Part Five: Attenuator Valves
RICHARD SIMPSON’s mini-series on model steam plants
There is also the disadvantage of the cooling effect of the gas tank being more of a concern as the gas is evaporating at a high rate continuously and so the gas tank invariably starts to cool, possibly to the point where the evaporation rate is affected. As I have already suggested, you can fit varying sizes of jet to try to match the burner output with the engine demand, however a significant improvement is to physically control the flame.
Above the valve is the spring, which sits on a screwed adjuster. This adjuster increases or decreases the spring pressure and so varies the effective set point to which the burner will regulate. The valve is therefore plumbed into the system with the connection to the bottom of the diaphragm going to any steam space outlet on the boiler; the gas inlet connection goes to the gas supply and the gas outlet connection goes to the burner. The valve can be mounted at any position, however vertically would prevent condensate collecting on the diaphragm and possibly prolong its life. I have one connected directly on to the boiler itself and although the valve does get hot I am reliably informed by the manufacturer that it should operate successfully like this.
Just by fitting this type of valve to your plant you will significantly save gas; have much more flexibility when operating the model; the power from the engine will be more consistent, plus you will not suffer the indignity of your safety valve lifting and spraying steam and water everywhere. If you do nothing else to improve the efficiency and ease of operation of your steam plant, then I would strongly recommend that you fit one of these valves. You really will be surprised at just how much they make steaming your model so much more pleasant.
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