Boiler

Abstract

A boiler is provided with: a boiler body in which the water level inside water pipes when combustion by a burner is stopped is lower than the upper ends of the water pipes; water supply means; control means which controls the water supply means depending on the water level in the boiler body; header water level detection means which detects a water level existing inside an upper header; and a downcast pipe. The control means performs first control for controlling the water supply means so as to lower a boiler body water level when the water level detected by the header water level detection means reaches a header set water level and second control for controlling the water supply means so as to raise the boiler body water level when the amount of drop in the boiler body water level reaches a predetermined amount after the first control.

1 . A boiler comprising:
 a boiler body including an upper header, a lower header, and a large number of water pipes to be heated by a burner, the water pipes connecting the upper header and the lower header to each other, wherein the water level in the water pipes when combustion by the burner is stopped is lower than the upper ends of the water pipes;   water supply means supplying boiler feed water into the boiler body;   control means controlling the operation of the water supply means depending on the water level in the boiler body;   header water level detection means detecting a water level existing inside the upper header by boiler water inside the water pipes being pushed up by air bubbles generated by boiling of the boiler water; and   downcast pipe allowing a lower part of the upper header and the lower header to communicate with each other, wherein   the control means performs first control for controlling the operation of the water supply means so as to lower a boiler body water level when the water level detected by the header water level detection means reaches a header set water level and second control for controlling the operation of the water supply means so as to raise the boiler body water level when the amount of drop in the boiler body water level reaches a predetermined amount after the first control.   
     
     
         2 . The boiler according to  claim 1 , wherein the predetermined amount is adjusted depending on any one or more of the pressure inside the boiler body, the temperature of supplied water, and the degree of concentration of boiler water. 
     
     
         3 . The boiler according to  claim 1 , further comprising external water level detection means placed outside the boiler body, the external water level detection means communicating with an internal space of the upper header and an internal space of the lower header through communication pipes and having an electrode detecting a boiler body external water level, wherein
 determination of the predetermined amount by the control means is performed using the electrode.   
     
     
         4 . The boiler according to  claim 3 , wherein determination of the predetermined amount by the control means is performed on the basis of the elapse of set time after the electrode detects the non-existence of water. 
     
     
         5 . The boiler according to  claim 1 , wherein
 the header water level detection means includes a first electrode detecting the header set water level and a second electrode detecting a water level lower than the header set water level, and   determination of the predetermined amount by the control means is performed using the second electrode.   
     
     
         6 . The boiler according to  claim 5 , wherein determination of the predetermined amount by the control means is performed on the basis of the elapse of set time after the second electrode detects the non-existence of water. 
     
     
         7 . The boiler according to  claim 1 , wherein
 the header water level detection means includes an electrode detecting the header set water level, and   determination of the predetermined amount by the control means is performed on the basis of the elapse of set time after the electrode detects the non-existence of water.