| 摘要 |
PURPOSE:To prevent a steam heater from becoming functionally useless in case where a steam flow control valve fitted to a inlet side of a radiating coil is fully closed or semi-closed, causing a suspended return flow or taking much more time to make a return flow of a steam from a liquid reservoir to a steam generator by a method wherein in parallel to a steam flow control valve fitted to the inlet side of a steam radiating coil, a sub-flow path with a non-return valve is provided. CONSTITUTION:When an operating liquid volume in the steam generator 4 become decreased, and a low liquid level condition is detected by a low liquid level sensor 5, then control valve 2 shut off the supply of fuel, thereby burning operation by a burner 1 is discontinued. Accordingly, the steam generator 4 becomes cool down, steam in the inside become condensed, after that when its inner pressure becomes below the atomospheric pressure, then, the operating liquid in the condensed liquid reservoir 13 starts its moving, passing through a steam pipe 6 to the steam generator 4 as a return flow. At this time, even if the steam flow control valve 8 in a closed position, most of the operating liquid may be returned through a sub-flow path 11. Since a flow resistance in the sub-flow path 11 is much smaller than that in the radiating coil path 9, upon completion of a return flow of the operating liquid, being sent out from the steam generator 4, the control valve 2 is operated and burning operation is started again.
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