VERTICAL mantle burners are still in use, though the inverted type has almost put them out of business. It is assumed that a new mantle is to be fitted to a vertical burner; take out the crutch which supports the mantle, and remove any fragments of the latter which may still be on the burner. Brush away any dust or flue with a camel-hair brush or similar brush with soft hair. The gas-fitter uses a little blower to send a current of air up through from the air ‘ports’ below; failing something of the sort, get a piece of rubber tube about ½ in. bore and fit to one end a piece of brass or copper tube about four inches long, which will enter the air ports. Put the metal end in place at an air hole, and blow briskly through the other end of the rubber. Pinch the tube after blowing and before taking an in-breath, or some of the dust may inadvertently be drawn into the mouth. Of course, a rubber bulb fitted to the metal tube would prevent this risk.
Leaving all adjustments as they are, turn on the gas and light it at the burner, without a mantle in place: the flame should be bluish at the inner cone and more of a purple colour at the outer part. It should be brisk and free, and not of a yellow or luminous type. The sliding collar which can be turned round partly to close the air holes should be manipulated slowly and gradually to stop any roaring; the collar in good burners can be fixed at the best setting by turning in a small screw. Another screw controls the gas supply, and should be turned in a little if a yellow or luminous flame is seen.
Put on a new mantle and flare it off by setting a match to it; this burns off the protective dressing with which the mantle is coated. Any manipulation of the mantle must be done before burning off, since the fabric is too fragile to be touched afterwards. Next turn on the gas and apply a light. In correct adjustment the flame should just fill the mantle; if too much gas is getting to the bunsen the flame will be too high and will come through the top. Alter the air-collar adjustment again if needed. Turn out the light and let the burner cool before replacing the glass chimney and ornamental shade.
The construction, though similar in principle to that of the upright burners, is different in some points. There is the sliding or rotating air-collar as before, but the gas control is usually a needle-valve operated by turning a milled metal or plain fibre disc at the end of the screw. Take off the globe; the mantle is held by lugs which fit on to recesses or brackets on the burner. Get a mantle of the proper size for that particular burner; take the old mantle ring to the shop to ensure correctness.
Brush out or blow the dust from the burner; owing to the inverted position this is easier than with the upright burner. Light the gas at the nozzle and adjust both gas and air supplies until the flame is the proper colour and not unduly noisy. Turn out the gas. Put on a new mantle and, after making sure it is in correct position, apply a match with the gas still turned off. Now turn on the gas and light at the mantle. Adjust the controls until the flame just fills the mantle and is otherwise satisfactory. Turn off the gas before replacing the globe.
Burners in a bad state may need to be unscrewed from the bracket so that the needle-valve can be cleaned This would have been indicated by a faulty flame at the nozzle when ignited at the preliminary test. Before replacing the burner, apply a little lead paint to the male-screwed end of the bracket to seal the threads and prevent leakage. Care is needed in dismantling and re-assembling any parts taken out for cleaning.
Burners with By-Pass
All that is needed at the end of the jet from the by-pass is a tiny flame which will ignite the main gas supply to the burner when the tap is opened. If the by-pass control screw is not opened sufficiently however, the by-pass will not light when the main tap is turned off. A few tests with the actual burner will disclose what is needed. Good burners have a steatite tip to the actual jet; the orifice may have become choked, and should in that case be cleared with a fine needle. Do not use a metal-worker’s broach or other like tool for this job, or the hole may be enlarged. The burner may have to be dismantled, if very dirty or corroded. As mentioned earlier, a preliminary test for this purpose should be made, before anything in the way of readjustment is done.