| 摘要 |
PURPOSE:To prevent an orifice plate from deforming permanently by forming communication grooves in the upstream surface of an insertion hole for the orifice plate or the surface of the orifice plate which faces it. CONSTITUTION:Plural communication grooves 21 are formed in the upstream surface of the orifice plate insertion hole 2A so that the inside of a tube communicates with the inside of a chamber 10. The liquid in the chamber 10 enters and exit from the pipe at room temperatures through the communication holes 21 and the gap between the insertion hole 2A and orifice plate 3. When the gap between the insertion hole 2A and orifice plate 3 is eliminated owing to thermal expansion and the sticking of scale at higher temperatures, the liquid in the chamber 10 enters and exits from the tube through the communication grooves 21. Thus, the communication grooves 21 allow the liquid in the tube and chamber 10 to enter and exit from each other, so the liquid in the chamber 10 is not charged hermetically. Therefore, when the temperature rises, the orifice plate 3 is prevented from deforming permanently owing to the overloading of the orifice plate 3 caused by a rise in the pressure of the liquid in the chamber 10.
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