I've just (about) completed a vertical centre-flue pot boiler as described by Tubal Cain in his book on the Williamson engine. This is fired by a methylated spirit burner, with 5 eighth inch diameter cotton wicks. This is in an enclosed firebox below the pressure vessel with air holes in the base, as well as a large 'hole' in the side through which the burner is inserted.
Well I fired it up last night for the first time aiming to determine the pressure the safety valve lifted (it should be about 15psi). All went well, but I packed up when there was a significant steam leak in the union joint to the pressure gauge (now fixed I hope).
The thing I'm curious about is the behaviour of the spirit burner. As things were warming up, the burner itself and its resevoir got pretty hot, and it looked as though the spirit in the resevoir was evaporating and coming up through the breather hole in the top of the burner. There was flame pretty much everywhere inside the firebox (not just from the wicks), and coming out of the hole through which the burner enters the firebox.
This is the first time I've ever tried a meths burner, so is the question is, "is this expected behaviour"?
Hi John My only experience is with the meths burner for a ST 504 boiler. I find it gets very hot, to the extent that a flame shoots a couple of inches out of the breather hole in the filler cap after it has been lit for 10 mins or so. I didn't actually find meths a very satisfactory method of firing a boiler, it's pretty much uncontrollable and it's expensive, I've ordered a ceramic gas burner which should get delivered next week, they make them in all shapes and sizes, if your not happy with the meths burner it might be worth investigating gas. Ron
I have a few hot air engines which work on" meths" and if i more than half fill the tank iget the same results as you, bleeding from the vent hole , and the tank gets warm, and then we get worried , I have had the fright of the tank catching light, (i keep a wet towel handy,) a bit frightenning aint it?.
Hi Steammadman The problem with the ST meths burner is even when the tank is full [about 1/2 litre!] it is still only enough to fire the boiler for about half an hour. I'm still 'patiently' waiting for the gas burner that should have been delivered a couple of weeks ago as well
With my meths burners I keep the tank away from the wick tube by making a steel tube horizontal about 2" long 1/4"dia from the bottom of the tank and silver soldered to the vertical wick tube(usualy 5/16"dia).For the wick I use a bundle of iron wire (26 swg),stainless would be better.The steel connecting tube reduces heat conduction,helping to prevent the meths from heating too soon.10 ml of meths does not last twice the time of 5ml,so some must evaporate,and it gets worse as the tank is filled more-go for short runs-about 1/4hr on 5ml.The wire wick should be about 1/4" above the wick tube,and even with the meths i have(shure it's not as pure as it used to be),the flame has nil or very little yellow.Another one or two wick tubes may be fitted to go under a boiler.
Thanks for that suggestion. I've done nothing with this boiler for a while having recently moved house, but I had thought about having a remote tank as you suggest. I hadn't thought of using a wire wick though. That sounds a good idea.
I read on the net about someone using rolled up wire gauze,think it may have been stainless.I'v got a large bundle of iron wire that mum used for floral work,stainless might be better,I think the idea is to reduce heat conduction from the flame area.The vertical wick tube should be as thin walled as possible,I make mine about 10 thou.I use single wick burners on some of my hot air engines,and flame gulpers,and 2@3 wicks on little steam boilers.