In the first part of our blog on the future of IEC 60601-1 we looked at the topics in the forthcoming amendment 2. In this second part of our blog we concentrate on some of the topics that might be added to a wish list for a future revision of IEC 60601-1.
Over many years working as a consultancy you begin to build up a picture of the tricky topics in 60601. The one that is definitely at the top of the list is insulation (or isolation) diagrams. 60601 at present does not reference insulation diagrams, but ultimately this type of diagram is one of the most important tools in helping understand the challenges in section 8 on Electrical Hazards. Design teams need to have a full understanding of the isolation landscape and test houses will generally include an insulation diagram at the start of the 60601-1 report.
|Insulation Type||Voltage||Required Creepage||Required Clearance||Measured|
Getting your head around the requirements for means of patient protection (MOPP) and means of operator protection (MOOP) coupled with the considerations for basic, supplementary and reinforced insulation is never an easy exercise and is further complicated by the understanding of APPLIED PARTS, PATIENT CONNECTION and the scope of ME EQUIPMENT. The latter group of characteristics does have good representation in 60601, through a detailed set of diagrams in the rationale defining the scope of APPLIED PARTS in relation to ME EQUIPMENT.
This philosophy could also be applied to define a set of isolation diagram examples, explaining how these could relate to a given device type. Figures 3 and 4 in 60601 are helpful in gaining an understanding of different elements can be considered, but not in understanding the isolation requirements.
The PEMS Bypass
We have previously written blogs on the importance of section 14 of IEC 60601-1 (programmable medical electrical system – PEMS) as providing a systems level view of ME Equipment and its role in safety relevant design. At present based on the presence (or lack) of programmable electronic subsystems (PESS) it is possible to omit this section e.g. in the case of a hardware only device. As section 14 defines many of the key architectural considerations for safety relevant devices then it would be desirable to make this section relevant for all devices but scale the level of rigour based on device risk.
Based on the fact basic safety forms part of the title of each standard in the 60601 series, it is highly unlikely that the term would disappear, but as 60601 is now very much risk driven, basic safety has really become a subset of RISK CONTROL measures
Components with High-Integrity Characteristics
This is another section in 60601 where more examples of how to realise the flowchart of Figure 5 would be very helpful. The rational for section 4.9 could reference applicable standards and methodologies to help verify the acceptance.
By Alastair Walker, Consultant