PRIMING A SVEA ============== CAVEATS AND WORDS OF DIRE WARNING - WHITE GAS STOVES ARE DANGEROUS. Use of white gas stove can lead to fires and explosions and as a result loss of property, injury and even the loss of life. The following describes my personal experience in operating a Svea stove. This is not meant to be replacement to or augmentation of the manufacturer's recommended procedure. Please consult the manufacturer's documentation for the proper use of this stove. The owners manual can be downloaded from the Optimus web site at: http://www.optimus.se/ The author makes no claim whatsoever regarding the accuracy or safety of ANYTHING in this article. Any item that may appear to be offering either technical, medical or legal advice is doing neither. Readers attempting to apply the methods described here do so at their own risk. INTRODUCTION - My favorite stove is the Svea 123. I think it's the most reliable stove I've ever seen or used but some people find it hard to start. All white gas stoves require some sort of priming ritual. Easy or hard is not the question - The only relevant question is how familiar you are with that particular stove's ritual. Here is how I light my Svea. This approach works reliably well for me in low altitudes and in temperatures down to the -10f range. In what follows, I'll talk about basic priming, dealing with flare up, warnings about overheating the stove and cold weather use. GENERAL PRIMING - I use the Svea with the built in windscreen. This can complicate the priming of the stove somewhat in that the priming pan is at the top of the fuel tank, which is well inside of the windscreen. This can cause a problem whenever I've tried using white gas to prime the stove, as I inevitably end up spilling the gas. This usually means that the stove is smothered in burning gas, which isn't so good. To get around this problem, I use a paste style fire starter, as recommended by Optimus in their owners manual. One of the most common in the US is the Mautz Fire Ribbon, which is sold at many camping supply stores. Colgan also sells a similar product. Essentially this is kerosene in paste form. It burns a bit on the sooty side of things, but it has the wonderful property of staying put while it burns. This means I can pick up the stove while the priming paste is burning and turn it sideways and the priming paste will stay put in the priming pan. The big The benefit of using this priming is that it allows me to light the priming paste while the windscreen is off and then put the screen back on while the paste is burning. Then, when the stove is primed, I can fire up the stove with the windscreen already in place. With this as a basic description, here is a step by step process for how I prime the Svea: 1 CLEAN THE JET & SET THE VALVE - The first thing I do is clean the valve jet by turning the key all the way counter-clockwise, which brings the cleaning needle up through the jet orifice to clean out any soot. Then, I turn the key all the way clockwise to securely close the valve. If the valve isn't securely closed, I've had problems with the stove loosing presure as it is heating during the priming. 2 REMOVE THE WINDSCREEN - When I remove the windscreen, I don't let the adjusting key come out from the windscreen. The chain that attaches the key to the stove is, or should be, just long enough to allow me to place the windscreen to the side of the stove while the key is still threaded through the windscreen. This is important because in a minute, I'm going to want to put the windscreen back on the stove while the priming paste is burning. This is infinitely easier if the throttle key remains threaded through the windscreen at all times. 3 CHECK THE FUEL LEVEL - Next, I check that the tank is full. The manufacturer recommends 2/3 full, which is something I have a hard time determining. If the fuel begins to come up the filler tube, I know I've overfilled the stove. I believe the stove needs some empty space in it to allow the stove to vaporize fuel correctly. I've found that overfilling the stove will cause it to sputter or flare up because it doesn't prime entirely. 4 CHECK THE O-RING - I always inspect the o-ring on the filler cap after filling up the stove. This seal is important. If the o-ring looks old and compressed, I replace the o-ring with a spare from Optimus. I carry one in my spare parts and repair kit. If the o-ring looks goods, I attach the fuel cap tightly. 5 PLACE A DAB OF FIRE PASTE IN THE PRIMING CUP - The priming cup is the small indentation on the top of the fuel tank and at the base of the burner assembly. I find that the size of the dab of paste is THE single most important variable to the priming. I tend to need more paste when the temperatures or the stove is cold and less when the temperatures and the stove are warm. The ideal amount is when the priming paste begins to burn out and the stove is fully primed. With too little paste, I find the stove isn't fully primed and sputters or flares up. If I use too much, I have to wait till the paste burns out even if the stove is primed since running the stove while the priming paste is still burning strong can starve the burner's fire of air. I've gotten better at guessing how much over the years. 