Petromax CP500 issue

Hi
I have had some issues with this lamp, not burning evenly, lots of black soot etc I stripped it down and noticed the jet was partly blocked and the pricking pin bent
I straightened the wire cleared the jet and reassembled put a new mantle in and tested all seemed good, well mostly
The mantle burns brightly however the light pulses bright then dimmer about once a second
If I turn the control knob down I can just about get to a point where the pulsing stops this is a tiny position, a fraction of a turn up and the pulsing starts a fraction down and the lamp goes out if I get the sweet spot the lamp will run smoothly for a few minutes then go out if I don’t quickly turn up, then the pulsing starts again

not sure what the next step is
The lamp is half full of paraffin
The pressure is good and steady
The mantle is a petromax one

many thanks for any suggestions

Simon

 

When you stripped it down did you clean inside the burner and air tubes and burner cap? An insect or some other small blockage would be worth investigating.

You said the pressure is good and steady. Try adding more pressure, there may not be as much pressure as you think in the fount. It's at least worth a try.

 

I’m just thinking out aloud here.
I’m wondering if the jet is screwed in tightly and sealing properly?
Cheers
Pete

 

Thank you
Will try more pressure
I did not clean inside the tubes - will re strip and try again
The lamp has really had not much use so I expected the tube to be relatively clear
Will have a look

 

Thanks
Yes the jet if firmly tightened- there is no seal under the jet is that correct? thanks again
Simon

 

That’s correct, there is no gasket type seal.
The actual seal is metal to metal contact of the jet to its seat. I have had instances where the metal to metal contact has been poor thus not properly sealing. The result was that the burner ran very rich, to much fuel in the fuel to air ratio.
Cheers
Pete

 

The pulsing could be the lantern hunting, I've a Petromax HK500 that does the same. Fitting brass gauze around the conducting rod (Part#101), near the top of the preston loop should cure it - there are other posts on here detailing this procedure. The Petromax website sells brass gauze for this, others have used brass wire.

 

What do they call this, the Leidenfrost effect? I know I spelled his name wrong... Anyway, all pressure lamps pulse it's just they pulse at such a rapid rate your eyes and brain can't, let's say stay in sync. In your case the hot burning kerosene is slightly quenched when more kerosene passes through the vaporizer causing a dimming effect. I am not sure exactly how to remedy this problem but I think changing the gap between the nozzle and the "J" tube sometimes clears up the problem. Decrease the gap opening, use the gage on the Petromax wrench to get the right setting.
Now, that I've probably really hosed this one up maybe someone can bail my a.. out of this hole!

 

Copper stranded wire
wound around the cleaning needle rod
Will inhibit the
Leidenfrost effect
And stop the blinking.
Make sur, wire has contact with vapourizer tube.

 

If you haven't got brass gauze you could wind copper wire round the pricker rod to assist heat transfer to the fuel. I've done this on lots of my Petromax clone lanterns and it definitely helps no end.

 

"Leidenfrost effect":
Problem is identified, the flow inside the vaporizer is to "even". So the outside is hotter then the inside of the fuel column.
Bending a wire or metal gauze around the needle rod will disrupt this even flow. Which give a better evaporation. So it is not a temperature problem but a flow problem.

How do you measure the pressure ? the pressure meter on the tank is just an indicator.

While writing I think about the shape of the mantle.
Round bulb like mantles tend to get more closely to the vaporizer and therefore better vaporizing the fuel then a U-shape. But this is just an idea.

 

Thank you all ! I have wound wire round the needle rod will run up this evening! Fingers crossed
Cheers
Simon

 

Hi
Much improved! Still pulsing but way less noticeable, maybe try more wire ? the gap between the jet and the be is 13.5 mm I have opened up as much as I can, could this be the issue ?
thanks for all the ideas and support
Simon

 

Hope you get it sorted out.
When you moved the pricker by a fraction of a turn both up and down away from the earlier 'sweet' spot, the flow was being regulated in some ways. This is not a supposed procedure in Petromax-styled lanterns. The pricker assembly does not function like a flow control valve.
The Leidenfrost effect sometimes does take place, to a greater or lesser extent within the vaporizer. This could usually be remedied with brass gauze or copper wire coils as had been suggested.
I'd also like to add that the Preston loop vaporizer should be completely cleared of dirt, carbon and varnished old fuel, especially inside the loop section, which could be heavily coked-up if this lantern had been heavily used before. This could also mean that fuel would short-circuit directly through the clearance between constricted part of the vaporizer and the pricker rod, all the way to the jet instead of taking the usual path round the loop. In such case, the fuel wouldn't vaporize as completely as normal.
In addition, if the pricker wire and rod had not been adjusted correctly, it could obstruct fuel flow at the jet orifice, creating a similar flickering/pulsing scenario.

