Hi all,
I seem to be having a chronic vaporizer clog issue on my 735 Stanley with a Cruban burner and pilot. I started off this season burning a mix of diesel and gasoline, about 60/40. I have had clogging issues all year. I switched out my vaporizer last winter because my old one had clogged up and cemented the cable inside it. I kind of made some design changes to try to address this issue. The first new vaporizer that I made is about 7' long (total length including the 8" stainless steel hot dog). I made the vaporizer loop of mild steel 1/4" Sch 40 pipe bent on my forge using a sand filler to make sure I did not collapse the tube. It was kind of difficult to get all the sand out but I think I eventually got it all out. Anyway with this set up if a ran a cable it clogged in about 10 miles, without a cable it clogged in 20 miles. I switched to straight #2 Diesel to see if that would help and had similar results. So then I bent up a vaporizer that was 1 foot shorter because I thought I was getting the fuel too hot. This time I made it about 30 miles without a cable until I got significant clogging. It always seem to clog near the junction of the loop and the hot dog. This joint does not leak and last time I tried covering it with ceramic insulation to try and keep it cooler. The vaporizer is about 1/2" to 1" above the burner grate.
So, am I headed in the right direction, should I take another foot of length off the vaporizer (this would mean a total length of 5 feet)? I know I could probably just switch to Kerosene and avoid some of this issue however I am trying to make this car run on readily available pump fuel so I can take it some distance from home where I would not be likely to find a source of Kerosene. Right now when things are burning well I do not have a smoky fire even when relatively cold, I can fire it up without using the start up valve and not have a smoky fire. My fuel pressure is 150 lbs. I assume that this means that the fuel is getting very hot right from the get go and when I really get going it gets too hot and cracks leaving the carbon residue that clogs things up. Is it just impossible to get a clean vaporization of #2 Diesel?
On the plus side my pilot now seems to be working flawlessly (I probably shouldn't have said this!) now that I have switched to a # 76 jet and 6-8 lbs of pressure. It does get blown out by the burner when it is working a full tilt unless I have my stack blower on. It relights as soon as the burner pressure drops as the burner cycles off. Thanks, Eric

Dear Eric
I’ve come to the conclusion there is no one answer to the problem.
This spring I made up two vaporizer for a fellow steamer, using ¼ inch 316L stainless.
They were made the same length as the plugged one to his request. Just shy of seven feet. My own feelings were they were two long.
I think it makes a big difference how you run your burner. I see some people turn their fuel down when going slow. Others keep it on full and let the steam automatic turn it on and off.
Kerosene cracks around 400 to 450 F, every hot dog or branch forks I’ve put a thermo probe on has been over 900 to 1200 F. Much two high in my opinion. Of course this is not measuring the fuel temperature. If the fuel is only in the vaporizer a few seconds it may never get to 900.
It also makes a difference where the vaporizer is positioned in the burner. I think it should be under the flame, heated only by the radiant heat and cooled by the fuel vapor coming in around it, not the blue tip of the flame. How you achieve this is questionable, you need to know your burner and how high the flame is under full pressure and draft.
This is only my opinion and I’m sure there are many others. I’ve seen the best of them having the same problem.

Rolly

Eric, I have suffered a great deal with clogged vapourisers and in my experience two causes stand out from the multitudes:

1 If you have fitted an enema, you must be absolutely dead certain that no steam at all is entering the vapouriser.
2 The superheater glows bright red when you are not sending steam through it and you have the fire on full howl, such as when you are standing at a traffic light and you have your eye on that hill in front of you....If part of the vapouriser is close to the glowing superheater the risk of clogging is increased.

Hope this helps, Kobus