We've been using our two Bowlfire heaters quite a bit lately. Not cold enough to have the central heating on during the day, but cool enough to need a little heat. They had been on for a couple of hours today when I went to give one of them a bit of a pump. After 3 or 4 pumps the pump knob shot back out with some force. Pumped it again and it did the same. I quickly released the tank pressure via the air screw and let the heater cool down. I have been told a number of times that an NRV cannot catastrophically fail, it will always be a slow leak. Well, I now know that it ain't true! I removed the pump and then the NRV to find that only the top part of the NRV came out. The pip, pip cup, spring and housing were rolling around inside the tank! Somehow, the bottom half of the NRV had managed to unscrew it'self. Bizarre. I know it was done up tight when I replaced the pip in the summer. I can only assume that the air going in under pressure from the pump had set up some sort of vibration in the NRV causing it to slowly unscrew . Has anyone else come across this? Terry
Not on a BBF but I've had 2-3 other items (one was a Monitor triple burner stove) where I've found the lower parts of an NRV in the bottom of the tank. Now I know how they got there!
Hi together, Once I experienced a sudden NRV failure during normal operation (not at pumping!) with my old Mewa lantern. I feel that it was good luck that I sat directly besides it when it happened. I managed to press in the pumpknob quickly and took it away from the puddle before the vapors reached anything hot (actually it ran with a 50:50 mix of petrol/kerosene). After that I still had to release the pressure from the running lamp, but fortunately that was no problem. It turned out that the rubber that I used for the NRV was obviously not suited for the petrol mix that was in the tank. Nowadays I'm very careful at selecting the proper material for sealings, and use mostly kerosene in lanterns which have the NRV only (and no positive shutoff valve like e.g. the Colemans). BR, Martin
It is true that normally an NRV fails with a slow leak but they can just let go. I have had it happen with an Optimus table lamp on display at a rally. So a rare occurance but this is one of the main reasons you don't run a lamp on gasoline if the pump NRV discharges into the fuel. ::Neil::
I can't help but believe it is old and worn NRVs that fail, correct? Surely a perfectly good and pliable rubber seal does not unexpectedly blow out does it? Only failures I've had is on parts that I should have replaced. Seems to me like a matter of lacking maintenance? Will
The NRV was not worn or old. The pip was a new Viton one fitted in August. The lower part of the NRV had simply unscrewed it'self from the upper part. It could have happened to a brand new NRV. No parts needed to be replaced, I simply reassembled it and it is now running happily 6 feet away from me. The only symptom before failure was that it had become easier to pump. I had assumed that this was just the sides of the pump leather smoothing out. In hindsight, I now realise that as the lower part of the NRV unscrewed, the passage of air into the tank was less restricted making pumping easier, but the pip still functioned correctly, preventing air escaping. It was only when the lower part finally disconnected that the pip could no longer form a seal and air escaped. An identical, but not the actual NRV: I suppose the moral of the story is: if a lamp or stove becomes easier to pump, check the NRV . Terry
Theres no locking mechanism on the bottom of the NRV so continual pressurising could cause it to unwind .maybe a bit of loctite on the threads would be a good move,,,,after all that bit is only nipped with finger pressure ,,if it needed to be tighter the knurling would have neen replaced with a hex.
Later Prentiss-Wabers addressed the issue with their internal pumps by placing a secondary cylinder with an air tube inside the fount into which the pump assembly screwed into from the outside. you had to unscrew it to do anything with the pip which was kept dry with this system. 1390107249-PW_tank.png
