my own view on the plug/fuse situation is that equipment with a detatchable lead should be fitted with a 10 amp fuse to 'protect the cable' that provides power to our nice piece of medical equipment.
The IEC 320 detachable mains plug is usually rated at 10A continuous. the cable attached to this is typically either 10A rated (1mm^2) or 6A (0.75mm^2) continuous. The moulded mains plug attached to this is typically 3A, 5A or 13A continuous depending upon the manufacturer and whether it's supplied by the device OEM or not.
It makes sense fusing to the value of the component in the mains lead with the lowest continuous current rating. We buy 2m and 3m RS 10A rated moulded detachable mains IEC leads these days (13A rated mains plug, 10A rated cable, 10A rated IEC320 plug) - they're more robust and when fused at 10A are fully interchangeable.
According to 60601-1 medical devices with detachable mains leads should be manufactured with fusing on both poles to to give L and N protection if mains is reversed. The fusing in the mains plug is intended to protect the mains cable and the intention of fusing the device is to protect the medical device only.
After a device is manufactured, unless it's disassembled or repaired, then it's unlikely that internal compnents will be disturbed so the significant risks associated with electrical safety issues will be due to failure of a component. If the device has been manufactured to 60601-1 for example then under any forseeable SFC then the risks should be acceptable.
One concern I have with the 3rd-edition 60601-1 manufacturing standard is that it is based more on the premise of risk assessment thus it's possible that we will see more "novel" interpretations of what are currently accepted methods of manufacture. I'm not against this but I believe that we could be put in a position where experienced engineers may have to adapt to new ways of thinking about risk RE: potential hazards.
I think 62353 may be the way forward for routine testing, i.e. routine PPM and after repair - it's already the norm in Austria and Germany under their product law I think. We probably don't need to test mains, enclosure and applied parts for SFC, except earth O/C. This should speed up safety testing as a routine but only by seconds in practice.
Acceptance testing guidelines, RE: EST, are in place in the NHS based upon DB9801 that refers to H&SAWA, etc. I think it's wise to perform EST routinely - it's the interval that EST is performed at, in my opinion, not whether it should be performed or not (on mains powered devices in particular). It's clear that IEC leads are particularly susceptible to hazardous failure so regular inspection is necessary.
Routine PPM, including EST, is necessary to ensure that equipment is inspected for physical damage and performance verification is carried out (due to the nature of the application and environment it's used in), not to dwell on EST above and beyond the really significant risks presented by damaged mains cables, exposed conductors, etc. Yes, EST is required on PPM - it can be visual and/or electrical according to HSE.
What's at issue is not whether EST should be carried out, it's what the appropriate intervals for PPM should be and whether there's a need to perform visual and electrical EST at every inspection. This obviously depends on the device, how robust it is, it's environment, usage and whether it's been disassembled or repaired, for example.
When safety testing does become a contentious issue is when it's carried out on acceptance when new products are introduced or when complex systems, e.g. video endoscopy stacks and IT connected medical devices, for use in high-risk patient areas are effectively being manufactured and commissioned in-house for use with other potentially high-risk devices, e.g. ESU, insufflators, lasers, anaesthetics, etc.
We have to consider the effects of active devices on patients who may be physically connected to multiple electrical or mechanical devices and vulnerable, i.e. incapacitated. We can't just ignore that there is a requirement for capable individuals to be aware of and analyse the risks under these circumstances - there's functional safety and clinical issues to consider a swell as electrical safety - it's part of the job.
When individuals on this site get the impression that others are "going over the top" when talking safety I think they may not realise that what's being discussed is safety as applied to manufacture, acceptance, routine testing and clinical use - they're not always distinct and seperate issues when considering evaluation of devices and incidents associated with them.
Some take-in the fundamentals to get a deeper understanding and others pick up what they need to do the job - what "level" safety related issues are discussed at depends on individuals' job-role, level of knowledge and experience.
