Are Overload Test Results expected to be maintained through out Life of Product?

[Nancy Allen]

Hoping someone can help...
Here are the facts:
We make mechanical (non electrical) Class ! devices. These attach to surgical tables and are used to position patients in the operating room.
When we design our products, we do overload testing to a 2.2 factor of safety. We base this testing on a test found in:IEC 60601-2-46Medical electrical equipment –Part 2-46articular requirements for the safety of operating tables, though we do not reference the standard in our CE self certification

Life testing is performed based on 5 years of use within the range of the specification (1X) rather than the 2.2 overload weight.
Here are the questions:
From a regulatory standpoint, is there a requirement (or if not a requirement, the expectation) that the 2.2 safety factor must be maintained through out the life of the product, or only that the product remain within specification.? The 60601 standard does not provide any time period for 2.2 load testing.
Assuming we don't use the 2.2 factor of safety after initial load testing, would the expectation be that the 2,2 should be maintained at least when FAI tested out of box by a customer, or should the testing be done to the spec?

Thanks much for any thoughts on this!

 

[Peter Selvey]

The mechanical test with a safety factor is normally time limited (e.g. 1min). This time together with the safety factor is intended to be representative of the lifetime stress on the device (e.g. 2.2 x rated load for 1 min shows the equipment can handle rated load for 10 years).

IEC 60601-1:2005, Clause 9.8.2 (which has the similar test as in IEC 60601-2-46) clearly indicates the safety factor test (1 minute) is intended to show the suitability for the service life. Also if you consider some of the higher safety factors in that clause (safety factors 2.5 - 12), it is clear that using these values for lifetime calculations would result in huge over design. Consider a normal load of 100kg rating x safety factor of 8, and then try to design the equipment for 10 years with 800kg rather than 100kg. These tests are really intended for just for 1 minute.