energy reduction testing acc. to 60601-1.
Often there are resistors included in the ECG cable with adequate clearance and creepage distances and pulse handling capability. Then there is no requirement on the connector.

Best regards
Martin
Thanks to MedMartin for your informative Post and/or Attachment!

Sponsored Links
  Post Number #10  
Old 18th April 2018, 09:10 PM
Peter Selvey

 
 
Total Posts: 907
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

Would have been good to jump in early here.

The limit of 4mm in 8.9.1.15 is intended to keep the isolation barrier at the normal 4.0mm limit for BF-CF isolation, and ignore the 5kV pulse in cr/cl assessments. Without this clause, manufacturers could be asked for distances up to 126mm (5kV, table 12).

So it is a relaxation for most devices. There are two scenarios where it is not a relaxation: where a BF/CF device intended only for 100-120V regions would normally have a limit of 3.0mm, and for Type B equipment which has no BF/CF isolation, in this case 8.9.1.15 would represent a increased limit.

The distance only applies to the 1.5kV.4mm barrier between the applied part (ECG circuit) and other parts as is normally required for BF/CF classified applied parts. It does not apply between parts of the circuit, for example between RA and LA electrodes. The reason is a little complicated but it comes down to understanding the whole purpose of Clause 8 and means of protection. Any requirement inside of Clause 8 (8.7, 8.8, 8.9 etc) has to be tied back to a identified MOP used to meet 8.1 and 8.4.

That does not mean the distances between RA and LA (for example) before the voltage limiting device are not important. I have seen cases of connectors with 0.3mm clearance being used at this point which makes no sense. Generally, for a rounded pads, 1mm is enough to pass 5kV pulse without breakdown. But anyway, it is an risk/engineering decision, not a limit from Clause 8.
  Post Number #11  
Old 2nd May 2018, 10:17 AM
Roland chung

 
 
Total Posts: 469
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

@ Peter

Have events been reported because the RA and LA pins are too close?
  Post Number #12  
Old 2nd May 2018, 11:38 AM
Peter Selvey

 
 
Total Posts: 907
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

No reports of incidents, but the situation does not lend itself to reporting. If the patient is being shocked in an attempt restart the heart, which does not work because the energy is being shunted due to pins that are 0.3mm apart, there is not going to be a smoking gun that "hey look over here, it was this device".
  Post Number #13  
Old 2nd May 2018, 12:23 PM
Roland chung

 
 
Total Posts: 469
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

Maybe this hypothetical situation is not that critical. You must know that there is a lot of defibrillation going on every day around the world, and further, it is unlikely that both defibrillator electrodes will contact the ECG electrodes directly.
  Post Number #14  
Old 7th May 2018, 04:32 AM
Peter Selvey

 
 
Total Posts: 907
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

The test includes a 400Ω resistor which (I guess) is intended to simulate the patient's resistance between defib pads and the ECG electrodes. So the test does represent more like normal condition, not direct contact.

In addition to the shunting of energy, there is also a risk of burns at the ECG electrodes, and maybe most importantly saturating or damaging the electrodes so they no longer useful for monitoring. So, it makes sense to have a well designed front ECG front end that handles the high voltage without causing any significant current to flow into the ECG. Full stop.

I guess the one point of overkill in the standard is 5kV, which apparently no-one uses anymore. These days they are typically below 2kV, and probably means around 1.5kV at the ECG electrodes. Even so, good engineering practice would be to design any parts of the circuit before the current limiting resistor (typically 10kΩ) to handle the high voltage without breakdown.
Reply

Lower Navigation Bar
Go Back   The Elsmar Cove Business Systems and Standards Discussion Forums > > >

Bookmarks



Visitors Currently Viewing this Thread: 1 (0 Registered Visitors (Members) and 1 Unregistered Guest Visitors)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Forum Search
Display Modes Rate Thread Content
Rate Thread Content:

Forum Posting Settings
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Emoticons are On
[IMG] code is On
HTML code is Off


Similar Discussion Threads
Discussion Thread Title Thread Starter Forum Replies Last Post or Poll Vote
Components in parallel to creepage\clearance rothlis IEC 60601 - Medical Electrical Equipment Safety Standards Series 9 13th February 2018 10:00 PM
IEC 60601 Creepage and Clearance Requirements on PCB AndrewJ IEC 60601 - Medical Electrical Equipment Safety Standards Series 5 19th January 2017 06:06 PM
MOP (Means Of Protection) - Creepage and Clearance questions fonk140 IEC 60601 - Medical Electrical Equipment Safety Standards Series 19 25th May 2015 02:56 AM
Creepage and air clearance under vacuum conditions Roland chung IEC 60601 - Medical Electrical Equipment Safety Standards Series 2 9th May 2013 11:12 AM
PCB Creepage and Air Clearance on 8 Layer Boards Nissim Shaked IEC 60601 - Medical Electrical Equipment Safety Standards Series 3 12th February 2013 07:49 AM



The time now is 04:33 PM. All times are GMT -4.
Your time zone can be changed in your UserCP --> Options.



Misc. Internal Links


NOTE: This forum uses "Cookies"