6 LIGHT THE PASTE AND REPLACE THE WINDSCREEN - While the priming paste is burning, I put the windscreen back on. This is easy since the priming fire is paste, so the flame and paste stay put. I find it easiest to tilt the stove slightly as I put the windscreen in place over the burner assembly. 7 WAIT - Waiting just the right amount of time for the priming fire to burn down is the second judgement call I need to make. If I wait too long, the stove begins to cool off and it looses its prime, which results in flare up. If I don't wait long enough, the stove might not be fully primed. Or, the stove might be fully primed but there is still enough burning paste in the priming pan that the priming fire takes the air away from the fire at the burner head. This can cause the stove to flare too. The goal of the priming ritual is to have a strong steady blast of vaporized gas coming out when I open the stove's throttle. My stove makes a strong hissing sound when it is fully primed and the throttle is opened. 8 LIGHT THE STOVE - I find lighting a fully primed Svea to be similar to lighting a propane torch. The pressure of the vaporized gas is so strong that it can blow out your lighter (or match). To get around this, while the stove is still off, I use my left hand to hold my lit lighter at the edge of the windscreen as close to the burner head as possible. Then, I use my right hand to gently open the throttle the smallest amount I can - just enough to let gas come out of the head. When I do this right, the vaporized gas hits the burning lighter and snaps into a flame with a pop. I pretty instinctively move my hand away from the stove when that happens, but I do try to use care to avoid burning my hand. I have horrible luck doing this in reverse. If I open the stove first and then try to hold a lit lighter to the burner, I find the pressurized gas just blows out the lighter. FLARE UP - All white gas stoves I have used or have seen operated are prone to flare up. Flare up results when the stove emits gas in liquid form instead of in vapor form. This results in a bright and large yellow ball of fire instead of the desired steady, strong and small blue flame of a fully primed stove. White gas stoves convert liquid gas into vapor through pressure and the 2 common mechanisms for creating and maintain this pressure are a) an air pump and b) heat from the burner itself. While the Svea has an optional air pump, I never use it and have never needed one. But, I should note that I live and camp in New England so I don't spend time at higher altitudes where the air pump may be needed. So, I rely entirely on heat to get and maintain the prime in the stove and thus avoid flare up. Assuming that there is no leak in the system (which would prevent the gas tank from building up pressure), my experience is that priming the Svea is entirely dependent on how hot the stove is. The colder the stove is, the worse the flare up can be. The following is a list of behaviors that I see from my Svea ranging from colder to hotter. In all cases, the answer is the same. I need to prime the stove more to build up more heat (and pressure). How much more depends on how the stove is behaving. + DRIBBLING FUEL - Sometimes the stove will have just enough pressure that liquid fuel will just dribble out of the jet. This is usually a mess, since the fuel ignites and the whole thing ends up covered in burning gas. There is nothing to do but to gingerly shut the stove off, let it burn out and try again. This has only rarely happened to me and when it has, it's almost always been a result of not having the valve shut all the way. So, the stove starts to build pressure but just as it does, it pushes liquid gas out of the partially open valve. This is why I ritualistically open and shut the valve at the very beginning of the process. This helps ensure that I always prime the stove with the valve shut tight. + SPRAYING LIQUID FUEL - This is the worst of the flare up situations that I've experienced and really the least common. This indicates a stove that is still relatively cold. It is hot enough to forcibly shoot out gas but the gas is still mostly liquid. If there is priming fire in the priming pan, this can be a fiery mess. Quick and careful handwork is required to shut the stove down. Avoiding this is the best option. + POOF, POOF, POOF FIRE BALLS - This is the first form of flare up that indicates something even close to enough heat to prime the stove. In this mode, the stove will actually light and produce the stong blue flame that indicates vaporized gas. But, the blue flame is interrupted by a series of large flare ups of bright yellow flame. This is classic flare up. It can singe eyebrows and knuckle hair. It can melt fleece and Gore Tex and tent vestibules. It's often accompanied by a poof sound. If the stove is in a safe place, the weather is good and I'm impatient, I can sometimes get a stove to pull out of this mode by turning the stove down as far as I can to limit the flare ups. I think turning the stove down helps build up more pressure while still staying lit. The balance I'm trying to get here is turned down enough to avoid the big flare up but turned on enough that the burner generates enough heat to increase the amount of priming. If I turn it down too far, the stove won't build up enough heat to reach full prime. I find the more successful approach for this is to just shut down the stove and wait for it to cool off enough to start over. When I was learning how