Today I got home and in the mail was a box, it was from Pelam in Germany and it had this inside Now the back story is a few weeks ago i took a pic of my mixing tube right after shutdown it was a deep red color.. I sent the picture to Petromaxs facebook (as i thought it was a cool looking pic)and they said something was wrong, it should not be red and sent me this as a replacement... There is this 3mm thick washer, threaded to match the tube and installed as seen. There is also no "mixing paddle" for the fine tuning which from reading, is very hit or miss anyway Thoughts on the washer? None of pelams or petromax's stock pics show a tube like this.
Looks like a simple solution to just deflect a bit of heat. My ceramics glow but not the main tube as it should get cooled slightly from the incoming fuel/air mixture.
Getting a red hot/glowing flame spreader/lower mixing chamber or whatever you would call that and a ceramic burner after running a hot lantern is quite normal and there's nothing wrong with it. However, you should NOT be getting the J-tube mixing chamber red hot even after hours of burning. If so, something's really not right, which indicates back burning within the mixing chamber. The new design from Pelam looks interesting. Normally, the heat deflector/heatsink is in the form of a shallow, inverted steel dish. But that's for earlier designs with two flat nuts securing the J-tube to the inner hood. Later Petromax designs do not have that. Well in my opinion, the dish serves to deflect the rising heat from the mantle towards the coil of the Preston loop as well as away from the J-tube.
@a10egress That's a very interesting setup you have and hoping to see this setup in action. I do have a question for you because I'm very surprised you received a package from Pelam because as far as I know Pelam doesn't ship to the US. Of course you could have had it sent to someone in Canada.
@Norman Well, Maybe someone at Petromax pulled some strings and got Pelam to ship to me. I wont question their attention to the matter and likely its due to me having helped Petromax a little on the social media scene.
So you think that a "washer" will keep the heat away ? The amount of heat produced will heat up anything that is in the way up. Like said, glowing is normal as long as you don't get a backfire. But you wll hear that for sure. Btw: the flat ring (aka washer) will heat up the bridge it the inner hood faster, since it has more contact surface. That is the reason why the "old guys" used a concave form, to minimize heat transfer contact. Btw2: its not your mixing tube that is glowing red hot but the burner head. As far as the picture shows. Would be nice if you can experiment with the different set ups: no disc, washer, old cup disc. I do see that there is no mixture screw on the new J-tube. So I guess that the noise would be less.
I use this style of dish above the mixing chamber a lot, in many PX lanterns. In German Pelam forum it's called 'Staukappe'. The effect of it is to deviate the flow of uprising burner exhaust gas further away from mixing tube. And as air is an excellent thermal insulator, the gap of increased distance from hot exhaust gas to the tube does the trick. Tube and chamber stay cooler. No red glow. You can cut such plate/ring from cans of tin , and with a radial cut , you mount it even without disassembling anything. Must see if I find a photo of this.
Hi all, I got a new Petromax 500cp just last week. Just yesterday I used it indoors, I noticed after 10 minutes of use the light output dims down significantly. Upon inspecting, I noticed the J-tube glowing was red. Thinking perhaps the jet was enlarged, i changed the jet and needle to a Butterfly ones i have. I relighted it, it still does the same thing after 10 minutes. What I did next was to use a salvaged J-tube from an old Butterfly inner casing i had laying around. Popped in the J-tube together with a part which looks like a thin domed belleville washer, fastens behind the gas chamber. I relighted, used for 4 hours the problem did not reoccur. I do not know what to make up of the situation. I do have Britelyt 500cp lantern, the j-tube is way longer than Pmax and the Butterfly one. Any thoughts?
As far as what I've experienced, the burning back into the J-tube has more to do with the condition of the J-tube itself rather than the presence/absence of the inverted dish/cup 'belleville washer'. It might be related to its overall tube length or inner diametre or some combination of them.
Perhaps the length would be the culprit? It was not doing that the first and second light up tho. I wonder the tightening clamp screw has got anything to do with this red tube phenomenon. The screw (part 21) has got the sharp end which adds a dimples onto the J-tube. Is it by tightening too much that the dimple got deep enough to disturb the already turbulent flow of the gas mixture, causing a back flame. I think it is obviously a backflame because of the sudden chronic dimming of the mantle. The J-tube then wants to become the glowing light source. I guess the backflame in this case is not large enough to cause the roaring in a strike back. But enough to get temperatures to elevate gradually. A 500cp lantern all of a sudden becomes a 10cp lamp.
To be frank, I really do not know the exact reasoning of this glowing red hot J-tube thing. There could be more than one cause. I've had an older J-tube assembly design (2 flat nuts that's without the items no.20, 21 & 22"clamping pieces) getting a back burn as well. So I guess this might not be the reason. I've tried inserting an additional stainless steel mesh inside the ceramic burner but that too didn't prevented the back burn. I've attempted various air gap adjustments ranging from way below the norminal 14.2mm to as much as 17.5mm(350cp unit) but nothing worked. I've even wrapped some asbestos cord as insulation of the tube from the hot, rising combustion gases, but that didn't resolve anything as well. Cleaned out the Preston loop and jet, tightened again, changing the ceramic burner cap, replacing the needle and tried various pricker heights, etc....but nope, nothing. It was only by replacing the J-tube that I finally managed to get that resolved. I was completely puzzled as there were no obvious or visible defects on the earlier J-tube. It was not dirty or cracked or anything.
As you can see in the diagram: part 33 is not a straight part. I am not an expert but I think the inventors of the pertromax design didn't came up with that idea just for fun. Also the new J-tube didn't or doesn't have the airmix paddle. Glowing red is something completely different then a blow back or backfire of the flame, you will know this for sure when it happens. What is the tank pressure and is this reliable ? manometer check ?
I'd say the entire J-tube would glow from dull to bright red after some minutes. If allowed to continue, it'll probably melt or burn through. And in all cases, the mantle would drastically dim upon such an onset. Most of the heat dwells in the tube and upper part of the hood. In many cases, the generator would be deprived of sufficient heat since the mantle would only glow reddish orange at best. Eventually, it'll start to flame outside and deposit soot all over the mantle, globe and burner assembly. That's as far as I would allow it to continue. I don't know what's going to happen if I did not depressurize and shut such a lantern down.
Perhaps what you think is true. The Butterfly J-tube I stuck into the Pmax now, isn't just a straight tube. it has some deliberate contouring here and there. Butterfly J-tube locks down with the 2 nut arrangement but in the pmax i merely use them to hold that dome disc in place. I did some mod to the clamping screw mechanism such that it wouldn't bite into the J-tube. But that Butterfly tube is not very new now, being salvaged. I am eyeing replacement J-tube from BL, significantly longer and the SS version has got that contouring much like in the image above. But as with most J-tubes now, lack the paddle screw. Or should I just stick with the Butterfly J-tube replacements? I think I have got one new somewhere in the house if I remember. The particular Pmax isn't as bright as the BL. Although both has got Butterfly mantles in them now. I am awaiting for other mantles Anchor and Pmax. Haven't got the drive to get Luxor ones yet. Or is it because of the pingpong ball sized Butterfly mantles causing the flame to travel back into the J-tubes?? The BL only got glowing SS burner and a bit of the J-tube glowing near the burner, thats all.
