Although the boiler has been lit before the water to the lowest water level can be seen at the water level, but after ignition, due to the furnace water temperature increases, the volume of the water level rise. With the further increase in the temperature of the furnace water, water vapor gradually generated steam, boiler water level to rise further. In other words, 'the boiler from the ignition began for a long period of time without water, economizer, such as no water flow, may be damaged due to overheating.
If the lower part of the drum and the economizer population installed a recycling tube, when the boiler in the ignition process is not on the water under the circumstances, the recirculation valve open, due to the economizer in the flue gas heating, Raised and produced part of the steam, severe small;
The water temperature inside the drum is low, steam-free, heavy, so that by the drum, recycling pipe, economizer tube composed of a loop. Recirculation tube is equivalent to the descending tube, the economizer tube is equivalent to the riser, the steamer in the boiler under the pressure of the push, continue to flow through the economizer into the drum, to prevent the economizer due to Water is overheated and damaged. When the boiler replenishment, in order to prevent water short circuit, water from the recirculation tube directly into the drum, recycling valve should be closed.
Cast iron economizer because of intolerance to water, does not allow the production of steam, it can not be used to set the recirculation tube method to solve the ignition process of the economizer cooling problem. Installed cast iron economizer boilers usually set up bypass flues to solve the problem of the cooling of the economizer during ignition.