to use this stove, this form flare up happened from time to time. When it did, it told me that I messed up the priming ritual. This almost never happens to me now. + FLUTTERING - This is the most common form of flare up for me at this point. When this happens, the stove is almost entirely primed. I get a blue flame out of the burner that indicates that the stove is vaporizing the fuel. But, the flame is still comparatively weak compared to when it is fully primed. And, the blue flame is interrupted by short, stacatto blasts of yellow flame. These bursts are shorter and sharper sounding than the poof, poof, poof of a real flare up. The size is also smaller. Where as a full flare up may be measured in feet, these little blasts are almost always less than a foot - still enough to burn things that get in their way but no where as uncontrolled as the fire balls. This form of flare up means that the stove is nearly fully primed so I almost always let the stove continue to burn so that the heat from the burner will heat up the tank more. Usually when this happens I turn the stove up to a point just below what will cause the larger fire balls. I think this kind of fluttering can be caused when I overfill the tank. I think it's hard for the stove to build up enough pressure if there isn't enough room in the tank for gas vapors. + PERFECT PRIMING - This is the most common outcome for me. This is *NOT* due to my outstanding moral virtue or elite skills. Rather, I'm very, very convinced this is a result of the experience that comes from using the stove for years and years. When the stove is properly primed, I get a steady and strong stream of vaporized gas that ignites instantly with no flare up of any kind. This happens almost every time I light this stove, which is a statement of the stove's reliability, not me. OVERHEATING THE STOVE - All stoves are potential fire hazards and white gas stoves are potential bombs that can explode. Since the Svea relies on heat from the burner to heat the fuel tank (which is filled with gas) to operate, overheating the stove can cause dangerous consequences. To reduce the risk of explosion, the Svea fuel cap has a built in safety valve. The idea of the valve is that the valve should release before the fuel tank explodes. As Colin Fletcher notes in his famous "The Complete Walker", this is only slightly less exciting than have the stove explode. I've overheated my Svea and many owners I've talked to have succeeded in doing this too. Most have only done this once, as it tends to make a big impression. While I'm glad that my safety valve worked as it should have and I avoided an explosion, I have no interest in doing it again. In short, the safety valve becomes a 4 foot blow torch as the stream of gas vapor instantly ignites in a plume of flame. There are 3 precautions that I take when using my Svea. FIRST, I'm always aware of the direction that the filler cap is pointing. I treat the filler cap like a loaded gun. Just like I always know where a gun is pointing, I'm hyper aware of what or who the filler cap is pointing towards. I don't let it point at people or things that can burn. SECOND, I am very cautious when using an auxiliary windscreen. The stock windscreen of the Svea is needed as a pot holder but it's often not enough for me when using the stove in windy conditions. However, putting another windscreen around the stove can cause the stove to overheat. My own experience and everybody I've talked to who's done this has overheated their stove while using a windscreen. THIRD, I regularly replace the filler cap assembly and carry a spare filler cap. This is one part of the stove that I don't want to fail. I should conclude this section with a counter-point. I feel infinitely safer with my Svea than I do with stoves that rely on external fuel tanks that are pressurized with plastic pumps. I've seen 2 such stoves in complete and uncontrolled flames. In both cases, the operator (not me) managed to melt the plastic pump and as the pump melted the external tank began to heat and spew flaming gas all over the place. While a pressure release valve that spews a violent yet directed and controlled stream of flame may sound horrifying, it is much less scary to me than the failure mode I've twice witnessed with stoves that use plastic pumps. COLD WEATHER USE - In cold temperatures, the Svea can fail to perform well if it is placed directly on a cold or frozen surface. The stove is made of brass, which is a good conductor of heat. This presents a two-fold problem which has an easy and inexpensive solution. Any cold surface like ice or cold rock will literally suck the heat out of the fuel tank. This will cause the stove to loose it's prime. If that cold surface is snow or ice, the heat from the stove will melt the surface, causing the stove to become unstable. For this reason, I carry a small circular bit of thin plywood that I've cut out with a jigsaw. I've sized this to be small enough to nest with my pot set, so it adds very little to my cook kit. Putting the stove on this keeps the tank from cooling and prevents the tank from melting the surface it sits on. Conceivably, this could catch fire, but if the wood is danger of burning, I think I have bigger problems involved with overheating the stove. I generally carry this wooden disk from November through April. Copyright by Dave Mann, 2008