PURPOSE: To prevent poor quality fluid to be handled from lowering a processing capacity, by disposing a jacket through which high temperature fluid is flowed around the outer circumference of a cylindrical member accommodating a filter net.

CONSTITUTION: A jacket 14 constructed of a steel pipe and a steel plate is disposed around the outer circumference of a cylindrical member 21 of a steel pipe. High temperature fluid, e.g., steam is supplied to a hollow portion of the jacket 14 through an opening 15 and an opening 16. A changeover unit 17 for the high temperature fluid disposed on the bottom of a changeover cock 8 shown by a two-dot-and-dash line effects switching operation of the high temperature fluid in association with the changeover operation of the changeover cock 8.