Stanley steam car Mixing Tube Fires

 Stanley Mixing Tube Fires by Pat Farrell (aka SSsssteamer) SACA
NW Steam Clinic September 27, 2019
​What are mixing tube fires? The mixing tubes of the Stanley steam car are where the vaporized fuel and atmospheric air mix to produce a combustible flame to fire above the burner grate. When the fire presents itself below the burner grate in the plenum, or in the mixing tubes below, that is not acceptable. This generally is called a mixing tube fire. What are the causes? Most common tube fires are started by a fire leak from around the burner to boiler seal. The pilot light inspection hole not being fire tight, as well as the super heater exit at the rear of the burner can also start mixing tube 
fires. A fuel flooded mixing tube fire is usually caused by a flooded burner. The flooded burner can
be flooded either by the main fuel jets, or by the pilot light being out causing raw fuel to build up in the mixing tubes and plenum. Mixing tube fires can also be started by forcing the burner too fast at firing up and flooding the burner with raw fuel. Instead, preheat well and build a slow hot fire. Tube fires can be caused by the fire dropping down out of the burner and into the plenum by the way of a cracked burner grate. The burner’s slots or its drilled holes can become too big and therefore dropping the fire down through them and into the plenum. A warped or heat damaged burner grate can be the cause for the over-sized slots. The burner grate’s plenum not being sealed tight enough around the burner grate, can also allow the fire to descend into the plenum. Flooding of the burner plenum can be caused by using too heavy of fuel for the too large of main jets being used. Thin your fuel with gasoline or reduce the size of your jets to help reduce fuel flooding. This flooding is also a problem found at higher elevations where the oxygen is thinner. Sometimes, old fuel will refuse to vaporize, and until that fuel is disposed of, the old fuel will be a problem. Partially plugged main jets can cause drooling that will accumulate creating flooding of the mixing tubes. Misaligned main fuel jets within the mixing tubes can flood a side of a mixing tube and thereby flooding the mixing tubes. Also a resulting fog of vaporized fuel blowing back outside of the mixing tube can result in a puddle of raw fuel and an eventual tube fi re. The main jets vapor spray should always do a perfect bull’s eye inside of the mixing tubes. What should be done? A roaring mixing tube fire should be extinguished as soon as possible to prevent further damage to the Stanley burner grate. The first thing to do is to eliminate the fuel source by turning off your main burner valve. If I have a roaring tube fire, I prefer to quickly pull off of the road and try to let the excess fuel burn itself off in a small flame. Continued driving fans the tube fire making it a hotter tube fi re and possibly doing excessive damage to your burner grate. Sometimes if my mixing tube fi re gets too large, I will use my Halon fire extinguished to keep the fire from getting too big and doing collateral damage. Never use a powdered fire extinguisher in your mixing tubes as that will plug your burner grate up solid with extinguisher powder. To resume firing properly, the excess fuel has to be burned off, so a smaller fire is encouraged into eliminating the excess fuel. If the burner has lost its fi re and it is blowing raw fuel fog into the air, turn the main fuel valve off immediately and drive until the fueled smoke screen has subsided and then pull over to relight the burner. The first lighting attempt is to light the fire from the top at the smoke bonnet’s access door. To prevent your body from being burned, stand upwind from the fuel vapor cloud when lighting. Next is to check your pilot light at the peek hole for being lit. Light the pilot light if it is still out. What is the collateral damage? Too much roaring burning of a mixing tube fire will eventually crack your burner grate. Plenum fires can also destroy all of your refractory materials located in your burner. Excessive tube
fires with fuel left uncontrolled can eventually burn your Stanley up. Always shut off your main fuel valve when leaving your Stanley unattended. Try to shut off your main fuel valve a quarter mile before arriving at your destination. That should clear out any stored fuel in your steam automatic system and prevent your main fuel from later cycling on and drooling fuel while the Stanley is parked. What can be done to continue driving while tube fi res persist? Sometimes while on the road, a quick fix for tube
fires is just not available. To survive this problem and to continue driving, these steps can be taken. Reduce your fuel pressure so as not to create too much internal pressure inside of the burner/plenum area. Reducing your fuel pressure to below 100 PSI can sometimes get you home. Get your Stanley rolling up to about 18 MPH or faster before slowly turning on your main fuel valve. This creates a draft so as to keep the fire burning above the burner grate and not in the plenum or mixing tubes. Some Stanley's have a stack blower that can be used to duplicate this need for a draft. Before using your main fuel valve, by using your firing up valve you can gently bring your fire temperature up to a good
firing rate following with firing with the main fuel valve. If your burner grates become sooted up from tube fires and it restricts the passage of the air/fuel vapor, remove your main fuel jets and if you have one, use your steam enema with full steam to clear your burner grate of any soot. I have also removed my smoke bonnet, and by blasting down each fire tube with an air nozzle, I cleared the sooted up the burner grate below of its blocking soot. Once I was in a blinding dust storm that blocked my burner grate with dust. My steam enema saved me that day too. Hopefully something in my above SSsssteamer experiences will help you in your steam car adventures. <