Quote: (Originally Posted by
AD_ward9)
The reason the scrubber falls into 61508 in an eCCR, is throughout 61508 there is an end to end requirement: one is not allowed to say, "our electronics ends here, so the fact that it is connected to a stick of dynamite with a burning fuse is not our concern, so the whole thing must have a SIL 4 safety level as that is what our electronics has". Does not wash. If the electronics is controlling the mechanics, then the mechanics and electronics together form the system. If the electronics is just injecting O2 but the system must remove CO2 for the user to stay alive, then the CO2 control falls into 61508. Just like on aircraft: you cannot say the wings are excluded from the safety case.
On both ethical and commercial grounds, we will apply the regulations exactly as they are written. EN14143 is easy - almost any decent design can meet it if the EN61508 compliance is ignored. EN61508 involves much more work. HSE are just really starting to pick up on this. Soon it will be just like trying to sell product that does not meet EN14143, if it does not meet EN61508 it has neither certification, so cannot have the CE mark. I think that will be good for diving generally, making it more accessible and with fewer personal tragedies.
Cheers,
Alex
In a nut shell the problem lies in the fact that the writers of 14143 had no idea of the implications of including 61508 in the clause as they did. The clause I quoted earlier is actually an oxymoron. This allows a reasonable argument for interpretation and "due dilligence" in the rationale that is put forward for the scrubber pack. We both know that no scrubber pack, even micropore can meet SIL4 without diversity, redundancy and monitoring. Ergo, to comply with the system requirments of a SIL4 design with current scrubber technology is nigh on impossible.
My advice would be to approach the certification body and find their interpretation of the clause and more importantly the competance of the person carrying out the certification part inclusive of 61508. As far as I know, there are no practitioners for 61508 appointed under the PPE directive. The CASS route you have chosen is by far the best approach.
IF ou can comply, then that is very good news for you and
very bad news for the competition.
I would suggest that in the case of any market surveillance enforcement under this clause would invoke the safeguarding clause and dispute of the standard (14143) in opposite corners.
If you do have problems in ensuring the scrubber meets SIL4, which I do expect, then the above may be your only recourse. This was the conclusion(?) of the head of the electrical and control system unit at the HSE whom I was casually chatting to today. I hope his opinion would be helpful to you.
Summary? Sure. To apply 14143 literally is predisposed to contradiction. 61508 would be for the entire system as you stated above. The official Journal has applied only the clause for presumtion of compliance leading to argument. The HSE say your right, but you can get out of it because I'm right if you argue it correctly. Go figure.
I can see some manufacturers getting into trouble if the certification of their products was challenged.
Brent