Interpretation of 60601-1 Figure J.5 (Isolation, example 5) for a rechargeable, battery operated device

[FrancoisA]

Dear all

I have a question related to interpretation of 60601-1, Figure J.5.
Our device is a body worn, 4.2V rechargeable battery operated device.
The design of the device makes it impossible to recharge it when in use on the patient, and this will be re-enforced in the IFUs.
It has no PATIENT CONNECTION, however the risks analysis shows that the charging connector itself might come in contact with the PATIENT in normal conditions.

As Figure J.5 suggests, do we need to provide 2 MOPPs between the internal electronics ( / the battery itself) and the charging connector (considered as an APPLIED PART as conclusion of the risks analysis) ?

If so, is it enough to justify that:

1 - The internal charging circuit comprises a diode, preventing reverse current flowing back from the battery to the connector, through this circuit
2 - Would 1 fail in SFC, and considering the test conditions of Figure 15, both the positive and negative pins of the charging connector would be shorted during the test, that this would short the battery, and PCM of the battery would then switch the device off (the battery is 62133-2 certified and tested for shorts both at pack and cell levels)

Could 1 and 2 be considered as the required MOPPS ?

Thanks, François

 

[Peter Selvey]

The rationale in the standard is a little misleading: a valid risk assessment is based on the probability of harm, not the probability of an event in the sequence. So, although the patient might touch the connector in normal condition, this alone is not enough to trigger the "quasi applied part" treatment. Rather, the real question is there any reasonable probability of harm if the patient contacts the part?

In most cases no, but in some cases yes. It needs more information about the function of the device and the actual applied parts to judge if this is a reasonable case.

If it is a genuine "quasi applied part", the justification 1 and 2 don't make sense, at least to me. It sounds more like there is no actual risk from the patient contacting the parts, but because the standard identifies the issue, there's a rough attempt to make up some kind of justification to avoid taking any action. It happens a lot in risk management.