Aktopp back in 2007 has about the clearest info I have found on the internal workings of the Optimus Pump Cap. These two images were like a beam of light revealing the simple and brilliant engineering that incorporates both an NRV and SRV into the cap. (I have taken the liberty to take his images from photobucket and put them into this post via the image uploader rather than using his original photbucket links ) The thread where aktopp posted these is here: https://classiccampstoves.com/threads/5518 That thread has some back-and-forth discussion about the safety of repairing the pump cap vs just replacing it. So are “new” caps actually NEW? If one orders a replacement pump cap does it have seals from 1970+ or are they new--say to this decade? It seems that replacing the NRV seal would not only be safe but prudent in an old cap. Replacing the o-ring SRV may or may not depending upon the strength of the spring….but if one just put a 1970 unfired pump cap on their stove is it actually any safer then replacing both seals in your old cap?
Took some more digging but I believe I have found a very good thread about this topic... https://classiccampstoves.com/threads/10615
Yes, John that is an excellent post. So does anyone actually know the age of "NEW" pump caps? It seems that refitting the seals in these old caps would be a much more prudent idea than trusting that some "New" cap that is 3 decades old would somehow be a better or a safer choice.
I'd say the most recent of Swedish manufacture would be 70's at a guess. Oriental clones of a Svea/Optimus 123 might produce newer examples of a cap/SRV ensemble. So, not exactly new then and 'unused' doesn't really count when the material that degrades (the nitrile seal) is susceptible to shelf life and not just the heat and pressure when in use on a stove. John
I think I will try grinding a hex to penta...as I agree, reworking the SRV and NRV is a more prudent than betting on a 3+decade 'new' seal. Thanks John.