 

It's good that it's made the pulsing problem better and if there's room to squeeze a bit more copper wire, go for it! On both my Anchor clones it reduced the pulsing to almost nothing but I read somewhere on the site that it never truly stops, it just gets so fast you can't see it.

Now we need to see a photo of it running!

 

Did you use or adjust the air mixing paddle ?
Is the main foot valve fully open ?
The wire should make a unstable fluid stream. Adding more wire doesn't sound logical.

If it is a design issue people like H. Lahde would have addressed it.

 

Simon, the gap between jet and mixing tube can be opened up
to 14,5 mm. It's a matter of testing.
How far does the cleaning needle look out of the jet?
Should not be more than 1 mm, better 0,5 mm.
All other hints were given. Good luck.

Matthias

 

Needle is just out the top of the jet
I put more wire round the needle holder basically as much as I could get in
I put the tube with the loop and jet in an ultrasonic bath today so all clean put back together running ok bit pulsing but not too bad dropped the pressure to 1 bar as at 2 there was a lot of burning outside the mantle I also managed to open the gap up to about 14.7 all working but not fantastic prefer the vapalux and Tilley lamps but good to get this one working again
Thanks for all the suggestions

 

If there's flame outside the mantle at 2 bar, the jet orifice is likely quite worn and need replacement. In fact, it could even go up to 3 bar without problems(although that is not necessary).
As for the gap, the usual 14,2...14,5mm does not always get you the best results, especially if you're dealing with a well-used lantern. Personally, I've sometimes pushed it beyond 15mm to get a more complete burn and could be anything below 17,5 to 18mm.
A 500cp or hk Petromax should burn a lot brighter than what is shown in your picture above.
There's a lot of interesting variables that could be tinkered with, particularly with Petromax-styled lanterns.

 

Hi the lantern has only run for a few hours maybe 20 max so I would be surprised if anything is worn out
It just seems flaky and not well designed- Petromax even sell some gauze to bodge in the tube ....
when I look at my other pressure lanterns then back at this one I wish I had saved the money buying a new lantern .....

 

Can't focus too well on the picture but is this an original German Petromex or a clone?

 

@spike589715
There are other ways that can cause the problem. Mister Leidenfrost is not always to blame.
The upper part of the generator 152 has probably clogged up on the inside. You can drill the part out 3mm.And the guide nod 101 must be clean. Now the kerosene has enough space to rise again.
Another possibility is that the lower part of the generator 153 has a leak in the riser pipe. It is very difficult to find,but, it also causes the flickering.
It may also be that the whole guide nod 104 is set incorrectly. It may also be that the carburettor valve 196 is stuck or the valve spring is broken.
Regards Reinhard

 

If this is a new lantern, am I correct to say this is the bare-brass version of the current Petromax range of products?
If so, this is not exactly the original Petromax produced by Graetz of Germany decades ago.
But that does not necessarily imply that its not as good.
From the picture, I was earlier thinking its an old Petromax that was stripped of nickel plating.

 

Hi yes a new (last 5 years) brass version says Germany on it and original .... probably made in China ?
Think I will give it a polish and use the vapalux and Tilley
Thanks
Simon

 

I don't know if its made in China or elsewhere. But the Petromax is still a registered trade mark in Germany.
Nevertheless, I don't think any Petromax lanterns are currently manufactured in Germany.
No questions about your preference to use the Tilley or Vapalux, Simon.
But I'd attempt further to make this Petromax as bright as what a Petromax 500cp should be before turning it into a shelf queen.

 

Can you guarantee the 20 hours max ? New / hardly used doesn't necessarily mean perfect, the jet could have been a duff one right from the start.

I agree and whilst you're doing that, you're learning about the intricacies of a different type of lantern which may come in useful in the future.

Henry.

 

If it's working properly a Petromax 500cp should outshine a Tilley by a very large margin! I'd persevere and get it sorted, you won't be disappointed.

Whenever I've had to use a lamp in a power cut, I rely on a Petromax clone to light each room we use.

 

Why ask for help here if you don't push through ?
All of us want to help, give advice but it becomes an unloved shelf thing.

 

Run a 500 CP P-max indoors?
Or more than one? Blimey.

 

@JonD Certainly. Open the windows, turn off the heating and remove excess clothing. Toasty !

Frosted glasses are available to reduce the glare if you can't find your sunglasses, the reflectors which slide down over the handle are effective too.

Henry.