Hi , these non-return-valves (NRVs) can be a problem on old stoves. If they are just sticking they can sometimes be freed-up by filling the pump-chamber with alcohol or kerosene, re-inserting the pump piston, tightening its cap and applying pressure. I hold the tank and rest the pump head against a door post or piece of solid wood. I then lean on it until the pump goes down into the cylinder and the liquid is ejected into the tank. If however you are having a paraffin back-flow problem, then as you realise, you need to remove the NRV. There is a special key for this but as you have a workshop you can easily make one. The flats on the head of the NRV which you need to latch onto are typically just under 5mm wide. If you get a 9in to 12in length of mild steel bar, and cut a notch about 5.1mm wide, and 5mm deep. at the bottom end, put a hole and tommy-bar on the other end, you have a homemade key which should do the job. The key has to be a snug fit on the NRV head and you need to apply some downward pressure as you turn the key, to stop it rising off, and damaging the soft brass head of the NRV. It is a normal screw fitting so you turn anti-clockwise to unscrew the NRV. The whole stove has likely been sitting dry for many years, so an overnight soak of the NRV in releasing oil, before attempting the dismantling, is a good idea. There has been some recent correspondence on the CCS website, initiated by my good friend Exeter Yak, who manufactures beautiful replacement parts for these veteran brass stoves. He is now producing replacement springs and washer "buckets" for NRVs. The actual washer is made of nitrile rubber, which resists the effect of kerosene in use. If you have 2mm thick nitrile sheet, you can punch plenty of washers. Some people get a large diameter nitrile rubber "O" ring, of about 3-4mm circular section, and cut short lengths to make washers. Your NRV washer was likely made in the 1960's or earlier so it might be getting a bit hard and tired by now! The NRV valve opens at about 10psi pressure, and allows air to enter the tank.The pump has to overcome this 10psi, plus any existing pressure in the tank. At the start of pumping this is only the hydrostatic head of the kerosene in the tank. However, as you keep pumping the back-pressure becomes greater. The 10psi NRV pressure setting, at rest, is really there to stop kerosene flowing back into the pump cylinder. I should say that the NRV valves generally have a soft lead washer, which helps them seal onto the tank seating. This washer sometimes stays in place when you extract the NRV and you are not aware of its existence. It is good to have the washer as if the NRV has been overtightened to get a fluid-tight seal they can be the very devil to remove later, and you sometimes are driven to un-solder the whole pump assembly to get access from the back! Good Luck with your fettling. Regards, Kerophile.
Nice Stove Hazet, very nice in fact. I concur with all that George says, in particular about fitting washers underneath your NRV's - it makes them much easier to remove. Apparently they are no longer fitted with lead washers, and a couple of months back I experimented with using different material. Fitted to a Radius 17 and fired up about once a week over the last 2 months . . . . . . and the pump tube is nice and dry, so seemingly no leaks I would always remove and replace the NRV complete on an old stove as you never know the condition of the nitrile seal or the spring, and I use this beast which I cobbled up myself with an angle grinder and a file : My next project will be one with a tapered fit, to remove one which collapsed during normal extraction, it is one of the style with a slot right across the head rather than just a hole and so is weaker as a result . . . . . poor design I reckon.
wow, thanks for all the info. i had looked around the site a bit and had seen a few pics of the tool i needed to make, so thanks for the pics and the other info is much appreciated. i will look further into possible causes of the leak and how to fix it. thanks! Mark, i don't know what to say other than thank you so much for your very kind offer. time is running out (heck, the campout is at the end of next week!), and it is looking less and less like i will be able to make it, although i am still trying. but to have my stove worked on by the hands of the masters would be great, i'd love to learn something or two (or 40). Jon
Hazent watch out like as master of all things watch out if he brings them tools from the 1700 period. They don't work on stoves
Hey, Hazet, You are very welcome, Jon! If you can't come for the weekend, try to make it for a day trip. I think that a few others are planning to drop by, on Saturday, and that would be a fine time to meet as many as will probably show up. We can fettle your stove together, and see how it turns out!! Now, one thing: Ain't no "masters", as far as I know, in the lot of us!!! Every Mother's Son on this site, and all that visit, are still learning, so none of us would qualify as a "master" of much! 8) But, we all teach each other, and we all learn from each other, and that's the most cool thing about the Lads that hang out here at CCS!!! It falls upon us all to learn and to teach, and along the way, we all have a flat-out blast!! 8) 8) In any case, I'll bring the tools and stuff, just in case you can show up, and we'll have some fun with your stove!! Take care, and God Bless! Every Good Wish, Doc P.S. If you do get to visit, why not bring your Coleman Solus, too, and we'll see about getting that one up and running, as well. Worth a try, anyway, eh?
Hi, I was fettling a 1930's Juwel No.1 today and decided to remove the NRV for inspection. Luckily this was easy with a new NRV key I had just been given as a birthday present. Here are some photos of the interesting NRV I removed from the stove: The NRV looks to be pretty conventional at first glance. However, the device is actually constructed differently from most of the NRVs I am familiar with. You expose the spring , piston and valve by unscrewing the base of the NRV. In this case the Juwel valve was in good condition and still had plenty of elasticity. It was a light tan in colour and could well have been natural cork. I turned it over, put it back in its carrier and hopefully it will be good for another 70+ years. Best Regards, Kerophile.
Hi Kero; I wish to thank you very much for your great posts. I enjoyed very much reading them and want to thank you for sharing your experience with the rest of us. There are two posts about removing and re-soldering pump cylinders. Both have detailed pictures and one of them is by a member who had made handles with threaded rods to be used for removing cylinders as solder is melted. I have tried to find and read them again but could not locate them. Could you kindly help me find them? yours Daryoush
Hi Daryoush, Thanks for your kind words. Have a look at these threads: https://classiccampstoves.com/threads/6371 https://classiccampstoves.com/posts/193583 https://classiccampstoves.com/threads/20444 Best Regards, Kerophile.
The 1930s Juwel NRV pictured above is the same construction as I have recently found in an unmolested and very little used early 1950s Burmos No.21. The only differences with the one pulled from the Burmos were that the Burmos had a slightly longer spring tube and the screw driver slot in the end was exceptionally (effectively unusably) shallow. The Bumos NRV pip was also cork, it was this that had required replacement. I checked but could not find any photos of a Burmos 21 with this type of NRV, has anyone else come across one? Ian. @kerophile @Spiritburner
Hi @igh371 Hi Ian, the above post reports my only encounter with one of these unusual NRVs. Best Regards, George.
Great info Kerophile....I'm having a backflow problem with my 17b tourist, will the tool be the same to make? regards John
Hi @john watson the dimensions at the start of the thread should be good for your stove. Best Regards, Kerphile.
I've had good luck working with pips so far. However, while working on my Enders Benzin-Baby 9063, the large rubber washer that held the pump shaft onto the cap of the pump had turned into cement. It took me four hours over one weekend (and that's not an exaggeration) to break, dig, soak in Kroil, heat and dissolve with acetone, the gasket. When the cap finally broke free from the shaft I was elated! Oh, what we do to save these gems and the joy it brings us is huge!
There is mention of a soft lead NRV washer earlier on this thread… I suspect I’m not going to like the answer but is this it? It was rattling around inside the tank until I shook it out… without it I’m guessing I’ll have some issues? c
@Automedon , no that is not the NRV lead seal. I don't reconise what that is. You can see the lead seal in pictures 5 and 6 here. NRV repair.
Interesting… and that begs the question, what is it from? It’s lead and I’m guessing must have had some kind of purpose? Oh well… best Chris
