Hi All,
Earlier this winter, when I fired up my 735 with the Empire burner, I noticed that the main fire was pulsing when I had the fuel turned on all of the way, boiler and burner hot, 200-500 lbs of pressure. To investigate this further I put a Y in the fuel line, just downstream of the boiler pressure regulator, and put a gauge on so I could look at the pressure at this point in the fuel system. Last weekend Bob Ullrich and I fired it up again. We started slow with the burner, because it was fairly cold and the fire was a bit smokey (burning #1 stove oil). With the fuel valve just cracked open, and a mild hiss from the burner, the vaporizer gauge read 30 lbs. After some steam started coming out the drip valve we upped the fire, with the fuel valve opened about 1/8 to 1/4 turn the pressure now read 90 lbs. I should state here that the fuel pressure cut off is set at 140 lbs, and I kept it there with the handpump as we were firing. So now things are coming along nicely, about 100 lbs on the boiler, and I open up the fuel valve 1/2 turn, at this point the fire starts to fluctuate, reading between 80 and 150 lbs on the gauge. It keeps up this fluctuation until I close the valve some, eventually I can get it to burn without fluctuating at 120 lbs on the vaporizer gauge. If I crack it open a bit more, the fluctuation starts again.
At 120 lbs I have a pretty good fire, although it does not hiss or roar like other burners I have heard. When it is pulsing up to 150 lbs. it sounds quite strong.
I was wondering if anyone had ideas on these fluctuations, and how they might be fixed so that I could run the burner at a steady 140 lbs?
Right now the car will maintain 25-30 mph on the level when it is still cold. I imagine that if I was to put 10-20 miles on it it might maintain a bit higher speed. The burner stays on all of the time, not cycling off, except if I slow or stop. The pilot seems to be working quite well.
Thanks,
Eric

Hi,,Just so were on the same page,,,
Is this Empire burner the one with the square door,,,,and a single large ventouri ??
Do you know what the dimentions of the cable are ? Ben

Hi Ben,
It is the Empire with the square door and the single venturi. It has a vaporizor that I think is thick walled stainless steel, about 6 ft long. I don't know all of the specifics because I borrrowed it out of a burner that Bob Ullrich had. There is no cable. I think the vaporizer is about 1/2 OD and 1/4 ID. Jet is a #52 drill size.
After posting and thinking more about this I realized that my pilot does the same kind of pulsing with the fuel turned on all the way, so I am thinking it has to do with the vaporization, and not some restriction in the fuel line?

I like for the pilot to serge,,,at twicks the needle and you know its LIT,,,
The vaporizer sounds thick,,,but no problem,,,
Without a cable it WILL serge I think,,,
There is more info here,,,,i am short on cable comments,,
All for now,,,Ben

I'd try a wire - about 3/16th braided stainless with the back end tigged to stop unravelling and the front end into a short length of steel rod so you have something to pull on to take it out. Just a few inches short of the full length of the vaporiser.

Without the wire you have too much volume of liqud fuel getting in there - lots of heat - huge expansion - can't get out of the jet any faster so it backs up the inward flow of fuel through the automatic and sets off a pulsation. With a wire you force the fuel out along the hot inside of the vaporiser pipe and don't get a slug of liquid down the middle and it doesn't get to the hottest part over the pilot as liquid. As you saw pilots also can pulse.

Mike

Dear friends in steam,

Years ago I had a similar problem with my Locomobile and the new Ottaway burner. The liquid petrol comes under pressure to the steam automatic and when the steam pressure is low, the automatic opens and the liquis is directed to the vaporizer and later on to the main nozzle of the injector system. When the steam automatic opens, o lot of liquid comes into the vaporizer tube, cooling it down and the vapor presses back the liquid. Then the vaporizer heats up again and when the vapor is gone through the nozzle, this cyclus starts again. This doesn´t mean only an unsteady fire but also a lot of thermal stress to the vaporizer system.
I could find a simple solution of this problem: A copper disc with a little hole of the same diameter as the nozzle in the connector between steam automatic and the vaporizer separates the zone of liquid petrol with the vaporizing zone. Only as much petrol comes through the hole in the copper disc as petrol vapor goes through the main nozzle into the injector. The result is a steady fire which is much easier to maintain.
Maybe your problem has similar sorces.

Happy steaming, Peter Wueringer from Vienna, Austria

Peter has highlighted another point - the size of the pipe from the automatic to the vaporiser. Often this is 1/4" which is far more than needed to pass the fuel. I used a 3/16th pipe, and filled the bore with 4 lengths of 0.036" copper wire to further reduce the amount of fuel between the automatic and the vaporiser. This helps. I actually tried a 1/8th pipe with approximately 0.070" bore - the burner still worked perfectly but I felt the thin pipe was too fragile, hence the 3/16th with wires. The steam automatic only opens 10-12 thou to pass the full rate of fuel so the pipe bore doesn't need to be any bigger.

Mike

Back in the forums,,,somewhere,,,I recall a check valve fitted,,,cant recall comments,,,Ben

On the SACA forum Jim Crank suggested for preventing a surging fuel supply to fire to: "Try inserting a small check valve in the line close to the burner. Imperial-Eastman has them. If it can't flow backwards, it cannot surge".

On Saturday took the car out again for a short, cold tour. Before firing I did the easiest of the suggested modifications, putting the copper wires in the fuel pipe between the vaporizer and the boiler pressure shutoff. This fix did calm the surging some, although it is still present. Will fit a cable in the vaporizer when I find the time and try again.